[rollei_list] Re: OT f-stop progressions
- From: CarlosMFreaza <cmfreaza@xxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Thu, 25 Feb 2010 17:49:12 -0300
It's true and one of the few exceptions is my Pentax A ED Green Star*
SMC 2.8/200mm (6 elements-6 groups)prime lens, great manual lens, the
first element has a pretty impressive diameter for a 35mm format lens,
the smallest f/stop is f 32. This lens has 8 big blades forming the
iris and they form like a second little iris around the f/stop
aperture from f/11 to f/32, it's like a little "flower" clearly
protruding from the iris aperture at f/32 to reduce difraction. I
don't recall if I used it at f/32, I think not because I always use it
camera handheld, this is its technical data:
http://kmp.bdimitrov.de/lenses/primes/tele/A200f2.8.html
Carlos
2010/2/25 Eric Goldstein <egoldste@xxxxxxxxx>:
> f/32 shot on miniature format would suffer from pronounced diffraction/poor
> resolution. That's why you don't see stops smaller than f/22 (often f/16) on
> 35 mm format lenses with very few exceptions...
>
>
> Eric Goldstein
>
> --
>
> On Thu, Feb 25, 2010 at 2:07 PM, Mark Rabiner <mark@xxxxxxxxxxxxxxxx> wrote:
>>
>> > actually there are 3 standard stops in that range, 16, 22 and 32.
>> >
>> > i hope this google doc links works, but here is a simple spreadsheet
>> > that shows the arithmetic for standard f-stops.
>> >
>> >
>> > http://spreadsheets.google.com/ccc?key=0AsQMiOSFwKfmdHZYRjhWZlZFdGZmdHRseV9nRU
>> > gwd2c&hl=en
>> >
>> > NB: what we call f22 is really closer to f23.
>> >
>> > -rei
>>
>>
>> The first lens I ever got my my first serious camera a just out Nikon F2
>> had
>> f 32 on it in the early 70's
>> It was a just out 45mm2.8 GN pancake. What the Germans would call a Blitz
>> lens as you could couple the f stops with the shutter speeds. GN means
>> guide
>> number. You could set it. Because of it going down to f32 you could shoot
>> with a non automatic flash as close as THREE FEET!
>> And get infinity in focus. But dark.
>> I got to know and love f32. But soon found it was the last I was ever
>> going
>> to see of it. Except in a view camera lens.
>>
>> F 32 and be there is what I say!
>>
>> I still have that lens by the way. Not AI'd.
>>
>> [Rabs]
>> Mark William Rabiner
>>
>>
>>
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>
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