Thursday, August 27, 2009

Throwing curves

It's always a pleasure to help editors get started with image restoration. Staxringold was looking for baseball-related images and asked for advice regarding copyright and technical issues.

Plate photography is one technological generation advanced from daguerrotype: glass plate photography does use a negative (which daguerrotype doesn't) but the photographic emulsion adheres to glass.

Ever have trouble getting stuff to stick to glass? Same problem here. Those two white spots top and center are places where the emulsion peeled away from the plate. Same with the larger white spots at upper right. At full resolution the image is also marred with hairline scratches. Glass plate negatives are very prone to damage; these are among the reasons film photography supplanted glass plates for most uses during the early twentieth century.

So it's rare that I give the thumbs-up to glass plate work as a first project. Staxringold wanted to do a baseball picture, this is Walter Johnson shaking the hand of Calvin Coolidge, and this image was less badly damaged than most glass plates.

The hardest decision about it was how to crop. The photographer in me wants to take three steps to the right in order to get that foreground barrier out of the way. That isn't possible without a time machine. So either we'll have to accept a major compositional problem or lose data. The issue here is which data is expendable. Staxringold's first edit is at left: he squared and centered the composition by cropping out the woman who wears a white dress.

That wasn't satisfactory so he tried a couple of other ideas including a portrait orientation crop at right. The difficulty with this is that it enhances the distracting presence of a man in full profile who stands behind Walter Johnson. It would be worse to cut off part of Mr. Profile and in order to lose him entirely we would also have to crop out part of Walter Johnson. Plus that darn barricade takes up a third of the image. So although the usual crop for a handshake photo would be vertical, that composition isn't successful here. I suggested a different approach.

We lose the lower half of Walter Johnson with a panorama crop, but this regains the sense of crowd scene including applause from the spectators at far right. The man in profile behind Johnson's left shoulder blends into the scene. This crop still has the handshake and sheds nearly all of the barrier. The hard part is he'll still have to patch and fix all the emulsion damage. Well, no compromise is perfect. Staxringold went away happy and was so enthusiastic that he soon nominated the following version for featured picture.

Staxringold is a great sport about these things. What caught my eye at first about the patching was the firm horizontal line. At far right the heads don't match the shoulders. Started out thinking we could do a little better, then (inevitably) worked on hundreds of overlooked dirt specks and hairline scratches. It would take a close view at 200% resolution on the full version to find those flaws, but they were there. Shoemaker's Holiday and I both helped clean them out.

The final step is to manage the histogram. Couldn't blog about the portrait of a great pitcher without making a pun, so the essential part of today's discussion is the Photoshop curves tool. It's a more sophisticated variant on levels: curves allows an editor finer control over brightness contrasts.

It almost feels like Coolidge and Johnson have come into sharper focus. Midtones dominate both of their clothes; notice how much sharper Johnson's pinstripes appear. The curves tool allows an editor to enhance contrast within particular ranges of brightness. That's why those pinstripes and Coolidge's lapel look more crisp. Now these two principal figures stand out better from the crowd, which is mostly darker toned. Viewers respond intuitively to subtle changes that convey information about what is important in a scene.

Mostly this is a moderate curves adjustment. The white point is moved normally to the brightest point where the original actually had data. The one unusual element about this particular adjustment is that I reduced the contrast slightly in the brightest part of the range. This accomplished two things: it helped prevent that woman in the white dress from becoming a dominant element and it reduced the shine on Johnson's forehead.

And that, in terms of image editing, is how to throw a curve.

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