7 Replies Latest reply on Feb 3, 2010 6:26 AM by igot2n0

    Converting to different color space

    igot2n0

      Dear Color Management Guru's,

       

      I have a question regarding converting digital files between color spaces. Is it correct to convert a file from a large color space like Adobe RGB to a smaller color space such as sRGB, or visa versa?

       

      Thanks in advance,

       

      TC

        • 1. Re: Converting to different color space
          Rick McCleary Level 3

          In two words... it depends.

           

          The basics are as follows:

          Converting from one color space to another will preserve the color appearance of the image within the limits of the size of the gamuts of the two color spaces. Converting from a smaller space (like sRGB) to a larger space (Adobe98) will result in no change in color appearance. OTOH, converting from a larger space (like Adobe98) to a smaller space (like sRGB) might change some of the colors (like saturated blues and cyans) because the smaller space simply is not capable producing those colors.

           

          From a practical standpoint:

          Only convert when you have to.

          For example, when preparing images for the web, you should convert to sRGB. In that case, yes, it's correct (and necessary) to convert.

          Another example - when preparing images for an offset press, you should convert to the proper CMYK color space. In that case, yes, it's correct (and necessary) to convert.

          • 2. Re: Converting to different color space
            igot2n0 Level 1

            Thanks for your speedy reply, Rick.

             

            I recently participated in a webinar and the instructor advised that you should 'never convert from from a large space like Adobe RGB to a smaller space like sRGB. Based on my mother's worldly advise, "never is a long, long time", therefore I look at the advise with a jaundiced eye. Furthermore, the instructor recommends that photographers set their cameras to capture in the sRGB space and then later convert to a larger space if the output device can accommodate it.

             

            My training as a film photographer makes me think that you would want to capture your files with as much data as possible. The webinar instruction is counter-intuitive to this. My thinking is that files that are recorded in Adobe RGB and converted to sRGB do indeed loose date. However, the data that is discarded are colors that do not exist in a sRGB file, may be outside of what is perceptible by the eye, is outside of the ability of the output device to record, or colors that do not naturally exist in the subject to begin with.

             

            More important than being right is to do it right. Is my logic flawed?

             

            TC

            • 3. Re: Converting to different color space
              Rick McCleary Level 3

              I recently participated in a webinar and the instructor advised that you should 'never convert from from a large space like Adobe RGB to a smaller space like sRGB.

              That's not good advice.

              Convert when you need to convert. sRGB for web. CMYK for offset, etc.

              Furthermore, the instructor recommends that photographers set their cameras to capture in the sRGB space and then later convert to a larger space if the output device can accommodate it.

              Also bad advice.

              Capturing in sRGB hamstrings you from the outset. Almost every output device (monitor, inkjet, digital press, offset press) can exceed the color gamut of sRGB in at least one dimension. sRGB is the lowest common denominator of color spaces.

              My training as a film photographer makes me think that you would want to capture your files with as much data as possible.

              You are correct.

              At the very least, capture in Adobe98. But you really should be capturing in RAW. It gives you the most leeway when editing the image.

              My thinking is that files that are recorded in Adobe RGB and converted to sRGB do indeed loose date. However, the data that is discarded are colors that do not exist in a sRGB file, may be outside of what is perceptible by the eye, is outside of the ability of the output device to record, or colors that do not naturally exist in the subject to begin with.

              Well, kinda...

              The changes are definitely NOT "outside of what is perceptible by eye."

              When moving from Adobe98 to sRGB, you lose a significant amount of color in the blue/cyan part of the spectrum. Try it. Take an image that's been captured in RAW and processed into Adobe98 (or, just captured straight into Adobe98) and contains a deep blue sky or the kind of turquoise you see in a swimming pool or tropical ocean. Convert that image to sRGB and notice what happens to those blues and turquioses. Yuck. But, it is what it is. If the image is headed for the web, that's what you're dealing with.

               

              __________________

               

              One question:

              Did you pay money for this webinar? You may want to try and get it back.

              Beware of the advice you hear on the internet.

              • 4. Re: Converting to different color space
                igot2n0 Level 1

                Actually, the webinar was free. I wanted to experience a free webinar with the intent to possibly participate in paid webinars in the future. I have worked really hard to keep my balance on the "bleeding edge of technology", and the dangerous part of this experience is that it caused me to question things that I know.

                 

                Here is another faux pas. The instructor also advised that cameras should be set to capture in sRGB, even when shooting raw, as the camera also assigns color space to raw files. Just goes to show that anyone can set up a webinar at GoToMeetings.com. BTW, I always shoot in Raw. When I began shooting digitally, the cameras ONLY shot in raw, and you had to process out a jpeg or tiff in post production. The habit still sticks today.

                 

                Again, thanks for your thoughtful replies.

                • 5. Re: Converting to different color space
                  Rick McCleary Level 3

                  ...the webinar was free...

                  Well, I guess you get what you pay for. :-)

                  ...the dangerous part of this experience is that it caused me to question things that I know...

                  I've found that, even when learning new stuff, listening to my gut always offers a good balance. It sounds like you've been doing this long enough that you can trust your gut. There's not THAT much in life that's completely counter-intuitive.

                  ...the instructor also advised that cameras should be set to capture in sRGB, even when shooting raw, as the camera also assigns color space to raw files...

                  Ouch! Wrong again!

                  RAW is RAW.

                  A color profile is not assigned to the image until you assign it in the RAW conversion software (Camera Raw, Capture One, or whatever you use.)

                  ...just goes to show that anyone can set up a webinar at GoToMeetings.com...

                  Yeah. It's the Wild West out there.

                  ...BTW, I always shoot in Raw...

                  You're on the right path, grasshopper.

                  Happy shooting.

                  1 person found this helpful
                  • 6. Re: Converting to different color space
                    Miguel Curto Level 1

                    Rick McCleary wrote:

                     


                    ...the instructor also advised that cameras should be set to capture in sRGB, even when shooting raw, as the camera also assigns color space to raw files...

                    Ouch! Wrong again!

                    RAW is RAW.

                    A color profile is not assigned to the image until you assign it in the RAW conversion software (Camera Raw, Capture One, or whatever you use.)


                    It could be so, many cameras shoot a JPG alongside with the RAW.You are probably embedding/converting that JPG to sRGB (not the RAW).It even makes sense as its the most close assessment you can make of that image in a non-calibrated monitor (and probably in most cases a non-aware ICC viewer).

                     

                    Not sure on this one but I imagine its even more so on those little TN panels built-in in cameras.

                    1 person found this helpful
                    • 7. Re: Converting to different color space
                      igot2n0 Level 1

                      There is only one scenario that I can think of where this advice can be considered sound. That is as follows:

                       

                      A photographer who knows little or nothing about color management seeks advice on a simplified workflow which generally results in acceptable results. Not only does the photographer know little about color management but will not likely put forth any effort to learn about color management in the future. In this case, my advice would be the same as the instructor of this webinar:

                       

                        1. Set your camera to capture in the sRGB color space.
                        2. Calibrate your monitor and use a custom monitor profile.
                        3. Set Photoshop's working color space to sRGB.
                        4. Set your output profile to sRGB.

                       

                      Other than the above scenario, I think that the information from this webinar is rubbish.

                       

                      TC