Re: [APML] Piggyback 4x5

["Joseph O'Neil" <joneil@multiboard.com>]

>3.  Most lenses for 4x5 cameras are not that fast.  I think the fastest is
>f/4.5 but most are around f/5.6 or even f/8.  I used a Caltar lens wide open
>at f/5.6 and the aberrations were terrible.  Stars at the corners looked
>liked alien mother ships! <g>  Most 4x5 lenses are made to be shot at f/11,
>f/16, f/32 or f/64.

-snip-
         Caltar lenses were int he past made by several different 
manufactuers.  Recent vintage they are suppoed to be made by Rodenstock, 
suppsoedly at the same standards as Rodenstock, but I have always wondered 
if they are exactly the same, why are they always less money?

         Still, you point is a good one, most LF lenses are not suitable 
for astro-photo use, IMO.  Your average "press lens", 135mm Ektars & their 
ilk are soft at the extreme edge even on daytime shots.

         The "trick " appears to be to get a lens that is for larger 
coverage then what you are shooting.  Fro exmapel, i am waiting for a 180mm 
lens (Schneider) to come back from being remounted in a shutter.  It covers 
5x7, with spare movements.  *Usually*, and i say this with some 
trepidation, the "gunky" stars will be in the outer 20% or so of the image 
circle, so when you use an "oversized" lens, you are basically using the 
"sweet spot" in th emiddle of the lens.
         Still, F5.6 is the average spped of a "fast" LF lens, and you'll 
probally stop it it down one stop to F8, making for a long, slow exposure.


>4.  I used Tri-X film, not too good for recording much except stars.  This
>was before E200 etc....  I didn't get into TP.


         If anyone wants to try just for fun, use Tmax, 100 or 400 
B&W.  It's probally the easiet 4x5 film to find anymore (tri-x is often a 
special order, in 4x5, believe it or not!  argh!).
         Red response still sucks big time, but reciprocity failure isn't 
nearly as poor as many other films, and IMO, matches E200 in this regard.
joe


http://www.oneilphoto.on.ca
http://www.multiboard.com/~joneil
Una salus victis, nullam sperare salutem


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