Hi all,
>From: Moose <olymoose@xxxxxxxxxxxxxxx>
>
>Many mounts can be used on the Can*n and E-1 with adapters. They then
>meter and shoot in manual or aperture priority modes. I don't know about
>the other adapters, but with the OM=> EOS adapter you can set it up so
>the DOF button closes the aperture down for metering and shooting.
Unlike the Zuiko lenses, most mounts are designed to keep the lens
stopped-down up to the selected f-stop (on the aperture ring). When mounted
on the camera, these lenses' auto-iris pin is pressed to keep the lens wide
open while focusing and/or metering, and the camera will release the pin
while taking the picture. Just the opposite of the OM -- lens keeps
wide-open *until* the body moves the auto-iris lever when firing.
Mountless Tamron Adaptall lenses behave in a similar way to Zuikos. Another
exception to the general rule are M42 auto diaphragm lenses (see below).
And Can*n FD lenses are the weirdest thing on earth, regarding to coupling
;-)
>>From: Peter Klein <pklein@xxxxxxxxxx>
>>
>>The Pentax *ist D meters with MF M42 and "K"
>>lenses with a single button push. Pentax released a firmware upgrade that
>>stops the lens down when you push the "green button," meters, and then
>>opens up again. It also stops down for shooting. So you get an aperture
>>priority mode with one-touch metering.
>>
>Interesting. That means they still use mechanical stop down for their
>newest AF lenses or included an electro/mechanical linkage in the
>design.
AF mounts from Pent*x, Nik*n and Min*lta do have a mechanical stop-down
lever. Min*lta AF lenses don't have aperture ring, though. Pent*x & Nik*n
AF lenses _may_ have aperture ring (not to be found on FA-J and G-series
lenses, resp.), but most bodies rely on electronic communication and should
leave the diaphragm ring at minimum aperture setting (or 'A' setting in
Pent*x), letting the body set the aperture (via the stop-down lever).
BTW, do you remember the OM-AF mount of the OM-77AF/88/101/707 ? It also
had mechanical stop-down, but no aperture ring and no meter coupling with
MF Zuikos...
OTOH, Can*n EOS and the E-1 have fully-electronic mounts, with no
mechanical stop-down action -- no auto iris with adapted lenses!
>>Obligatory OM content: Unfortunately, the *ist does not take MF
>>Zuikos. If it did, I'd buy it in a heartbeat. And if the E-1 treated MF
>>Zuikos as the *ist does legacy Pentax lenses, I'd buy *it* in a heartbeat,
>>too.
Please note that M42 lenses can be mounted on the *ist via the usual M42-K
adapter, and the new firmware may meter with them, but the auto-diaphragm
action of the MF Pent*x-K bajonett lenses is lost. In fact, 'auto-only' M42
lenses (those without the Auto/Man switch) would work wide-open *only*,
because the M42-K adapter doesn't press the auto iris pin.
>The problem is that most current AF lens systems rely on an
>electronically activated mechanism in the lens to stop down the
>diaphram. So adding a mechanical mechanism to stop down legacy lenses
>adds cost in a very competitive market.
As I previously said, N, P and M do keep mechanical stop-down action as a
standard. Another matter is the meter coupling with the aperture ring -- if
any!
>C abandoned backward compatability with the FD mount with
>introduction of the EOS line some years ago.
But that's not only a matter of diaphragm coupling -- the mount itself is
completely different (breechlock vs. bajonett). Same with Min*lta -- only N
and P kept their original bajonetts.
>N keeps backward
>compatability only in their high priced pro bodies, which have the
>mechanical stop down mechanism needed.
Again, the mechanical stop down is standard for all AF Nik*ns, as is for AF
Pent*xes. What it's lost in all but the higher priced pro bodies, is the
coupling with the aperture ring (called "AI" by Nik*n).
>I thnk the displays of the E-1 and 300D are pretty similar. It's been a
>while since I tried them out side by side. The 300d gains by having a
>bigger image size and loses by maving a mirror prism. None of the APSish
>or less sensor size DSLRs are anywhere near as easy to focus manually as
>OMs, but I have good visual acuity and just have to pay a bit more
>attention.
As already noted, all AF SLRs (either film or digital) have screens
intended for *composing* with a slow zoom lens -- they're optimized for
brightness, not *focusing* accuracy/easyness at all.
>From: Winsor Crosby <wincros@xxxxxxxxxxx>
>
>Just a few thoughts. The reason there are focus assist lights is that
>no one has figured out how to autofocus in the dark. I can understand
>why people don't like the lamps and I have mine turned off too, but to
>do it as a blanket practice and then complain about how badly it works
>with the assist tool provided by the maker turned off seems maybe a
>little perverse?
I once tried to take a pic of a car in a garage with the 300D (AF lens and
flash, which also acts as AF assist light). The garage was in near total
darkness because lighting was broken -- fortunately someone put a bit of
fluorescent paint on each column!
...No way to focus, no matter how many times I tried, in different angles
and with the AF assist flashing as mad. Manual focusing was obviously
impossible, thus no pic was taken :-(
>I have a D100 and its focus system is not as good as that in a D1X or
>D2H. So you work with it. With almost all AF cameras with multiple
>focus points the center one is most powerful in dim light and will
>focus on horizontal and vertical detail.
[snip]
>Place your subject in center, mash the shutter release down half
>way, reframe and push the shutter release down the rest of the way. It
>will lock focus in near darkness that way.
That's exactly what I do with my 300D. It didn't work in the garage, though ;-)
[snip]
>And only a ground glass with
>no focus aid. But some people opted for ground glass only focusing on
>this list with their OMs because they felt it was more accurate that
>than the focus with the split image or microprism.
But the matte field in screens for manual cameras have a 'texture' that
makes focusing much easier. For instance, focusing on the 2-4 (no split
image/micropism) is *much* easier (and accurate) than on the 300D's screen,
which lacks the "snap" of the 2-4 -- even with the same lens.
>The other focus
>issue is slow lenses. Most people opt for a slow zoom on their digital
>camera which would not exactly snap into focus on a 35mm SLR. Pop a 1.4
>or 1.8 lens on your digital and you might be surprised how easy it is
>to focus manually.
Again, not necessarily. The 300D screen is surprisingly bright even at
f/5.6, and there's no visible increase in brightness at apertures larger
than f/2.8. However, *some* fast lenses are easier to focus -- they must be
quite sharp wide-open in order to have the requiered "snap".
Enjoy,
...
Carlos J. Santisteban
<cjss@xxxxxxxxxxxxx>
<http://cjss.galeon.com>
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