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08-12-2018, 12:24 PM - 4 Likes   #1
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Pentax K-1 with Canon S-type screen from focusingscreen.com

Many moons ago I ordered the Canon "S type" focusing screen from Focusing Screen. Finally installed it today.

The metal shim in my camera was 0.5mm. The screen came with two plastic shims of 0.2mm, and one shim of 0.3mm. What I found most accurate was one 0.2mm shim. The shims are exactly the correct shape, and clip into the camera properly with the clip to the right of the main latch. Kudos to them for the attention to detail.

I used live view to calibrate, with a Pentax-A 50mm f/1.2 lens focusing on a tilted ruler on my desk. Did many iterations of the test, as each attempt at manual focus comes out a little different. I might wind up a bit more accurate with a 0.25mm shim, but it sure seems close enough.

The process is pretty easy with good hand-eye coordination and mechanical intuition. The two latches (screen and shim) work very nicely, better than in the Pentax LX in my opinion.

The screen really is pleasant to use with the 50/1.2 lens.

As Canon warns, the S screen gets dramatically dark at f/4.0. The Pentax-A 28-70/4 kit zoom is pretty dark. But f/3.5 is OK in my opinion.

The only f/4.0 lenses I have are that kit zoom, and Pentax-FA 20-35/4.0. The latter will be a bit of a bummer, although I've never really warmed up to zoom lenses. My A and FA primes are all f/3.5 or faster, so I think I'll be OK with this screen.

Obviously, the other choice is one of the Nikon screens, which don't have that cliff. But with so many interesting fast manual-focus lenses in my stable, I think I'll be happiest with this screen. I had a pretty poor hit focus "hit rate" with the Samyang 135/2.0 when I used it for a concert with the stock screen, I expect it to be more usable now.

The O-ME53 magnifier is still going to stay on the camera...

08-12-2018, 12:51 PM   #2
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Very interesting, John!

I wasn't even aware that it was possible to change the focus screen for the K-1... I'd always been led to believe it wasn't. That's my learning for today!!

How do you find it impacts the in-camera metering? I'm assuming it does, given that the screen causes darkening much faster than the stock screen. Do you have to gradually increase EV compensation for slower maximum aperture lenses? That would be my guess...
08-12-2018, 04:22 PM   #3
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I'm quite surprised that you have such a dramatic change in shims. I wonder if the K-1 stock screen would have benefited from this change also.
08-12-2018, 04:37 PM   #4
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The thickness of the two screens is different. Didn't try to measure, didn't want to scratch either. My impression from a little web search is that you pretty consistently need thinner shims on a K-1 to use a Canon screen.

I haven't checked the metering at all. I suppose there's some risks, I suppose I'm used to the LX where the final metering is OTF. Hopefully since I shoot in raw, I can adjust any errors in post-processing. (Not much to do with focus in post!)

08-12-2018, 04:57 PM   #5
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QuoteOriginally posted by John Shriver Quote
I haven't checked the metering at all. I suppose there's some risks, I suppose I'm used to the LX where the final metering is OTF. Hopefully since I shoot in raw, I can adjust any errors in post-processing. (Not much to do with focus in post!)
I think it's worth doing some tests for this, John. My concern would be that - due to the darker image - you risk over-exposing your shots, which is generally more difficult to recover in post-processing than under-exposing. If you're only shooting with fast aperture lenses, you should be able to come up with a single EV compensation that more-or-less works. But I suspect that you'll need to compensate further when using slower lenses...

Of course, my concerns could be unfounded... but I'd hate to think you might take lots of great shots and find they're over-exposed to the point where they're unrecoverable

Last edited by BigMackCam; 08-13-2018 at 02:19 AM.
08-12-2018, 06:04 PM   #6
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I'm curious how this turns out, as a K-1 with S-type focusing screen has been what I've wanted for a while.
08-12-2018, 07:52 PM   #7
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QuoteOriginally posted by UncleVanya Quote
I'm quite surprised that you have such a dramatic change in shims. I wonder if the K-1 stock screen would have benefited from this change also.
I too wondered about that.

QuoteOriginally posted by John Shriver Quote
The thickness of the two screens is different. Didn't try to measure, didn't want to scratch either. My impression from a little web search is that you pretty consistently need thinner shims on a K-1 to use a Canon screen.
I would expect the two to be different, only not that much. Looking at your test setup, I would suggest a flat target. Slant target is too difficult to determine intended point of focus.

QuoteOriginally posted by John Shriver Quote
I haven't checked the metering at all. I suppose there's some risks, I suppose I'm used to the LX where the final metering is OTF. Hopefully since I shoot in raw, I can adjust any errors in post-processing. (Not much to do with focus in post!)
Yes, there are risks, though it should be easy enough to test if you have a hand-held meter and a gray card to use as reference. Evaluate all of your lenses having A-contacts. They should all meter to the same EV at maximum aperture. As for adjustment in PP, there are limits. Unlike film, clipped highlights are unrecoverable. Ditto for clipped shadows (no, the sensor is not long-tailed regardless of what one may read on the Web).

The more serious concern would be with standard K and M42 mount lenses using stop-down metering. The "cliff" at f/4 might prove problematic and unpredictable at common shooting apertures. Hand-held manual metering might end up being a good option.

As with the other users on this thread, I am interested in your experience with this screen and hope it works out well.


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08-12-2018, 08:01 PM   #8
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This is where I get confused. Why does the thickness matter, when the lower surface is the plane of focus? The shim holds the screen a set distance from the mirror but thickness I thought didn't matter.

08-13-2018, 02:06 AM   #9
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I have some LX and MX focussing screens, bought in the eighties. Wil they work on a K-1? If so, one more reason to get one.
08-13-2018, 06:02 AM - 1 Like   #10
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The shim thickness matters because the screen is mounted against a condenser under the prism, and the holder below it is sprung. The shim is above the screen. But what matters is where the bottom of the focusing screen is, as that's the matte surface.

My understanding is that LX and MX focusing screens are too small, they fall through the frame. They are also much thinner.
08-13-2018, 07:22 AM   #11
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QuoteOriginally posted by John Shriver Quote
The shim thickness matters because the screen is mounted against a condenser under the prism, and the holder below it is sprung. The shim is above the screen. But what matters is where the bottom of the focusing screen is, as that's the matte surface.

My understanding is that LX and MX focusing screens are too small, they fall through the frame. They are also much thinner.
Ahhh. Is that a different arrangement of shims from the K-3?
08-13-2018, 11:26 AM   #12
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Good to see results of someone swapping this screen on the K-1. I have one of these kits sitting on my desk.

Any thoughts about the warnings of the display overlay being sensitive?
08-13-2018, 01:31 PM - 1 Like   #13
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QuoteOriginally posted by UncleVanya Quote
This is where I get confused. Why does the thickness matter, when the lower surface is the plane of focus? The shim holds the screen a set distance from the mirror but thickness I thought didn't matter.
The shim fits between the screen and the bottom of the pentaprism with plane of focus being at the underside of the focus screen.


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08-13-2018, 01:33 PM   #14
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QuoteOriginally posted by John Shriver Quote
My understanding is that LX and MX focusing screens are too small, they fall through the frame.
That is my understanding as well. Of currently available screens, only the Canon product is big enough to be cut down.


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08-13-2018, 01:36 PM   #15
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QuoteOriginally posted by stevebrot Quote
The shim fits between the screen and the bottom of the pentaprism with plane of focus being at the underside of the focus screen.


Steve
On a K-3 as well? It has been a while since I pulled my screen.
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