Newsgroups: rec.photo
From: acs@csri.toronto.edu (Alvin Chia-Hua Shih)
Subject: Re: EOS 630 (650 and RT) Interchangable screens - any experience?
Distribution: na
Date: 19 Dec 92 03:57:54 GMT

In <1992Dec18.213135.18699@cbnewsm.cb.att.com> ka1gt@cbnewsm.cb.att.com (robert.m.atkins) writes:

>Has anyone used any of the alternative screens available for the EOS 630
>series of cameras? Are they difficult to install? Is there any metering
>problem with non-standard screens? The Canon literature I have doesn't
>seem to mention any problems, but at the back of my mind I seem to recall
>that somewhere I saw something to the effect that metering could be a 
>problem.

I have 3 focusing screens: bi-split, quad-split, and double crosshair.
(I felt like trying the last two out, and got them pretty cheap.)
They're all original Canon screens.  (I don't know about Beatty's 3rd
party screens.)


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 when pressed.

So, the operation is to:
  1. Insert tool into existing screen so that the "grabber arms"
     take hold.
  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.  (I do recall an N8008s owner saying that his metering
was off when he tried to use a screen with a manual focusing aid, and
that the included instruction sheet said so.)

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 again, this is all subjective.)


The bi-split is the most useful for manual focusing, since it's easy to
tell much adjustment is required, and in which direction.  The quad-
split seems to be better for plain "focus confirmation", but worse for
focus assist.  I haven't figured out the double crosshair yet.  (Help!)

The only other screen I'd want is the grid screen.  Canon makes one
that's all matte.  I'd prefer one with a bi-split focusing aid.  I
think Beatty makes one, but I can't justify spending that kind of money
right now.  (And I don't know about exposure compensation.)


With the bi-split, I do notice that the AF doesn't always agree with
the focusing screen.  The AF likes to go just a tad long.  This is
particularly apparent at 300 mm (on my 100-300/4.5-5.6 USM).  I played
around with the AF so that it had to go from close-to-far and far-to-
close, and it still insists on focusing a tad long.

I'm quite not sure what to do about this.  I tried my bi-split and my
100-300 on my friend's 630 (which I helped him buy, and which seems
newer than mine) and it seems to have the same problem.  Maybe I'll
give Canon a call sometime.

ACS
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Newsgroups: rec.photo