Hi,
I had to go rather quickly over the list's posts today as I don't have much
time (busy at work, you know), so maybe your question has already been
answered (although I didn't see a reply):
> However, what's unanswered is this: when I view thru a telescope (2000mm
> f:10), using various eyepieces, the image is very bright, but becomes dark
> on the matt standard-issue screen in my OM1n. Not only that, but it's only
> on the matt surface that the image is dark--on the split-image/microprism
> aid, it's as bright as thru the tele's eyepieces. Ditto for various
> lenses--no matter how slow or fast they are, the focussing aid's image is
> bright as ever, and even perfectly sharp and focussed, stopped down lens
> or no. It's probably a virtual image?
[...]
> How does that work? How do the focussing aids work?
It's a long time ago that I had optics in a physics class, so I'm not 100%
certain anymore, but I think this is a phenomenon inherent to any type of
lens, where the image that is produced by rays of light coming in
perpendicularly through the very centre of the lens (i.e. in this case: the
ones that are projected on the centre of the focusing screen) should always
be sharp as these rays are not "bent" by the lens, contrary to the rays
coming in at other angles, or other parts of the lens. Correct me if I'm
wrong here.
As far as the brightness goes, I think the centre of focusing screens such
as the 1-13 etc. all consist of clear glass, so you can think of that, as if
you were looking through a window.
> So there seem to be an inverse relationship between finder brightness and
> fosussing ease. If that logic hold true, then the 2-series Oly screens
> will make for harder focussing under certain conditions, yes?
That sounds pretty much correct. Let's compare the 1-4 against the 2-4, you
will notice that the 2-4 screen produces less well defined out of focus
details than the 1-4 screen does, that is, with the 2-4 the out of focus
parts look much coarser than with the 1-4. Therefore, I guess that the
brightness of the 2-4 screen is obtained by having less "grains" on the
focusing screen than are present on the 1-4, hence I take the relationship
to be: more grain = better detail = darker image. Again, I'm not 100%
certain, but to me it seems that that is the trade off that exists in these
screens...
Hopefully I haven't just made an *rse of myself, but I think these are the
proper explanations for these phenomenons...
Cheers!
Olafo
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|