16 Replies Latest reply on Sep 2, 2015 4:39 PM by d@v!dm

    ACR Lens correction not applying

    borisd65712864 Level 1

      Hello.

       

       

       

      I use ACR 9.1 to edit DNGs that I get from raw footage shot with my 7D.

       

       

      When I try to apply "lens correction profile"; the correct lenses are detected, profile is shown as "applied", but nothing is changing.
      If I change the settings "deformation" or "vignetting", there's no change.

      The only way I can get a visual change, is when using "manual" changes in the "manual" tab.

        • 1. Re: ACR Lens correction not applying
          ccastleb Adobe Employee

          Hi,

           

          We are not aware of any issues with lens corrections and the Canon 7D.

           

          Are you also seeing this with the .NEF files from the camera?

           

          Do the corrections fail to change images shot with specific lenses or all lenses you have tried?

           

          If you post link to a sample raw or DNG image I can take a look.

           

          Thanks,

           

          - Chris

          • 2. Re: ACR Lens correction not applying
            ssprengel Adobe Community Professional & MVP

            You use the phrase “raw footage”.  Do you mean you area expecting lens corrections to apply to video?

            • 3. Re: ACR Lens correction not applying
              borisd65712864 Level 1

              I have the same issue with all type of lens. The lens is properly detected from the metadata, but no change is applied when I move the slider.

               

              Yes since my videos are DNG sequences...

               

              Here's a DNG sample:

               

              MEGA

              • 4. Re: ACR Lens correction not applying
                ccastleb Adobe Employee

                I see that the sample DNG you posted appears to be cropped (1728x972). I can see a very small correction being applied for both vignetting and distortion, but given the image is cropped, the full correction will not be applied.

                 

                - Chris

                • 5. Re: ACR Lens correction not applying
                  ssprengel Adobe Community Professional & MVP

                  I don't see any distortion correction occurring at the corners, but I can see vignetting correction occurring.  It is more obvious if I turn up the vignetting correction slider to 200 and toggle the Enable Lens Corrections on and off.  The histogram moves left-right as an indication of the brightness changing and the image obviously becomes brighter with the corrections enabled and 200 set as the amount.

                   

                  How was this DNG created?  I think I can see in the EXIF that it came from an .MLV file, originally.

                  • 6. Re: ACR Lens correction not applying
                    ccastleb Adobe Employee

                    Hi Steve,

                     

                    I can see a slight distortion correction when zoomed in. There may be more to this than the image dimensions. I'll let both of you know what I find out.

                     

                    - Chris

                    • 7. Re: ACR Lens correction not applying
                      ssprengel Adobe Community Professional & MVP

                      I turned off the GPU in ACR and now I can see maybe a 1/3 pixel movement of some edges near the handlebars at the bottom.  With the GPU on, there was a momentary flash of low-res preview that obscured the tiny shift.

                      • 8. Re: ACR Lens correction not applying
                        ccastleb Adobe Employee

                        Following up...

                         

                        The main cause of the profile making a very modest correction is due to missing metadata about the sensor format factor and the original resolution of the image. ACR is unable to determine a correct sensor format factor, so it falls back to one that makes it seem that the image is from a much smaller sensor.

                         

                        The conversion from movie sequence to DNG must be stripping some data or it isn't present in the source sequence that is being converted.

                         

                        - Chris

                        • 9. Re: ACR Lens correction not applying
                          ssprengel Adobe Community Professional & MVP

                          Can’t there be central crops as well as resized-down video frames?  How can ACR assume it is one vs the other?

                          • 10. Re: ACR Lens correction not applying
                            borisd65712864 Level 1

                            Oh! Sorry for haven't been able to notice the change. Now I get it, it makes sense... It's not croped. But yep, the MLV converter may don't handle the metadata correctly :/.
                            I didn't thought about that, smart guess.

                            • 11. Re: ACR Lens correction not applying
                              d@v!dm Level 1

                              Hi, I'm the author of the tool used to create these DNGs from the MLV format. The MLV format is one developed by the Magic Lantern hack for Canon cameras. This format is basically a dump of raw sensor data with some metadata. A spec is here: RAW Format v2.0 - Google Sheets .

                               

                              If you'd like to explain which DNG tags specifically ACR is looking for to figure out how the image is cropped/down-sampled, and how it interprets them, I would be more than happy to add them to the DNGs produced by my converter. I can find no tag in the DNG spec that relates to "sensor format factor" as you say. I suppose that ACR just assumes this from the UniqueCameraModel tag. So I guess we need to make ACR think that this is a 'proxy' DNG made from the standard full size raw file produced by the camera. This seems to be somehow related to 'OriginalDefaultFinalSize' and 'OriginalDefaultCropSize', though it's not clear what values should go there (because it's not clear what ACR is 'assuming' based on the specified UniqueCameraModel).

                               

                              Canon cameras typically have 3 different video readout modes. The standard mode uses 3x downsampling (skipping every 2 out of 3 lines), so for a camera with a sensor size of the 7D of 5184 x 3456, the raw sensor data in video mode is 1/3 of that: 1728 x 1152 (note that is the same resolution as the OP's DNG in a 16:9 aspect ratio). Making things more complicated is the fact that Magic Lantern allows recording at lower resolutions, but these are a crop, and the crop can be moved around. So in the DNG metadata we would also have to specify somewhere, an x,y offset from center. The next video mode is know as 'crop mode' and it is crop of sensor at a 1:1 pixel ratio, so the FOV here is much smaller. I assume that lens correction would work correctly as is, in this situation as you have shown that ACR seems to be assuming that the DNG is a crop. However, it is also possible to shift this crop around, and so if it's not centered, we would need some way to specify the x,y offset of the crop. Finally, when switching to 50/60 FPS, there's another sensor mode. This mode is like the first, except the down-sampling is not symmetrical, it is typically 3x5 (skipping 4 out of 5 rows to improve readout speed for high FPS). This results in a non-square pixel aspect ratio.

                              • 12. Re: ACR Lens correction not applying
                                MadManChan2000 Adobe Employee

                                Hello,

                                 

                                Camera Raw / Lightroom needs to know the sensor area (or crop factor) to map the pixels of the source image to the physical model of the lens profile. ACR calculates this from the EXIF (not DNG) metadata. You can do this in one of two ways:

                                 

                                1. Use the FocalPlaneXResolution, FocalPlaneYResolution, and FocalPlaneResolutionUnit tags.

                                 

                                2. Use the FocalLength and FocalLengthIn35mm tags.

                                 

                                Of these two options, I recommend #1 because you'll have more precision. (For #2, FocalLength has tag type rational, which is fine, but FocalLengthIn35mm is an integer. That's an issue for short focal lengths.)

                                 

                                Cheers,

                                Eric

                                • 13. Re: ACR Lens correction not applying
                                  d@v!dm Level 1

                                  Thanks for the tip! It seems to be working: https://bitbucket.org/dmilligan/mlvfs/commits/f026ffedf411ce5613daa694808d6fe913ed30e6

                                   

                                  So I suppose there's no way to deal with non-centered crops?

                                  • 14. Re: ACR Lens correction not applying
                                    MadManChan2000 Adobe Employee

                                    Glad to hear it.

                                     

                                    No, unfortunately, I don't know of a standard EXIF tag that would enable us to ascertain how an image has been cropped off-center (and thereby do the correct mapping of pixels to the underlying lens geometry).

                                    • 15. Re: ACR Lens correction not applying
                                      ssprengel Adobe Community Professional & MVP

                                      Is there a way to specify an effective-crop of the image but retain all the pixels so the lens-correction can be done to the entire set of pixels, but then the off-center “virtual” crop applied when the image is read from the DNG? 

                                       

                                      This is how Canon raw files are when you specify a non-2:3 aspect ratio, the entire set of pixels are there, but the camera says that only a certain portion are to be used.

                                      • 16. Re: ACR Lens correction not applying
                                        d@v!dm Level 1

                                        Yes, good idea. We can use 'ActiveArea' to specify a crop and just add some black pixels on the sides. Typically this is used for OB (optical black) reference areas on the sensor. (There might be some other tags too for doing some cropping like this, that might be more appropriate, I will have to look into it).