Tuesday, August 31, 2010

Photography Case Study: "They Come in Threes"

Well, we've come to it. A composition I like, but with terrible technical image quality. Totally smoked, really. Useless at any size larger than a 4x6" print. Perhaps some day serendipity will strike again — while I'm visiting Thermopolis, no less — and I'll have a second chance.

There are no second chances.

So I'm stuck with this, which should be a winner, but a number of mistakes cost me the image.

You can, as they say, tie a bow on crap, but it's still crap. I haven't spent much time in post because there just isn't any saving this image. But it was instructive for me to have a look at it to see where I went wrong. This was one of the first images I took on a dSLR and I didn't really have a clue about the differences between digital capture and, say, a Nikon FE.

Alright, let's get to the tech specs so I can start tearing into this.

Nikon D80, Nikkor 17-35mm, 22mm, f22, 1/800 sec., ISO1600, program auto with matrix meter and no exposure compensation. No flash.

Two numbers above stand out and ruin the image. Each digital camera has it's own "DO NOT EXCEED" ISO sensitivity. To add to the problems, that setting is rarely the highest numbered setting, and that setting may change with conditions. On the D80, with such a challenging high-contrast shot, ISO 400 would probably have been the highest safe setting (if that). Whoops.

The second problem is that tiny f stop. The larger the number, the smaller the diaphragm. Larger diaphragms (smaller f numbers) collect more light but at the cost of depth of field, and at extremely large settings, other problems crop up, too. Smaller diaphragms (larger f number) collect less light for greater depth of field at the cost of longer exposures or higher ISO settings. And extremely small aperture settings cause diffraction. (See Rockwell for a technical discussion on diffraction. For those uninclined, squint. Notice how things begin to go fuzzy?)

Again, there are no hard and fast rules. Different lenses on different camera bodies suffer from diffraction at different times. When shooting critical work, things can get even more complicated because many lenses don't hit their prime until you begin to stop-down a bit. If you know you've got an important shot but don't know enough about your setup to make a decision, remember two things:

· f8 and be there. f8 is almost always a safe choice, stopped-down enough to avoid blurry corners but not so small as to cause diffraction.
· Use the lowest ISO possible. Whichever ISO setting you use will be determined by circumstances, but set it as low as possible.

So what did I lose by shooting at ISO 1600 and f22? Let's have a look:

Shoot me now! It looks like I smeared Vaseline on the front of my lens. Everything has gone blocky and splotchy, with noise everywhere. Look at the poor cow's horn: sharpening artifacts at the edge and nasty color banding throughout. There's zero texture left in her fur, either. This is after some post processing. You can note similar problems in the full image; look especially at the sky, where JPEG banding and splotching are immediately apparent.

This brings us to a point: post processing is important, even vital. But you can't save pixels in Photoshop that were never there to begin with. You only have the data you collected when you pulled the trigger to work with.

This was always going to be a challenging image to capture because of the high dynamic range. That's the distance between the darkest and lightest areas in a photo. Dark brown bison with blistering white snow are hard to capture even when you're not doing stupid things with your aperture and ISO. Unfortunately, fill flash (to lighten the bisons' fur) was impossible here because of the distance they were from me — flash efficiency drops exponentially as distance increases — and because of the truck mirror.

So, even if I had set ISO and f stop correctly, could I have gotten this image? Maybe if I had bracketed, that is, taken two exposures one after the other at different shutter speeds. (You can bracket for about anything: ISO, f stop, white balance, saturation, &c.) Bracketing for HDR (high dynamic range) merge without a tripod and still subject matter is difficult, though, and would have required a lot of time in post. If you move the camera, change zoom or your subject moves, that's it.

As a general rule of thumb, newer cameras can handle difficult situations like this better than older cameras (like the D80, which had other shortcomings as well). Auto D-Lighting is a setting in newer bodies that tries to combat these difficult situations. Would it have worked here? If I had all my other settings correct, that is, shooting at about ISO 400, f8, 1/60 sec., perhaps. I may need to open up one stop for those figures to work, to f5.6, which presents depth-of-field issues. But in such harsh light ISO 800 is probably out of the question, and I don't know if I could have held the camera steady enough at 1/25 sec.

Let's talk composition.

Fortunately, there isn't much to discuss. I can see three things I would have changed and one of them was beyond my control.

· Windex the mirror, idiot.
· Park further back than I did, which would have put the two foreground bison higher in the image with less wasted sky and enlarged the bison in the mirror. I would have also needed to have moved the jack in the back of the truck (the red handle sticking up), which I should have done anyway.
· Ask bison #1 to turn anti-clockwise just a hair so her aspect is about the same as the other two.

As I mentioned, there really isn't anything I could have done about point #3 above. Maybe — maybe — I could have approached from a slightly different angle and split the difference between the two foreground bison. But probably not.

So, had I ironed these issues out, what makes this image compelling, even if it's garbage? There are three elements, the bison, that are more or less the same. They're facing the same direction, mostly at the same aspect. They get smaller. Unfortunately, the top 1/4 of the image is wasted space, and there's too much image clutter in the mirror, with all my junk in the truck and the distracting urban-camouflage paint.

Here's the out-of-camera original:


f 8 and be there.
Keep your ISO down.

It's a hard world out there, to grab what initially looks like a great image, just to see it fall to pieces when you get back to the computer and look at it with a critical eye. I've got a hard drive full of these suckers, and I'm sure we'll return to them at points in the future.

Image grade.

Original: F
Post: D

While I still love the concept, the execution kills this photograph. It's worthless, except as fodder for photography discussions on the blogs. With lots of post processing, I might be able to salvage enough of this image to make it useful as a small photo for the web. Additional post processing includes much more work on the sky (sensor spots, JPEG banding and splotching), Photoshop removal of the jack handle from the bed of the truck and trying to clone in some texture on the bison. If I really wanted to get fancy, I might use some pixel stretching techniques to rotate the mirror anti-clockwise and try to get bison #3 standing level, too. That would have been much, much easier if I had just adjusted the mirror before shooting.

Next time...

Friday we'll have a peek into this photo:

"Fireside Chat"
Things are looking better already!

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