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04-19-2021, 04:32 PM   #1
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Pentax ME-F Dust in Pentaprism

Hello my fellow Pentaxians, Pentaxites and Pentaddix,

I inherited my grandfather's silver Pentax ME-F a while back and have always loved it. It is the original standard silver metal finish and wanted another one in all black to carry around so I could have the silver for color negatives and black for B&W negatives (for obvious reasons).

Now I love the all black ME F but after doing a basic clean, ensuring there is absolutely no dust or particulates in the mirror assembly, I still notice large fragments in the pentaprism/laying on the focus screen.

My question, is there a simple, non-risky way to check the innards of the focus screen? Worried about mucking up other aspects of the camera, and am a bit intimidated of doing surgery on my new friend.

Since it doesnt affect image quality should I just let it be?

Thank you my beautiful Pentabulons.

04-19-2021, 04:36 PM   #2
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Here is a photo of the viewfinder screen showing the dust.

I've check the lens on other bodies, it is clean. And visually inspected the mirror. Also clean
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SM-G955U  Photo 
04-19-2021, 04:52 PM   #3
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I would probably leave it be if it doesn't affect the photos. But you'll get some more responses from people that have actually done it. I know the focus screen is pretty delicate.
04-19-2021, 04:56 PM   #4
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I would expect the bits to be on the bottom of the screen, and accessible with a blower or camel hair brush.
Probably deteriorated pieces of the mirror cushion foam.

04-19-2021, 09:46 PM - 1 Like   #5
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A couple look like bugs. I have seen them before. I call them shutter bugs and cleaning them will be a chore. You have to remove the top cover and the circuit board that goes over the prism. The circuit board goes over the top and down the rewind side of the prism. The board plugs into a socket near the bottom of the camera. It is not too hard to unplug but getting it plugged back in can be difficult. If the circuit board is off you need to loosen the set screws on either side of the prism to remove the prism and clean the screen. You could try to loosen the set screws and carefully lift the prism a bit without damaging the flex circuit to try to blow stuff out, but those bugs tend to stick where they are. They are annoying but do not affect pictures.
04-20-2021, 01:44 AM   #6
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Many times debris gets between the focus screen and pentaprism. There are often times gaps that allow stuff to get in there from the mirror box. Using a blower can make it worse.

If the focus screen is removable from the mirror box you need to remove the screen and clean off the debris. If the screen is not removable you have to remove the camera top, circuit boards or wires/connectors from the prism and finally the prism to clean this area.

If you don't have the tools or the patience than a professional CLA is in order.
04-20-2021, 08:50 AM   #7
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QuoteOriginally posted by DonV Quote
I would expect the bits to be on the bottom of the screen, and accessible with a blower or camel hair brush.
Probably deteriorated pieces of the mirror cushion foam.
Oh yes, I have blown enough air in there a hurricane would be jealous. It magically seems to be on the inside.

---------- Post added 04-20-21 at 08:51 AM ----------

QuoteOriginally posted by Not a Number Quote
Many times debris gets between the focus screen and pentaprism. There are often times gaps that allow stuff to get in there from the mirror box. Using a blower can make it worse.

If the focus screen is removable from the mirror box you need to remove the screen and clean off the debris. If the screen is not removable you have to remove the camera top, circuit boards or wires/connectors from the prism and finally the prism to clean this area.

If you don't have the tools or the patience than a professional CLA is in order.
Interesting, I will have to see if there is any access from the mirror/shutter cavern. It does speak to a larger issue with the camera if dust is somehow penetrating the pentaprism from some unseen gap or deteriorated seal.

---------- Post added 04-20-21 at 08:53 AM ----------

QuoteOriginally posted by pentaxus Quote
A couple look like bugs. I have seen them before. I call them shutter bugs and cleaning them will be a chore. You have to remove the top cover and the circuit board that goes over the prism. The circuit board goes over the top and down the rewind side of the prism. The board plugs into a socket near the bottom of the camera. It is not too hard to unplug but getting it plugged back in can be difficult. If the circuit board is off you need to loosen the set screws on either side of the prism to remove the prism and clean the screen. You could try to loosen the set screws and carefully lift the prism a bit without damaging the flex circuit to try to blow stuff out, but those bugs tend to stick where they are. They are annoying but do not affect pictures.
Only slightly intimidating. I have recently removed the top cover of a Canon AE-1 to remove debris caught in the advance lever, but did no disassembly of the prism and/or flex circuit. I would like to avoid that. But it does seem concerning if dust or bugs are somehow entering the case from a broken seal or some other means of entry. Sadly the best case scenario would be that someone opened it in the past and failed to remove the dust prior to resealing. I would hope there are no holes or anything allowing foreign objects into the prism.

---------- Post added 04-20-21 at 08:55 AM ----------

QuoteOriginally posted by ramseybuckeye Quote
I would probably leave it be if it doesn't affect the photos. But you'll get some more responses from people that have actually done it. I know the focus screen is pretty delicate.
Yes, otherwise the viewfinder is quite bright and beautiful covergirl. But would love a spotless view. I will update if I decide to take her to the operating room.

05-16-2021, 11:21 AM   #8
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QuoteOriginally posted by Not a Number Quote
Many times debris gets between the focus screen and pentaprism. There are often times gaps that allow stuff to get in there from the mirror box. Using a blower can make it worse.

If the focus screen is removable from the mirror box you need to remove the screen and clean off the debris. If the screen is not removable you have to remove the camera top, circuit boards or wires/connectors from the prism and finally the prism to clean this area.

If you don't have the tools or the patience than a professional CLA is in order.
The focus screen is removable on an MEF. If you undo the two screws in the flat plate above the focus screen it will swing down. BE CAREFUL. and be aware you could introduce more dirt than you can remove.
05-18-2021, 05:34 PM   #9
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QuoteOriginally posted by redbirdpete Quote
The focus screen is removable on an MEF. If you undo the two screws in the flat plate above the focus screen it will swing down. BE CAREFUL. and be aware you could introduce more dirt than you can remove.
Very useful information, thanks. I'll store it away for future reference.
05-19-2021, 07:50 AM   #10
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QuoteOriginally posted by Sprky1285 Quote
Hello my fellow Pentaxians, Pentaxites and Pentaddix,

I inherited my grandfather's silver Pentax ME-F a while back and have always loved it. It is the original standard silver metal finish and wanted another one in all black to carry around so I could have the silver for color negatives and black for B&W negatives (for obvious reasons).

Now I love the all black ME F but after doing a basic clean, ensuring there is absolutely no dust or particulates in the mirror assembly, I still notice large fragments in the pentaprism/laying on the focus screen.

My question, is there a simple, non-risky way to check the innards of the focus screen? Worried about mucking up other aspects of the camera, and am a bit intimidated of doing surgery on my new friend.

Since it doesnt affect image quality should I just let it be?

Thank you my beautiful Pentabulons.
Looks like it could be the foam breaking up in the mirror box. Best send it to Eric for a CLA, he will fix it up like new.

Phil.
05-19-2021, 10:27 AM   #11
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QuoteOriginally posted by redbirdpete Quote
The focus screen is removable on an MEF. If you undo the two screws in the flat plate above the focus screen it will swing down. BE CAREFUL. and be aware you could introduce more dirt than you can remove.
Thanks,I may or may not try that. Do not want to ruin anything but those fragments do get a bit annoying.

---------- Post added 05-19-21 at 10:29 AM ----------

QuoteOriginally posted by gofour3 Quote
Looks like it could be the foam breaking up in the mirror box. Best send it to Eric for a CLA, he will fix it up like new.

Phil.
Oh definitely. I had to clean some pieces of foam out that had deteriorated. Just unsure as to how they went from the mirror box to the prism assembly.

I considered that, but the camera functions flawlessly in all other aspects, seems like a pricey venture just to clean some dust. but as stated it is a bit annoying. Perhaps it is wroth just sending off.
05-19-2021, 11:35 AM - 1 Like   #12
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QuoteOriginally posted by Sprky1285 Quote
I considered that, but the camera functions flawlessly in all other aspects, seems like a pricey venture just to clean some dust. but as stated it is a bit annoying. Perhaps it is wroth just sending off.
A CLA is more than that. You will get new light seals, mirror foam, light meter adjustment as well as a full inspection. It's something that you budget for when you get a new " old" camera. Price is usually under $100 if no issues are found.

Then your ME-F will be good for another 40 years!

Phil.
05-21-2021, 05:48 AM - 1 Like   #13
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QuoteOriginally posted by gofour3 Quote
A CLA is more than that. You will get new light seals, mirror foam, light meter adjustment as well as a full inspection. It's something that you budget for when you get a new " old" camera. Price is usually under $100 if no issues are found.

Then your ME-F will be good for another 40 years!

Phil.
Good point
02-25-2024, 02:02 PM   #14
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Dust in Pentaprism

Hi Sprky. I just now joined the Pentax Forum specifically to ask if you ever found someone to clear out the debris in the pentaprism of your Pentax ME. Like you, I find peering through that veil of soot annoying. I'm not comfortable with digging into the top of my ME. Your post was so well written and perfectly explains the problem.

Before starting my own post on this topic, (almost 3 years after yours,) I would appreciate if you would share with me any actions you were able to take or refer me to a realistically priced service technician, etcetera.

Thanks,
Joe
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