Thursday, January 12, 2012

Using a Color Checker and Lightroom's Tonal Adjustment Tool to Ensure Proper Exposure

Here are a few simple steps that will help produce perfectly exposed images using the Munsell Color Checker and Adobe Lightroom.

In Lightroom's Develop screen, you will see the image Histogram and, while this image looks pretty good to start, the exposure is just a little low.
Click image to enlarge

Use the color picker and click on one of the neutral squares in the color chart to get a good color balance.

Use the Exposure slider to bring the value of the white square to read about 96.5% - the image will look very bright at this point.

96.5 is the CIE Lab values for white square on the Color Checker.

Using the Tone Curve, set the curve to Linear and limit the highlights to 90%

Click on the Tonal Adjustment Tool and move the cursor over one of the next neutral squares on the color checker. Here it reads about 77% RGB - the actual Lab value for this square is 66.7.

Click on the square with the Tonal Adjustment Tool and drag the cursor down until the value reads 66.7. 

Usually, once the middle values about right, all the others pretty much fall into place. You can spend a lot of time tweeking the curve to try to get the values perfect, but I find that a nice organic curve without too many adjustments makes the most pleasing reproduction.

I am looking forward to Adobe Lightroom 4, which is currently in Beta. It looks like it will have even better tonal controls.

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