11 Replies Latest reply on Jan 20, 2012 3:16 PM by D Fosse

    Colorchecker passport and the DNG profile editor

    D Fosse Adobe Community Professional & MVP

      I finally got around to getting a Colorchecker passport to use with the DNG profile editor.

       

      I was secretly hoping I could save time by shooting the chart on location and make an instant profile out of that - then the colors would be at least "close ballpark" so I would just have to apply white balance and then move on to more specific adjustments. But of course it wasn't that easy, it still takes a fair bit of color tweaking to get right in most circumstances.

       

      So I'm wondering if my energy would be better spent trying to perfect one good dual illuminant general profile. For this I would use 3000 K tungsten at one end and 5500 K studio flash at the other. Or would it be better to use overcast daylight? In either case it's obviously important to ensure the chart is absolutely evenly lit.

       

      And then I should probably have a separate profile for fluorescent tubes.

       

      I'm curious what other people's experiences with the colorchecker/DNG profile editor are? How are you using it?

        • 1. Re: Colorchecker passport and the DNG profile editor
          Yammer Level 4

          I have the full-size Color Checker, which I bought on its own, without any software. I use it with the DNG PE software from Adobe. The best profile I ever made was on a mostly overcast day last year, as it enabled me to avoid any recipe adjustments I had made to previous attempts, and it just worked well for 95% of my old photos with all sorts of light.

           

          I have never attempted a tungsten chart. I guess I just thought it would be too difficult, as I am not a big user of strobe/studio lighting. I don't do much photography in artificial light, so I guess it's never been a problem. The stuff I have done seems to be okay without the second profile, not to say that it couldn't be better.

          • 2. Re: Colorchecker passport and the DNG profile editor
            D Fosse Adobe Community Professional & MVP

            Yammer P wrote:


            The best profile I ever made was on a mostly overcast day last year, as it enabled me to avoid any recipe adjustments I had made to previous attempts, and it just worked well for 95% of my old photos with all sorts of light.

            Yes, I can see why that might be a good way. Doing HSL adjustments on any of the 18 color patches is good and well, but if you have to make a lot of them that may be an indication that the profile isn't good to begin with.

             

            The studio light (which I use at work) is predictable and not really the most pressing problem. The idea was mainly to use stable light sources, but I suppose even the flash units could have spectral peaks and valleys that could throw the whole thing off.

             

            Outdoors, with shifting light conditions, is much more challenging in terms of getting colors right (as far as "right" goes of course), so that's where I mostly need the profile(s).

             

            Anyway, I'm just feeling my way around this stuff for now. Any and all views are welcome.

            • 3. Re: Colorchecker passport and the DNG profile editor
              deejjjaaaa Level 2

              btw, here is the alternative solution = http://www.qpcard.com/en_b2c/ , they now make chart and software to generate dng profiles

              • 4. Re: Colorchecker passport and the DNG profile editor
                Yammer Level 4

                D Fosse wrote:

                 

                Yes, I can see why that might be a good way. Doing HSL adjustments on any of the 18 color patches is good and well, but if you have to make a lot of them that may be an indication that the profile isn't good to begin with.

                 

                Oh, I've never tinkered with the patches themmselves. I've always thought that was a recipe for disaster (no pun intended). No, in the past, I've only played with the tone curve and the RGB saturation levels, as I used to find that the default rendering looked desaturated. The last time I shot the ColorChecker, I tried the resulting profile without any adjustment, and it was spot-on—addressing issues I was having with skin and sky luminance, and foliage saturation. This and the fact that I'd not adjusted the recipe made me think that I'd got the shooting conditions just right.

                 

                I've found that there could be a lot more information on how to shoot the ColorChecker in natural light. I'd certainly advise against shooting in direct sunlight, even at 45 degrees. Bright cloudy days seem the best for me.

                • 5. Re: Colorchecker passport and the DNG profile editor
                  D Fosse Adobe Community Professional & MVP

                  Ah, I see.

                   

                  Maybe I'm overcomplicating this. I'll try to shoot the chart in overcast daylight and try the profile out for a while, see how well it works over time. But I need to wait for a day when the cloud cover is just right, too rapidly shifting now. I've abandoned the idea of using artificial light, at least for now.

                   

                  My problem with the Adobe standard profile (for the Nikon D300) has been the opposite, I always need to tone down saturation, particularly in blues and deep yellows. I think it boils down to the blue channel out of the camera, but I can't pinpoint it. Hoping a new profile can correct that.

                  • 6. Re: Colorchecker passport and the DNG profile editor
                    Yammer Level 4

                    Three more things to consider:

                    Wear a neutral top. There's a chance your photo could pick up a cast from your colourful top!

                    Don't shoot the card wide open. Use f/8–11 to avoid vignette, and, while you're at it, make sure the card isn't too close to the edges of the frame, where the outside patches could be darkened.

                    Defocus slightly. My card seems to have a slight texture to it, so I thought it might help to soften it up a bit.

                     

                    Also, and I don't know how critical this is, use right-click on a grey patch to set white balance in DNGPE. And, I can't remember where I read that spot metering patch 24 (Grey 4) gave you the best exposure, so it also seems like a good patch to WB.

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                    • 7. Re: Colorchecker passport and the DNG profile editor
                      D Fosse Adobe Community Professional & MVP

                      Very good tips, thank you!

                      • 8. Re: Colorchecker passport and the DNG profile editor
                        ssprengel Adobe Community Professional & MVP

                        The color profile changes with the lighting, so a profile that was computed for daylight won’t be right for tungsten or fluorescent.  Keep in mind that a custom camera profile is the set of corrections on top of an existing Adobe profile that the DNG has assigned to it, perhaps Adobe Standard, and all Adobe profiles are dual-illuminant profiles, so it makes sense you’d want to also create a dual-illuminant profile for general purpose use that has the same two lighting scenarios as Adobe used:  2850K and 6500K.  The 6500K is the tricky one because full sun is warmer, closer to 5000K, and you need the right amount of haze to create 6500K sunlight, unless you are using standard D65 bulbs, indoors, which is likely what Adobe does.

                         

                         

                         

                        I use a dual-illuminant profile for general purpose use, but since the WB-Tint values of both the tungsten and daylight ends are close to zero, lighting that has a tint not close to zero needs a separate profile.  The common example is the greenish light from fluorescents, and I have several single-illuminant profiles for various artificial lighting scenarios with WB-Tint values that are relatively non-zero.  I also have ones for very red sunsets and very blue twilight.  If I had studio lighting I’d make a profile for that.  Sometimes I make a custom profile for a church or other venue that has significant non-neutral walls or ceilings, or where sunlight through the stained-glass windows shining on the walls are giving a significant color-cast including a non-zero tint value to the lighting.  If you know you’ll be doing some shots near a large amount of tall, green vegetation then a custom color profile can correct for the green tinge to the ambient lighting coming down from above mixing in with the sunlight. 

                         

                         

                         

                        Adding to the suggestion about wearing neutral clothing, I’d argue for dark neutral clothing because something lighter clothing will reflect environmental colors (sunlit vegetation or brick walls, etc, outdoors) and not be neutral. 

                         

                         

                         

                        Besides non-neutral clothing, try to avoid areas that have green grass or tree leaves or brick buildings that also color the light and reflect off the colorchecker.   For the sunlit shots, I put my colorchecker face up on the sidewalk or parking lot, to avoid coloration from the grass and far away from trees or buildings especially in the direction I’m pointing the camera, so the only lighting is direct sun and ambient blue-sky, possibly diffused by hazy clouds.  I point the camera down at the colorchecker, at a 45-degree angle and at a compass direction and not directly toward the sun, nor directly away from the sun.  I try to shoot the target that is face up on the ground perhaps at a 90-degree angle from the sun to minimize any residual glare from the colorchecker’s slightly non-matte surface.  Obviously directly away from the sun, the color-checker will have my shadow on it or I will be blocking the light from the sky near the sun.

                         

                         

                         

                        I use the same sort of process for the tungsten end, choosing a room with neutral walls and put the target relatively flat on the floor facing up, perhaps tipped up somewhat toward the light, but not so much as to have any glare from the lighting, either, in other words, not with the lighting directly behind the camera, but somewhat over to the side.

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                        • 9. Re: Colorchecker passport and the DNG profile editor
                          D Fosse Adobe Community Professional & MVP

                          Is it your experience that a "one-shot" profile from the chart, on location, is reliable (provided it is shot carefully, of course)? I mean without any further tweaking - just set white balance and you're basically there?

                           

                          This was my initial hope, but I got some disappointing results. That could be because I didn't shoot the chart with all the precautions.

                           

                          I usually need accurate color more than pleasing color, and I frequently find myself going back to double-check. But often that is not possible, of course.

                          • 10. Re: Colorchecker passport and the DNG profile editor
                            ssprengel Adobe Community Professional & MVP

                            I judge color accuracy with Imatest by applying the profile to an image of the color-checker, exporting a TIF and plotting the color-error.  The color-error points with longer lines between the square and triangle indicating more color error in a particular patch and the average of all the color-error lines being an overall indication. 

                             

                             

                             

                            Here is a somewhat dated gallery of a few plots using various ways to calibrate, including the pre-DNGPE ACR Calibrator script, with the color-error average in parenthesis after the WB temperature, and a lower number is better:

                             

                            http://www.pbase.com/ssprengel/_tech_adobecalibration

                             

                             

                             

                            The scripts work by computing the positions of the HSL calibration sliders based on a profile, and seem to be the closest, but some more advanced folks have suggested that you should run the script, first, for a regular Adobe profile, then compute the DNGPE profile using those HSL values to optimize the accuracy.

                            • 11. Re: Colorchecker passport and the DNG profile editor
                              D Fosse Adobe Community Professional & MVP

                              Hmm...seems to be quite a bit of deviation there.

                               

                              I hadn't really planned on getting too scientific about this, it's more important to me to quickly reach the point where the color is basically right, or as right as one can reasonably expect. A piece of relatively solid ground to work from. I'll play around with this thing and see what I can make out of it.

                               

                              So now I've handed out the "helpful answer" points I have, and they really were helpful. Thank you both. I don't expect there is any "correct" answer.