Olympus OM enthusiasts' digital prayers have been answered ...

In article , Bruce
writes

The suggestion that the least telecentric lenses are always those with
tiny rear elements is completely risible.

Nobody said that is *always* the case.
I gave an example, which is certainly the most common situation, where
it *IS* the case.


In some cases, they are
among the *most* telecentric!

That is a completely ridiculous statement - we can all restrict our
comparisons to the "some cases" which *can* be worse. In most cases
that is NOT the case. I referred to the entire OM range.

There are many aspects of the OM 18mm which demonstrate it's poor
telecentricity. However poor rear telecentricity is guaranteed
*because* it has a small rear element. That, together with the proximity
of the rear element to the focal plane (it projects into the lens mount
and just clears the mirror!), restricts the angle of incidence of the
principle rays at the corners of the focal plane to very oblique angles:
the very problem that Olympus claim makes such a non-telecentric lens
unsuitable for digital. Yet it works extremely well and is one of the
most sought after OM Zuikos for FF dSLRs!

The implied converse, that a larger rear element means the lens is
closer to telecentric is *complete nonsense*.

That is *not* the implied converse. Only an idiot thinks that "all cats
are furry animals" implies "all furry animals are cats"!

The converse is that telecentricity, more specifically
rear-telecentricity which is the version under discussion here,
*requires* a large rear element!

Should Bruce Almighty dispute that, I am sure he can point us to a ray
diagram which shows otherwise. (That doesn't mean a diagram showing that
telecentricity *can* be worse on a large rear element design, that is
obvious with the standard textbook design of a front-telecentric lens
being such an example.)
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)

Why would a user of the 24x36mm OM-1/2/3/4 be anxious for a 1/4 frame
(17.3 x 13 mm) look-a-like?


--
Mike

On 2/9/2012 19:50, Mike wrote:
Why would a user of the 24x36mm OM-1/2/3/4 be anxious for a 1/4 frame
(17.3 x 13 mm) look-a-like?


Not anxious, but there are things to like: "Free film" (well, once
you've more or less heavily invested in equipment and any necessary
peripherals), "instant developing" (though if you shoot raw that also
takes some time & most images can use some adjusting before printing or
viewing), some quite decent lenses (some of the very few WA zooms I've
found to be good - I normally use Zeiss & Leica with film) and very
compact and light (even compared to the original OM series).

What I like less it that the "form follows function" idea got lost in
translation and the useless false pentraprism adds quite a bit to the
effective size of the camera.
Also the hand grips seem to be a lame attempt to label the camera as a
"pro" model (marketing predominating over content).
Perhaps Olympus should introduce some oversized white telephoto lenses
which can be parked at the side of sport fields, then they'd have
succeeded in emulating the ultimate marketing brand....

That said, if the image quality is as good as it should be and the
camera seems tough enough, I'll probably end up buying one when they get
affordable. A water resistant, tough (hopefully) camera with decent (or
hopefully more than decent) quality and tiny but good lenses is
something to like.

But I'll still use my film Leicas and Rolleiflexes when I want to do
something special...