----- Original Message -----
Sent: Wednesday, April 03, 2002 12:20
PM
Subject: Re: [APML] Large Format
Question
Hello Shekhar:
I've included some replys to your questions:
Shekhar Borde wrote:
Craig,
>
> 1. The lenses for these cameras were generally
meant to be stopped down
> to f/16. Some have nice large
apertures for focusing but that's all
> they're good for. If
your lucky you might get away with f/8.
>
f/8 is pretty fast for a large format lens (from what I know of them,
which
is very little). Is there a particular lens that you
think would be pretty
good at f/8 w.r.t sharpness over the entire
field and even illumination
out to the edge? I have heard
that LF lenses have a fairly steep light
falloff towards the edge
if they are not stopped down to f/16 or more.
A nice lens design I've heard
good things about is the old "Ektar" series, in particular the 135mm which if
I remember correctly was an f/2.8 . And yes, the Large Format lenses have
terrible vignetting until their stopped down
The other problem is flexure. You
can't really use bellows with this thing
can you? Is there
a fixed length extension tube (for lack of a better term)
that
one can get use between the lensboard and film back? It could be
the correct length so that the camera is approximately focused at
infinity.
A helical focuser or something equivalent would then
let you fine tune the
focus by a few mm on either
side.
This is why I suggested the old
Press Cameras because they were built to take a lot more punishment then even
modern "Studio" view cameras
> 2. Unlike 35mm and medium format, the
4x5 film holders do not have a
> pressure plate to hold the
film flat. The use of small f-stops helps to
> compensate for
this.
>
I know Hutech (www.hutech.com) sells a large format (4x5) vacuum
back
which is basically a modified Toyo or Horseman. It's
not cheap though.
I have noticed that there is a much larger
market in Japan for these
things.
Jack Schmidling (http://user.mc.net/arf/cam.htm)
sells a more affordable
version of a 4x5 vacuum back.
Sounds Interesting, I'll have
to check it out, Thanks
Shekhar
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