12 Replies Latest reply on Mar 28, 2010 7:11 AM by Bill_Janes

    Camera profiles, tone curves, exposure and saturation

    Yammer Level 4

      I've been using a homemade camera profile ever since the DNG Profile Editor was released. I much prefer the colours achieved using a profile from a ColorChecker card to the supplied profiles.

       

      My first profile was based on a photo taken using Adobe Standard, but I didn't like the way the lighter tones looked washed out. So I created a custom curve in DNGPE, with a small dip in the top half of the diagonal. That made the lighter tones more colourful .

       

      A few months later, I created a new default point curve, with less of a boost in the lights. This helped with detail in skies .

       

      Recently, I've become aware that I'm adjusting the Brightness slider a lot, and I realised this is because my profile's tone adjustment is lowering the brightness of the mid-tones. So, rather than set the default to 60, I've created another profile, with a tone adjustment higher in the midtones and lower in the lighter tones. It's better by default , but I'm not happy with the lighter tones again .

       

      Now, I seem to be dropping exposure by about 1/3 stop to bring colour back to people's faces. I use a Nikon D300, and some people do say that it is prone to over-expose a little, but I am shooting raw, and I wouldn't have thought this was a problem when there isn't any clipping.

       

      I'm using a default Contrast of 25 and Medium Contrast point curve. When I slide the exposure down, I can see the (ProPhoto) histogram 'un-bunching' at the high end, and this seems to correspond with colour coming back into people's cheeks.

       

      Help. I'm confused. Is camera raw doing something with saturation at the top  of the tone curve?

        • 1. Re: Camera profiles, tone curves, exposure and saturation
          MadManChan2000 Adobe Employee

          Generally, Camera Raw will push highlight colors to clip towards white. Hence they look less saturated the farther up the tonal scale you go. When you bring tones back down to the midtone area, they appear more colorful.

          1 person found this helpful
          • 2. Re: Camera profiles, tone curves, exposure and saturation
            Yammer Level 4

            So, there's nothing I can do?

             

            If so, does it not matter if I reduce the luminosity of the light areas using Exposure, Point Curve, or Camera Profile tone adjustment curve? Is the effect always the same?

             

            Also, another question, if I may: Is there a way to set an exposure offset in a Camera Profile, or is this something only done in CR defaults? It would be handy to be able to control it from the profile for those photos already given develop settings. AFAIK, you can't apply an "offset preset" to photos already with settings (where values are adjusted by an offset amount), you can only set new absolute values.

            • 3. Re: Camera profiles, tone curves, exposure and saturation
              MadManChan2000 Adobe Employee

              Using the various methods of bringing down the highlights will have different effects (tone curve vs exposure), depending on the profile. Some profiles have lightness-dependent color effects, and you will see these more often if using minus Exposure.

               

              I'm not clear on what you're trying to accomplish.

               

              If you're just trying to increase overall saturation of an image, I would first experiment with Vibrance or Saturation, outside of the profile.

               

              If you're looking to increase saturation only in specific hue ranges, try the saturation controls in the HSL panel.

               

              If you're looking to increase saturation only in specific hue & saturation ranges, you'll want to use the control point mechanism of the DNG Profile Editor to make targeted adjustments. This is a case where you'd have to modify the profile itself.

               

              If you're looking to increase saturation only in specific lightness ranges, then I'm afraid we have no tool publicly available at present that can help you do that.

              1 person found this helpful
              • 4. Re: Camera profiles, tone curves, exposure and saturation
                Yammer Level 4

                Sorry, Eric. I want to increase (fix) saturation in lighter subjects without having to darken the whole photo, or kill the Lights with too much Recovery.

                 

                Can you please expand on what you mean by "Some profiles have lightness-dependent color effects, and you will see  these more often if using minus Exposure"? I based my profile on Adobe Standard, which seems to come out a bit on the bright side anyway.

                • 5. Re: Camera profiles, tone curves, exposure and saturation
                  Yammer Level 4

                  In order to combat the lack of saturation in my photos using home-baked profiles, I had been using Vibrance at 10 and Saturation at 10 as my defaults. It occurred to me that Vibrance was designed to avoid disturbing skin colour too much, so I swapped these settings for Vibrance 0 and Saturation 20. This seems to have helped the effect of decolouration in skin lights.

                   

                  I'd still be interested to know if there's any way of adding an exposure offset to camera profiles, if anyone can explain.

                  • 6. Re: Camera profiles, tone curves, exposure and saturation
                    MadManChan2000 Adobe Employee

                    Hi Yammer P, you can't add an exposure offset to a profile directly, but as you know you can have a + or - exposure bias built into a per-camera default, or a preset.

                     

                    On the other hand, you can have a tone curve specific to a profile. For example, in the DNG Profile Editor you can use the second pane to edit a profile's tone curve. So if the highlights by default are a little light for your taste, you can edit the profile's curve to bring them down a bit. Then save the new profile.

                     

                    I understand what you're saying about wanting to add saturation to lighter areas without making the whole image darker. We don't have a control that does that directly yet, though some others like Saturation can help (as you've discovered) if used moderately.

                    • 7. Re: Camera profiles, tone curves, exposure and saturation
                      Yammer Level 4

                      Thanks, Eric.

                       

                      The increased Saturation default is working well for me, at the moment.

                       

                      I may try a new Exposure default, once I've had time to get used to my latest camera profile. At the least, it should reduce the workflow on new images.

                       

                      The problem with an Exposure Preset is that it overrides any existing setting, rather than adjust an existing setting. An offset in a camera profile would automatically apply exposure compensation without the need to change any develop settings. I assumed this was possible because of the significant brightness differences between profiles on the same camera, but I'm now thinking this might be more to do with Gamma than Exposure.

                      • 8. Re: Camera profiles, tone curves, exposure and saturation
                        Bill_Janes Level 2

                        Yammer P wrote:

                         

                        Now, I seem to be dropping exposure by about 1/3 stop to bring colour back to people's faces. I use a Nikon D300, and some people do say that it is prone to over-expose a little, but I am shooting raw, and I wouldn't have thought this was a problem when there isn't any clipping.

                         

                        Before assuming that your D300 is overexposing, check out the BaselineExposure that ACR uses for your D300 (see the DNG Specification on the Adobe Web site). For the D3 it is +0.5 EV and this can cause the image to be appear overexposed when opened in ACR with the default settings. I think the D300 behaves similarly. To correct for this you can use -0.5 EV exposure correction in ACR and set this as the defualt is you so desire. To see if the NEF is really overexposed, I would recommend using Rawnalize (do a google search).

                        • 9. Re: Camera profiles, tone curves, exposure and saturation
                          Yammer Level 4

                          Thanks, Bill.

                           

                          I had a quick look for the specification, but couldn't find a reference to the D300. I did however find it mentioned in several threads, here and elsewhere, lumped in with the D3 as having a +0.5 BE setting.

                           

                          But, I know enough about raw to realise that this doesn't really affect the quality of the processed image, as there's plenty of headroom in the data, even if ACR shifts it to the right a bit. I've been finding anything from -0.3 to -0.5 EV (if at all) usually fixes most of the highlights and 0-10 Recovery manages the rest without spoiling their impact. Like Eric says, the conditions and camera's metering (and human) can be a bigger influence on exposure.

                           

                          I have a copy of Rawnalyse, by the way, but I never really understood it, to be honest. Anyway, I can usually tell if I've blown the highlights by their (lack of) response to attempts to control them, through use of Recovery, software Grads, and Adjustment Brush etc., and it's usually my fault!

                          • 10. Re: Camera profiles, tone curves, exposure and saturation
                            Bill_Janes Level 2

                            Yammer P wrote:

                             

                            I had a quick look for the specification, but couldn't find a reference to the D300. I did however find it mentioned in several threads, here and elsewhere, lumped in with the D3 as having a +0.5 BE setting.

                             

                            But, I know enough about raw to realise that this doesn't really affect the quality of the processed image, as there's plenty of headroom in the data, even if ACR shifts it to the right a bit. I've been finding anything from -0.3 to -0.5 EV (if at all) usually fixes most of the highlights and 0-10 Recovery manages the rest without spoiling their impact. Like Eric says, the conditions and camera's metering (and human) can be a bigger influence on exposure.

                             

                            I have a copy of Rawnalyse, by the way, but I never really understood it, to be honest. Anyway, I can usually tell if I've blown the highlights by their (lack of) response to attempts to control them, through use of Recovery, software Grads, and Adjustment Brush etc., and it's usually my fault!

                            I don't have a D300 NEF, but if you convert to DNG you can look at the metadata with any exif reader and see the BaselineOffset. The ISO sensitivity of the D300 is very similar to the D3 as shown in Bill Claff's data. The both have a nominal base ISO of 200, but the effective ISO rating to produce 18% saturation is about 140. This results in highlight headroom of 0.5 stop and I think this accounts for the Adobe offset.

                             

                            http://home.comcast.net/~nikond70/Investigations/Sensor_Characteristics.htm

                             

                            Having headroom is not a good thing if you want to maximize dynamic range and minimize noise. You could look at Michael Reichman's essay Expose to the Right on the Luminous Lansccape site.

                             

                            http://www.luminous-landscape.com/tutorials/expose-right.shtml

                             

                            A more scientifically correct explanation of the rationale of exposing to the right is given by Emil Martinec who is a professor of physics at the University of Chicago. In judging exposure to the right, you can't necessarily rely on the camera or ACR histogram, so it pays to use Rawnalize or a similar program to look at the raw data without any tone curve having been applied.

                             

                            http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/noise-p3.html#ETTR

                             

                            As an example, here is an image that appears properly exposed in ACR using the default settings and the Adobe Standard profile.

                             

                            013_ACR.PNG

                             

                            Looking at the histogram in Rawnalize, we see that we have a full stop of underexposure:

                             

                            13_rawnalize.png

                            • 11. Re: Camera profiles, tone curves, exposure and saturation
                              Yammer Level 4

                              Thanks, Bill. I'm familiar with the expose to the right mantra, and I usually try to butt the histogram up to the right on the camera's LCD, but not religiously so, as that extra hidden stop comes in handy sometimes.

                               

                              When optimising noise, I have thought to myself that there is no reliable easy way of measuring blown highlights, as both the camera histograms and CR histograms don't show raw clipping. Like I said above, you only really know you've blown it (literally and figuratively) when all the recovery tricks fail and the histogram refuses to flatten out.

                              • 12. Re: Camera profiles, tone curves, exposure and saturation
                                Bill_Janes Level 2

                                Yammer P wrote:

                                 

                                When optimising noise, I have thought to myself that there is no reliable easy way of measuring blown highlights, as both the camera histograms and CR histograms don't show raw clipping. Like I said above, you only really know you've blown it (literally and figuratively) when all the recovery tricks fail and the histogram refuses to flatten out.

                                Of course, the raw channels blow at different levels of exposure because of white balance, and the green channel blows first with daylight and neutral colors. Highlight recovery works when at least one channel has intact data, so the failure of highlight recovery means all channels are blown. If the green channel only is blown, highlight recover works, but the resulting colors may be off. It is best not to blow any channel, and you may not be able to judge this by looking at recovery.

                                 

                                For illustration, here are some MacBeth color checkers bracketed at one stop intervals and exposed near daylight with a Solux lamp:

                                 

                                ACR_composite.png

                                 

                                Looking at the files in Rawnalize, the green channel in 0002 is just short of clipping, but the red and blue channels still have headroom. The succeeding files have progressive clipping.

                                 

                                Rawnalize_02.png

                                 

                                And here, recovery is done with the exposure tool to have the 4th patch from the left on the bottom row at a pixel value of 150 in ProPhotoRGB. As you can see, recovery is reasonably successful except for the last exposure. However, in 0005 it is not possible to bring the first 3 patches in the bottom row below a pixel value of 255 because all channels ase clipped.

                                 

                                ACR_composite2.png