Re: [Largeformat] Optimal aperture

["Pete Caluori" <pcaluori@hotmail.com>]

>From: David <davidsnd@yahoo.com>
>Reply-To: Largeformat@egroups.com
>To: Largeformat@egroups.com
>Subject: [Largeformat] Optimal aperture
>Date: Fri, 1 Sep 2000 08:04:34 -0700 (PDT)
>
>Hello all you LF'ers,
>
>I've been on this list for about a couple weeks now
>and appreciate reading your posts.  It's great to get
>ideas from others using the same medium.  I have a
>question:
>
>I have a 180mm Nikkor and a 100mm Ektar Super Wide
>that I use with my newly acquired 4x5 field camera
>(thanks Jess) and am very satisfied with the results
>of both.  I would like to know if any of you know what
>the optimal aperture would be for these lenses (the
>aperture at which lens aberrations and refraction are
>minimally affecting the image quality)  Any help would
>be appreciated.
>
>Thanks,  David

Greetings David,

I dont mean this as a wise crack, but since all lenses are different, why 
not test your's to determine optimum aperture.  You don't need to go through 
great expense to do this.  You can use B&W negative film and simply look at 
the negatives; there's no need to print them.

Choose a fine grained, sharp film - Kodak's Technical Pan film is excellent 
in this application - and shoot a finely detailed subject that completely 
covers the frame all the way out to the edges.  Then make a test shot at 
each aperture and evaluate the negatives with a loupe on a light box.

What you will most like observe, is a sharp central image and soft corners 
with the aperture wide open.  As you stop down, the corners/edges of the 
image will most likely sharpen to equal the center.  Then if diffraction 
becomes problematic you will see the entire image soften as you stop down 
further.

Good luck!

Regards,  Pete