RE: [APML] 4x5 astrocamera (again?)

[Wei-Hao Wang <wang@IfA.Hawaii.Edu>]

Hi Kirk,

It's difficult to answer.  First, I use E100S a lot but almost never 
without pushing.  Even when the lens is fast (F2.8-F4), I tend to 
decrease the exposure a little and push it by 1 stop.  I just want a 
little more contrast.

With slow lens (F5.6) and two hours of exposure, the quick answer is, 
push no more than 1 stop.  Two hours are usually enough for E100S at F5.6.

A more detailed answer depends on the sky brightness (the light 
pollution) at your site.  If the sky is very bright, you may want to
decrease the exposure to make the sky look dark on the slide but
push 2 or even 3 stops to bring up the nebulas, Milky Way, or whatever.
Think it in this way:  The brightness on celestial bodies are fixed.
If the brightness of the sky background increases, then the contrast 
between the background and the celestial bodies decreases.  This is why
we need to push to compensate the contrast loss.

This is not that critical if your final productions are digital files.
You can do lots of things to modify the brightness and contrast.
However, this is critical if you want to view through a light box on 
your original slides.  In this case, the exposure-push combination needs 
to be very accurate to produce nice looking slides.

Check out these:
http://www.ifa.hawaii.edu/~wang/gallery/picutres/summer_mw-2003.htm
http://www.ifa.hawaii.edu/~wang/gallery/picutres/cassiopeia.html
Isn't the color of E100S beautiful?  These are just from 645 and 67
formats.  A well exposed 4x5 E100S will look awesome on a light box.

Cheers,

Wei-Hao



>From: Kirk Carbo <kcarbo@lobosservices.com>
>To: "'Discussion of Film Astrophotography'" <astro-photo@seds.org>
>Subject: RE: [APML] 4x5 astrocamera (again?)
>Date: Thu, 6 May 2004 16:56:41 -0500 
>
>Wei-Hao
>
>That's very interesting.  I have thought about doing more wide field shots
>with my view camera and slide film.  I was thinking a 4x5 slide is so large,
>it wouldn't even need to be printed.  It would look beautiful on a light
>box.  Are the on films being pushed needing 2 hour exposure or one hour?
>
>Kirk Carbo
>

______________________________________________________________________
Wei-Hao Wang  :)

Institute for Astronomy at University of Hawaii

Address:                       Phone: 808-956-9867                  
2680 Woodlawn Drive            Personal Website:
Honolulu, HI 96822             http://www.ifa.hawaii.edu/~wang
______________________________________________________________________



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