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.

Standardized Digital Imaging and Archiving Procedures - TDWG 2011

TDWG 2011, October 18

Below is a copy of the presentation that I delivered at TDWG, covering everything from the use of color checkers, resolution and image size, color spaces, and the selection of digital camera equipment. The link will take you to Google Documents where you can view the presentation online or download it as a .pdf.

Click to download .pdf

Not included in the .pdf is this video of Elizabeth Kiernan, NYBG Herbarium Intern, digitizing specimens:

Lightroom How-to: Batch Color Balance Using Munsell Color Checker

One of the great things about Adobe Lightroom is the ability to batch color balance photos. We include a Munsell (Macbeth) Color Checker in every shot. Here's how I color balance using the eyedropper tool.

 Open a representative image

Our photographers shoot hundreds of pictures in a day. The camera settings and lighting is always the same which makes color balancing batches of images easy. The color checker is always in the same location.

Zoom in to 100% magnification (press the 1:1 over the navigation)

Select the eyedropper tool

Position the eyedropper and click

You'll want to find a neutral tone. For some reason I find the second lightest square to work best for me. Make sure you are only selecting the grey area. And click. That's it! It's color balanced.

Return the color picker

I kind of wish that once you make a selection by clicking that the eyedropper tool would return to it's original place. It doesn't. Make sure to put it back. If you don't navigation can get a little confusing.

To batch process, select all the pictures (CTRL A) and use the SYNC command.

Select-all thumbnails (they'll be highlighted when selected)

Sync brings up the synchronize menu - I sync all the global adjustments

Confirm

Once the adjustments are synchronized, you'll see the little +/- symbol in the corner of the thumbnails. This means the picture was edited.

Double check

It's a good idea to double check some of the images - just to make sure they look okay.

Munsell Color Values in Lightroom

A very important part of image quality control is having a properly calibrated monitor on which to evaluate exposure and color balance. Unfortunately, my monitors and my viewing conditions are less than ideal for image evaluation. I have two Dell flat screen monitors that are fine, but depending on what angle I view them at, the images can look too bright or too dark. I also have an enormous east-facing window behind me which fills my room with great sunlight and is very cheerful, but terrible for looking at my monitors (and the room light conditions change by the minute). So, I check image quality "by the numbers" using the Munsell Color Checker by X-Rite.

Every NYBG Herbarium specimen photographed includes a mini color checker (discontinued - now being replaced with the Color Checker Passport).

You may notice that we have cut the Color Checker in half to fit it along the top edge of the image. This is a trick I picked up from Rob Gerhardt, the imaging specialist at the Whitney Museum of Art. Thanks Rob!

I used to know the RGB values for the Color Checker in terms of 8 bit values, but  now Adobe Lightroom uses percent white as RGB values. So, I did a little math to figure out what values I wanted in % form. They are as follows:

I have seen this discussed on other blogs and we are all coming up with similar results so I am comfortable recommending these values to others.