------------------------------------------------------- FidoNet PHOTO Conference<->InterNet EMail List To subscribe to the list, send an EMail message to: listserv@wnybbs.net With the words: SUBSCRIBE PHOTO To Unsubscribe: UNSUBSCRIBE PHOTO To post a message to the list, send E-Mail to: photo@wnybbs.net ------------------------------------------------------- --- * Origin: WNYBBS FidoNet<->InterNet E-Mail Gateway (1:2613/10) --------------- FIDO MESSAGE AREA==> TOPIC: 137 PHOTOGRAPHY Ref: F5G00032 Date: 04/15/98 From: "BOB HAYES" Time: 04:13pm \/To: ALL (Read 0 times) Subj: Re: Comparing Photos From: "Bob Hayes" Subject: Re: Comparing Photos > Not when you measure character/mm. > > For instance, I have a picture taken with Minox B, Techpan rated > at ASA 25, developed in Rodinal Special fine grain developer > "ONE WAY STREE" "ONE" measured 1.5mm in a 10 x 12 " enlargement > that is 2 char/mm . The enlargement factor was 31 x from Minox > 8x11mm film, and the resolution = 62 character/mm on film. > > Which is about twice the resolution of any 35mm lens I tested. I know I won't be the only one to catch it, but I'll be the only one to tease you Martin. If you had shot a sign that was spelled right, your numbers would be different. giggle ------------------------------------------------------- FidoNet PHOTO Conference<->InterNet EMail List To subscribe to the list, send an EMail message to: listserv@wnybbs.net With the words: SUBSCRIBE PHOTO To Unsubscribe: UNSUBSCRIBE PHOTO To post a message to the list, send E-Mail to: photo@wnybbs.net ------------------------------------------------------- --- * Origin: WNYBBS FidoNet<->InterNet E-Mail Gateway (1:2613/10) --------------- FIDO MESSAGE AREA==> TOPIC: 137 PHOTOGRAPHY Ref: F5G00033 Date: 04/15/98 From: BRUCE FEIST Time: 08:22pm \/To: ALL (Read 0 times) Subj: Re: Comparing Photos From: Bruce Feist Subject: Re: Comparing Photos Hi, Martin; Martin Tai wrote: > The standard film used in lens testing is Kodak Technical Pan. Why? Who sets this standard? > You cannot use different film for different lens, as film > contributes to unsharpness budget. I agree that it's a bad idea; my choice was based on pragmatism rather than sound experimental technique. On the other hand, a camera with a faster film proved sharper with most lenses than one with a slower film, which is more likely to be valid -- it may have understated the result. > Get a USAF lens test chart from Edmond Scientifc. I'll investigate this. > If you want to use ads, you need to quantitize the sharpness > One way to do it is to seek the smallest characters you can see > in the print under a loup, then measure the lens of character > then convert in to characters per mm on film. That would be a good thing to do, if I want to make my results more precise. I'm looking forward to seeing how my Minox does! Bruce ------------------------------------------------------- FidoNet PHOTO Conference<->InterNet EMail List To subscribe to the list, send an EMail message to: listserv@wnybbs.net With the words: SUBSCRIBE PHOTO To Unsubscribe: UNSUBSCRIBE PHOTO To post a message to the list, send E-Mail to: photo@wnybbs.net ------------------------------------------------------- --- * Origin: WNYBBS FidoNet<->InterNet E-Mail Gateway (1:2613/10) --------------- FIDO MESSAGE AREA==> TOPIC: 137 PHOTOGRAPHY Ref: F5G00034 Date: 04/15/98 From: BRUCE FEIST Time: 08:40pm \/To: ALL (Read 0 times) Subj: Re: Comparing Photos From: Bruce Feist Subject: Re: Comparing Photos Hi again, Martin; Martin Tai wrote: > -> kind of scale easily, and street scenes have too much variability. > > Not when you measure character/mm. Point well taken. By the way, I tried your suggestion; the result was rather low! I seem to be resolving a maximum of about 7-8 characters/mm. Actually, it's a bit better than that; that text was clear in some of the Leica photos, and it could have been smaller, but that's the smallest size in the ad. Of course, this is with commercially developed mass-market color film, but even so it seems out of line with the numbers you used as examples . > For instance, I have a picture taken with Minox B, Techpan rated > at ASA 25, developed in Rodinal Special fine grain developer > "ONE WAY STREE" "ONE" measured 1.5mm in a 10 x 12 " enlargement > that is 2 char/mm . The enlargement factor was 31 x from Minox > 8x11mm film, and the resolution = 62 character/mm on film. > > Which is about twice the resolution of any 35mm lens I tested. This isn't really fair comparison, given that by necessity the Minox film you used is ultra-sharp; 35mm systems don't need their sharpness to be as great per mm of film. As you said in your prior post, you have to use identical film for the measurement to be valid . What were you comparing the Techpan to? Bruce ------------------------------------------------------- FidoNet PHOTO Conference<->InterNet EMail List To subscribe to the list, send an EMail message to: listserv@wnybbs.net With the words: SUBSCRIBE PHOTO To Unsubscribe: UNSUBSCRIBE PHOTO To post a message to the list, send E-Mail to: photo@wnybbs.net