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08-14-2007, 08:42 PM   #1
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Split Prism Focus Screen Issues

Hi All,

Just wanted to report on the split prism focus screen that I just recievd today.
I blew $30.00 on this one:

Split Image Focus Screen for Pentax DL K100D - (item 140146268760 end time Aug-15-07 18:36:19 PDT)

Apparently, the K1000 screen @ 1.35mm compared to 1.42mm does make a difference even though the seller makes a claim as if this is better or something.

Anyway, the package arrived and after dinner I paitiently went through the steps to install it in my K100D.

Cons:

1) After taking it out of the SD memory card like case then working it carefully out of the miniature zip lock bag I discovered that it was wrapped in some kind of tape. This tape is what is shown in the picture at the link above. I was thinking it was an optical tape to keep it clean and to pull dust off in case there was any. Needless to say it was a pain in the $%@#%!^ to get off of the screen.

2) I used a bulb blower on it before putting it in only to discover a huge hair galloping across the center on the screen when first looking through the view finder. After several removals....installs....removals...etc. I gave up and ran it under luke warm tap water and blotted it dry with a lens cloth. This at least got the hair off of it but I could still see a few small dust particles which I figured I'd have to live with.

3) Starter taking pictures. Interesting results. Back focusing. Inorder not to jump to any quick conclusions, I set up my tripod and did the 3 in a diagonal row battery test using an SMC-A 50 1.7 @ f5.6 (I did this so I could compare results with my kit lens at 50mm if need be). Sure enough, when manually focusing with the split the center battery was soft and rear battery was coming into focus. Then I used the focus assist to lock in a green hex. Perfect results!





These were taken at f5.6 so you can imaging what it would look like at f2.8 and below!!

Pros:

1) Screen is as bright and clear as the OEM screen.

2) Matte circle gives good indication of when your close to focus.

3) No blacking out at higher f stops which has been reported before. Split circle stays clear on both sides throughout f range.

4) Focus assist compatable. In fact, the focus circle is slightly above the center red focus square which is less distracting than if they had lined up.

Conclusions: This screen is pretty useless for the reason I bought it. I tried removing the copper shim which made it rear focus even worse then turned it around which gave the same or worse results. I may try the shimming it out .07mm if I can come up with a slick method and material for fabricating one and if it will fit under the sheet metal clamp. I'll report it here if it helps. I have not run the full exposure tests at all f's and probably won't unless the shim works.

What a shame. I was really hoping that this would help with focusing my manual primes a low f. Oh well, you roll the dice and move your mice............
My wallet was the only thing hurt.

See Ya,

Chuck

08-14-2007, 09:00 PM   #2
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Have you tried it on anything further away?

I'm planning on getting one myself, but mostly for photographing wildlife at a distance. I'm suddenly wondering if it'll help with that.
08-14-2007, 09:08 PM   #3
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Yes I did...that's where I first began to notice the problem. I've never seen a scenerio where the up close focus test was different from a distance test. Basically, up close just shortens the dof making the results more dramatic. I would'nt recommend this particular screen even for long range zooms. I'm finding My new el-cheapo Tamron 70-300 XR DI has a very short dof at zoom. But then again, it's AF.... no need for the split focus screen.

Chuck
08-14-2007, 09:32 PM   #4
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I've noticed with my Takumars and Chinese screen that there will be a wee bit of what I will call "focus creep", lacking a better term. That is to say, when the prism shows a dead perfect match-up at wide open aperture, stopping the lens down gradually introduces an offset between the upper and lower portions of the prism. Having done your test with an "A" lens, I don't think you could see that.

Not that it makes a difference....just throwing it out there. Your problem seems to come from the thickness of the screen. There seem to be several folks in China peddling these things. I made sure to get mine based off the recommendation of someone I know from the forum (Finn) who had ordered one and had a good experience with it. Bought mine off the same guy and it works just fine.

08-14-2007, 09:41 PM   #5
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I got a similar one (~$40 Can) although the guy charged in friggin pounds. Back then it seemed like everyone did.

It helps reduce alot of eye strain when manual focusing because you can easily tell given the spilt image and the microprism collar focus aid. I agree that when using long telephoto lenses it gets a little trickier because of the thin dof but I must say that the focusing screen improves MF speeds ALOT! (so does practice! :P)

When I'm using the matte screen, I'm very cautious and slow and I'm always waiting for that green light to pop up. With the split image focusing screen, I line up the halves and snap away.
08-15-2007, 04:11 PM   #6
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I also have a bit of a back-focus issue with the screen I bought. It probably really is a hit-and-miss thing.

Mike and Pete, can you guys post the link(s) where you got your screens? I'd like to try ordering one again, but this time from a dealer that you guys recommend.
08-15-2007, 04:47 PM   #7
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Chuck how did you set the diopter?

If the diopter is off this could cause manual front or back focus.
08-16-2007, 07:12 AM   #8
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Split Focus Screen Success!!

Hi All,

Last night after a lengthy meeting at church, I tried to find some suitable materials for shimming out the focus screen. Based on the measurements given on the ebay RJ Camera post, I looked for various materials around .07mm - 0.1mm. I also knew that I needed to match the profile of the copper colored shim which is a very thin horseshoe shape so I needed either a stiff material or something with a little stick to it. I discovered that the LCD screen protectors are right around .1mm thick. I removed the copper shim and carefully traced around it with an X-acto knife while holding it firmly on the screen protector. After cutting around, I peeled it off of the backing and applied it to the shim. I placed the shim back in the camera with the lcd protector material facing out. I installed the focus screen which now rests against the lcd protector shim, and took a couple of test shots. AF indicator and 45deg split now coincide perfectly!! At least as perfectly as I can tell. The results were excellent!

I then proceeded to get a view through one of my screw mounts which gave me the V-8 moment of understanding where the black out in one side comes from at higher f. This I can deal with because the split screen is really a focus aid for low light shooting and I use my A 50 more than any of my Takumars.

I'll have to try out the kit lense and the Tamron 70-300 today to see if I have any problems with metering. I took some shots late in the afternoon with my A 50 1.7 at around f8.0 and the histogram looked normal. I would only test further if there was a very noticeable change in exposure.

Also, I now realize that if I want to change the screen back to the OEM I'll have to remove the protector vinyl from the copper shim. What I need to do is somehow place the protector vinyl over the shim sticky side up then line up the focus screen over top of it and get the protector vinyl to stick to the focus screen. ( That will be an exercise in tedium) That way, the two are interchangable and I won't need to go through the stick and peel process when changing out the screens. This of course, is only if there is a reason to go back to the OEM screen.

Thanks for the comments and a place to post!!

Chuck

08-16-2007, 04:27 PM   #9
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Can you post some pictures of your handiwork? I wanna try your mod also, as it might fix the slight backfocus I'm having with my screen. Thanks!
08-16-2007, 08:10 PM   #10
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vinzer,

I just got everything in and it's working. Please don't make me do it again!!

The photoless steps: I don't think you'd see the clear vinyl in photos anyway.

This is only applicable for the 1.35mm thick focus screen purchased from RJ camera accessory store on ebay run by jinfinance.

There's other ways to skin this cat but here's exactly what I did. Consider though that once you do this the vinyl protector will have to be peeled of the shim before you can put the OEM screen back in. I used the Digital Concepts Universal Screen Protectors. Thickness may vary from one type to another, so if you own a set of calipers you can check the thickness of whatever kind you own. Remember, all you want to accomplish is to add .07 - .10mm thickness to the copper shim behind the focus screen. The profile of this shim addition should be exaclty the same as the shim.

1) Remove the focus screen and copper shim that's in the recess behind it.

2) Get a new piece of LCD screen protector still on the backing and lay it down clear side up.

3) Line up the corner of the shim with one of the square corners of the clear screen protector vinyl. This gives you two straight edges that you won't need to cut. Press down on the shim with a finger tip to hold it in place.

4) Using a very sharp razor blade or x-acto knife, cut around the profile of the shim. You only need to cut through the clear vinyl. Try not to cut all the way through the backing. You'll have to move your finger at least once so be careful to make sure you maintain proper alignment when doing this.

5) After tracing the profile, lift the shim off and check to see if you've cut the vinyl everywhere. If not, carefully finish the corners and any other spots you might have missed.

6) Using the corner of the razor blade or the end of the hobby knife, peel the newly cut vinyl off of the backing. Take your time because this is a very thin cross section and it's easy to tear. Try not to handle it with your fingers.

7) Apply the sticky side to the shim being careful to align all edges. Press it down good with your finger tip once you have it lined up. Trim away any vinyl that may be around the outside edge if possible.

8) Put the shim back into the camera with the vinyl side facing you. The focus screen will touch the vinyl rather than the metal. Verify that the shim is seatted correctly in the recess.

9) Bulb blow the focus screen really good and reinstall. It may take a little extra pressure to latch the retainer.

10) Test focus using a ruler, focus chart, etc.

Hopes this helps.

Chuck
08-16-2007, 08:26 PM   #11
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Thanks for the information Chuck. My first accessory I'd like to get is a split-prism screen. I can't afford the Katz Eye one so I'd like to get one of these cheap Chinese ones for now.
08-16-2007, 09:11 PM   #12
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QuoteOriginally posted by vinzer Quote
I also have a bit of a back-focus issue with the screen I bought. It probably really is a hit-and-miss thing.

Mike and Pete, can you guys post the link(s) where you got your screens? I'd like to try ordering one again, but this time from a dealer that you guys recommend.
I got mine from this ebay seller. Haha you should see some of the bs he writes in the auctions. Like for the pentax screens, he claims its better than ones from the other provinces..lol. Anyhow the screen works well.

eBay Canada Seller: cowy07: Lenses Filters, Film Camera Accessories on eBay.ca at low prices
08-17-2007, 07:38 PM   #13
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QuoteOriginally posted by Chuck Lee Quote
I just got everything in and it's working. Please don't make me do it again!!
Sorry, just thought you might have taken pictures while doing that. Will try out your method later. Thanks!
08-17-2007, 07:41 PM   #14
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vinzer,

That was indeed very irresponsible of me, considering there was a K10D sitting there while I was doing it! I'll try to do better next time.

Chuck
08-17-2007, 11:14 PM   #15
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QuoteOriginally posted by Chuck Lee Quote
vinzer,

That was indeed very irresponsible of me, considering there was a K10D sitting there while I was doing it! I'll try to do better next time.

Chuck
Nah, I don't think that's irresponsible. Besides, your instructions are clear, anyway.

At the very least, I'm thankful you shared your method with us. I was thisclose to buying another screen, without even attempting your method. If all checks out well, you'd have saved me cash.
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