Friday, October 3, 2008

first steps - color correction

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.


Anonymous said...

you drop off the grid?

Rick Mead said...

no - just taking a break. I will be back in a week or so. Lots of computer issues and a serious case of the mondays