36 Replies Latest reply on Nov 4, 2012 1:21 PM by spl00

    Difference in TIFF and RAW import with ACR (how to fix)?

    spl00 Level 1

      I'm experimenting with a workflow, so whilst this may seem like an odd thing to want to make work, I have a geniune reason for doing what's described below:

       

      I have Canon CR2 RAW files from a 7D, Photoshop CS6 13.01 64bit, with ACR 7.1.0.354, running on Windows 7 64bit.

       

      1. I import a CR2 image via ACR, with no changes to any sliders; opening it as Adobe RGB (1998); 16bit

      2. I then save the image as a TIFF file, leaving "ICC Profile: Abode RGB (1998)" selected in the Color section of the file save dialog

      3. If I then close all files, and reopen the CR2 and TIFF image, they (as expected) appear to be identical

      4. After closing all files again, I then open the CR2 and make an exposure adjustment (e.g. -1.00)

      5. Using Bridge, I select the TIFF file, right click and select Open in Camera Raw. I make the same exposure adjustment as for the CR2

      6. Now, the adjusted CR2 and adjusted TIFF are different. A colour shift is noticable, and for a severe exposure change (i.e. +4.00) the shadow detail in the CR2 is a lot lighter

       

      Here are two cropped areas from the files (with a 4 stop push), showing some branch/leaf and grass detail respectively. The TIFF has a greener colour cast for the grass, but much darker shadows:

       

      TIFF

      TIFF.jpg

      RAW

      RAW.jpg

       

      I appreciate that the CR2 is still a RAW file, and as such has the original Bayer pattern data, but is there any way I can make ACR adjustments to a TIFF (taken from a CR2) to behave in the same way as the original CR2?

        • 1. Re: Difference in TIFF and RAW import with ACR (how to fix)?
          Jeff Schewe Level 5

          spl00 wrote:

           

          I appreciate that the CR2 is still a RAW file, and as such has the original Bayer pattern data, but is there any way I can make ACR adjustments to a TIFF (taken from a CR2) to behave in the same way as the original CR2?

           

          No...your TIFF is hitting the gamut limits of Adobe RGB. The TIFF has been gamma encoded in the Adobe RGB color space which is a far more clipped color space than what the raw file can have. You should be adjusting the raw image for optimal tone & color. While you can open a TIFF in ACR, you will NEVER have the full capability of adjustment the raw file had. If you are trying to come up with a workflow that doesn't adjust the raw file but applies all the tone/color to the TIFF I would say that would be a very poor workflow.

          1 person found this helpful
          • 2. Re: Difference in TIFF and RAW import with ACR (how to fix)?
            spl00 Level 1

            Thanks Jeff.

             

            Is it possible then to do away with the colour space encoding? Taking a very simplistic approach; the TIFF file is representing RGB values, with 16bits per pixel per channel. I understand the 7D RAW files have data to 14bits of 'accuracy', so in terms of quantisation and clipping I'm not trying to squeeze samples into a smaller dynamic range. As such, I'd assume that ultimately somewhere within the ACR process, it's dealing with RGB values (with some precision, perhaps 16bit, perhaps more) and applying the exposure/shadows/highlights etc sliders to that data. It feels to me therefore that it must be possible somehow to do this with TIFF data in a way that would yield identical results.

             

            The odd thing is that if I make the exposure correction to the RAW before I import, then save as a TIFF, the imported RAW and saved TIFF look identical (so the TIFF, with its colour space can still represent the desired colours - but not if it's saved uncorrected, then adjusted with ACR afterwards).

             

            The workflow is in essence an idea to blend the data from multiple RAW files, but as I obviously can't write image data to a RAW file, I was hoping to take RAW data into TIFF, blend it with some homemade software, then bring the resulting TIFF into Photoshop via the ACR plugin. If the behaviour of ACR with TIFF files is greatly different from CR2 files then that might knock the idea on its head.

            • 3. Re: Difference in TIFF and RAW import with ACR (how to fix)?
              conroy Level 5

              Start by creating a ProPhoto profiled TIFF from the CR2 and you may have better results.

              • 4. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                spl00 Level 1

                Thanks conroy. That helped (i.e. it's better, but still different). It seems then that what I need is a way of selecting an ICC profile during the ACR import with an impossibly wide gamut (or no ICC profile); such that it doesn't cause any problems? Unfortunately you only get Abode RGB, ColorMatch RGB, ProPhoto RGB and sRGB.

                 

                I did randomly try opening the RAW with the ProPhoto profile, then used Assign Profile to change to "Don't Color Manage This Document" before saving as TIFF (or selecting Wide Gamut RGB). No cigar with that approach.

                 

                May be out of luck sadly.

                • 5. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                  Level 5

                  ProPhoto RGB is the exact equivalent of Camera Raw's internal color space.  It doesn't get any wider than that.  It contains even stuff beyond that which the human eye can see and recognize as color.  It is, in effect, the "impossibly wide gamut" you envision.

                   

                  Colors cannot exist outside a defined color space.  Having no defined color space (profile) is an impossibility within the laws of physics.

                   

                  What seems to escape your grasp is that a demosaic'ed, converted image can never ever have the latitude of a raw file.

                  • 6. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                    Level 5

                    http://dpbestflow.org/color/color-space-and-color-profiles

                     

                    Excerpt:

                     

                    ProPhoto RGB - This color space was designed as a universal standard for high-bit image editing, and includes all the colors that the human eye can see. ProPhoto RGB is a very popular color space for experienced Photoshop users. Because the space is so wide, it's not appropriate for 8-bit images. ProPhoto RGB is not always the best choice for a working space. Because 15% of the color space is beyond the range of human vision, color mapping is happening in ways that are impossible to see…

                    • 8. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                      spl00 Level 1

                      > ProPhoto RGB is the exact equivalent of Camera Raw's internal color space.  It doesn't get any wider than that.  It contains even stuff beyond that which the human eye can see and recognize as color.  It is, in effect, the "impossibly wide gamut" you envision.

                       

                      OK, that's good to know.

                       

                       

                      > What seems to escape your grasp is that a demosaic'ed, converted image can never ever have the latitude of a raw file.

                       

                      I should probably explain that I have a software engineering, rather than art/imaging, background. Coming from this point of view, I'm considering each pixel (in a 16bit file) as having a sample for R, G and B (each of which can be 0-65535). The RAW file has, as I understand it, no inherent colour space, as it's the recording of the cells in the camera's sensor. Whilst the Bayer pattern means that each individual pixel is only R, G or B (with the 'smarts' behind RAW conversion producing an RGB triplet for each pixel), even if the sensor was truly 16bits per sample, the RAW (in terms of sample range per pixel) couldn't have more latitude than the converted image - surely?

                       

                      As I mentioned earlier, I'm assuming (though accept I could be wrong) that the ACR plugin will perform a demosaic step to get an RGB sample per pixel, then apply the algorithms used to change exposure, shadows etc. At the RGB sample stage - it's just a set of numbers. Ignoring the colour profile, it should be feasible to have, say, a TIFF file that contains RGB samples whose values are the same as those used in the ACR stage for a RAW before the effect of the sliders - however, I guess there must be some limitations caused by the profiles that's affecting the results when a TIFF is brought back through the ACR plug in. That is of course unless the algorithms for the sliders work on the Bayer data directly, but that would surely require logic for each different type of sensor, so would be very complex to implement.

                      • 9. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                        Level 5

                        spl00 wrote:

                         

                         

                        …The RAW file has, as I understand it, no inherent colour space, as it's the recording of the cells in the camera's sensor…

                         

                        That would be, of course, nonsensical.  The raw image exists within the color gamut of the sensor.

                         

                        Unfortunately, I don't have either the time or the stamina—due to serious medical conditions—to continue this discussion.  But there are are many misconceptions and errors in your approach.

                         

                        I can only recommend that you do a lot of reading on the subject and that you take any further discussion to the Adobe Camera Raw forum, where gurus like Jeff Schewe, Thomas Knoll (creator of Photoshop and of Adobe Camera Raw) and Eric Chan contribute from time to time:

                         

                        Adobe Camera Raw

                        • 10. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                          Level 5

                          spl00 wrote:

                           

                           

                          …I guess there must be some limitations caused by the profiles that's affecting the results when a TIFF is brought back through the ACR plug in…

                           

                          The limitations are not caused by any "profiles" but by the nature of the TIFF file itself:  It is no longer a raw file!  That's what we've been trying to tell you all along.

                           

                          …a demosaic'ed, converted image can never, ever have the latitude of a raw file.

                           

                          YES, the adjustments are performed on the raw data, and, YES, the Adobe Camera Raw team must have a precise determination of the individual characteristics of each sensor.   It's a gargantuan task performed by the ACR team and it explains why new camera models are not supported right out the gate!

                           

                          I repeat: Colors cannot exist outside a defined color space.  Having no defined color space (profile) is an impossibility within the laws of physics.

                           

                          Again:  Adobe Camera Raw

                          • 11. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                            ssprengel Adobe Community Professional & MVP

                            The numbers from a sensor are linear with the number of photos hitting them as attenuated by the color of the filter in front which generally matches the maximum color-sensitivity of the three different color receptor cells in the retina.

                             

                            Human vision is very non-linear, being much more sensitive to dim variations than bright variations, so to convert the photosite photon-linear numbers, even after debayering, to human-vision-linear numbers requires a color profile (determined by Adobe for each camera specifically) and very non-linear gamma curve be applied along with a white-balance formula that adjusts the relative RGB numbers of the raw data. 

                             

                            So RAW numbers after debayering to RGB are linear with numbers of photons within a particular color (R, G or B), while TIF numbers are assumed to be linear with human-vision sensitivity.

                             

                            If you look at a raw file data that has been stretched from black to white, without applying the gamma curve it will look dark:

                             

                            http://wwwimages.adobe.com/www.adobe.com/content/dam/Adobe/en/products/photoshop/pdfs/line ar_gamma.pdf

                             

                            It is probably possible to reverse-engineer camera-sensor numbers from TIF numbers given a particular camera profile, gamma curve, and white-balance, and mid-tone exposure value, but this is never done in photo-editing program.

                            • 12. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                              Jeff Schewe Level 5

                              spl00 wrote:

                               

                              Ignoring the colour profile, it should be feasible to have, say, a TIFF file that contains RGB samples whose values are the same as those used in the ACR stage for a RAW before the effect of the sliders - however, I guess there must be some limitations caused by the profiles that's affecting the results when a TIFF is brought back through the ACR plug in.

                               

                              You are forgetting that the raw data is linear and a TIFF in ProPhoto RGB has a gamma 1.8.

                               

                              The bottom line is a raw file and rendered file will have differences when processed through the ACR algorithms…so the exact same settings when applied to a raw file will be slightly different when applied to a rendered file. Nature of the beast…what you are trying to do is simply suboptimal.

                               

                              You would be better served doing the majority of the tone and color corrections on the raw file in ACR. If you then want to do slight or sublet adjustments back in ACR, ok…but just understand that ACR was designed first and formats as a raw image processor. Yes, you can also process JPEG and TIFF with useful adjustments, but I think it's an unreasonable expectation that you can achieve EXACTLY the same adjustment on a raw file and a TIFF…I think you need to rethink what you think you are trying to do.

                              • 13. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                JJMack Most Valuable Participant

                                spl00 wrote:

                                 

                                I'm experimenting with a workflow, so whilst this may seem like an odd thing to want to make work, I have a geniune reason for doing what's described below:

                                 

                                I have Canon CR2 RAW files from a 7D, Photoshop CS6 13.01 64bit, with ACR 7.1.0.354, running on Windows 7 64bit.

                                 

                                1. I import a CR2 image via ACR, with no changes to any sliders; opening it as Adobe RGB (1998); 16bit

                                2. I then save the image as a TIFF file, leaving "ICC Profile: Abode RGB (1998)" selected in the Color section of the file save dialog

                                3. If I then close all files, and reopen the CR2 and TIFF image, they (as expected) appear to be identical

                                4. After closing all files again, I then open the CR2 and make an exposure adjustment (e.g. -1.00)

                                5. Using Bridge, I select the TIFF file, right click and select Open in Camera Raw. I make the same exposure adjustment as for the CR2

                                6. Now, the adjusted CR2 and adjusted TIFF are different. A colour shift is noticable, and for a severe exposure change (i.e. +4.00) the shadow detail in the CR2 is a lot lighter

                                You stated you have a geniune reason for doing the above. Would changing

                                1.) Opening the RAW file through ACR as a Smart Object instead of a Raster layer.

                                and Changing

                                2.) Saving the Image as a Layered Tiff file instead of a flat file

                                be the same to you. If its the same to you still have access to the images RAW data in the Smart Object layer.  When you reopen the Tiff File in Photoshop you can reopen the embedded RAW File smart object in ACR by double clicking on the smart object icon in the bottom layer in the layers palette.  ACR will be working with the Images RAW data and not a raw conversion that has had white balence and other post processing processes applied.  You should be able to make the same exposure change you made when you reprocessed the RAW file. When you comit the change the embeded smart object will be updated in the opened tiff file document in Photoshop. Remember from bridge open tiff file in Photoshop then reopen the smart object in ACR.

                                • 14. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                  spl00 Level 1

                                  ssprengel, Jeff, JJMack - thanks for the constructive replies

                                  station_two - after your use of mildly aggressive language ("What seems to escape your grasp") in your first post, I had money that your subsequent response(s) would be on the lines of "I'm too busy to explain it to people like you". Thankyou for confirming my expectations (sometimes I wonder if some people engage in forum discussions for the sole purpose of trying to get themselves [and possibly others] riled)

                                   

                                   

                                  So... back to trying to find a construcive solution: If the algorthirms for the adjustments in ACR do operate directly on the Bayer data (before demosiacing to RGB per pixel) then operating on the TIFF (or any other demosaiced RGB data) will indeed be a non-starter. Without (probably unlikely) input from an Adobe developer however, we can't know for sure.

                                   

                                   

                                  > So RAW numbers after debayering to RGB are linear with numbers of photons within a particular color (R, G or B), while TIF numbers are assumed to be linear with human-vision sensitivity

                                   

                                  Understood (I'm familiar with gamma, camera sensor behaviour, exposing to the right etc). Ultimately though, it should be possible to produce an RGB file that is also linear (i.e. not adjusted for human vision) to then bring back into ACR. However, if that's simply not possible with ACR, then that's also a non-starter (and wouldn't help anyway if the adjustments operate on the Bayer data directly).

                                   

                                  I did look briefly into opening the RAW as a smart object, but sadly I didn't think that'd help. The goal I'm trying to achieve is an experimental idea to blend parts of images together from multiple exposures; but to achieve a single RAW file with that data as if it came from the camera (thus it could be brought into ACR to get the benefit of - from my point of view - the useful and intuitive adjustment sliders). Clearly that would require reverse engineering the particular RAW format for the camera being used (and each and every camera you'd want to support) - thus, it's not really practical.

                                   

                                  I'd hoped to be able to convert (without edits) the RAW images into TIFF (or some other lossless RGB container that I can read programmatically), do the blending to produce a single TIFF, and then bring that back into ACR.

                                   

                                  Whilst it's more convoluted, I suppose it might be possible to generate the unedited TIFF files purely for the purposes for getting data about the images, then using that to create a set of masks. Then, as Jeff suggests, perform adjustments to the RAW files in ACR, and use the masks to blend the imported (and now corrected) RAWs into one image. Not ideal, but perhaps worthy of more experimentation.

                                  • 15. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                    Noel Carboni Level 8

                                    spl00 wrote:

                                     


                                    I'd hoped to be able to convert (without edits) the RAW images into TIFF (or some other lossless RGB container that I can read programmatically), do the blending to produce a single TIFF, and then bring that back into ACR.

                                     

                                    I think the misconception here may be that Camera Raw can be employed as a cog in the machine, when it's more like a complete machine in itself.  It's moved well beyond making some kind of simply defined rendition of the raw file - in other words it's far beyond a "debayering" tool.  It's an end user tool.

                                     

                                    -Noel

                                    • 16. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                      spl00 Level 1

                                      Hi Noel,

                                       

                                      Yes, you may well be right. It might be worth a mail to the ACR forum when I can get the time to write something a bit more descriptive of what I'm trying to inject. Probably only the guys that actually work on the ACR code would be able to answer the questions, but I don't know if any of those guys lurk there.

                                      • 17. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                        Noel Carboni Level 8

                                        FYI, Jeff Schewe is an insider, though not an engineer who works on the product directly I don't think.

                                         

                                        -Noel

                                        • 18. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                          JJMack Most Valuable Participant

                                          spl00 wrote:

                                           

                                          I did look briefly into opening the RAW as a smart object, but sadly I didn't think that'd help. The goal I'm trying to achieve is an experimental idea to blend parts of images together from multiple exposures; but to achieve a single RAW file with that data as if it came from the camera (thus it could be brought into ACR to get the benefit of - from my point of view - the useful and intuitive adjustment sliders). Clearly that would require reverse engineering the particular RAW format for the camera being used (and each and every camera you'd want to support) - thus, it's not really practical.

                                           

                                          That seems to be what others do with independant smart object layers.  First you open the RAW file through ACR into Photoshop as a smart object layer. Then you use menu Leyer>Smart Objects>New Smart Object via Copy.  That creates a second independant smart object layer that is identical to the first smart object layer.  You then double click on the senond layers smart object icon in the layers palette to open it in ACR. It will open with the same settings as in the first smart object layer in ACR. You change these settings in ACR and click on the OK button. When you do that Photoshop will update the the embedded smart object in the second smart object layer. You will then have two conversion of the RAW file in Photoshop you can add Layer mask and smart filters to. You can use all of Photoshop Layer adjustment and blending options to bring out more detail in you images.   Do not just dupe the smart object layer, dups share a common smart object. You need to create additional versions with independant smart object layers. Create as many as you need use menu Layer>Smart Objects>New Smart Object via Copy....

                                          • 19. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                            Level 5

                                            Sorry, spl00.  I meant no offense or disrespect, but if you found my post objectionable, it was my bad and I apologize.

                                            • 20. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                              Level 5

                                              spl00 wrote:

                                               

                                              …only the guys that actually work on the ACR code would be able to answer the questions, but I don't know if any of those guys lurk there.

                                               

                                              As I typed in post #9 above: 

                                               

                                              I can only recommend that you… take any further discussion to the Adobe Camera Raw forum, where gurus like Jeff Schewe, Thomas Knoll (creator of Photoshop and of Adobe Camera Raw) and Eric Chan contribute from time to time:

                                               

                                              Adobe Camera Raw

                                               

                                              I would also recommend that you access the forum through its web interface with your web browser rather than through email.  One of the disadvantages of accessing the forums through email is that you never get to see any edits to the posts, as edits are not broadcast.

                                               

                                              Another disadvantage i that you cannot attach or upload any images through email.

                                              • 21. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                                spl00 Level 1

                                                Having used forums for many years, I feel I've gotten quite good at spotting personality types and predicting people's behaviour (on forums). However, I must admit I wasn't expecting to read...

                                                 

                                                > Sorry, spl00.  I meant no offense or disrespect, but if you found my post objectionable, it was my bad and I apologize.

                                                 

                                                ...for which I can only say a geniune thankyou, and apology accepted. You've actually posted a great deal of useful information on this thread, and I was going to take up your suggestion of posting a more specific question in the ACR part of the forum (for which I've finally gotten time to do tonight). I have been viewing the forum via the web interface BTW, but thanks for the tip.

                                                 

                                                JJMack - thanks for the further info on smart objects. I've used Photoshop for many years, but would say that I know a reasonable amount about only a very small subset of features, and smart objects aren't something I've used. I'll have to dig into them a bit deeper, as the ability to go back and make changes in ACR after opening the file could prove to be very interesting.

                                                • 22. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                                  Neal_Alan Level 1

                                                  I found this whole thread very helpful.  I wanted a stronger understanding of more detail about RAW files and did a search and stumbled upon this.  I knew the general concept and textbook explainations that you search and find and the basics they teach you of the differences of RAW vs TIFF vs JPG.  My question before searching, and what led me here, was that I thought that a RAW file and a TIFF created from that RAW file were essentially the same in terms of overall information or fidelity .  I had just learned in doing some tutorials about opening a RAW file into Photoshop as a smart object.  Thus when the smart object RAW file is clicked on to be edited that the original RAW file is edited/accessed in Camera Raw and then thrown back into Photoshop.  I took from this that there (forgive me for any ignorance) that RAW files had more 'fidelity' than a TIFF made from that RAW file.  From what the original poster questioned in step 6 that there was a difference in color shift from the CR2 adjusted file to the RAW adjusted file is due to adjusting of the TIFF file is adjusting clipped or discarded info that the original RAW file has to it.  SOO something must happen in the creation of the TIFF from the RAW file.

                                                   

                                                  I have a question on on opening RAW files as smart objects in Photoshop if someone can answer or redirect me properly I would appreciate it.....Is there any limitations that you have by opening RAW as smart object in PS?  Can you not do certain things to smart objects, like use certain filters or adjustment functions in Photoshop? Thanks!

                                                  • 23. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                                    Lundberg02 Level 3

                                                    As far as I can tell, you can already do in ACR what the OP  wants to do with some kluge software. Or at least acieve all the exposure and emphasis tricks tat anyone could want.

                                                    • 24. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                                      spl00 Level 1

                                                      The kludge I'm wanting to attempt (potential good name for the program BTW) would involve automatically blending parts of multiple RAW files into a single RAW that could then be opened in ACR. I'm not aware that ACR can open/blend multiple RAWs, so I'm presuming that isn't currently possible.

                                                       

                                                      I suspect it would be possible in PS itself (by opening multiple RAWs then performing some processing) but I'd like to see if I could do it all in one external operation. Lack of time at the moment is meaning I'm not getting many opportunities to progress said kludge.

                                                      • 25. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                                        c.pfaffenbichler Level 8

                                                        Can you not do certain things to smart objects, like use certain filters or adjustment functions in Photoshop?

                                                        You can not paint or clone stamp etc. on a Smart Object directly but would have to do it on a new Layer with the appropriate Tool settings.

                                                        Liquify does not work on SOs by default, but there used to be a plug-in available that enable this – don’t know if it’s been updated for CS6 and in any case it seemed not very useful as the Mesh would not be saved automatically.

                                                         

                                                        SOO something must happen in the creation of the TIFF from the RAW file.

                                                        If you have read up on RAW you may have read that RAW-files are one-channel files with 14-bits depth (or thereabouts) and each pixel basically only records one of the three colors (the patterns for which one may vary).

                                                        From that the 3-channel-color information for all pixels has to be interpolated, so something has to happen indeed.

                                                        • 26. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                                          Neal_Alan Level 1

                                                          What happens in PS when you open as RAW as smart object and then rastorize?  What file format does it render it to?  You technically haven't saved it as any thing so I am wondering what does it do at the rastorize point.  In respect to color space, when you open RAW as smart object does Adobe PS assign it to what you have you defaults setup as?  I would assume that is the case but am not totally sure because if you can then go in and edit the smart object RAW and it goes into Camera RAW then it must still be in Pro Photo color space.  I am just curous how PS default color space settings affects this process of opening RAW as smart object.  Thanks for responses and info, this is giving me a lot more understanding on everything.

                                                          • 27. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                                            Lundberg02 Level 3

                                                            What would be gained by blending multiple RAW image portions?

                                                            • 28. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                                              spl00 Level 1

                                                              Probably nothing if it doesn't work, but the (crazy) plan was an experiment to produce a single RAW that doesn't suffer from a great 'feature' provided by recent Canon DSLRs - namely terrible banding problems in shadow detail.

                                                               

                                                              I've no doubt this can be done in stages in PS, but the goal is to produce a single linear DNG RAW with the shadow detail replaced from a brighter exposure (and obviously brought down to match the exposure of the base image). Experiments with multiple RAW files seem to show that it would be beneficial, but I need to work out the affect of exposure on the samples within a RAW file.

                                                               

                                                              A brief play with ACR shows that (as long as samples aren't clipped) adjusting the exposure of a RAW to match that of another bracketed shot (of the same scene) does result in very similar RGB values for the corresponding pixels (i.e. an exposure at EV0, with +2 on the slider tends to match an exposure taken 2 stops brighter). It's clearly not just a simple case of +1 stop == 2x the RGB values though, so I presume there's some formula for doing this. I also presume it doesn't need intimate knowledge of the original sensor, as bringing non-RAW files into a HDR program must (I guess) do something similar (in order to create a 'virtual' image with a large dynamic range from pictures with different exposures). If anyone understands the relatioship between changes in exposure and the resulting RGB values on a pixel then I'd be grateful for some pointers.

                                                              • 29. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                                                Noel Carboni Level 8

                                                                How would fooling with the raw file data be better than converting a number of images and combining them afterward?

                                                                 

                                                                 

                                                                Astronomers combine multiple exposures all the time to average out (or statistically reduce) the noise in any one exposure.

                                                                 

                                                                Since banding is often positionally dependent (not to mention cameras moving between frames being common, even with good tripods) are you thinking you'll be aligning the multiple exposures?  Given that lens responses are often non-linear that could prove more difficult than you might think.

                                                                 

                                                                Astronomers often dither images - moving each sub-exposure some pixels this way and that - to overcome these issues, and they have special alignment processes that transform each of the sub-exposures to achieve alignment before combining the data (called "stacking").

                                                                 

                                                                Given what you've described, I think you're attacking this in the wrong place.

                                                                 

                                                                Oh, and by the way, you can generally overcome most of the banding noise via the Camera Raw noise reduction that's already implemented, and for what's left I actually have created a good banding noise reduction tool in my dSLR Tools actions set.  Feel free to post a sample raw file showing what you're talking about.

                                                                 

                                                                -Noel

                                                                • 30. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                                                  spl00 Level 1

                                                                  I wouldn't claim to have a deep understanding of the problems with current Canon sensors (there are many on photography forums going into great detail regarding the differences between the Canon sensors and the Sony Exmor units used in some Nikon bodies); however, the main issue appears to be with trying to push shadow detail. Even a relatively modest push can start to expose banding in shadow areas, and I've not yet seen any noise reduction that's capable of tackling this sufficiently (certainly in a way that'd give you detail like trying the same thing with an exposure from an Exmor sensor). Given the vitriol directed towards Canon on the issue by even some Canon owning landscape pros - who are, based on their work, clearly skilled photographers and PS users, I presume there is no current way of adequately fixing this on a single exposure.

                                                                   

                                                                  I've noticed that if you take a lighter exposure, reduce the exposure in ACR, open it in PS, then later try to lift the shadows, you'll still get pretty good results (because the original detail was bright enough to not suffer from the banding problems on the sensor). Hence the idea to replace pixels with shadow detail in the 'base' image with the corresponding pixels from a lighter image (by reducing the exposure to match). Note this isn't an attempt at any sort of HDR - it's simply an experiment to produce a single RAW file that would withstand lifting of the shadow detail.

                                                                   

                                                                  Any form of auto alignment of the images would be 'version 2'; though with mirror lock-up, a remote release cord, and a good tripod, I've tended to find little need for alignment between bracketed shots. The bigger issue is usually moving objects in the scene (leaves etc.)

                                                                   

                                                                  Oh - to answer the question in your first sentence - simply convenience (if it works). Occasionally I have no choice but to combine multiple exposures due to the dynamic range of a scene. However, I often find that I'd be OK with a single exposure if I could just raise the shadows in an image a little... but often a little more than I can get away with on a Canon sensor. The convenience of being able to adjust a single RAW in ACR would save me a lot of time vs. having to open multiple RAWs then blend shadow detail from multiple images. I'm not a fan of the general HDR 'look', so have never found just bringing multiple images into a HDR tool gets a result I like.

                                                                  • 31. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                                                    Noel Carboni Level 8

                                                                    I raise the brightness of shadows in my Canon EOS-40D images all the time without trouble.  Yes, I can cause banding noise, but I deal with it.  Your presumption that there's no good way to deal with it may be wrong. 

                                                                     

                                                                    Like I said, please post a raw file as an example; I'd love to help advise on ways to do NR effectively.

                                                                     

                                                                    -Noel

                                                                    • 32. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                                                      spl00 Level 1

                                                                      I'm not in front of a machine with my data at the moment, but here's an example of the kind of thing I'm talking about: http://www.fredmiranda.com/5DIII-D800/index_controlled-tests.html

                                                                       

                                                                      I'd suggest that if you could make 5D3 pushed shadows (from a single exposure) look like those off a D800 you'd win yourself a lot of friends amongst Canon shooters! I'm using a 7D, and the banding is significantly worse than the 5D3.

                                                                       

                                                                      My understanding is that the signal to noise ratio in shadow details on the Canon sensors at the moment is sufficiently low at base ISO that any NR is just going to smooth out the noise (there's not enough signal to poke through that noise).

                                                                      • 33. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                                                        Noel Carboni Level 8

                                                                        spl00 wrote:

                                                                         

                                                                        I'm not in front of a machine with my data at the moment, but here's an example of the kind of thing I'm talking about: http://www.fredmiranda.com/5DIII-D800/index_controlled-tests.html

                                                                         

                                                                        I'd suggest that if you could make 5D3 pushed shadows (from a single exposure) look like those off a D800 you'd win yourself a lot of friends amongst Canon shooters! I'm using a 7D, and the banding is significantly worse than the 5D3.

                                                                         

                                                                        Let's get something straight right off:  No amount of noise reduction is going to equal an image in which less noise is captured.  Unfortunately (for Canon owners) the Nikon technology has just leapt ahead sufficiently far that it's simply making less noisy images with more megapixels.  Canon will either respond with something new or fold.  I hope the former, as I'm a Canon shooter myself.

                                                                         

                                                                        However, I'm here to tell you the banding noise, specifically, can be mitigated.  Very few folks have figured out how as I have.  This is one of the images from the page you linked to untouched (top) and after the run of my Vertical Banding Noise Reduction action (bottom).

                                                                         

                                                                        But this image would have benefited greatly from more noise reduction dialed-in during raw conversion, perhaps enough not to need my action at all.  Unfortunately, the raw file isn't available.  People sometimes don't realize just how good the noise reduction in Camera Raw actually is.

                                                                         

                                                                        VBNR_Demo.jpg

                                                                         

                                                                        -Noel

                                                                        • 34. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                                                          spl00 Level 1

                                                                          > Let's get something straight right off:  No amount of noise reduction is going to equal an image in which less noise is captured. 

                                                                           

                                                                          Absolutely... but hence my plan to try to automate some blending of exposures.

                                                                           

                                                                           

                                                                          >Canon will either respond with something new or fold.  I hope the former, as I'm a Canon shooter myself.

                                                                           

                                                                          There seems to be sufficient noise (pardon the pun) from insiders to indicate there will be a high megapixel Canon body 'soon'. Hopefully that'll tackle the DR and banding problems too, but I suspect (certainly based on Canon's recent pricing) that it won't be cheap.

                                                                           

                                                                           

                                                                          >However, I'm here to tell you the banding noise, specifically, can be mitigated.  Very few folks have figured out how as I have.  This is one of the images from the page you linked to untouched (top) and after the run of my Vertical Banding Noise Reduction action (bottom).

                                                                           

                                                                          > But this image would have benefited greatly from more noise reduction dialed-in during raw conversion, perhaps enough not to need my action at all.  Unfortunately, the raw file isn't available.  People sometimes don't realize just how good the noise reduction in Camera Raw actually is.

                                                                           

                                                                          Well, I have to say I'm very impressed with that result. OK, of course there's still plenty of noise, but the (almost total, to my eyes) elimination of the banding makes it far less objectionable. Is the action you've created something you've shared (or would be willing to share)?

                                                                          • 35. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                                                            Noel Carboni Level 8

                                                                            It's part of my commercial dSLR Tools actions set.  There's also a version of it in my Astronomy Tools set, as astroimages tend to get pushed to where pattern noise shows.

                                                                             

                                                                            It's a bit tough to balance the aggressiveness of the action so that it gets all the noise but leaves the detail, but I've made a stab at it.

                                                                             

                                                                            For larger banding I've been working on an update to that set that does things on a larger scale, and somewhat more aggressively.  I should have that update out in the next few months.

                                                                             

                                                                            -Noel

                                                                            • 36. Re: Difference in TIFF and RAW import with ACR (how to fix)?
                                                                              spl00 Level 1

                                                                              Impressive. Where is that actions set available? I'd certainly consider it if it'd help some of the images I've taken where it wasn't possible to bracket.

                                                                               

                                                                              No time to play further with the blending experiments this weekend, so no progress sadly.