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Annoying dust in MX viewfinder

Posted 30/04/2021 - 14:36 Link
I have recently acquired a Pentax MX 50mm f1.7 which is in lovely condition, however, as expected the door light seals are disintegrating and I'll replace them but most annoyingly there are two or three large'ish dust particles on the top surface of the focussing screen which just seem to drag the eye to them when trying to focus. I understand that the screen can be dropped down by releasing the catch behind the mirror buffer (which I'll replace) but I wondered if anyone new of any issues that might crop up when doing so? Thanks in advance.
danofmk
Posted 30/04/2021 - 15:33 Link
Personally I've never had any issue in giving those screens a gentle clean. Not sure if others will say that's madness, but never does any harm for me

Cotton buds seem to work
womble
Posted 30/04/2021 - 16:00 Link
Try taking the screen out and just giving it a burst of air first. That might work. You can get screens on ebay etc. fairly easily but be aware that although the MX and LX screens are physically the same, they do impact the exposure readings. With print film probably not enough to worry about but you'll notice it with slide film.

K.
Kris Lockyear
It is an illusion that photos are made with the camera… they are made with the eye, heart and head. Henri Cartier-Bresson
Lots of film bodies, a couple of digital ones, too many lenses (mainly older glass) and a Horseman LE 5x4.

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Posted 30/04/2021 - 17:40 Link
Thanks guys, it's mainly the 'just release the catch and it drops down etc and then ...put back.......' that concerns me - is it really that easy, no shims or any other bits to fall out that I don't know about? I've been caught out in the past and I suppose I'm getting paranoid in my dotage.
bjolester
Posted 30/04/2021 - 19:48 Link
I once cleaned a very dirty focussing screen of a Nikon FE2, and had success with soaking the screen for some hours in "Green Clean" Optic Liquid, and afterwards holding the screen under lukewarm water to rinse the screen of Optical Fluid and debris. The screen was left to air dry before re-installing. I managed to remove all of the dirt on the focussing screen, without touching the screen except along the edges. No brushes, cotton buds or wipes were used. "Green Clean" make many types of optical cleaning products, amongst others DSLR sensor cleaning kits. Their Optical Fluid contains no alcohol or any other strong chemical substances.

For me the most difficult part was to remove and re-install the focussing screen. But I guess practice is the way to gain self confidence in this task, similarly to other aspects of life.

Good luck with your endeavour
Bjørn

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bjolester
Posted 30/04/2021 - 19:48 Link
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Bjørn

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pschlute
Posted 30/04/2021 - 20:19 Link
Use air only on your screen.
bjolester
Posted 30/04/2021 - 20:43 Link
pschlute wrote:
Use air only on your screen.

Sometimes air will not be enough to remove debris from a focussing screen. In such instances I would not hesitate to once more use the method described above - not only on a Nikon FE2, but even on a Pentax SLR.
Bjørn

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