A few weeks ago I was approached by a local business to do some client color correction of before-after images taken at different times. Last week I began preliminary work around designing a work flow that would maximize productivity while giving a consistent result. The biggest hurtle I have found is white balance. Color temperature will drive you batty if you aren't careful. Ideally one would like to have a 50% gray card in every image (or at least a reference image ... but let's keep on dreaming) Adjusting white balance within Camera Raw, Lightroom, Aperture, etc is easy enough; however, without a common gray tone what is a color corrector to do? Assuming you are working with two images designed to be similar - like my before and after photos the subject should have a comon tone in the image somewhere. For example - if you have a headshot with before after on a makeover find an area of skin that is simiularly lit and similar in tone - skin is a great starting point. In Lightroom I simply use the eye-dropper tool to sample the area I want to set as my grey point. The image looks WAY off - but the cool thing is that both images look the same ... very odd looking but none the less the same. I record the two white balance settings from the adjustment, noting the delta between the two numerical results (Camera Raw and Lightroom have two WB sliders that have a numerical value of +/- 100). I take the one that is closer to 0 and shift one slider until the result is desierable which is then followed by the same numerical adjustment on the secondary image. Let me clerify. If I have two images who's adjusted WB is -15/-3 and -10/-6 and I have determined on the second image that -6 needs to be moved to 0 that means the first image will change from -3 to +3. The top numbers are adjusted in the same way. The result differes per-image and you may have to try a few times to get it down pat; however, wether your color correction ends with WB correction or not - it is something that will make the rest of your adjustments easier.
As soon as my production machine is back up and running I will have a video tutorial on this - because I know it can be confusing. If you have any questions or color correction tips please feel free to post them in the comments.
