This Old Camera: June 2012

Thursday, June 28, 2012

Katz Eye focusing screen

I can see clearly now, the shim is gone...

I just received my Katz Eye focusing screen and installed it into my D200. I was a little worried about the warning on the site about heavy order volume, but I got my screen in 3 weeks which is great given they seem to be made to order. The screen came very well packaged - in a bag, in a foam-lined plastic case (with my name, model number, and date it was checked for quality control, even!), in a bubble wrapped pouch, in a box, in a padded envelope! The screen also came with a nifty custom installation tool (basically a fine flathead jewelers' screwdriver with a notch to manipulate the retaining wire). Installation was amazingly painless, although requires some care. I didn't bother trying to exactly center the screen: there is a slight left-to-right slop you can try to correct but it is cosmetic only.

I got the screen because I tend to use a lot of manual focus AI and AI-S lenses. I started with a 50mm f/2 non-AI'ed lens back with my D40 (one of the few digital bodies that can use them) and have since collected a decent lens kit. I never had trouble using manual focus lenses with the D40: I could usually snap to acceptable focus like an AF lens. However, ever since my D40 died and was replaced with my D200 I had trouble with manual focus lenses. The image in the focusing screen would look in focus but the photos would be soft when I looked at them on a computer. I fiddled with the diopter adjustments and different lenses but never sussed it out.

As it turns out, the problem was not fixed by the Katz Eye screen. I'd use the split image rangefinder, align the two halves and look at the resulting photo and still get softness. The split image rangefinder finally allowed me to pinpoint the problem: I saw that I was constantly focusing in front of where the split image rangefinder showed perfect focus. I then used an AF lens to check that when the camera was actually focused perfectly the split image rangefinder was slightly off - I could see a little stairstep between the halves.

Now I was fairly certain the new and old focusing screens were both out of their proper position (something I don't think I could have proven with my old screen), and thankfully the screen position can be adjusted. Nikon uses thin metal shims under the focusing screen. My camera had 2 shims installed, they came out when I took out the factory screen and I dutifully poked them back into position before installing the Katz Eye screen. After a quick Google search, I read that removing a shim causes back focus. Given my camera was front focusing, this seemed to be just the ticket. I opened up the camera again, popped out one of the shims, and reinstalled everything else. Perfect focus!

I do wish I could get the screen with only the split image range finder (no microprisms), and that the D200 would let me turn off the "Focus Area Frame" as it blocks important parts of the image - although using the "wide frame" helps.

Long story short, my Katz Eye screen going to make manual focus fun again, and I am thankful.