RE: 200 f2.5 question, how can filter ring be 77mm?

2001-11-13 Thread J. C. O'Connell
SILLY ME I THOUGHT THEY WERE DESIGNED TO MEET A SPEC. jco > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED]]On Behalf Of Kent Gittings > Sent: Tuesday, November 13, 2001 9:54 AM > To: [EMAIL PROTECTED] > Subject: RE: 200 f2.5 question, how can f

RE: 200 f2.5 question, how can filter ring be 77mm?

2001-11-13 Thread Mick Maguire
]]On Behalf Of Knut Kampe Sent: Friday, November 09, 2001 12:59 PM To: [EMAIL PROTECTED] Subject: Re: 200 f2.5 question, how can filter ring be 77mm? At 09:18 09.11.01 -0600, you wrote: >Lets not forget in this discussion of the maximum f/stop of a >lens that the f/stop measurement is taken fr

RE: 200 f2.5 question, how can filter ring be 77mm?

2001-11-13 Thread Kent Gittings
Behalf Of Knut Kampe Sent: Friday, November 09, 2001 12:59 PM To: [EMAIL PROTECTED] Subject: Re: 200 f2.5 question, how can filter ring be 77mm? At 09:18 09.11.01 -0600, you wrote: >Lets not forget in this discussion of the maximum f/stop of a >lens that the f/stop measurement is taken fr

RE: 200 f2.5 question, how can filter ring be 77mm?

2001-11-09 Thread Kent Gittings
Correct. It can be larger but not smaller. Kent Gittings -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Frank Wajer Sent: Friday, November 09, 2001 11:43 AM To: pdml Subject: Re: 200 f2.5 question, how can filter ring be 77mm? > Lets not forget

Re: 200 f2.5 question, how can filter ring be 77mm?

2001-11-09 Thread Knut Kampe
At 09:18 09.11.01 -0600, you wrote: >Lets not forget in this discussion of the maximum f/stop of a >lens that the f/stop measurement is taken from the relationship >of the entrance pupil and the focal length. The actual diameter >of the front element is not part of the equation. >William Robb How

Re: 200 f2.5 question, how can filter ring be 77mm?

2001-11-09 Thread Anthony Farr
The f.no. calculation assumes that the lens is a simple design, eg. a single element or more likely a symmetrical design such as view cameras use. In practice a lot of long lenses are of the telephoto design which means they have a teleconverter built in. I bet the front element of this lens is

Re: 200 f2.5 question, how can filter ring be 77mm?

2001-11-09 Thread Frank Wajer
> Lets not forget in this discussion of the maximum f/stop of a > lens that the f/stop measurement is taken from the relationship > of the entrance pupil and the focal length. The actual diameter > of the front element is not part of the equation. The entrance pupil is always smaller or equal to

Re: 200 f2.5 question, how can filter ring be 77mm?

2001-11-09 Thread William Robb
Lets not forget in this discussion of the maximum f/stop of a lens that the f/stop measurement is taken from the relationship of the entrance pupil and the focal length. The actual diameter of the front element is not part of the equation. William Robb - This message is from the Pentax-Discuss Mai

Re: 200 f2.5 question, how can filter ring be 77mm?

2001-11-09 Thread Fred
>on kmp.bdimitrov.de I saw the specs of the 200 f2.5 lens. It says that >the filter ring is 77mm, but this means that the lens cannot be f2.5, >as that would mean a minimum 80mm filter ring! Can anyone explain? BTW. >Isn't it save to have some margin between the filter ring and what is >calculated

Re: 200 f2.5 question, how can filter ring be 77mm?

2001-11-09 Thread Knut Kampe
At 13:34 09.11.01 +0100, you wrote: >On Fri 2001-11-09 (11:30), Frank Wajer wrote: >> on kmp.bdimitrov.de I saw the specs of the 200 f2.5 lens. It says that the >> filter >> ring is 77mm, but this means that the lens cannot be f2.5, as that would >> mean >> a minimum 80mm filter ring! >> >> Can

Re: 200 f2.5 question, how can filter ring be 77mm?

2001-11-09 Thread Antti-Pekka Virjonen
>On Fri 2001-11-09 (11:30), Frank Wajer wrote: >> on kmp.bdimitrov.de I saw the specs of the 200 f2.5 lens. It says that the >> filter >> ring is 77mm, but this means that the lens cannot be f2.5, as that would >> mean >> a minimum 80mm filter ring! >> >> Can anyone explain? It's not uncommon

Re: 200 f2.5 question, how can filter ring be 77mm?

2001-11-09 Thread Tom Rittenhouse
- The optimist's cup is half full, The pessimist's is half empty, The wise man enjoys his drink. - Original Message - From: Frank Wajer <[EMAIL PROTECTED]> To: pdml <[EMAIL PROTECTED]> Sent: Friday, November 09, 2001 5:30 AM Subject: 200 f2.5 question, how can filte

Re: 200 f2.5 question, how can filter ring be 77mm?

2001-11-09 Thread Martin Trautmann
On Fri 2001-11-09 (11:30), Frank Wajer wrote: > on kmp.bdimitrov.de I saw the specs of the 200 f2.5 lens. It says that the > filter > ring is 77mm, but this means that the lens cannot be f2.5, as that would > mean > a minimum 80mm filter ring! > > Can anyone explain? A good observation. In fa

Re: 200 f2.5 question, how can filter ring be 77mm?

2001-11-09 Thread Rfsindg
Frank, I can't explain, but it is definitely a 77mm filter and cap sitting on the one I have here. Regards, Bob S. [EMAIL PROTECTED] writes: << on kmp.bdimitrov.de I saw the specs of the 200 f2.5 lens. It says that the filter ring is 77mm, but this means that the lens cannot be f2.5, as th

200 f2.5 question, how can filter ring be 77mm?

2001-11-09 Thread Frank Wajer
Hi, on kmp.bdimitrov.de I saw the specs of the 200 f2.5 lens. It says that the filter ring is 77mm, but this means that the lens cannot be f2.5, as that would mean a minimum 80mm filter ring! Can anyone explain? BTW. Isn't it save to have some margin between the filter ring and what is calcu