Archived posting to the Leica Users Group, 2004/01/09
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]- ----- Original Message ----- From: "Seth Rosner" <sethrosner@direcway.com> To: <leica-users@mejac.palo-alto.ca.us> Sent: Friday, January 09, 2004 12:59 Subject: Re: [Leica] DR Summicron MTF (was: For your information) > Akhil wrote: > > > The reason I asked about chromatic abberations is because I have several > DR's S/Ns ranging from 1,7xx,xxx to 2,2xx,xxx and also examples of the later > 50mm Summicrons; not one of the DR's gives me the "snap" of the later > lenses, yet your data seems to indicate comparable MTFs. I am trying to > figure out why. > > Chromatic is only one of the aberrations that degrade images. Well, I mentioned chromatic abberation as, TTBOMK, white light MTF's cannot measure it. Perhaps a little clarification is in order. When analyzing at data it is important to know how and under what conditions the data was obtained, hence my questions on the light source, distance etc. I'm looking forward to seeng the curves when your article is published. >As Erwin Puts > has correctly stated, different lenses have what he calls different > "fingerprints". What fingrprint pleases you, says Erwin, is a matter of > taste. Again, he's right. As to your DR Summicrons, at what apertures are > you shooting? The contrast of the DR at f/2 does not match the current lens, > as I have written. OK- but this was not in your original post. > So if you shoot mainly wide open, your negs and slides > will not have quite the "snap" of the current 50. DR contrast gets closer at > f/2,8 and is very close indeed at f/4, 5,6 and 8; in fact at these > apertures, DR contrast at some points on the film plane exceeds that of the > current 50. So in comparing lenses, one has always has to ask what am I > looking for at each of the parameters. Yes. I do use the lenses at wider openings. K64 is my film of choice. > Also remember that "sharpness" is not a objective, quantifiable value as are > contrast and resolution. Sharpness is the impression the human eye gets from > perceiving an image. A high contrast, medium resolution image is going to > appear "sharper" than a medium contrast, high resolution image. Because at > any level of frequency, 5, 10, 20, 40 or more line pairs/mm, sharper > definition of the edge of the image (greater contrast) will enhance the > impression of sharpness. > As you have read from other LUGGERS, there are those who really like the > singular quality of the images that the DR/Rigid produces. And if they do > not need f/2 most of the time, it is the lens they will use most of the > time. > I like the DR- I wouldn't own a bunch of them if I didn't. - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html