Re: birding-aus RFI - kowa scope conveter

Subject: Re: birding-aus RFI - kowa scope conveter
From: mark chappell <>
Date: Wed, 11 Aug 1999 08:45:28 +1000
>      Good evening,   I have recently made a down payment on a Kowa scope
>-   TSN something or other..............  I am toying with the idea of
>buying a  Kowa photographic converter. I am not the backend of a wildlife
>photographer nor  have I ever tried to take any wildlife shots however i
>am optimistic that  perhaps with this new flash setup i may be able to
>have a go....I recognise that  there are limitations with this but I would
>like these limitations spealt  out. Finally my question; Have any Birding
>ausers had any  experience with taking photos using the above set-up? If
>so is it a reasonable  proposition? Any feedback, admissions of pros or
>cons would be very  welcome.   ta muchly, Ken Cross

Dear Ken:  I've little experience with Kowa scopes (they're supposed to be
very good) but I have done a lot of wildlife photography with various
lenses, including a Questar scope.  I think the usefulness of the Kowa
scope + photo adapter depends a lot on what you want from it.  If you are
looking for documentation-type images, it's probably OK.  However, I'm a
bit skeptical that it will yield really high-quality photos (as one sees
printed half- or full-page in glossy nature publications).  Most
telescope-camera setups are combinations of fairly high magnification and
low speed (light-gathering ability).  This means you have serious problems
of camera shake (which requires a BIG tripod to solve, or perhaps a beanbag
if you have something handy -- like a car window -- to prop the setup on),
coupled with slow shutter speeds.  You can partially get around this by
using fast film, but that also degrades image quality compared to slower
emulsions (such as Kodachrome 64).  Depending on the particular scope, you
may also experience darkness in the corners of the image (in other words,
the image doesn't quite cover the whole 35mm frame).  Other matters of
possible concern:
-- convection cells in the atmosphere ("heat waves") are often a problem --
they are magnified along with everything else.
-- wind-induced vibrations (until you try it, you won't believe how
frustrating it is to attempt to use a long lens on a windy day).
--  due to the low light levels, it may be difficult to focus the image
(many viewfinder screens are designed for reasonably fast lenses and become
fairly hard to use at low f-stops)
-- vibrations due to the camera's mirror and shutter motions, even if the
equipment is on a strong tripod (see below).
-- how close does it focus?  If your scope is equivalent to an 800 mm lens,
you will need to have a minimum focus distance of about 3-4 meters for a
frame-filling picture of a small bird.

As I said earlier, I've had a Questar for about 25 years, and it is
absolutely wonderful optically when used as a telescope.  However, I've
never been able to get photos from it that approach it's real optical
capability.  Despite use of a heavy metal brace between camera and
telescope, an extremely heavy tripod, and lifting the camera's mirror
before shooting (to eliminate mirror shake), the images were never as good
as I wanted.  After some experimentation I found that even without the
mirror movement, the motion of the first shutter curtain was sufficient to
shake the setup very slightly, producing image blur (and this was with a
Nikon camera with a quiet shutter).  Note that this shutter motion is
always present, but when using 'regular' lenses it is small enough to have
little or no effect on the image -- unlike at the very high magnifications
of the Questar (equivalent to roughly a 1600 mm lens).  So I went back to
using 'regular' telephoto lenses (400-600 mm), which magnify much less but
produce better images.

Having said all that, you probably won't know how the Kowa will work until
you try it.  You may have better luck than me, but these are some issues to
be aware of.  Hope this helps,  Mark Chappell

       Mark Chappell, Biology Department, UC Riverside
              until Aug '99:  C/O Dr. Bill Buttemer
       Dept. Biological Sciences, University of Wollongong
       Wollongong NSW 2522 AUSTRALIA

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