Newsgroups: rec.photo
From: acs@csri.toronto.edu (Alvin Chia-Hua Shih)
Subject: Re: Canon 10s Vs Nikon N90, Which one?
Date: 25 Dec 92 05:43:28 GMT

In <BzssK3.Kp6@ra.nrl.navy.mil> tse@ra.nrl.navy.mil (Anthony Tse) writes:

>In article <1992Dec24.205338.11007@jarvis.csri.toronto.edu> acs@csri.toronto.edu (Alvin Chia-Hua Shih) writes:
>>In <1992Dec23.194028.18483@jarvis.csri.toronto.edu> I wrote:
>>3.3) Screens?
>>What you want is a *real* focusing screen with a split prism or
>>microprism focusing aid.  Can a camera really be "pro" or even
>>"semi-pro" without decent screens?

>   Why do you want a split or microprism screen?  First off, with
>AF, you don't need focusing aid.  [...]

AF isn't perfect.  There are still low contrast and low light
situations where AF will fail where the eye can still see (you know,
for those situations where you have TMAX at EI50000 :-).  This is
especially true with slower lenses.  In additon, the CCDs are colour
blind.  So, there may be times when you can *easily* see details that a
monochrome sensor cannot.

A split screen does the job of the electronic rangefinder, except it
requires no power, and does not suffer the limitations of AF
technology.

>                           [...]  Second, if you ever use a fast
>lens, you'll know that split screen or microprism is useless.  A fast
>lens has such small DOF that unless you are lucky, there won't be
>enough feature for the split screen to split or microprism to merge
>(for example, a tight head shot with a 1.2 lens that has a DOF of about
>1/4", where are you going to find vertical feature on someone's face
>to split the split screen?  If you focus on say the person's arm to
>use the split screen, her face won't be in focus anymore.)  [...]

Of *course* you put the feature of interest where the split is, and
then recompose.  That's what you do with the AF sensor too.  The most
common area of the face suggested for AFing is the eye, since it has
both light and dark regions.  However, being a small region, may AFers
like to tweak the focus manually (especially easy with USM lenses)
since AF may decide that the person's glasses are more interesting than
the person's eye.

Personally, I use zooms.  If I'm going to lug a camera around all day,
I'll take the versatility of the zooms over the quickness and sharpness
of a prime.  (Though I'm finding that it's actually my Quantum Turbo
that's the backbreaker. :-) In addition, for the hobby shooter, a zoom
is much more economical.  For most, a good zoom is "good enough" for
most things.

Notice that the lenses for the F-90 (under 200 mm) are all zooms?  That
way, Nikon can push it out the door without mounting a massive effort
to modify the manufacturing of its current AF lenses (or delay the
introduction).  Are you saying that the AF-D lenses aren't good for
professional work?

Unless there's some revolution in optics waiting to happen, I don't
foresee any f/1.2 zooms!

>                                                     [...]  One of the
>few things that I like about AF cameras (obviousely, I don't use one)
>is that they all seems to have bright plain focusing screen.  I
>absolutely hate it whenever someone hand me their camera with that
>pin hole zoom and all you see is that black blob in the middle of the
>focusing screen.

Sounds like their camera doesn't have full-aperture metering!  :-)

I have a 100-300/4.5-5.6 USM.  Even at 300/5.6 (which is laugably dark
compared to f/2.8 like more fortunate zoomers have :-), I have no
problems with the screen so long as my eye is centered properly in the
viewfinder.

>-Anthony

ACS
-- 
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|   |   | __|      Democracy is not a way of getting better solutions.     |
| - | --|__ |           It's just a way to spread the blame.               |
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Alvin_C._Shih____________________acs@csri.utoronto.ca______________________|
From: peterd@hpgrla.gr.hp.com (Peter Davidoff)
Date: Tue, 29 Dec 1992 18:30:02 GMT
Subject: Re: Swelling of wet paper
Organization: Hewlett-Packard, Greeley, CO