Keeping Detail in the Highlights

Coin Photography — Keeping Detail in the Highlights

There are eleven pages about photographing coins:

Black Background — White Background — Photographing the Edges — Using Extension Tubes — Choosing the Best ISO Setting — Choosing the Best Aperture — Choosing the Best Exposure — Editing the Background — Keeping Detail in the Highlights (this page) — Processing Your Image — Some Final Tweaks

ealing with Lost Detail

This first process requires a remote-controlled camera and Photoshop, or an equivalent. The detailed instructions given here are correct for Photoshop CS4, but will certainly work well with other versions of Photoshop.

There are some coins that are so bright and shiny that it is impossible to take a photo without finding that there are highlights in which all detail is lost. It doesn't matter how much you adjust levels or curves, there is no information there to recover.

This situation can be rectified if you have a secure mount that will let you change camera settings without shifting the camera or the coin even a tiny amount; or a camera that can be managed from a distance, so that you do not have to touch it in between shots. My Canon EOS 450D, and its lens, can be managed from the PC using software that came with the camera, so I can adjust the settings with the mouse. It might also be possible to set your camera to take several "bracketed" shots with a single command, which might be worth trying if all else fails.

The process is to first take a normal photo, with the correct exposure to give you a naturalistic, light image of the coin.

Then reduce the length of the exposure until your preview image shows that there is just the start of detail in the highlights, and take a second shot. It is critical not to move the camera or the coin even a small amount on between photos, or the two images will not align properly later on.

Selected highlights on dark photo, and highlights merged onto a light photo.

Bring the darker shot up in Photoshop. Then, set the brush colour to white. You can do this by first setting the colours to default black and white by pressing D, and then bringing white to the top by clicking on the two-headed arrow next to the colour squares. Use your brush to place a white blob over one corner of the frame, to form a key for the correct alignment of the two shots later in the process.

Then, with the brush colour still set to white, use the menus to go into select/color range. Pick the dropper with a plus sign next to it, and use it on the image to select a shade that is just off white, so that only the highlighted areas are selected. The pure white corner will automatically be included in your selection. If you get too much of the coin in your selection, your final image will be low in contrast and will look flat and unappealing, so press control-Z to undo that selection and try again. Then, using select/modify/feather, feather the selection. I use a 10 pixel setting for this.

Light photo before and after merging in highlights from the dark photo.

Then, copy your selection. Control-C will do this fine. Move to the lighter image, and paste the selection. It will be well out of alignment, and this is where the white corner becomes useful.

Select the marquee tool and pick up the pasted image with control-left click. Then lift your finger off the control key, but keep your finger on the left mouse button, and move the selection so that the white blob fits into the corner, where it should dock into place neatly. (If you keep pressing the control key, the corner won't dock.)

Now you should see that the detail is in place where there once were blown-out highlights. If you think the result makes the coin look too flat and dead, which can happen if you have copied and pasted too much, try reducing the opacity of the new detail layer; if that doesn't work, go back and redo your selection, using the dropper on a lighter tone this time.

Now you can carry on with your normal image processing. You might want to merge in the new layer first. You can see the final result for this coin by clicking on one of these images.

This might seem like a lot of fuss and effort for one photo, but if you want perfect results, or you want to make sure all the surface details of your coin are recorded, this process will work very nicely. Like all these processes, it doesn't take long once you have done it a few times.

educing the glare

For some coins, although there are areas of glare, the detail is not completely blown out and can be brought back without the need to take two photos. This technique just needs Photoshop, or an equivalent package.

These photos show the technique applied to Securitas on the reverse of a small coin of Constans, with enlargements of the head at each stage.

Start with a single, flattened image and do this first:

Demonstration of how to keep detail in the highlights.

– Set the colours to default black and white by pressing D.
– Bring white to the top by clicking on the two-headed arrow.
– Select a colour range using select / color range from the menu. This will select the pure white pixels. I use "fuzziness" set to 50.
– Add to that selection by clicking the dropper with the plus sign below it in the selection dialogue box; then go to your image and click on an area that is not quite pure white. You should aim to select only a small part of the image, but definitely more than just pure white. If you get too much, press control-Z to undo that selection and try again.
– Feather your selection using select/feather from the menu. I usually set feather at 5 or 10 pixels. (This is the stage shown by photo 1, and so far this is the same process as shown above.)
– Now press control-J to ceate a new layer with your selection.
– Make that layer invisible by clicking on the eye in the small box next to the thumbnail in the layers display; go on to work with the original image to make it less dull and more realistic, as shown at photo 2, without worrying about the glaring highlights; and when your work is done ...
– Bring that valuable data right back by clicking the eye next to the thumbnail again, before you flatten your image for final saving. The de-glared image is shown at photo 3.
For the best results, if you need to lighten the image, do it on an adjustment layer below this saved information. Any darkening can be done in a layer above it.

With some images, you might want to work on a RAW image instead of a good quality JPEG. The RAW image will contain more detailed information. But for most coin-related purposes, a JPEG will probably do all you need.

There are eleven pages about photographing coins:

Thanks are due to the members of the Forum Classical Numismatics Discussion Board, and especially Doug Smith, for helpful comments on the subject covered by this page.

The content of this page was last updated on 29 January 2011