11 Replies Latest reply on Nov 3, 2009 12:50 AM by silvex

    Color Shifting

    silvex Level 1

      I have sent my 50D over to canon after I noticed a color shift of 500K+ shooting outdoors. This is the 3rd time (I am not ranting here, just want to know wassup) and the second time the worked on the CMOS, since the hues were shifted -- no clue what that means. Of course using a CWB solves ANY WB issues. To make things even MORE interesting. Canon emailed a shot of their red sign with white canon letter outside of the irvine service center. I sampled the white letters on the sign and are pretty neutral. The shot was an jpg, so I requested a RAW of that shot...

      The first screenshot is without any color correction (eye dropped in ACR 5.5), whereas the second one I clicked on the #1 color sampler. Clicking on the #2 sample makes color temp 5450/+9 and clicking on the #1sets a color temp of 5400/+9 -- pretty close.

      Any clues ?

      BTW Canon is saying that 50D has no WB issues.

        • 1. Re: Color Shifting
          MadManChan2000 Adobe Employee

          Which firmware version do you have on your 50D?

           

          Canon had some WB issues with the 50D in earlier firmware versions when WB was manually set (e.g., to Daylight), according to their own web site:

           

          http://web.canon.jp/imaging/eosd/firm-e/eos50d/firmware.html

           

          Eric

          • 2. Re: Color Shifting
            silvex Level 1

            It has firmware 1.0.7

            • 3. Re: Color Shifting
              Tim Lookingbill Level 1

              Let me see if I understand this correctly.

               

              Your camera's AWB setting renders neutral targets like the one pictured in sampler #1 with a bluish hue when lit by indirectly bounced outdoor light from outside coming into what looks like the inside of a garage with the doors open. Correct?

               

              Looks to me like it's giving an accurate looking rendering considering all the color cast contamination coming from whatever the outdoor light is reflecting off of from outside and bouncing around off of the warm colored concrete floor, beige white looking walls and whatever else is in that room/garage. Not sure, I'ld have to see the setup.

               

              Testing your camera's WB needs to be assessed lighting your neutral target using direct sunlight with the sun positioned 45 degrees off horizon, no clouds covering it, away from any color contamination like a green grass lawn and trees and/or colored surfaces like brick walls reflecting direct sunlight off of them. Shoot the target at 45 degree angle between the sun and the lens with the sun at your back (form a triangle beam reflection pattern) out on a paved street and see what you get. Also test using the "Daylight" setting as Eric Chan pointed out in that firmware fix link.

               

              I can't see magenta anywhere in both images.

              • 4. Re: Color Shifting
                silvex Level 1

                Tim, thanks for the feedback. Shooting with daylight WB will set it at 5200 and will be ok  around mid morning/afternoon. Afterwards, it will be just plain wrong. Here is another frame shot on sept 25, 2009. Clear skies with the target on the frame at about 45 degrees. Clicking on the target makes the WB spot on. Clicking on any of the cars also gives a pretty close WB. I understand about color casts and the limitation of AWB. The thing with my 50D is that it is shifting about 500K+ on almost every situation. Thus causing me to supects that it is not working ok.

                • 5. Re: Color Shifting
                  silvex Level 1

                  Here is another indoor shot with a white door being the largest subject. White ceiling and white tile floor...400K color shift.

                  • 6. Re: Color Shifting
                    Tim Lookingbill Level 1

                    So you're saying that your camera's AWB shifts by 500K+ going by the Kelvin numbers read in ACR's As Shot menu whenever the position of the sun in the sky changes within the scene you're shooting? That's what AWB is suppose to do. It does this with my own camera. As long as it keeps the same appearance somewhat from shot to shot with the changing position of the sun, then the camera's AWB is doing its job. The numbers are meaningless. Tell you what, point the camera into the shadows of that house and see if its AWB tries to warm it. If it does then it's doing its job.

                     

                    That image you've posted has your camera metering its selection of what it considers neutral using the shadows of the houses, the paved road, concrete driveway and blue sky. None of those surfaces is spectrally flat and will exhibit some cast and will change according to the changing position of the sun. Your camera has to take an average of the entire neutrals in the scene and use its own algorithm to compare it against what it defines as 5000K which is what most camera's AWB balances for. Maybe your camera balances for 5500K.

                     

                    You should take a shot with your hopefully neutrally flat neutral target at arms reach from the camera as the dominant object in the frame and see if your camera's AWB meters to make it blue looking viewed in ACR. If it does make it blue with direct sunlight shining on it then your camera has a different definition of what balancing to 5000K WB should look like and/or ACR is delivering its own interpretation or your camera is balancing for a different internal Kelvin reference number.

                     

                    The Kelvin numbers in ACR are a guesstimation/interpretation by ACR. There are past threads here that explain why.

                     

                    BTW both images look acceptable as a somewhat accurate representation of a typical daylight scene. There may be some interpretation by the camera in rendering this appearance. I do see what you're trying to find out which is whether this interpretation is intentional or an issue with the internal electronics of the camera.

                     

                    Below is sample images I took with my Pentax K100D showing As Shot ACR WB numbers and their appearance of similar objects in your image with the sun positioned lower in the sky with the fourth image having the sun positioned similarly in your image. Some were taken AWB and others not as indicated. Your Canon's AWB seems to render on the cool side for daylight. Don't know if this is with ACR or with the camera. But with my images I don't need to click on the WhiBal card to make the WB look correct as my eyes saw the scene. I don't know why that is with yours.

                    • 7. Re: Color Shifting
                      silvex Level 1

                      Your scene looks way better in AWB than mine. Your camera is within +/-50K mine is within +/- 500K. So in summary, don't trust  Canon's AWB and just use greycards. In my case I use expodisc most of the time for daytime outdoors. Here is a photo taken Oct 23, 2009 of the grey target filling most of the frame.

                      • 8. Re: Color Shifting
                        Tim Lookingbill Level 1

                        Geez! That is an odd AWB.

                         

                        Have you used other gray targets other than the Expodisc to rule out the target?

                         

                        Which of the two images looks more accurate to what you saw? I'm assuming the Expodisc doesn't look that blue.

                         

                        Do you have other camera's to test their AWB against this target?

                         

                        What does Canon Service Center make of their interpretation of neutrality?

                         

                        I guess this is what makes camera's different between brands. I've been told that they all have slightly different metering for their auto exposure as well.

                        • 9. Re: Color Shifting
                          silvex Level 1

                          Here you go... macbeth color chart...

                          • 11. Re: Color Shifting
                            silvex Level 1

                            I just posted my other target photos I did about a month ago. If you notice that even with the targets the color temp is going to vary for about +/- 50, but nonetheless gives neutral (pretty accurate color) -- when clicking in the mid gray portion of it. Canon service says that the camera is fine, but after I sent more phots. Alead tech will look at it. The camera can't set proper WB (or close) with calibrated targets. I am almost filling the frames with these target shots. I also had a similar issues with a 40D and Canon said the same thing. Except that they did say the WB was off and they did not know why, but did fix it. They did not. So I sold the 40D and got the 50D. So like you said different cameras have different WB, but my take is. They all should be "within" reason given good conditions.

                             

                            pretty frustrating and just wanted to make sure I was not doing something odd or saw something odd in my white balance test.