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DIY Focus Screen shims
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PostPosted: Thu Feb 22, 2018 10:01 pm    Post subject: DIY Focus Screen shims Reply with quote

Hi all,

I shoot a Nikon D3400. It was my entry-level purchase to learn about photography. I've outgrown it, by far, but even a modest upgrade is not within my budget at this point in time.

Anyways, all of my lenses are manual. That's not totally true, the camera came with the zoom kits lenses, but I don't like them. I inherited a Zuiko 50mm 1.4 and some of the Vivtar TX telefotos, and have expanded my collection a bit.

Becoming super critical of focus with these manual lenses, I realized that my camera's view finder is worthless for focussing. Most people have blamed me for owning an entry level camera, and I agree that I'm pushing the equipment beyond what it was desigend to do.

But "buy a new camera" is not only financially not an option, it also doesn't satisfy my scientific curiosity...WHY is it out of focus? Is there SOMETHING I can do besides throw my camera in the garbase in artistic rage? So I went down that rabbit hole and ordered an e-bay split-prism focus screen. Still no good.

Long story short:
The D3400 comes with a stock shim on the focus screen of 0.1mm thickness (measured by me). I experimented with adding shims, etc, only to discover that the stock setup has a FRONT focus issue (on a different note: the AF indicator has a terrible BACK focus issue). Adding shims was only making it worse.

So I found out that I needed a THINNER shim and given how much difference I saw in my experimentation, I dead-reckoned that 0.05mm would about do the trick.

I bought some 0.05mm shim stock and cut a new shim. It's not the cleanest work I've done, but now the focal plane in the viewfinder matches, to my satisfaction, what hits the sensor. Not perfect, but much much better.

It's amazing what a difference 0.05mm makes.

So now, combined with the eyepiece magnifier from Nikon and the thinner shim, focussing is no longer a guessing game. It was driving me nuts.

Anyway, has anyone else experimented with this sort of thing?

And as a followup, I do have my eye on an upgrage, but I now have NO PATIENCE for cameras with poorly calibrated view-finder optics. I also appreciate mirrorless much more now, because what you see is what you get, which is great for manual lenses.

Anyone have and input as to what DSLRs are the most solid or precise in the view-finder area? I'd like to keep my lense collection.


PostPosted: Thu Feb 22, 2018 10:12 pm    Post subject: Reply with quote

Welcome to the forum, tadd.

As long as the focusing screen is removeable/replaceable, you can easily shim it
with all sorts of materials: paper, Scotch tape, etc...

I've recently dialed-in the screen on my Canon; I posted about it recently.
You may find some of the included information helpful:


PostPosted: Sun Apr 15, 2018 1:07 pm    Post subject: Reply with quote

I have great success shimming with self adhesive foil, the type used for sealing air conditioning ducting. It is about 0.02mm thick, easily cut with scissors and the adhesive makes it easy to put in place and if necessary build up in layers.

PostPosted: Sun Apr 15, 2018 3:19 pm    Post subject: Reply with quote

Welcome tadd

Where are you located? Smile

PostPosted: Wed May 23, 2018 10:52 pm    Post subject: Reply with quote

Hi all, thanks for the replies.

I did end up using all kinds of stuff, including scotch tape around the edges, as a shim for testing before cutting stock. I also cut one from some card stock for testing.

@SkedAddled: thanks for the link. I did indeed get pretty carried away trying to figure which way to shim. Turns out I had it the hard way and needed LESS shim, which means a new one, since you can't add to it.

@visualopsins: I'm in SoCal, Long Beach area.

I confirmed that the pro setup (the 50mm AF-S f1.4 on the D800E) was out of calibration somehow. The lens just won't focus where you point it, and it's off by more than the AF fine-tune can adjust. Pretty frustrating. So it even happens on the expensive stuff.

I since committed to an upgrade to a used D610 and couldn't be much happier. Well, I WOULD be happier if Nikon would accept 95% view-finder coverage in exchange for some magnification, but when the mirror and focus screen are squeeky clean, the view finder is quite crisp. So I'm happy now, and no more shimming for me.