Hi everyone. I'd like to give infrared film a try with my Leicaflex SL system. I haven't noticed any kind of "infrared indexing mark" on the focus ring on any of my lenses. Other camera makers seem to include these. Is shooting this kind of film out of the question if I can't know which to point to adjust the focus of my lenses? Did Leitz forget about this fine point? Or am I missing something?

-- Bo Pryszlak (natabo@aztec-net.com), May 25, 2001

Answers

Maybe it's because they are so damn sharp!

Hell, I bet radio waves, micro waves, infrared, visible light, ultra violet, x-rays and even gamma rays all converege on the same point on the film!!!

Go R lenses!

-- Mike Foster (mike567@acgecorp.com), May 25, 2001.

                    SPECTRUM  OF LIGHT
       _______________________________________________________



       UV                                        RED    INFRARED
       
       |<---------- most            lens -------------|



               |< ---------- Leica lens ----------------------| 




 Most lenses passes UV, but left IR light undercorrected to fall 
behind the film plane, therefore, for most lenses an IR index is 
necessary for IR photography; most lenses also need UV filter to
cut out UV light.  



      Leica lenses are designed to cut out UV light completely and 
their in focus spectrum is shifted to include IR, therefore, no UV 
filter is necessary (except for protection purpose ) and no IR index 
is necessary

-- martin tai (martin.tai@capcanada.com), May 26, 2001.

Hi Usually shifting for focus when using ir film is not needed especially if you use f16 or so , especially if you shoot at infinity.By the way , I have found the the summicron is a bit too sharp for ir which benefits from a softer focus.

Leonid

-- leonid kotlyar (murkacat@hotmail.com), May 26, 2001.

My Vario-Elmar 28-70/f3.5-4.5 was made by Sigma, but it is not identical to Sigma 28-70/3.5-4.5-- the lens coating conforms to Leica redintion, and there is no IR index marker

My Sigma 80-200 zoom for Contax has red IR index mark, so I suspect that Sigma 28-70 lens must have IR mark.

-- martin tai (martin.tai@capcanada.com), May 27, 2001.