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09-03-2014, 09:00 AM   #1
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Focusingscreen shim

I have a S-Type focusingscreen from focusingscreen.com, and the accompanying shim doesn't fit well, or it is very hard to fit. I've been at it for perhaps 2 hours now.

I've had some issues focusing for some time and today wanted to have a really close look at it, when I realized it's the shim not fitting properly that is the cause. The focusing accuracy would thereby be uneven across the viewfinder.

What can I do about this?

09-03-2014, 09:42 AM   #2
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Ask focusing screen for a new shim? Maybe they supplied the wrong one?

Or try the shim from the original screen. If you have a micrometer you can check the thickness of each to see if they match.

When I did mine on the k-x I had to trim pieces of post it notes to make things correct as far as thickness of the shim, but it did fit into the camera correctly. I don't remember what the shims supplied were made of, maybe plastic? Is it possible to trim any excess away?

I'm assuming it does not fit because the shim is to wide?
09-03-2014, 10:56 AM   #3
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I ordered a K type focusing screen from focusing screen.com & I think that it came with 3 or 4 shims with different thicknesses.
Did you only receive one shim?
If you received more than one shim, do all of them not fit correctly?
09-03-2014, 10:59 AM   #4
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It's been a while I bought the focusingscreen. I've had it working perfectly fine but then other times being really off and it's only today I realized that the bottom half would allow me to nail the focus while the upper half would not.

I've been trying and trying tonight and can't get any better results. I'd be happy now if I could get same results as before I starting messing around.

I even tried using the stock screen and focusing is uber bad:

Upper left corner: front focus
Lower left cover: nailed it, or maybe slight front focus
Lower right corner: front focus
Upper right corner: severe front focus

Seems I might have bent the tray and have tried to straighten it up again. Its a mess now :/

---------- Post added 03-09-14 at 20:02 ----------

gmiyamoto: I received 5. 3 look alike and the forth is orange while the 5th is made of metal. They are all identical in shape and all of the white/transparent ones seem to be with same thickness.

09-03-2014, 11:27 AM   #5
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You are placing the shim under the little shim clip, aren't you ?

https://www.pentaxforums.com/forums/115-pentax-k-5/142225-focus-adjustment-wa...ml#post1485440
09-03-2014, 11:32 AM   #6
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Not sure what that means. I'm placing it on the tray and then the screen on top of it.

---------- Post added 03-09-14 at 21:26 ----------

I give up. I've been at it for so long and tried lots. Right now I can focus accurately on the left side, while the right side is very off.

This thing about some areas being more accurate than others isn't random. It's been left side = accurate and right side = not accurate the entire evening.
09-03-2014, 12:31 PM   #7
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Have a look at the photos in that link. The shim has to go between the pentaprism and the focusing screen. So with the tray down you put the shim in first and latch it up under the little clip so that it is held against the bottom of the pentaprism. Then you put the screen into the tray, line it up and close the tray up to the shim, latching the tray clip. The idea of the shim is to space the top screen face from the pentaprism bottom face by the right amount.

09-03-2014, 12:48 PM   #8
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hmmm, so what you are saying is that the order have to be: pentaprism, shim and then screen?



I tried that order a couple of time after your previous reply, but was not able to lock the tray/holder in place.

Edit: Yes, that is what you are saying. I was seeing the photo in a completely different way. The focusing screen/tray part didn't make sense at all because I didn't "see" it as being lowered

I'll give it a try again - after I've had some food.

09-03-2014, 12:52 PM   #9
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There should be a thin aluminum frame that sits between the shim and pentaprism.
You might want to check to see if it is seated properly.
09-03-2014, 12:55 PM   #10
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That little shim clip is the key
09-03-2014, 03:31 PM   #11
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You guys are right. I had to look really from a steep angle, but it's there and placing shims is now much much easier.

But... front focus is increasing as I add more and more shims! :S And even without any shim, I have front focus going on.

I had a look at my other K-30 and it has a metal shim up there. I tried inserting the metal one and then the stock screen, but focusing is still way off. Now what?!
09-03-2014, 03:35 PM   #12
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QuoteOriginally posted by Zafar Iqbal Quote
I have a S-Type focusingscreen from focusingscreen.com, and the accompanying shim doesn't fit well, or it is very hard to fit. I've been at it for perhaps 2 hours now.
You have my most sincere sympathy. The shims sent with the S-type screen are quite flimsy and very difficult to position without damaging the shim. I tried to use my set to shim a KatzEye and gave up after a couple of hours.

QuoteOriginally posted by Zafar Iqbal Quote
hmmm, so what you are saying is that the order have to be: pentaprism, shim and then screen?
Yes, the shim fits between the pentaprism and the focus screen. As shown in the comment above there is a small retaining clip that the top edge of the shim must fit behind.

QuoteOriginally posted by gmiyamoto Quote
There should be a thin aluminum frame that sits between the shim and pentaprism.
You might want to check to see if it is seated properly.
The "thin aluminum frame" mentioned above is the factory shim. It may or may not be present. If you need to add thickness you put the plastic shim between metal one and the screen. I did not try it, but the thought occurred to me to take the metal shim out and affix the plastic shim to it with a few (very) tiny spots of sugar water. If the wrong size a little soak in water should free the shim.

Please note also that the shim clip is released using the small black tab to the right of the bright silver clip.


Steve

---------- Post added 09-03-14 at 03:37 PM ----------

QuoteOriginally posted by Zafar Iqbal Quote
But... front focus is increasing as I add more and more shims! :S
Yes, front-focus will increase with added thickness. Did you remove the stock shim? There should be some back-focus if no shim is present.

Steve
09-03-2014, 03:40 PM   #13
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Question: If I'm getting front focus, would I need to add or remove (use thinner) shin?
09-03-2014, 03:43 PM   #14
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Be sure too that the screen is properly seated before attempting to snap the frame in place. You want the back edge of the screen to be up against the two metal pieces at the area of the frame hinge and centered side-to-side in the frame itself.

The KatzEye instructions are very good for this:

http://www.katzeyeoptics.com/files/install_11.pdf

The illustrations on the PDF are click-through links to large versions of the same images.


Steve

---------- Post added 09-03-14 at 03:56 PM ----------

QuoteOriginally posted by Zafar Iqbal Quote
Question: If I'm getting front focus, would I need to add or remove (use thinner) shin?
Good question. The terms are not real well-defined. The diagrams and tests on focusingscreen.com are pretty good.

Focusing Screen--How to adjust focusing screen--

If was able to use the first method with a known good focus attained using focus peaking in magnified live view (K-3). AF might suffix for your K-3. The key is to determine whether the distance L1 is greater/less than distance L2 in the diagram when focus to the sensor plane is attained. You can determine this by the direction the lens moves when correcting the screen focus to the true focus point (L2 decreases when focusing towards infinity).

If L1 < L2 you have front focus and need less shim. If L1 > L2 you have back focus and need more shim.

Additional instructions regarding shim removal...

--Pentax K3 K5 K7 K30 focusing screen front focusing revise guide--

Steve

Last edited by stevebrot; 09-03-2014 at 04:01 PM.
09-03-2014, 04:10 PM   #15
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Thanks for the link.

Even if I remove all shims, I'm still getting FF. I guess that's why I originally had the shims "the other way around": between tray and screen.

I found my old thread: https://www.pentaxforums.com/forums/151-pentax-k-30-k-50/196727-s-type-focusingscreen.html

Can't believe it's been that long and tbh focusing have been working just fine till jan/feb thi year, while I was on a month long trip. I wasn't able to nail the focus at all and it really puzzled and surprised me.

Once I got home, I wanted to check it out, but now it worked as it used to - but then again, it wouldnøt and then again it would.

but as I discovered tonight, if I use the lower part of the viewfinder, I'd get accurate focus but not when using upper half.

I still find it strange though that I didn't notice this for about a year, but have instead been noticing variations since jan/feb.

It then led me to believe my lens might be faulty so I just tried with my Samyang 85mm f1.4 - same results :/

I'll try once again to add the shims as I did originally.
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