11 Replies Latest reply on Jun 16, 2015 1:10 PM by medphysiks

    Auto WB and magenta tint

    medphysiks

      I think I do OK using my camera's WB presets.  For example, daylight gives me a color temp that I'm usually happy with if it's sunny outside.  The part where I get confused is the tint.  The preset always has zero tint, which works sometimes, but other times, it's too green (like if I'm under tree cover).

       

      This brings me to Lightroom's auto WB.  It has a tendency to add a ton of magenta to the image.  This happens if there is some green in the shot (which has been often lately since I shoot outdoors in the parks).  Anyway, how do I know what tint is correct?

      Here's an example shot.  I first set a custom WB using my Expodisc.  I was expect this to be pretty close to technically correct.  When imported into LR, temp = 5700 and tint = -4.  Seems pretty reasonable (see first shot below).

       

      Next, I used the dropper tool and clicked on a white pole in the background.  Temp = 5750, tint = +4.  OK, not too far off from the Expo.  Pretty reasonable.

      Finally, I click auto WB and the temp = 5350 (which is still reasonable to my eyes) but the tint goes to +30.

       

      All these white balances can't be correct, so what gives?  For any outdoor shot with green in it, LR likes to always set the magenta tint to around +30.

       

      WB as shot using Expodisc

      EMT_0760-2.jpg

       

      WB set using dropper tool on white pole

      EMT_0760-2-2.jpg

       

      LR Auto WB

      EMT_0760-2-3.jpg

       

      Also, here's another more drastic example of some of the inconsistency I'm seeing in LR.

       

       

      Expodisc Shot (temp 6300, tint +12 magenta)

      EMT_0743.jpg

       

      Dropper tool on grey card (temp 6300, tint +27 magenta)

      EMT_0743-2.jpg

       

      LR's Auto WB (temp 4050, tint 0)

      EMT_0743-3.jpg

       

      How do I know which method to trust??

        • 1. Re: Auto WB and magenta tint
          wobertc Adobe Community Professional

          Think about how "Auto" would work-

          LR thinks an overall 'Green' image has too much green tint, so it applies the opposite tint- MAGENTA!

          If LR thinks an image has too much 'Red' it tries to neutralize by applying opposite- BLUE!

          Exactly what you are seeing in your images.

          Don't use "Auto", instead (if your monitor is calibrated) use your vision to balance it as you like it.

          If you have an area in your image that you know is near mid-tone GREY, use the Dropper/Picker in the WB panel to set WB. (Note- White and Black areas do not work with the picker, as they have equal colour channels 0:0:0  255:255:255, so LR thinks they are already 'balanced' )

           

          And- I could see very little difference in your 3 images of the trees! they all look the same to me. The last dollar bill is definitely 'blue'.

          • 2. Re: Auto WB and magenta tint
            medphysiks Level 1

            Thanks, that makes sense.  I guess where I get confused is how to know if an image really does have too much green tint to it.  For example, if I take a picture of my office wall (which is all pale green), AWB will want to add a lot of magenta tint to the image.  In this case, I would say it's incorrect because the wall really is green.  On the other hand, if I have a white wall, but I illuminate it with a green light, then neutralizing that color is the correct thing to do (unless I really want the wall to appear green).

             

            A more practical example is shooting wildlife in the woods. Here's a real-life example.

            18249789438_bc3f35d195_k.jpg

            This was taken with the daylight preset.  I think the color temp could be bumped up a little, but aside from that, it's very green.  AWB will want to add a bunch of magenta to this image.  In cases like this, it seems to make the deer look better, but it also takes away from the natural ambiance of the scene.

             

            When I play around with images in LR, the AWB seems to add too much magenta, maybe taking the tint from zero to +30.  Often times, it seems like the best setting is somewhere in between.  In the end, does this just come down to personal preference/artistic vision?  In the image above, I can either leave it as is (close to how I remember it looking in real life) or change the tint to give the deer brownish fur (like we're used to seeing).

             

            Thanks!

            • 3. Re: Auto WB and magenta tint
              trshaner Adobe Community Professional & MVP

              medphysiks wrote:

              I think I do OK using my camera's WB presets.  For example, daylight gives me a color temp that I'm usually happy with if it's sunny outside.  The part where I get confused is the tint.  The preset always has zero tint, which works sometimes, but other times, it's too green (like if I'm under tree cover).

              If you're shooting raw image files the image data remains unchanged regardless of the in-camera WB setting. LR simply reads the Temp and Tint values when WB is set to 'As Shot' and then applies them to the image. There's very little benefit to change the in-camera WB setting when shooting raw files.

               

              medphysiks wrote:

              I first set a custom WB using my Expodisc.  I was expect this to be pretty close to technically correct.  When imported into LR, temp = 5700 and tint = -4.  Seems pretty reasonable (see first shot below).

              The Expodisc is a simple diffuser that optically integrates the image in an attempt to set the camera's white balance reading to the "average" WB value. This is similar to how LR's Auto WB control functions, but not exactly the same. As

              • 4. Re: Auto WB and magenta tint
                medphysiks Level 1

                Thanks!  The reason I like to set my WB in camera (even shooting raw) is that I find it produces a more pleasing result (to me).  Sometimes, I don't even fiddle with it in LR.  With AWB, each shot has a different WB, sometimes even under the exact same lighting.

                • 5. Re: Auto WB and magenta tint
                  wobertc Adobe Community Professional

                  I believe that Auto-WB in LR (and Auto-WB in camera!) will always be inconsistent, since any change to subject colors (under the same light) will influence the auto-WB result. Even cropping an image then applying Auto-WB can show a variation in WB result.

                  For consistency, if you shoot 'raw', (as above WB does not alter 'raw' image data) it is best to leave camera set to the sensors 'native' WB of 'sunny' and use a grey card (not the expodisc)  in one frame allowing a batch correction with the WB picker tool in LR to correct all images taken in the same light.

                  After that it is all visual and subjective- to your desire!

                  • 6. Re: Auto WB and magenta tint
                    medphysiks Level 1

                    Sounds like a plan, thanks.  I've been experimenting with my grey card, but it seems inconsistent.  Maybe it's not as neutral as it's supposed to be.

                    • 7. Re: Auto WB and magenta tint
                      wobertc Adobe Community Professional

                      There are 'Grey' cards for Exposure, and 'Grey' cards for White Balance. They are not the same! In fact some Exposure Grey cards are definitely OFF-balance when used for WB.

                      So check your card type, do some more reading-

                       

                      A good article can be found at this link-

                      Understanding White Balance

                       

                      and-

                      http://www.slrlounge.com/school/tutorial-understanding-white-balance-color-temperatures-in -8-simple-steps/

                      • 8. Re: Auto WB and magenta tint
                        b2martin_a Level 2

                        When using the Expo Disc you point the camera at the light source to set the white balance, not the image.  This is not the same as averaging the image to set the white balance. 

                        • 9. Re: Auto WB and magenta tint
                          trshaner Adobe Community Professional & MVP

                          medphysiks wrote:

                          I've been experimenting with my grey card, but it seems inconsistent.  Maybe it's not as neutral as it's supposed to be.

                          The18% Gray card was originally created in the old "film"days for setting the camera's exposure and could also be used when printing for determining white balance. The White Balance card is a relatively new and created specifically for digital cameras. It has 90% (or higher) reflectance and provides a higher amplitude signal (i.e. less noise) in-camera. This makes for more accurate readings provided the camera exposure has been properly set to prevent clipping the white card image in-camera (i.e. highlight clipping).

                           

                          You can also change the LR White Balance picker sample area in LR4 and later, which will provide more accurate readings. More here: Lightroom: Add options for larger sample sizes for White Balance Eyedropper Tool

                           

                          I use a ColorChecker Passport to create custom camera profiles for normal lighting (Sunny Daylight, Tungsten, Flash). Develop presets are created for these camera profiles using just 'White Balance' and 'Calibration' for each lighting condition. My LR default Develop settings are set for Sunny Daylight.

                          • 10. Re: Auto WB and magenta tint
                            medphysiks Level 1

                            That probably explains why I like the Expodisc and dislike using AWB.

                            • 11. Re: Auto WB and magenta tint
                              medphysiks Level 1

                              Thanks!  I've heard those Passports are nice.  I might look into that someday.