Hi Brian, Joel, William, Ken, Chuck and all,
From: "Brian Swale" <bj@xxxxxxxxxxxxxxx>
>And remember, due to Olympus designing vibration-induced image degrade
>into the OM system because of the particular aperture stop-down system
If you mean that the auto-aperture pin must be _pushed_ instead of released
in order to stop it down to shooting aperture, then Oly was not alone: Canon
FD and the venerable M42 thread used similar auto-diaphragm operation.
>having extra mass on the camera, or using a tripod
>combined with prefire mirror raising and aperture stopdown,
Or the slow, delayed, smooth auto-iris action of the OM-2S Program (in any
mode).
>were the only
>ways to get the best out of the manual Zuiko lenses.
I agree that several telephotos (eg. the 200/4) were severely affected by
vibration, but standard and wide lenses should be rather inmune to this, and
_some_ of them were far from stellar performers, IMHO.
>It's ironic; now that the OM system is largely redundant, the excellence of
>the manual Zuiko lenses is being appreciated by Canyon digital users
>(apparently, so I'm told), and this is possible because the aperture stop-
>down mechanism is set well before exposure is made.
Or the higher mass of the bulky EOS bodies... or the comparatively slow
mirror action (motor driven instead of spring driven)... or many Canonistas
used to all-in-one slow zooms...
>I think one of the reasons that the PEN series of film cameras was (is)
>capable of delivering such good images, is that a different lens operating
>system was used.
Well, the Pen-F system had a similar auto-iris mechanism to the OM -- kept
wide-open until pushed. But, having tried both systems in the GF-1 (with no
auto-iris to degrade) I've been surprised by the higher performance of Pen-F
lenses -- esp. the 40/1.4, way better than the earliest OM 50/1.4. I think
the smaller format made things much easier.
>I often wonder if the fortune of Olympus, in the OM era, would have been
>different (better), if this design flaw had not existed to degrade image
Some think about the lack of a 400/4.5...
From: Joel Wilcox <jfwilcox@xxxxxxxxx>
>I think they did know insofar as the manual for the OM2 suggested a
>technique to trigger the shutter that involved damping the
>tripod-based camera and lens with one hand while squeezing off the
>shot with the right index finger.
Zeiss also published a similar procedure for 'high resolution photography'.
From: "William Sommerwerck" <grizzledgeezer@xxxxxxxxxxx>
>As for bulky lenses... I still don't understand the difference between a
>regular lens and a "digital" lens, which is supposed to provide more-even
>edge illumination. I assume this is done by moving the exit pupil farther
>forward, which makes the lens bigger, but I don't know.
Yes, unfurtunately this means heavy retrofocus designs, in order to reduce
the output angles...
>(I can't find a good
>explanation of the optical "meaning" of "exit pupil",
It's just the image of the rim of the iris, as seen from the back, thru all
the involved lens elements...
>or much about how its
>position affects the lens's performance -- other than that, the farther it
>is from the film plane, the greater the reduction in cos^4 effects.)
Yes, since being farther means a smaller (less bent) angle. Usually the
cos^4 law is composed of the cosine of the _input_ angle (no way to modify
it) and the cos^3 of the _exit_ angle, as defined by the position of the
exit pupil.
But modern lenses (esp. wides) use such kind of optical trickeries that the
cos^4 law (or even cos * cos^3) is rarely accurate...
>The OM cameras were truly "Leica SLRs", and
>are among the most-elegant cameras ever designed.
Agreed 100%!
From: Ken Norton <ken@xxxxxxxxxxx>
>In the final print. Pixel-peeping on-screen and a nice high-quality print
on
>paper is another thing altogether.
Sure. But then there's the "spatial frecuency distribution" of noise -- in
other words, some noise almost disappears when downsizing, while others (eg.
the GF1, unfortunately) keeps quite visible unless a severe reduction is
used :-(
>I don't mind the fact that these high-MP sensors aren't cleaner than
lesser,
>older sensors with fewer pixels. With the E-1, the noise is not only there,
>but it's BIG noise because the sensor has fewer pixels. The 5Dmk2's
>per-pixel noise level isn't much better than the E-1's, but the noise is
>positively tiny which means that it disappears in most final prints.
It is a factor, but check also previous paragraph.
>Not all noise is evil. I actually prefer a little bit of it as it provides
>texture to the images. I've compared the E-1's noise pattern to that of
>other cameras
Yes, I have seen the (comparatively high) noise on the E-1 quite film-like
and thus more "tolerable" for many... and shooting raw with the GF1 gives
almost the same benefit (and TONS of detail)
>However, Leica has proven with the M9 that it can be done and done very
>well!
That's OK. The M9 has some issues with extreme wides, not seen on the M8,
though.
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
>AFAIK a digital lens can be digital in the sense that it's telecentric
>(as Olympus envisioned) or in the sense that the rear element is
>shaped/coated to avoid reflections from the sensor back onto the rear
>element.
It's an interesting thought!
>However, I think this has all been
>obviated by cleverly designed micro-lenses over each pixel position.
But not fully -- the "other Ken" reports some problems of the M9 with a few
non-retrofocus extreme wides. And if the microlenses were optimized for an
acute angle, they wouldn't be as good for long lenses...
Cheers,
--
Carlos J. Santisteban Salinas
IES Turaniana (Roquetas de Mar, Almeria)
<http://cjss.sytes.net/>
--
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