Re: UV was Re: IR film & X-Rays ?

["Willem-Jan Markerink" <w.j.markerink@xxxxx>]

On 30 Sep 96 at 2:34, Tom Benedict wrote:

>TMax 100, at least, works ok for UV (note I said "ok").  Exposures are
>long, the wavelength range is quite short, and focus shift can get to
>be a problem (same problem as IR, but in the opposite direction).

Well, I always thought that was the case too, but it seems as if UV
requires adjustment in the same direction as IR. At least Guenter 
Spitzing's book says so....and you also get into problems with 
infinity focus, since modern lenses have very little slop beyond 
infinity....;-))
The focus-error vs wavelength plot is a basically a symmetric 
hyperbole I believe, not one that runs to opposite ends with UV vs 
IR. 
For some nice ASCII art on these plots by Andy, check my homepage:
http://www.a1.nl/phomepag/markerink/mainpage.htm


> The pinhole camera will answer some questions since you can get the
> full UV spectral range without any attenuation.  You can also use a
> much smaller pinhole (shorter wavelengths), and get better resolution
> as a result.

On a side note: pinholes work better with UV than IR, because 
(edge) diffraction is less with shorter wavelengths. I have read 
argument in favor of pinholes more than once for UV photography.




 
 
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<w.j.markerink@xxxxx>
[note: 'a-one' & 'en-el'!]

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Topic No. 3