Small craters or bubbles in the viewfinder

[seany65]

Hello all.

I've just received a Minolta 110 slr mkII, and on the outside it seems to be in very good condition and seems to be working properly, but a film will tell.

Anyway, there are a number of very small irregular blotches randomly placed in the viewfinder, I'm presuming on the focusing screen. I'm of the impression that these were where fungus has been and which has been cleaned off because from what I can see the blotches are actually clear and see-through. What's puzzling me though, is that in some of these blotches there is what looks to be a fully round "circle" which seems to be either like a crater or a bubble, as when the camera is tilted this way or that, there is a crescent shaped "shadow" on the edge, which changes size and can change exactly where it is on the edge of the circle. There is only one cirlce/crater/bubble in any blotch, it is always in the centre and is a different size compared to the other circles, and seems to be dependant on the size of the blotch it is in. These cirlces/craters/bubbles are also clear and see-through. One of these craters is on the top rangefinder wedge and does not look like it's in a blotch. One small crater looks like it's at the end of a snailtrail which leads to a small blotch that is slightly thicker than the trail.

Is there anything that is used to clean fungus which could cause these craters/bubbles? Could someone have tried to make the focusing screen brighter but made a bit of a pig's ear of the job?

Thank you for any help anyone can give.

 

[seany65]

I'm about to try and post a photo of the viewfinder:

How do I make the post so that when you click on the pic you get the full-sized pic?

The Craters/Bubbles aren't too clear, even in the big pic. I'm fairly sure a previous owner has been messing about with the camera as there are also black bits in the 'finder, which I presume got in when the top was off. I know the screens aren't normally swappable, but can they be swapped during a repair? There are two small screws on the back on either side of the eyepiece, does anyone know if I unscrew them would I be able to take the eyepeice out and clean it to see if I can get rid of the slight "fog"?

Any help would be much appreciated.

 

[retinax]

The clear blotches sure look like the matte side of the screen is damaged or if you're lucky, they are oil drops that can be washed off. Screens can be washed veeeeery gently by immersion in water with dish soap, then rinse with distilled water or veeeery gently blot dry. Only touch the edges if you can, use tweezers (but I've found no ill effect from touching the surface gently with clean fingers - oil is the enemy). Do not wipe, do not attempt to clean in situ, that would be a recipe for disaster.
Black bits usually come from degraded foam. Fog may also be on the prism, that can be cleaned like a lens. But maybe that camera has a pentamirror arrangement? That probably can't be cleaned.
You may have to live with some imperfections, I find I can.

 

[seany65]

Thanks for the info, retinax.

I've no clear idea how to get it out or if I can get it out yet. The eyepiece does look like it's on a single plate, that is held in place by two tiny screws, which if removed looks like it would give access to the prism. I've no idea if the prism is screwed in place or if the inside of the top of the camera has been moulded specially so that the prism just slides out. Probably not that simple though.

Would the matte side of the screen be the side that faces the mirror?

When you say screens can be washed by immersion, do you mean just leave it in to "soak" and then "soak" it in distilled water?

To blot dry, should I use paper kitchen towel, (The stuff that's thicker than toilet roll paper)?

By Dish Soap do you mean washing up liquid?

Do I take it that 6% food grade Hydrogen Peroxide is out?

You believe the clear blotches are oil, not fungus? That may help me live with it, if nothing can be done.

Thank you.

 

[retinax]

Thanks for the info, retinax.

I've no clear idea how to get it out or if I can get it out yet. The eyepiece does look like it's on a single plate, that is held in place by two tiny screws, which if removed looks like it would give access to the prism. I've no idea if the prism is screwed in place or if the inside of the top of the camera has been moulded specially so that the prism just slides out. Probably not that simple though.

1) Would the matte side of the screen be the side that faces the mirror?

2) When you say screens can be washed by immersion, do you mean just leave it in to "soak" and then "soak" it in distilled water?

3) To blot dry, should I use paper kitchen towel, (The stuff that's thicker than toilet roll paper)?

4) By Dish Soap do you mean washing up liquid?

5) Do I take it that 6% food grade Hydrogen Peroxide is out?

6) You believe the clear blotches are oil, not fungus? That may help me live with it, if nothing can be done.

Thank you.

I've taken the freedom to number your questions, easier this way.
1) I don't know this camera, on must 35mm SLRs it seems to be the other way around. You'll see in time. With most modern-ish plastic screens, the other side has a fresnel structure and is just as fragile.
2) Yes, no mechanical cleaning, running water or moving it around in the water at most.
3) I think that's ok, but something softer might be safer. Again, don't wipe, just blot!
4) Yes, wasn't aware that's an American/British difference.
5) No idea, never even seen the stuff, what do people use it for?
6) I really don't know, but don't see how fungus would make it more translucent.

 

[seany65]

Thanks for the new info, retinax.

1) I'll now presume that the matt side faces the prism on this camera as well. If that's the case, I'm not sure how oil would get onto it, unless someone has had the prism out, but what would the oil be for in a viewfinder?

5) Hydrogen Peroxide is used to clean fungus off lenses. At least that's my understanding of what I've read on this forum. I'm presuming that the "6%" bit is how diluted the solution is. I'll presume that what it's diluted with is clean water, but I don't know if it's distilled(?) water. Perhaps "food grade" means you can also wash vegetables with it? I've used it on several lenses and cameras, though not to remove fungus, and it seems to make the lenses look a bit cleaner.


I've had a response from a shop that sells only 2nd hand photo gear and it seems that they think the blotches are fungus and it would very difficult to clean off.

 

[retinax]

Yes the oil hypothesis is questionable, bit very likely. I don't think fungus is likely either. Peroxide is a oxidans and as such a desinfectant, it would certainly be helpful to kill off fungus and bleach visible traces, but for cleaning as such, does it help? I don't know. I meant I don't know what "food grade" would be good for, but yes, I see applications in the food industry.
Maybe you can just use the camera as is? Looks perfectly useable. Living with imperfections is great practice for other things in life 🙂

 

[seany65]

The camera does certainly seem to be otherwise useable, but for me the question of whether what we can see is just "annoying oil" or "filthy fungus".

If oil, could it still go a bit runny in heatwave (which is seems we'll be getting on Sunday) and drip onto the mirror or somehow onto the rear element of the lens.

If fungus, could spores spill out onto the film cartridge and then fall off and eventually infect my other photo-gear?

Both may be unlikely and perhaps I could live with the former but probably not the latter. Unless I can find a repair manual and understand it enough to think I could have a go, am I prepared to pay a tech to find out?