Archived posting to the Leica Users Group, 2010/03/21
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Le 21 mars 10 ? 19:27, Henning Wulff a ?crit : > > At 11:08 AM +0100 3/21/10, philippe.amard wrote: >> Le 21 mars 10 ? 01:08, John Nebel a ?crit : >> >>> >>> Philippe, >>> >>> Rabs put it this way: "it's a medium format camera in a 35mm >>> package. Delight in its deceptiveness." >>> >>> S2 has an f/2.5 lens vs the M's f/1.4 (or f/1.0 or even f/.95) and >>> is slower due to the larger image circle. The S2 sensor is >>> 45x30mm and the M's is 36x24mm. >>> >>> Maybe it is not correct, but I was thinking of a projector as an >>> analog, move it farther from the screen and the image is bigger, >>> but darker. Twice the diagonal size, 1/4 the brightness as the >>> lamp has to illuminate the equivalent of four of the original >>> images. Makes me think of the Meno. >>> >> >> 80/2,8 = 40/1,4 = 28.5714 >> >> you get different aperture (f) values, but the amount of light is >> the same as the 'hole' is the same, or am I completely mistaken in >> the aperture calculation formula? >> >> http://fr.wikipedia.org/wiki/Ouverture_(photographie) >> >> I would bet that the absence of faster f value on a MF/LF sensitive >> media lenses results from other considerations such as angle and >> light fall out in the outer parts of the sheet/film/sensor. >> >> >> At the other end of the size spectrum, if we take the Pana 4/3 >> pancake you'd get 20/1.7 = 11.7647 a smaller hole, hence slower >> speeds? unless compensated by the electronics ? with less fall-out >> issues? >> I really don't know. >> >> >> Thanks >> Philippe > > > If the hole is the same size (physical aperture, not relative > aperture or f/ number) then the amount of light is the same, but the > sensor/film is larger, and that amount of light is spread over a > larger area so that's why the relative aperture is the one that > makes sense, and is what we use. Well, I never made a difference in the reading of my Gossen Lunasix when I used to shoot the Mamiya C3 or another 24x36 manual camera ... I must have always got something wrong then. > > Faster lenses on MF cameras don't exist because: on a 6x7 camera > (approximately twice the linear magnification of 35mm) an f/1.4 > normal lens would weigh about 6x as much, and would probably cost > more by an even larger factor if it was approaching decent. this makes perfect sense to me. > Then there is the focussing and dof issue. I also get this. > Then there is the film flatness issue. So you would wind up with a > 3kg, $10 to 25k lens that you couldn't reliably focus and had > insufficient dof. Not a big seller. OK > > Your comments about m4/3 I don't understand. However, fast lenses in > smaller formats have existed for a while, I know this Henning - the thing was about the smaller diameter allowing light to get in - f 0.9 doesn't make sense if you don't know the focal length , hence the diameter and the amount of light that gets in I guess. This was why I had doubts about the 4/3 , which have no faster lens than 1.4 for 50 or 2 at 200 ... Puzzles me - I'll get back to my Instamatic as soon as I find film :-) Thanks for the input Henning. Bien cordialement de Metz Philippe > like the 13mm f/0.9 Switar for Bolex 8mm. It was a truly superb lens > and it was for sale 50 years ago. 8mm movie film never produced > crystal clarity, but that Switar was able to get the most out of it. > > -- > > * Henning J. Wulff > /|\ Wulff Photography & Design > /###\ mailto:henningw at archiphoto.com > |[ ]| http://www.archiphoto.com > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information >