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Changed the D70 focusing screen


joseph_wisniewski

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OK, I went and did it.

 

http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=008onY

 

The D70 screen is much smaller than the D100 screen (or any other Nikon screen). It's actually built for the DX sensor.

I measured my screen is 20.33x25.36mm. I only have one D70 screen to measure.

 

The thickness is the same as every other Nikon screen I've measured, 1.61mm +/- 0.01mm.

 

I took a K2 screen for a Nikon FA, which is 36.76x24.80mm, scribed it, made Pec-Pad vice grips, and hacksawed off the short ends, removing about 5mm of material from each end, then finished those ends on the diamond grinder. Then removed 2.22mm of material from the long ends on the diamond grinder, cleaned it up, and gave it a try.

The results were:

 

1) AF and metering are still preserved. Metering accuracy appears unchanged.

 

2) MF is very accurate.

 

3) The D70 screen is offset 3mm vertically. If you cut the new screen so that it's centered in the 20.33x25.36 rectangle, it's trash. Your split image appears offset towards the top of the screen. You have to be 3mm away from the long edge. I'll post a sketch later.

 

4) The split image section of the focusing screen protrudes from the surface of the screen by a considerable distance. If you clamp the screen in Pec-Pad vise grips to work on it, you'll damage the edges of the split image area. I'm going to make clamping jigs for the diamond disc grinder that will not put pressure on the center of the screen. The water cooled DD grinder removes screen material so fast I have no qualms about using it for removing 5.7mm of material from the short edges.

 

Now, to order an FM3a K3 screen or two, and try again.

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Vivek, before you cut...

 

I had estimated the offset at 3mm, by looking at how much taller the screen was than it needed to be to cover the format. This morning, I actually tried to measure the offset, and got a smaller value: 1.33-1.36mm.

 

1.36mm was by measuring how far off center the split image was in a photograph taken with a point and shoot looking through the viewfinder of the D70 with my screwed up screen installed.

 

1.33 was from a better photograph of the original D70 screen, lit from an angle to show the Fresnel pattern. I'll probably use 1.33 for the next screen I cut.

 

And I learned that a K2 screen needs -0.2 stops of exposure compensation, when in centerweight or matrix metering, but is dead on in spot metering mode. (Or you may decide that not compensating, and letting the camera overexpose by 0.2 stops is "exactly" what the D70 needs).

 

I'm anticipating a K3 screen will not need any exposure compensation, at all.

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Thanks, Joe. I haven't put the blade on the screen yet.

 

Instead, I was busy with putting a chip (from 35 to 80mm f/4 - f/5.6 AFD zoom). I have, for now housed it in a wrecked E-series lens. It is devoid of the glass and has the 52mm filter thread that came with it and an added 39mm screw mount. So, I have been using this as a chipped (focusing) extension ring. For whatever reason, It is recognized as the correct zoom lens but only with a maximum aperture of f/4.8 and a focal length of 50mm. It does work and is a joy to exploit the matrix metering for some of the macro lenses (no to mention the pop-up flash as a TTL flash).

 

Vivek.

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  • 2 weeks later...

Joseph -

 

Any interest in selling me a pre-modified D70 screen? I liked your solution, but I don't have access to the proper tools. I have been having all sorts of trouble using the camera with my manual lenses, and even my AF lenses at times. I really miss the old diagonal split screen focusing aid as I have in my FE. I would pay for the screen, have it shipped to you, and pay you for your time modifying it...

 

My guess is that there is a market for this, and you could probably sell a bunch of 'em on eBay. Consider that there are something like 70,000 D70's being delivered every month right now, and Thom Hogan says that production is increasing to 90,000 per month by this fall. Something to think about.

 

Thanks!

 

Jon Gilbert

Jupiter, FL

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I'm currently looking at the D70 and 10D and not terribly excited with either, in large part because I really like manually focusing with a split-prism screen. If I do go the D70 route, sign me up as someone who'd love to buy a split-prism screen from you or whomever.
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  • 5 months later...

I echo the sentiments of everyone else. This is an awesome upgrade! I'm going to take this to my repair guy and see if he can do it, but if you would take clients for this repair I'd definately sign up. The D-70 is a decent tool, but viewfinder is definately lacking.

 

Also: a little better magnification in the eyepiece would be nice too. Anyone know if this is possible without putting a big long thing on the eyepiece. As I look through the viewfinder now, there's a lot of black area around the image. If there was a way to fill it up a bit, it would definately help with focusing.

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  • 2 weeks later...

Joseph, does the split image preserve the central spot metering? I thought the AF sensor and the meter are above the focusing screen, so how is it possible to preserve the spot meter accuracy? At least from what I've heard, those AF bodies (F-801s) which had split image screens available from Nikon did not spot meter with the split image screen.

 

Also, I'm unable to get your e-mail address from photo.net. Something must have changed because the response mails do not get through. Did you get the e-mail that I have requested your e-mail?

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