Just remove the rubber eyecup. It'll allow your eye to get
closer. However, it is worth checking to see if the plastic
around the eyepiece is abrasive to your glasses (particularly
plastic lenses, or special coatings). Rub the exposed eyepiece
frame briskly on a remote corner of your vision-correcting lens,
or on an old pair of glasses.
The two virtual images are projected at different distances. Try
borrowing a technique from microscopy. That is, look through
the viewfinder with both eyes open! By doing so, you may be able
to "fool" your viewfinder eye to focus on a farther point; one
that may be closer to the distance of the images in the
It may also be worth trying out some diopter-adjustment lenses
for the viewfinder. These are usually selected by
trial-and-error, so you might have to search high and low for a
Canon dealer with a good selection of them in stock.
It blocks stray light from entering viewfinder when your eye is
not up to the eyepiece--like when shooting from a tripod. Since
the exposure is determined from light bled from the viewfinder
image, light entering the pentaprism could find its way to the
exposure sensor. This could cause underexposure.
There is nothing terribly special about this piece. If you lose
it, just remember to cover the eyepiece with your hand or
something else opaque when the exposure reading is being taken.
(Mike Coren points out that caps from Kodak film canisters can be
substituted in a pinch!)
The dust is usually on the mirror or the focusing screen. If you
view your camera with the lens off in the right kind of light,
it should be visible to the naked eye.
Just take one of those blower bulbs and force some air over the
mirror and screen (DON'T used compressed air NOR solvents!).
If it's really persistent, you might try using a very fine brush,
but I'd only do that if I were really annoyed, since the dust
in the viewfinder doesn't affect the image on film (except in the
RT), and you can damage the mirror and screen by touching
The screens are pretty easy to change. They each come with a
little tool that is shaped like a screen on a handle. There are
little "arms" which allow the screen to be gripped from the
inside of the metal frame in which the focusing screen is
mounted. On the handle, there is a small lever that releases the
screen from the body when pressed.
So, the operation is to:
1) Insert tool into existing screen so that the "grabber arms"
2) Release the screen by pressing the lever.
3) Set the screen into the screen holding case.
4) Grab the new screen from the screen holding case.
5) Insert into body. (There should be a "click" when it is locked in.)
6) Remove tool.
It's much easier to understand from the instruction sheet (since
it has diagrams). In any case, this method seems more foolproof
than the tweezers method used on the EOS-1 and other bodies.
The only trouble with installing a screen (EOS or otherwise) is
dust. If you get dust between the screen and the pentaprism, you
have to remove the screen, etc. (Well, I guess there is also the
worry of dropping the screen and destroying it, but the tool has
been pretty reliable.)
As far as I can tell, every focusing screen comes with the same
instruction sheet, and there are no warnings regarding exposure
compensation. Canon say that no exposure compensation is required
under normal conditions.
Subjectively, it seems that the lighter the focusing aid looks
(like in the double crosshair), the darker the rest of the screen
looks. So, Canon may be compensating by adjusting the darkness of
the surrounding matte. (But this is all speculative.)
Note however that there may be exposure problems under unusual
circumstances, such as when using the FD->EOS macro adapter.
Metering considerations may require the use of only certain
screens (see sections 9.18 and 4.3).
For general shooting, the "cross-split" (Type "L") seems most
useful since it gives feedback as to how the focus needs to be
adjusted. It is also more versatile than the "new split" (Type
"B") in that it works the same both horizontally and vertically,
and allows one to use detail in two directions instead of one.
For slow lenses, I do not recommend the "microprism" (Type
"A"). It is hard to line it up in a way that avoids the little
microprisms from going dark. It also gives no hints as to how the
focus needs adjusting.
The Type "B" screen seems to be quite effective with lenses as
slow as f/8-f/9. If you keep your eye in the center of the
viewfinder the split part of the screen does not "black out". It
may even be usable at f/11. Canon specifically state that this
screen is usable with lenses slower than f/5.6. Canon also confirm
that its performance in this regard is better than that of the
Type "L" screen.