Sanford Posted February 25, 2005 Share Posted February 25, 2005 Somebody asked me this today and I had no answer. Link to comment Share on other sites More sharing options...
stephen hazelton Posted February 25, 2005 Share Posted February 25, 2005 On the misc lens I have, some have finder mark, some don't, for no apparent reason. Maybe relates to popularity of IR at the instant they designed the lens. Supposedly some lenses are corrected well enough into the IR that they don't require a focus shift. And if you shoot through a red filter (and not the opaque ones), you shouldn't need a focus shift. Link to comment Share on other sites More sharing options...
eliot_rosen1 Posted February 25, 2005 Share Posted February 25, 2005 Leica stopped putting IR markers on its M lenses sometime in the late 60s or so. Why, I don't know. They probably thought they were no longer useful. Link to comment Share on other sites More sharing options...
alan_wilder1 Posted February 25, 2005 Share Posted February 25, 2005 My recollection from previous Leitz publications on the matter was that the position of the mark would differ for various types of IR film. Therefore, they advise the photographer to determine the position on their own through trial and error focus bracketing for a given IR film. I distinctly remember this from G.Osterloh's book because he had a picture of a 90/2 with a series of lines taped to the distance scale to be used for such purpose. AFAIC it's either b.s. or Leitz being overly consevative since they're the only ones that does this. Link to comment Share on other sites More sharing options...
jtdnyc Posted February 25, 2005 Share Posted February 25, 2005 Like Alan, I recall older publications that claimed different IR films would have different points of focus. However, I wonder whether the issue was really the filter used, rather than the film. For example, a visually opaque filter would have a different wavelength cut-off than a deep red filter would. A focus mark appropriate for one filter might not be appropriate for another. There are in fact lenses that are corrected for IR as well as visible light, but Leitz/Leica never claimed that the Summicron 50 is one of them. By the way, to get an approximate IR focus, simply move the focused distance to the d.o.f mark for f/5.6. (I believe it's the righthand d.o.f. mark that is approximately where the IR mark used to be.) That, plus a small aperture, should give sufficient depth of field for adequate focus. Link to comment Share on other sites More sharing options...
ronald_moravec1 Posted February 26, 2005 Share Posted February 26, 2005 I have done extensive testing with most Leica lenses and IR and must agree with Mr. Davis. All the lenses that are marked are 5.6 on the right side and the ones that are not, I correct to that point for Kodak HIE and 092 filter. Older more simple glass seems to work better than more complex lens formulations. 3.5 Summaron, 3.5 elmar 50, 90 elmar, 135 Hector, all work very well in IR refocused to 5.6. 12&15&25 CV are fine too, as are 21 pre asph and the 28 with the 49mm filter size. If you shoot R, the 28 shift is a killer with IR and is marked at 5,6. 35/70 first zoom with 60mm filter is ok, but you need to figure where the 5.6 mark whould be if the lens were marked. I can`t remember how I did mine as there is no dof scale. Probably copied distances from fixed focal length lenses. The only total flop I had was the 70/210 zoom, but perhaps I just need to work some more with it. It is fine for normal photography. All my work has been with 092 and 093 filters. I use a an aux finder with the R cameras so I don`t have to remove the opague filter. FINAL Caution. Tape over the pressure plate of the R cameras or you WILL get a waffle pattern all over your negs if the film has no anti-halation backing. I`m going to dedicate a original Leicaflex to IR and add a Lee Polyester between the film rails. This camera has a smooth pressure plate like the m. Any meter in a m or r body or the clip on meter should be set to 800 or 1000 and you can meter right thru the filter. Observe normal meter practice and get a good average, not a tree that that is supposed to turn white. I don`t bracket or meter in full sun. 1/250 at 6.3 with the 092, add two stops for the 093. Follow above instructions for shade. Develope per Kodak instructions for D76 undiluted, I think it is 8 min or 8 1/2. Link to comment Share on other sites More sharing options...
eliot_rosen1 Posted February 26, 2005 Share Posted February 26, 2005 The position of the IR mark is also dependent upon the particular lens. Thus, the current 90/2 and 135/3.4 lenses which are apochromatically corrected would probably require little or no IR correction. An APO lens is not necessarily fully corrected for the IR spectrum, but its degree of correction would be greater than for the corresponding non-APO lens. Of course, none of the 50 mm lenses has APO correction, although the current 50/1.4 M ASPH does use APO glass. Leitz was probably correct to omit the IR index mark, because the position where the mark should be is so variable. But I have also heard that the F/5.6 tick mark can be used as a first guess, at least for 50 mm lenses. Link to comment Share on other sites More sharing options...
Uhooru Posted February 27, 2005 Share Posted February 27, 2005 There are some good website info on IR. ONe of them said the Summicron's were sufficiantly corrected. I used my M6 Summicron 50 and 35, red 25 filter. Set film speed to 340 and got good results. I didn't compensate focus at all. Developed as 125 PanX in HC 110. The only problem I had was learning the hard way that you must load the stuff in complete darkness, I mean complete. While we're talking why not show some?? <img src="http://d6d2h4gfvy8t8.cloudfront.net/708516-lg.jpg"> Link to comment Share on other sites More sharing options...
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