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Camera Geekery: Split Prism Lens Photos

September 15th, 2009 Leave a comment Go to comments

Okay. This is definitely a post aimed square at the Camera Geeks.

If you’re a modern camera geek, you might not know about Split Prism focusing screens. By a simple rule of optics, these screens are an almost ideal focusing aid — and it shames me that they are no longer seen in most modern cameras.

More geekery and photos under the cut.

I am one of the people that fell into ignorance of this marvel of a tool. The film cameras I had worked with in the past were too low-grade to have a split prism lens, and the few mentions of this tool I’d been around slid around my awareness and washed away with the tide.

A New (Old) ToyUntil I acquired an old Nikkormat (1965-era Nikon, Japanese Brand) and was reminded forcibly of its benefits. This convinced me within a minute of my need to acquire another camera toy toy..

Since I didn’t really have any cash I forgot about it until a recent trip to Coney Island, where the lack of a precision focusing tool made me lose a bunch of manually focused shots, driving me slightly batty.

So I did some research, and found Katz Eye Optics. They manufacture after-market focusing screens for a bunch of cameras. 110 dollars later, I’d ordered a lens to be sent to me as quickly as possible. (For those of you interested, the lens ordered does NOT have the opti-brite treatment or any special crop marks.)

40D - Before ShotSo. How was the installation, and how is the screen?

Well, installation was simple since the 40D allows for user-swapped screens. It wasn’t hitch free, I found a tiny speck of dust on the screen itself after several debugging sessions (which involve removing a delicate piece of plastic and huffing on the mirror and the screen) — I found the spec, got lucky in removing it, and moved on. Some knocking around to make it centered, and I was set.

The screen itself is tiny, clearly a well polished and produced device, and very delicate. Katz Eye thoughtfully provides a little plastic tweezer/tool to hold the item — and as you can see here I had a little bit of fun holding it in my right and shooting a picture with my G9 in my left…

Split-Prism Focusing Screen… and how is it? I was convinced in 2 seconds. See, the optics in the screen offset the split image if you are out of focus. There’s absolutely no doubt. If you aren’t on a vertical that makes it clear, the microprism ring around the split prism gives you a second aid.

Don’t understand? Read more about Split Prisms..

Can I recommend this? Well, if you’re purely auto-focus, you might not want to bother with this, using the high-speed focusing screens that come from Canon and Nikon might suffice. But if you use manual lenses or adjust — this is almost essential. Do it!


Wait, why am I trying to explain? Here are three shots – see for yourself.

Through the Viewfinder - Out of Focus
Compeltely out of focus.

Through the Viewfinder - Near Focus
Almost in focus….

Through the Viewfinder - In Focus
SNAP! Focus!

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