----- Original Message ----- From: "Gene Johnson" <genej2@xxxxxxx> To: <pure-silver@xxxxxxxxxxxxx> Sent: Monday, March 14, 2005 3:33 PM Subject: [pure-silver] Re: Tominon, Ysaron > BTW, with regard to these lenses, Doesn't anyone but me > think it's > interesting that they should make them exactly 127mm f4.7? > > I think this is a limitation of the shutter maximum aperture. For instance, Kodak made two versions of the Ektar used on the Medalist camera. The Medalist lens was 100mm, f/3.5, the stand alone version for 3x4 press cameras was 105mm, f/3.7. The ratio of the focal lengths and stops is exactly the same. Someone once said that Rudolf Kingslake said in a lecture that both lenses used exactly the same elements but spaced to change the focal length. I think that can't be quite true because such a change would probably throw off all the corrections. But, you never know and I don't have the prescriptions for either lens. The 127mm, f/4.7 Ektar as used on press cameras, is limited by the maximum clear aperture of the No.2 Kodak Supermatic shutter. The next larger size shutter is much larger and operates only to 1/200th second rather than to 1/400th. 127mm is exactly 5 inches and is the right diagonal for 3-3/4 x 4-3/4. The Kodak Ektar is remarkable in being able to cover 4x5 with corner to corner sharpness at f/8. This lens was used on 4x5 press cameras because press photographers wanted a slightly wide angle lens. The 135mm Tessar, which was standard on 4x5 Speed Graphics is also somewhat wide angle for the format. Normal is 152mm. --- Richard Knoppow Los Angeles, CA, USA dickburk@xxxxxxxxxxxxx ============================================================================================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.