I did a dumb thing today...

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Dan - 30 Dec 2003 04:00 GMT

... I removed the focusing screen on my Mamiya C3 TLR for a good cleaning
and now for the life of me I can't seem to remember the order in which it
goes back (focusing screen first then glass plate or vise versa) and whether
they are facing in the right direction. (up/down). I still have the shims
and I know where they go but the focusing screen has me stumped.

Can someone out there please help me fix my screw-up?

Thanks
Dan

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Roland - 30 Dec 2003 08:23 GMT

> ... I removed the focusing screen on my Mamiya C3 TLR for a good cleaning
> and now for the life of me I can't seem to remember the order in which it
[quoted text clipped - 6 lines]
> Thanks
> Dan

No problem. I have just taken mine apart. The focussing screen goes below
the glass plate with rough surface touching rough surface. If you scrape it
with the back of your nail you will be able to tell the ground glass side of
the glass plate and the fresnel ridges of the focussing screen. This are the
two surfaces that touch each other. These are held in place by two brass
brackets. The brass makes contact with the plastic fresnel screen (that you
refer to as the focussing screen) and not the glass plate.

Be very sure you have all the washers and spacers in place when you remount
this on your camera. This is critical to accurate focussing and the lack of
awareness of this is probably the source of the talked about "soft focus" of
these cameras (in reality the standard lens should be extremely sharp if
everything is correctly adjusted). These spacers tend to need to increase
with time as the top of the lens housing gets pushed back usually because of
the camera being dropped. It nearly always lands on the viewing lens through
Sod's law and pushes the viewing lens further back and so the focussing
screen needs to be raised, and even angled, to compensate. This is done with
washers and spacers.

The rest you know how to do but if you hit a problem then email me.

Roland

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Mxsmanic - 30 Dec 2003 09:25 GMT

> If you scrape it with the back of your nail you will be able
> to tell the ground glass side of the glass plate and the
> fresnel ridges of the focussing screen.

I hope both are made of glass and not plastic, if you're going to be
running your nail over them.

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Roland - 30 Dec 2003 10:36 GMT

> > If you scrape it with the back of your nail you will be able
> > to tell the ground glass side of the glass plate and the
> > fresnel ridges of the focussing screen.
>
> I hope both are made of glass and not plastic, if you're going to be
> running your nail over them.

No, the fresnel screen thingie is made of plastic. Running the back of your
nail over it (I mean finger nail and not done hard but just to get a sense
of which side is smooth and which side is rough) will not damage it or leave
a mark or a smear.

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Mxsmanic - 30 Dec 2003 11:20 GMT

> No, the fresnel screen thingie is made of plastic. Running the back of your
> nail over it (I mean finger nail and not done hard but just to get a sense
> of which side is smooth and which side is rough) will not damage it or leave
> a mark or a smear.

Famous last words ... but it's your camera.

I'm not even willing to run my finger over glass. Indeed, I'm not
willing to touch optical glass with my fingers at all.

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Roland - 30 Dec 2003 11:38 GMT

> > No, the fresnel screen thingie is made of plastic. Running the back of your
> > nail over it (I mean finger nail and not done hard but just to get a sense
> > of which side is smooth and which side is rough) will not damage it or leave
> > a mark or a smear.
>
> Famous last words ... but it's your camera.

I do partly disassemble cameras, shutters and lenses from time to time.

> I'm not even willing to run my finger over glass. Indeed, I'm not
> willing to touch optical glass with my fingers at all.

The back of your nail, so long as your hands are clean, will not have grease
on it and is soft compared with optical glass or even the coating and so
will not leave a mark. The front of your hand will have grease and sweat on
it, whether you just washed your hands or not, and this can indeed leave a
mark on optical glass and even etch the coating if bad enough and left for a
long time. Focussing screens do not matter that much as this does not affect
the picture being taken. For lenses you have got to be more careful but
mainly because of the lens coating. If you are cleaning an old uncoated lens
then washing up liquid, water and finger tips are the order of the day. In
fact the ridges in fingertips help hold the cleaning fluid and so keep it in
contact with the glass as well as acting like a soft abrasive.

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stacey - 31 Dec 2003 01:58 GMT

>> If you scrape it with the back of your nail you will be able
>> to tell the ground glass side of the glass plate and the
>> fresnel ridges of the focussing screen.
>
> I hope both are made of glass and not plastic, if you're going to be
> running your nail over them.

Probably are plastic and I laughed when I read this as well. Like why not
just hold it to a light at an angle rather than scratch the screen to see
which side is rough! :-)

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Stacey

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Roland - 30 Dec 2003 12:05 GMT

> > ... I removed the focusing screen on my Mamiya C3 TLR for a good cleaning
> > and now for the life of me I can't seem to remember the order in which it
[quoted text clipped - 28 lines]
>
> The rest you know how to do but if you hit a problem then email me.

Another thing useful to know (if you are not used to this sort of thing) is
that tiny screws can be stuck on the end of screwdrivers using a tiny amount
of axle grease. This can save you a lot of time reassembling when tiny
screws are involved.

I am not advocating that we all mend our own cameras. In fact I would
recommend the opposite for you average camera users out there. For me it is
a fun thing to do with old cameras that did not cost me much to buy and
would not be worth the expense if they were professionally maintained. I
like to use old, high-quality cameras. If older than me then so much the
better. I get as much enjoyment from shooting with them as the photographs I
take using them. But if you do go down the path of fixing old cameras
yourself then ALWAYS DRAW DIAGRAMS AND TAKE DETAILED NOTES when you
disassemble. Number each step. Note smooth/rough surfaces. Note screw
lengths and look. Disassemble over a surface that will catch fallen screws
and other pieces and show them up. When you open up something like take the
top off a camera then I usually do so with the camera under bedclothes to
catch any springs that fire out. This sort of work is not for those who lack
patience or lack a degree of care.

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Dan - 31 Dec 2003 06:29 GMT

Thanks for your help Roland. I put it all back as you explained and it works
just fine. I will be saving your post for next time.

Thanks again
Dan

> > > ... I removed the focusing screen on my Mamiya C3 TLR for a good
> cleaning
[quoted text clipped - 61 lines]
> catch any springs that fire out. This sort of work is not for those who lack
> patience or lack a degree of care.

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Roland - 31 Dec 2003 10:24 GMT

I was very gladdened to hear that. I wouldn't like the thought of one of
these excellent Mamiya C3's going out of service due to an accident when
somebody tries to fix it themselves. Please, people, if you are ever tempted
to take apart one of these old cameras to do your own maintenance then MAKE
DETAILED NOTES AND DRAW DIAGRAMS and number it and pay careful attention to
detail so that you can reverse the actions you took to dismantle it and so
get it back together again. Make sure you do this on a surface that can
catch dropped screws and show them up clearly. Do not "open" anything,
especially the top of a camera, unless you can catch a maybe flying part.
Use axle grease to stick screws on to the end of your screwdriver and hold
spacer washers in place otherwise your reassembly might take so long you
have to take a break. And that "break" might turn into days and your camera
remain in pieces, never to get reassembled. There are a lot of excellent MF
cameras out there that can be bought very cheaply but only remain viable if
you maintain them yourselves. But maintaining cameras is a skill and
disicipline that must be learned.

> Thanks for your help Roland. I put it all back as you explained and it works
> just fine. I will be saving your post for next time.
[quoted text clipped - 78 lines]
> lack
> > patience or lack a degree of care.

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Roland - 30 Dec 2003 12:34 GMT

> ... I removed the focusing screen on my Mamiya C3 TLR for a good cleaning
> and now for the life of me I can't seem to remember the order in which it
[quoted text clipped - 6 lines]
> Thanks
> Dan

Also I noticed there is a faint line across the plastic fresnel screen
thingie about a quarter the way in. You need to orientate this so that the
line is to the front of the camera. It is a guide for doing close-up work
telling you that the image you are taking will be lower because the lenses
are not at the same level.

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