[RobG]

Any thoughts whether using a sensor cleaning kit on the mirror and focussing screen would do any harm? I figure that something design to do no harm to the sensor shouldn't damage the mirror or focussing screen.

[Radar]

I think the surface of the mirror and focussing screen are far more sensitive to damage than the sensor. I think I read somewhere there is a coating over the sensor, so when you clean it's not the actual sensor you are touching.

From experience of changing focus screens the least touch and you see it.

[RobG]

I think the surface of the mirror and focussing screen are far more sensitive to damage than the sensor. I think I read somewhere there is a coating over the sensor, so when you clean it's not the actual sensor you are touching. From experience of changing focus screens the least touch and you see it.

Hmm... I'll have to try a blower first. It's just that there's a spot of dust on the sensor, so I thought it would be worth trying it on the mirror and focussing screen. I don't want to damage either, but it didn't seem likely that the sensor cleaning kit would damage them. Certainly not the focussing screen. I'd expect the mirror to be more difficult, especially because it can move.

[pschlute]

Agree with the above, don't touch the focus screen. if it is dirty get it professionally cleaned or buy a new one.

I have never cleaned a mirror either.

[Madaboutpix]

Wouldn't even contemplate using the Lollipop of Death on the mirror, nor the focussing screen, for that matter.

[Radar]

Hmm... I'll have to try a blower first. It's just that there's a spot of dust on the sensor, so I thought it would be worth trying it on the mirror and focussing screen. I don't want to damage either, but it didn't seem likely that the sensor cleaning kit would damage them. Certainly not the focussing screen. I'd expect the mirror to be more difficult, especially because it can move.

I use an Arctic Butterfly brush to clean the sensor, because I can't control where the debris is blown to with a blower.

[photoptimist]

The focusing screen is very sensitive to scratches. It's made of molded plastic and the fresnel/ground-glass surface consists of very small and delicate texturing of the plastic. Even the plastic tip of a rocket blower can damage it by denting or burnishing the texture.

Cleaning the focusing screen can be done with a rocket blower (just make sure not to let the tip touch the surface). If the screen is really dirty, oily, or gets a finger print, you could take it out, rinse it in diluted dishwashing liquid, then distilled water, then blow off the remaining droplets. Never wipe the screen with anything and avoid any solvents (IPA might be OK or it might fog the screen).

The mirror is delicate in its own way -- easily tarnished by oils -- and the mirror's proximity to the focusing screen makes it hard to clean. I only use a rocket blower on the mirror and make sure not to let the tip touch it's surface, either.

When I do a sensor cleaning, I do blow any dust off the mirror, focusing screen, and mirror box walls first before going into "sensor cleaning mode" just to reduce the amount of crap floating around in there when the mirror flaps during picture taking. Also, during "sensor cleaning mode," I make sure to blow any dust off the PDAF sensor lens on the floor of the mirror box.

[pschlute]

IPA might be OK or it might fog the screen

Really

[pres589]

Let me preface this post with saying that I don't know if this is the most right way to do things or not. I'm also going to mention a mistake I made literally yesterday. Nobody hassle me about it.

Focusing screens I've successfully cleaned, I can only list one; my MX had a lot of disintegrated bits of mirror damper pad on it. I cleaned it with water and a q-tip. I took it out of the camera and did it as lightly as possible after first giving it some air blasts with a blower. Tweezers to hold it by the tab makes this easier.

Yesterday I was doing a bunch of work to a Chinon CE-4 including replacement of the mirror damper pad. Same situation. Only this time, for reasons I cannot explain, I used 70% isoprophyl alcohol on a q-tip. It left some fogging and streaking on the screen that I cannot get clean using water. The screen on this camera is not removable without a full tear-down which I am not willing to do. The center of the focusing screen where the main focusing aids are (micro-prism + split-prism) were left perfect but the rest of it is not great. The camera is usable but I kicked myself pretty hard for doing this when I should have known better.

Short version; use air, see if you can just live with it, if it's really bad either talk to a shop that knows Pentax cameras or figure out how to do it yourself. I would only use water and a bunch of q-tips so that when one has collected any particles or contaminants it is replaced with another clean one.


As for the mirror I've cleaned them using dry q-tips, just trying to lift whatever might be on the mirror off. No real idea what solvent would work best / be safest here. Water, probably, but that seems like asking for streaks. I don't know that the mirror is really as delicate as others are saying but I have no reason to doubt others that have been doing this longer than I have.

[photoptimist]

Really

LOL!!!!

No one would waste a delicious India pale ale on cleaning a focusing screen.

"Lite beer" on the other hand could easily be used in place of water for rinsing!

[rogerstg]

Hmm... I'll have to try a blower first.

With respect, that should always be your first move when cleaning any photography equipment.

[RobG]

With respect, that should always be your first move when cleaning any photography equipment.

With respect, I already tried it on the sensor, and persistent dust on a previous occasion was the reason I bought the sensor cleaning kit which worked perfectly the only time I've been forced to use it.

[clickclick]

"Lite beer" on the other hand could easily be used in place of water for rinsing!

It's my understanding that the foaming action lifts dirt and helps to rinse it away.

[stevebrot]

(IPA might be OK or it might fog the screen).

It depends on the material used for making the screen. Given the number of negative experiences shared on this site and other places on the Web, the risk is probably high enough to suggest avoiding cleaning, soaking or rinsing with IPA (isopropyl alcohol) or other solvents. I have wondered about wetting agents such as photoflo (used as final rinse during film negatives processing) to avoid water spotting, but don't have a ready supply of recent-made screens to test various approaches. I have asked my friends that do camera repair and they are mum about recommendations, the standard response being to leave the task to the pros.


Steve

[gatorguy]

It depends on the material used for making the screen. Given the number of negative experiences shared on this site and other places on the Web, the risk is probably high enough to suggest avoiding cleaning, soaking or rinsing with IPA (isopropyl alcohol) or other solvents. I have wondered about wetting agents such as photoflo (used as final rinse during film negatives processing) to avoid water spotting, but don't have a ready supply of recent-made screens to test various approaches. I have asked my friends that do camera repair and they are mum about recommendations, the standard response being to leave the task to the pros.


Steve

I've cleaned my focusing screens a few times without issue.

My process needs plastic tweezers, three small brand new unused plastic cups with lids, one with purified water and one drop of dishwashing liquid, the second with purified water only, and the third with purified water and one drop of dishwasher rinse aid. ( I can't remember where I learned this but I didn't come up with it)

- Using the plastic tweezers remove the screen by the tab only. NEVER touch the screen itself and DO NOT use metal tweezers. Theres' inexpensive plastic ones made specifically for focus screens. If anyone needs help on this step Stevebrot has explained it before as well as linked the excellent document originally provided by Katzeye. Read it.

-With the screen now out use a rocket blower on the interior with the camera upside down

-Put the screen in the first cup, lid on, and swirl the screen in the first one for a few seconds. Let it sit for a minute of two.

-Empty the liquid, very carefully transfer the screen to the second cup, and gently swirl it around again for several seconds to remove any soap residuals.

-Empty the liquid again, transfer the screen to the third cup with the rinse aid, which is meant to help prevent water spotting. Gently swirl again, dump off the liquid and pick it up with the plastic tweezers you have (you do have them, right?) and let the liquid drip off for several seconds at least maybe a minute.

-Place the screen on a clean lens cloth and cover with another until totally dry. You don't want dust settling on it while drying.

-Blow out the camera with a rocket blower again "just in case", then reinstall the screen.