Spam (madbodger) wrote,
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madbodger

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Manual focusing a DSLR

I was taking some low-light pictures with my DSLR a while back, and was having poor luck getting sharp focus. The wide aperture was exacerbating a problem I've noticed for a while. It also got me to thinking. I never had that problem with my old SLR, was my vision going or what? I really missed the split prism and microprism focusing aid in the SLR. And that was the clue I needed. Modern DSLR bodies are generally designed to be used with autofocus lenses, but most my lenses are older models that are optically just fine, but don't have any autofocus ability. Because they're designed for autofocus, they don't have the manual focusing aids I'm used to. The LCD screen is useless for fine focusing, and it's hard to get it exactly right using just the viewfinder.

Fortunately, there's a market for retrofitting old-style microprism focusing screens into modern DSLR bodies. A little poking around and reading reviews yielded two main contenders that have offerings for my camera. Haoda and focusingscreen.com. Prices between the vendors are basically similar (not exactly cheap at around $72, but this is a specialty item and genuinely useful), and presently I decided to go with focusingscreen.com, as they offered more choices (four) for my target camera, and generally seemed to have more info (such as installation instructions with pictures) available on their site. I opted for the Nikon-style K3 screen, as it was similar to the one in my old F-series body, with a split prism in the center and a microprism ring around it. I'm accustomed to this arrangement, and I know it works well for me. There's a nice writeup of screens there and focusingscreen.com offers a comparison of their offerings there (odd url, "privacy.php", and I like the page heading reading "Let's see what we have here"). The English on the site is a little dodgy, but easily understandable. The installation procedure looked like something well within my skills, so I wouldn't need to take the camera to a shop.

The site mentioned that the machine that cuts the focusing screens would be down for maintenance, but I went ahead and ordered anyway, figuring I'd get one that was cut with a freshly serviced machine. Shipping from Taiwan was fast, it was sent on the 22nd and arrived two days later. I picked it up today (I had to go to the post office to sign for it). It was very well packaged in a sealed bag in sealed bubble wrap in a box in a plastic shipping envelope, and included a very nice container for the screen itself, a plastic tool to manipulate the screen without scratching it, a nice pair of fine-point tweezers, two finger cots, and a pair of transparent plastic shims for fine-tuning the focus plane. The focusing screen box was shrink-wrapped with a little sticker reading "Opened packing can't returns." There was a sheet of paper reading "Dear all, Thanks for your using very much. Please read the instruction before installation to make it more smoothly." It also listed their URL to access the detailed installation instructions.

After dinner tonight, I decided to give it a whirl. I fed the (Chinese) installation instructions page to Google translate (it's clear enough from the pictures alone, but I wanted any useful details from the text). It starts off "Please send your little brother", which I assume means you don't want kids running around whilst performing surgery on your nice camera. It also suggests turning off fans and windows and so forth to keep down dust. The installation was actually pretty easy. Remove the lens, invert the camera, pop free the retaining bail, remove old focusing screen, put in a shim and the new screen (right side up, with notched corner on the left, toward me), snap the retaining bail back into place. Easy.

Then I installed a lens, cranked the aperture all the way open, and did several test shots. They were pretty close, but the camera was focusing slightly too close. This meant I needed to move the focusing screen in or out slightly. I mused on how the optics worked briefly, and decided that I needed to move the focusing screen out, away from the lens. So I opened it up again, removed the shim, and put it all back together. Another trial showed that it was focusing correctly now (in effect, the focusing screen was the same distance from the lens as the film plane). Now it's easy for me to use my nice old lenses with the new camera and get sharply-focused shots. Originally posted at Dreamwidth.org comment count unavailable comments

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