Re: [APML] Two BIG-telephoto-lens-related questions

[Matt BenDaniel <matt@starmatt.com>]

At 05:05 PM 5/13/2002, Emmanuele Sordini wrote:
>Hi folks,
>I've run into a VERY big telephoto lens, a 500mm-FL (f/4.5) Pentax SMC. 
>It's a little monster (weighs in at 3+ kg), it is about $800 used but in 
>mint condition and comes with its original case; it originally had a 
>Pentax bayonet mount that was subsequently converted to a Nikon one by a 
>very skilled machinist. Now come the questions:
>
>1) Is this lens any good for AP? I searched the 'Net extensively for some 
>reviews/shots, but I found almost nothing. I understand this lens is not 
>very common, but since it boasts a 11-cm objective lens, I've a hunch it 
>could be profitably used for AP.

My friend Daniel Verschatse just bought a Pentax 600mm f/4 and tried it for 
astro. First you must realize that securing such a lens to a mount in a 
flexure-free way is not trivial. Also, even though they're expensive, these 
lenses do tend to have chromatic aberration that will show up even on color 
film. You may be able to partially repair that using RegiStar. Daniel is 
keeping his Traveler.

>2) This may seem to be a dumb question, but have they ever made focal 
>reducers (or other thingies that could be used as such) for such long 
>telephoto lenses? I know that I could use a shorter FL lens, so it's not 
>as much of an issue as it is with telescopes, where you can't have one for 
>every potential need :-)) but I don't think I was the only one to ever ask 
>this question.

I've never heard of a focal reducer for Pentax lenses, and even if there 
were one, it would probably vignette.

>Any thoughts/ideas/experiences to share?
>Thanks in advance and clear skies from boggy Notherrn Italy,
>
>Emmanuele

--
Matt BenDaniel
matt@starmatt.com
http://starmatt.com


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