13 Replies Latest reply on May 9, 2013 7:52 AM by Vit Novak

    Baseline Exposure

    Yammer Level 4

      Can anyone tell me what, if any, is the Baseline Exposure value of the D800, or how to find it? My D300 had a value of +0.50EV, but I can't work out where that value is found either.

        • 1. Re: Baseline Exposure
          Yammer Level 4

          I worked it out.

           

          I downloaded ExifTool, converted my camera's raw file to DNG, moved it to the same folder, and ran exiftool with the filename as the only argument, redirecting the output to a text file.

           

          It looked something like this:

          exiftool _name123.dng > d800.txt

           

          I now know that Adobe Camera Raw boosts the exposure of the D800 by 0.35EV.

          • 2. Re: Baseline Exposure
            deejjjaaaa Level 2

            alternatively you can get dcptool , decompile your camera's profile(s) and see that in xml output... then change it to zero, compile back to dcp and replace the original profile(s) w/ that zeroed one... why do you need hidden pushes/pulls ?

            • 3. Re: Baseline Exposure
              Vit Novak Level 3

              Nope, value in dcp should stay to avoid pushes/pulls built in acr

              • 4. Re: Baseline Exposure
                Andrew_Hart Level 2

                Yammer P wrote:

                 

                I worked it out.

                 

                I downloaded ExifTool, converted my camera's raw file to DNG, moved it to the same folder, and ran exiftool with the filename as the only argument, redirecting the output to a text file.

                 

                It looked something like this:

                exiftool _name123.dng > d800.txt

                 

                I now know that Adobe Camera Raw boosts the exposure of the D800 by 0.35EV.

                I performed the same procedure on one of my Canon 5D2 .cr2 files and got an Exiftool Basline Exposure reading of 0.4 - which presumably means a boost of + .4 of a stop.

                 

                If you have the patience and the time Yammer P, I would like to understand more clearly what is going on here.

                 

                First, I had not appreciated that in using the DNG Converter to convert .cr2, .nef or whatever to .dng, it invoked the Camera Raw plug-in. Yes, I know that you can perform the same file conversion in ACR itself , but I had never given any thought as to what was actually happening during the conversion process. Is the .cr2/.nef  file actually being developed and then somehow converted back to the new .dng raw file format, or what precisely is going on?

                 

                Secondly, whilst the conversion from .cr2/.nef to .dng involves boosting the Baseline Exposure, there is no second boost when you open the new .dng in ACR. I certainly can't notice any change/increase in the exposure. Some flag must be set during the conversion to .dng which ACR recognizes. Do you know if this is correct, and if so, where the flag is located, presumably in the exif data?

                • 5. Re: Baseline Exposure
                  deejjjaaaa Level 2

                  > Nope, value in dcp should stay to avoid pushes/pulls built in acr

                   

                  yes, I overlooked... it shall be corrected to compensate such adjustments.

                  • 6. Re: Baseline Exposure
                    Yammer Level 4

                    For the last 6 years, I have loosely practised ETTR in photography. It's not a religion, but I often take a second shot with ETTR, if I have time. This week I learned that this is a contentious subject, and I received quite a bit of abuse on photography forums for it. Still, it's a free country, and I can be just as misguided as anyone else, if I want.

                     

                     

                    When I had a D300, I used a combination of a custom in-camera profile and ACR baseline exposure removal to give me a better idea of recorded exposure. The in-camera profile, based on 'Neutral', was low in sharpening/contrast/etc and had a flat curve; the baseline exposure of 0.5EV was subtracted from the ACR default. This way, Raw analysis software, Nikon NX and ACR all started with roughly the same-looking image, and the histograms on my camera were nearer to what ACR, NX and Rawnalyze gave.

                     

                    I'm no expert, but I understand that Adobe introduced the concept of Baseline Exposure as a way of standardising output between different cameras for any given exposure. It's an offset which is introduced with the camera profile to get everyone 'singing from the same hymn sheet', in terms of resulting brightness from any given exposure. For my last two cameras, this involves making the image a little brighter by default.

                     

                    There's no real need for me to change the default Exposure setting, but I have anyway. When Bridge generates HQ previews, the thumbnails no longer turn up a notch, and my first glimpse of the histogram in ACR is closer to what I expected. It keeps me happy.

                     

                    The use of DNG Converter in discovering the Baseline Exposure is what some people call a 'kludge'. It's actually already built into Adobe camera profiles, but, because they are compiled, you can't just load 'em up into Notepad and read it. Converting Raw files into DNG has the side-effect of adding Adobe's Baseline Exposure value into the metadata, which you can then read quite easily with EXIFtool, or similar.

                     

                    You don't actually need ACR to run DNG Converter. It is a stand-alone utility, and comes with its own copy of the profiles. DNG Converter decodes the different proprietary formats and repackages them in a standard open format. It doesn't demosaic/process them in any way, as far as I know.

                     

                    The conversion to DNG doesn't boost the exposure, it just documents the Adobe-specific metadata, which is already present in the profile. So there's no need to worry about brightness changes in conversion. The Raw image, whether it is CR2, NEF or DNG, etc, will always receive the same adjustment in Adobe software, and only receive it once.

                     

                    Anyway, the last time I went through this particular learning curve was 2008. When I was recently refining my workflow with the new camera, I couldn't work out why the previews/histograms were b-/righter than the back of the camera, and then I remembered Baseline Exposure. And here we are.

                    • 7. Re: Baseline Exposure
                      Andrew_Hart Level 2

                      Many thanks.

                       

                      That's quite a bit to digest and a lot more involved than I ever suspected.

                       

                      Very appreciative of your detailed response.

                      • 8. Re: Baseline Exposure
                        Yammer Level 4

                        Andrew_Hart wrote:

                         

                        That's quite a bit to digest and a lot more involved than I ever suspected.

                        Sorry!

                         

                        I'm still a bit shell-shocked from the beating I took over the last few days, so I wanted to explain myself properly, before people got hold of the wrong end of the stick.

                        • 9. Re: Baseline Exposure
                          Vit Novak Level 3

                          Yammer P wrote:

                           

                          Anyway, the last time I went through this particular learning curve was 2008. When I was recently refining my workflow with the new camera, I couldn't work out why the previews/histograms were b-/righter than the back of the camera, and then I remembered Baseline Exposure. And here we are.

                           

                          Things changed a bit since, or more correctly, with latest dng specification

                           

                          There are two tags now - Baseline Exposure and Baseline Exposure Offset. First one is whether built in ACR or written in the dng raw file. Second one is usually in the profile (v4 profiles). Total shift of exposure is sum of these two

                          • 10. Re: Baseline Exposure
                            Yammer Level 4

                            Vit Novak wrote:

                             

                            There are two tags now - Baseline Exposure and Baseline Exposure Offset. First one is whether built in ACR or written in the dng raw file. Second one is usually in the profile (v4 profiles). Total shift of exposure is sum of these two

                            Is there an easy way of finding out the Baseline Exposure Offset, Vit?

                             

                            BTW, can you remind me please, what is a v4 profile, and how can you tell it's v4? Are you talking about the few "Camera" profiles which are actually labelled v4?

                            • 11. Re: Baseline Exposure
                              Vit Novak Level 3

                              You can check it using latest versions of exiftool ord dcptool. Generaly, its value (if present) is equal to negative value of BaselineExposure built into ACR or written into dng file

                               

                              v4 was just a kind of internal mark for camera profiles with latest color conversion workflow. Camera profiles generated last year or two are v4, and are recognisable by the presence of 3 newly introduced tags - Baseline Exposure Offset, Profile Look Table Encoding and Default Black Renderer. However, only several profiles actually had v4 in the name (made prior to publication of dng specification - for D700 and some other cameras from my remembering)

                               

                              Adobe standard profiles are still - so to say - of v1 type (although latest profiles are enhanced with additional lookup tables that were not present in older adobe standard profiles).

                              • 12. Re: Baseline Exposure
                                Yammer Level 4

                                Well, for the D800 profiles, decoded using DCPtool, BaselineExposureOffset appears to exist in both Adobe and Camera Standard profiles, and is zero in Adobe Std, and -0.35 in Camera Std. Presumably, the tone curves compensate for this difference.

                                • 13. Re: Baseline Exposure
                                  Vit Novak Level 3

                                  Quite possible. I didn't check all profiles, but only a few

                                   

                                  Having some nonzero exposure shift (a sum of both tags) like in Adobe standard isn't problematic in PV2012, because of (undocumented) change of procedure for exposure correction. Instead of hard clipping that was causing troubles in previous versions (enhanced by usage of Photo Pro, resulting in issues like blown blue turning into oversaturated violet), a kind of soft clipping is used now, so result is essentially similar like leaving exposure shift at zero (by usage of baseline exposure offset tag that has negative value of Baseline exposure value) and doing it with raised tone curve, which is used in camera v4 profiles (and was emulated in v3 profiles for some cameras as temporary solution). That way, Adobe profiles are simplified because all of them have the same (implicit) tone curve, that can be omitted from the profile, so whole profile package is a bit smaller.