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03-18-2010, 06:57 PM   #16
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QuoteOriginally posted by milesy Quote
Dont you mean Litre???
Americans (USA) use the spelling liter/meter over English spelling of litre,/metre etc.

03-18-2010, 06:59 PM   #17
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QuoteOriginally posted by GoremanX Quote
Because it's nearly impossible to have the distance between the CMOS sensor, the autofocus sensor and the focusing screen be completely identical while keeping the product affordable. This is true of all SLR cameras, which by their very nature introduce some variance in their component location. Those are 3 components which are in 3 completely different plcaes within the camera. We're talking super-thin shims here and tons of precision.

edit: Focusing Screen--How to adjust focusing screen--
I guess you're right. We are talking about fractions of a mm. It's just that when you consider .20mm vs .40mm, it's doubling the smaller shim - which seems like a big variance in that context.
03-18-2010, 09:41 PM   #18
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If we now all can stick to UK english, we will not have any problems English not being my native language makes it already difficult enough and next one finds that about every english speaking country has it's own version
03-18-2010, 10:20 PM   #19
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QuoteOriginally posted by Ira Quote
What's a millimeter? Can't you guys explain this in fractions of inches instead?

METRIC!? HELL NO! WE WON'T GO!

Too much work, and too hard.
imperial is so simple compared to metrics

Pete

03-18-2010, 10:33 PM   #20
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QuoteOriginally posted by joeyc Quote
I find this entire post very interesting, but I am intrigued as to why there would varying shim sizes. Any thoughts here? Seems that would make QC more difficult or at the very least allow for a larger variance.
Following on from GormanX's posts to you, I think the ability to adjust for focus on two planes is fantastic. There is the ability to calibrate the AF focus adjustment through the AF Adjustment feature and also we can calibrate the focus confirmation on the viewfinder by adjusting the shims. As GormanX pointed out, there are three things that have to line up in order to get correct focus as they are all in different positions, the sensor, the AF module (which is behind the mirror) and the focus confirmation on the ground glass screen under the pentaprism.

If either the AF module or the focus screen is out by a fraction, then this shows up as a large difference on the sensor and therefore the image won't be sharp where you want it to be sharp.
03-18-2010, 10:37 PM   #21
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QuoteOriginally posted by frank Quote
Hey Lance, nice info you posted here.

I noticed the same thing w/ my K7, and my friends' K7s have the same problem. We bought those split scressn from focusingscreen.com, but we all feel the focusing is just a tad bit off. It's more obvious when using a fast lens as you addressed above.

I thought about taking out the stock shim and putting in a thinner one, but haven't given it a try yet. I might do so over the weekend. Needs to find a clean place w/ nobody moving around. W/ two little kids around, I can't do this at home
Hi Frank,

How are you? Long time no talk. I hope the family are all well.

You can get different shims from Pentax ranging from .10mm through to .50mm. I know I stated .10mm through to .40mm in my original post, but I have since found out that they make them also up to .50mm. I have ordered a set from .10mm through to .40mm to cover all bases.
03-18-2010, 10:41 PM   #22
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QuoteOriginally posted by Warren s Quote
The Katz Eye screen is made of glass not plastic?

I would imagine its not as prone to scratching duing handling or installation ?
The Katz Eye is made from high grade glass and has a finely etched pattern for excellent focusability. It would be difficult to scratch, but care should always be taken when handling them so as to not get dirt and grease on it. Katz Eye provide a pair of spring loaded plastic tweezers to assist in insertion and removal of the screen.

You can use this same tool for removing the shims. Care must be taken not to touch the surface of the pentaprism and this is why using the plastic tool provided is a good idea.
03-18-2010, 11:27 PM   #23
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QuoteOriginally posted by Lance B Quote
Hi Frank,

How are you? Long time no talk. I hope the family are all well.

You can get different shims from Pentax ranging from .10mm through to .50mm. I know I stated .10mm through to .40mm in my original post, but I have since found out that they make them also up to .50mm. I have ordered a set from .10mm through to .40mm to cover all bases.

Hi Lance,

Nice to see you here too. Haven't been to the other forum for a long time, but I'm sure you are still very active there

The kids are great, all grown up now. Thanks for asking btw.

I didn't know you could order this thing. I got a couple of plastic shims along w/ the split screen from focusingscreen.com. Thought about giving them a try first and see how. Thanks for sharing this.

03-19-2010, 01:42 AM   #24
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QuoteOriginally posted by Transit Quote
imperial is so simple compared to metrics

Pete
What do you call simple? I inch equals approximate 0.02778 yards People that can calculate with that must be bloody intelligent. Not to talk about a grain which is 1/7000 of a pound
03-19-2010, 01:44 AM   #25
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QuoteOriginally posted by sterretje Quote
What do you call simple? I inch equals approximate 0.02778 yards People that can calculate with that must be bloody intelligent. Not to talk about a grain which is 1/7000 of a pound
I'm pretty sure he was being sarcastic. Just look at that big smile...

besides, no-one can make that statement with any seriousness.
03-19-2010, 04:10 PM   #26
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Lance, thanks for posting -- it inspired me to finally do something about the poorly-focusing cheapo eBay focus screen I had in my K20D.

I like old lenses. I like weird lenses. I like fast lenses. And most importantly, I need *cheap* lenses. So I have picked up a variety of old Takumars (including an SMC Tak 55/1.8 and an Auto Tak 85/1.8), and I also managed to finagle one of those Cosina 55/1.2 lenses. I love them all, but they are quite difficult to focus.

I was never able to get very good focus on the stock screen, so I ordered an eBay replacement screen. I think it was the jinfinance model. But when the two sides of the split prism were lined up, my fast lenses were NEVER in focus.

I read a lot on the subject, and figured out that because I had front-focus, the existing focus screen shim was TOO thick. Bah, I thought. I can't just modify the one that's there.

Eventually I got annoyed and put back the stock focus screen, relying on the focus-confirmation beep rather than my eyes.

So anyhow last night, finally, after reading this tread I decided to take action. I took out the stock screen and the shim, put back the split-prism screen without any shim, and took some test shots. Aha, now I was back-focusing a bit.

I put a few layers of masking tape onto wax paper, then cut out some VERY NARROW (less than 1mm) strips of tape with a razor blade, leaving a tail of wax paper off one side. Peeled the wax paper backing off, and mounted two narrow strips to the top side of my split prism screen, one along the top edge, and one along the bottom, right at the very edges.

It took some experimentation, but now I have PERFECT manual focus using the prism. It turned out to need three layers of blue 3M painter's tape.

I'm very pleased!
03-19-2010, 04:39 PM   #27
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Lance -

Can you post from exactly where you purchased the shims and do you have an illustration or photo of where these shims are inside the camera? It seems my Katz Eye screen does not agree with my AF beep and I'd like to fix that, but I want to know exactly what I'm doing and have the right materials first.

Thanks.
03-19-2010, 04:57 PM   #28
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Shims

So where do you get these shims from. Does Katz supply them?
03-19-2010, 05:04 PM   #29
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QuoteOriginally posted by Lance B Quote
...The screen is a ground glass screen with 1/3rd grid lines for composition and Opti-Brite treatment. There are no other focus aids other than the ground glass screen, there is no split prism or microprism collar. ...
Lance - which Katz Eye screen is this?
I looked at the ones for Pentax and didn't see any without focus aids. Is this one custom?
03-19-2010, 05:17 PM   #30
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QuoteOriginally posted by mel Quote
Lance -

Can you post from exactly where you purchased the shims and do you have an illustration or photo of where these shims are inside the camera? It seems my Katz Eye screen does not agree with my AF beep and I'd like to fix that, but I want to know exactly what I'm doing and have the right materials first.

Thanks.
Mel, When I went through this with my K7, Rackel Katz was kind enough to send me the K7 part numbers:

77240.M02200A - 0.15mm
77240.M02200B - 0.20mm
77240.M02200C - 0.25mm
77240.M02200D - 0.30mm
77240.M02200E - 0.35mm
77240.M02200F - 0.40mm
77240.M02200G - 0.45mm
77240.M02200H - 0.50mm
77240.M02200I - 0.55mm

You will need to order them from Pentax USA. They are quite cheap, only a few dollars each.

If you look inside your camera with the screen out, you will see a small release just to the right of the latch for the focusing screen.
That latch is holding the shim in place.

My camera had the .040 shim in it, and I found the .025 shim to be the best one, though I suspect the .030 one might be better, except it came to me bent, and so is unusable.
My manual focus is much better than it was.

The OP is incorrect about the screen orientation. The image is focused on the bottom of the screen, not the top, and the shim is put in place to correct for slight differences in screen thickness that will affect where the focus plane of the screen is located.
The focus plane of the screen is not on the prism side as the OP indicated.
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