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07-15-2011, 03:53 PM   #1
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Focus screen "stock" replacement - Calibration?

Hi there,

I just joined the forum after getting a K-X and reading a ton of awesomely supportive and informative posts here. Well done, you guys!

After some searching regarding replacing focus screens, I couldn't find a specific answer to my initial conundrum;

My focus screen is hazy and made worse by an attempted cleaning so it's going to need to be replaced. The stock "brass" shim is still in there. Assuming that I have it replaced with a stock focus screen (nothing fancy) and ensure that stock shim is there, is there any calibration needed?

Thanks,

Noah

07-15-2011, 04:49 PM   #2
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No need to.
07-15-2011, 07:12 PM   #3
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Thanks for the reply.

I'm hoping that whatever "stock" screen they replace it with is actually from the manufacturer - It's an independent shop that I go to who I trust, but also have their own way of handling things.

Is it also safe to assume I'm splitting hairs if I start worrying about minimum focus at f1.7 on an older lens after the replacement? In other words, is that a little too neurotic?

I'm new to digital photography and things like minor back-focus when wide-open are kind of a given in the film world, but I don't know if they're within reason on a DSLR.
07-15-2011, 11:24 PM   #4
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"Stock" screen should be the original OEM screen from Pentax. It can still be ordered easily from Pentax so there is no reason not to use it. In fact, you can order it from Pentax and replace it yourself.

Since the image is being projected onto the upper side of the screen, replacing it will not affect the precision at all. Just remember not to over-push the metal clip when installing the screen. Otherwise the frame might be pushed out of alignment.

07-15-2011, 11:57 PM   #5
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How would I know if it were out of alignment after the fact? Would my focus just be off?
07-16-2011, 12:49 AM   #6
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QuoteOriginally posted by kidblue Quote
Would my focus just be off?
True.
07-16-2011, 05:49 AM   #7
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Hi, Noah.

I've replaced and recalibrated a couple of stock screens with split screens. Not a big deal, you just need to be careful you don't touch or scratch the screen. I'd wear latex surgical-type gloves while handling the screen, just in case you brush against the surface of the screen.

Assuming you replace the screen with the original Pentax replacement, you shouldn't have to recalibrate. If you go for an aftermarket split screen, you may need to order a set of shims from Pentax (around $6) and recalibrate the focus. Not difficult but can be time-consuming, as you need to remove the screen, re-shim, install the screen, take a test shot, remove the screen, try another shim, reinstall the screen, take another test shot, etc., 'til you get it right.

The good news is checking the focus is a snap with a split screen. Just lay a ruler on the table and take a shot of it at a 45 degree angle with the fastest lens you have, manually focused, and wide open. (I used a 50mm 1.4) The narrow depth of field will let you zero in on the correct calibration for your screen. Focus on the 6-inch mark with the camera fairly close to the ruler. (A foot or thereabouts.) Ideally, it should be in the sharpest focus in the finished test shot, with points to the front & rear gradually fading to out of focus.

If you use manual focus lenses a lot, I highly recommend going for a split screen. It makes accurate and quick focusing MUCH easier.

Good luck!
Bobbo :-)

Last edited by GibbyTheMole; 07-16-2011 at 05:55 AM.
07-16-2011, 05:55 AM   #8
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QuoteOriginally posted by kidblue Quote
My focus screen is hazy and made worse by an attempted cleaning so it's going to need to be replaced. The stock "brass" shim is still in there. Assuming that I have it replaced with a stock focus screen (nothing fancy) and ensure that stock shim is there, is there any calibration needed?
You can grab an OEM replacement(new) here for under $20.00USD: PENTAX K-x KX FOCUSING FOCUS SCREEN FRESNEL PART NEW | eBay

Also there's no need to worry about the shim etc.
Just leave everything as is, and everything will be fine.

PS. I've ordered several stock screens from this seller(K200/20, Kx), shipping was quick and all were as advertised.

Hope this helps.

07-16-2011, 10:04 AM   #9
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Not to go off on a tangent, but I'm surprised to see all this emphasis on split focus screens. I've shot film my whole life, and still do, mostly on Leica rangefinders, which use split focusing (slightly different style) and basic Fresnel/grid, like this stock Pentax, on my Nikon S.L.R. for years. I always found the split screens to be confusing, especially looking through the lens. Maybe not wider than f2.8, but frankly, I've always been surprised at a sharp image shot at a wider aperture than f2.8!

There's no doubt that it's a matter of taste. One thing I definitely noticed was how dark the K-X's viewfinder is with the stock screen compared to my film cameras. Is this common?

Also (last technical question, thanks for bearing with me!) - If I were to have my repairman handle the installation (he'll replace the mirror damper foam as well, which has flaked), I can just ask him to check and calibrate the focus, which would be just as normal a process for any camera repairman on this type of equipment as it would be on my Nikon or Leica film camera, right?
07-16-2011, 02:20 PM   #10
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QuoteOriginally posted by kidblue Quote
Not to go off on a tangent, but I'm surprised to see all this emphasis on split focus screens. I've shot film my whole life, and still do, mostly on Leica rangefinders, which use split focusing (slightly different style) and basic Fresnel/grid, like this stock Pentax, on my Nikon S.L.R. for years. I always found the split screens to be confusing, especially looking through the lens. Maybe not wider than f2.8, but frankly, I've always been surprised at a sharp image shot at a wider aperture than f2.8!
I think split screens are a hit and miss in terms of liking. Though I can say without a doubt that most of the benefits stems from MF lenses and the limitations of using them on DSLR's. Granted the latest Pentax bodies have taken the edge off with much improved Live View features. Though were no sooner ahead when shooting in direct sunlight etc.

QuoteQuote:
There's no doubt that it's a matter of taste. One thing I definitely noticed was how dark the K-X's viewfinder is with the stock screen compared to my film cameras. Is this common?
My wife shot a Kx for a short time and we improved the screen brightness by installing a Katzeye w/optibright. Granted it wasn't dramatic, but it was definitely an improvement over stock(1 stop). Though it was a rather expensive upgrade imo.

QuoteQuote:
Also (last technical question, thanks for bearing with me!) - If I were to have my repairman handle the installation (he'll replace the mirror damper foam as well, which has flaked), I can just ask him to check and calibrate the focus, which would be just as normal a process for any camera repairman on this type of equipment as it would be on my Nikon or Leica film camera, right?
I would assume so.
Just be sure to include exactly what you want repaired when you send it in.
I've had a number of mishaps in terms of miscommunication when it came to CLA and so now, I actually send in diagrams(true story). It was really annoying to have our camera's come back without the work done on them.
07-16-2011, 02:25 PM   #11
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Living in a gigantic city (Los Angeles) has its perks, like being able to find a repair shop made of actual "brick and mortar" so I can drop the camera off, say it needs something simple like a focus screen and foam and look a dude in the eye and say "Shoot a quick test wide-open at minimum focus before you give it back to me."

I also just realized that scenario can actually result in quick calibration or changes because that test isn't waiting for film to come back from a lab. I immediately like this digital thing.
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