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04-10-2017, 04:15 AM   #1
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Pentax LX focus screens?

I have a new to me Pentax LX. It has a matte screen with a very faint centre circle. From this mir.com page it's possibly a SE-25, but from the descriptions it might also be a SA-21, SA-23 or SA-26, or even possibly a SD-21 if the description rather than the picture is to be believed. I didn't worry about it when buying, as one of my MXs has a matte screen (presumably a SA-3 from this bdmitrov page), and the MX is lovely to use. But I'm having real difficulty focusing with the LX. I read somewhere that the MX viewfinder is much brighter than the LX viewfinders, and that this has an impact; I didn't expect this to be such a big deal.

Anyway, the way forward seems to be to buy a more standard split image/microprism screen, presumably a SC-21. But the usual flea site only seems to have very expensive focus screens on BIN, and last time I looked didn't have any. Can anyone (a) advise me and (b) suggest where I might be able to find one? (My usual goto site ffordes doesn't have one, not sure where else to look.) Or (c) suggest anything else that might explain my focusing difficulties...

Thanks!

04-10-2017, 04:59 AM   #2
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Until you can find a more suitable LX screen, you can try the MX screen in it as they are completely interchangeable except using an LX screen in an MX requires a very minor metering compensation.
04-10-2017, 06:17 AM   #3
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QuoteOriginally posted by LesDMess Quote
Until you can find a more suitable LX screen, you can try the MX screen in it as they are completely interchangeable except using an LX screen in an MX requires a very minor metering compensation.
That sounds like a good idea but... I thought changing focus screens required a special set of tweezers that came with the new screen. I don't have any such thing... Is it safe? Using the known MX screens seems like a good thing for comparison. I have one matte and one split screen (two different cameras).
04-10-2017, 06:44 AM   #4
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After a little practice I only use my fingernail now.

04-10-2017, 08:14 AM   #5
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Here you have a detailed description of the LX focusing screens:


Pentax LX - Info on Various Focusing Screens


Genuine pincette is not a must, you may remove the screen using alternative tweezers.


Read the instructions carefully and visually inspect your camera so as to recognize every step before taking any action.


Make sure you have a smooth surface where to place the screen once you have removed it from the camera.


It is an easy process, all you need is confidence.
04-10-2017, 09:57 AM - 1 Like   #6
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Eric Hendrickson recommended against adjusting my MX exposure meter
when I installed an LX focusing screen as the difference is negligible.

Chris
04-10-2017, 04:32 PM   #7
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I've always found my LX finder to be slightly brighter and clearer than my MX finders. I have the split-prism with micro-collar in the LX, a split-prism with micro-colllar in one MX and a matte screen with circle (as you describe in your LX) in the other. For whatever reason, I find the LX the easiest, the MX with matte second, and the MX with prism the most difficult to focus. All that is relative though - they're all easy to focus.
04-10-2017, 11:32 PM - 1 Like   #8
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Tweezers with this tip shape seem to work best for me

amazon.com: Professional Flat Square Tip Tweezers: Health & Personal Care?tag=pentaxforums-20&

You should only grab the screen with the tweezers on the little tab that sticks out, just try not to lose your grip on it. Do all the blowing with a blower in there when the screens are in place, you want to avoid blowing stuff underneath the screen when it's out. I think I used a tiny screwdriver to pull the little release back on my MX.

This is kind of fraught work, so try to organize the work area to make it easy on yourself. An articulated lamp like a luxo type of thing is Really Helpful. A magnifying glass to observe if the screen is seated properly before you put the frame back down is helpful too.


Last edited by Ranchu; 04-10-2017 at 11:43 PM.
04-11-2017, 12:15 AM - 1 Like   #9
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QuoteOriginally posted by ChrisR Quote
I have a new to me Pentax LX. It has a matte screen with a very faint centre circle. From this mir.com page it's possibly a SE-25, but from the descriptions it might also be a SA-21, SA-23 or SA-26, or even possibly a SD-21 if the description rather than the picture is to be believed. I didn't worry about it when buying, as one of my MXs has a matte screen (presumably a SA-3 from this bdmitrov page), and the MX is lovely to use. But I'm having real difficulty focusing with the LX. I read somewhere that the MX viewfinder is much brighter than the LX viewfinders, and that this has an impact; I didn't expect this to be such a big deal.

Anyway, the way forward seems to be to buy a more standard split image/microprism screen, presumably a SC-21. But the usual flea site only seems to have very expensive focus screens on BIN, and last time I looked didn't have any. Can anyone (a) advise me and (b) suggest where I might be able to find one? (My usual goto site ffordes doesn't have one, not sure where else to look.) Or (c) suggest anything else that might explain my focusing difficulties...

Thanks!
On the tab of the focusing screen, if you look carefully, you will see the model number of the screen. It's not easy to see. This should tell you which scree you have in your camera.

Regards

Chris
04-11-2017, 05:14 AM   #10
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I've had a look inside both the LX and MX; I can see the tab in the former, but can't see anything on it, and I can't see the tab in the MX. I'm not very confident about changing them over yet. I found UK fleabay suppliers for flat square tweezers, ranging from 1 to 80. The cheaper ones are described in broken English and mention drugs, which is a bit odd. We do of course have normal family tweezers available in the house, though the first one I found has a slanted end.

I've also just made a more careful side by side comparison of the finders, both with 35mm f/2.8 lenses on and no filters. Yes, the LX is marginally brighter than the MX! Not much in it. I think I had a CPL on earlier, d'oh!

The matte circle in the MX is more clearly visible than that in the LX. The image in the MX is definitely more clearly focused at infinity. I'm beginning to wonder if there's something else going on. I did wonder about dioptre settings, but I can't see any adjustment; I think the supplier said it was a FA-1W finder...

I've just checked the manual, slid the finder out a bit and confirmed it is a FA1-W finder. The manual says the dioptre is adjustable with a small screwdriver that comes with the finder, and of course I don't have one. It looks like a flat cross-head screwdriver is needed. Hmmm.
04-11-2017, 05:28 AM - 2 Likes   #11
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The tweezer will only need to reach the tab after you release it as well as reinserting the other.

Any screwdriver small enough will work to adjust the diopter. The FA1W has a wider diopter adjustment range then the FA1 and the only finder I still don't have.
04-11-2017, 06:45 AM   #12
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Bingo! Turned it all the way to +1, then back in increments. At something like -1.5 I'm getting what looks like a nicely sharp image. We'll see in normal use (and I'm not putting another film in it until I get the 3 test films back from Filmdev today), but I'm very hopeful we've cracked it. Thanks everyone!

I do love forums like this.
04-17-2017, 11:35 PM   #13
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QuoteOriginally posted by ChrisR Quote
Bingo! Turned it all the way to +1, then back in increments. At something like -1.5 I'm getting what looks like a nicely sharp image. We'll see in normal use (and I'm not putting another film in it until I get the 3 test films back from Filmdev today), but I'm very hopeful we've cracked it. Thanks everyone!

I do love forums like this.
The LX is a marvelous camera in so many thoughtful little ways
E
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