How To Correct Coin Lighting Problems In Photoshop

Short of setting up axial lighting for my camera, I recently found a Photoshop technique to improve the lighting on my coins. Currently I shoot with a single halogen, which makes the coin too dark on one side, as seen below. Even with the lighting set to incandescent, the color is still too blue in this raw photo:

Here's the original photo


Before I adjust the tonal range, here's an easy trick to ensure your coin photo is as round as the original. In Photoshop, drag down guides to align to three sides of the coin. Then select the marquee tool, and drag the tool from where two guides intersect while holding down the shift key. Continue dragging to the opposite corner bounded by one guide and release. You now have a selection which is a perfect square the same height as the coin photo. Now drag a fourth rule to complete a box around the coin. If your coin's shape is distorted, one edge will appear inside or outside this box. Now, using the Transform tool, it's an easy matter to drag this side and fix the shape.

The first step to adjust lighting with any photo is to open the Levels window and see where the tonal range fits within pure white and solid black. As shown below, the highlights are too dark. To adjust, simply slide the white input triangle to where the image data begins. I leave the shadow area alone for now.



Here is the result. It's a slight improvement, but the color is still off and the lighting falls off noticeably in the direction of the arrow.



Here is where I fine-tune the lighting. Select the "create new adjustment layer" icon (bottom arrow) and pick "Curves". The Curves window opens. Now, adjust the curve upward to lighten the dark side to match the other side of the coin. When you do this, one side of the coin will become way too bright. This will be fixed by clicking on the adjustment layer, selecting the gradient tool, and drawing a gradient to even out the lighting on both sides (top arrow). This is a trial and error technique to find the right match to the coin as seen.



Now it is time for color correction. I like to use "Color Balance". Launch the window and adjust the sliders to make the photo resemble the coin under good lighting. Again, there are no rules- and you learn from practice.



Finally, I'll use the rules around my coin to drag the circular marquee and punch out the background, leaving the white underlying layer. This is done by dragging the circular marquee around the box, and then hitting the "add layer mask" icon in the Layers palette- it's very easy. Here is the final result--an improvement?



It's possible to shoot decent coin pics with a cheap point/shoot camera. I shot this photo with a Canon SD790IS (hand-held).