25mm f/2 Photar data required

[pgk]

Hi All

I've just joined here and am looking for some data. I have a late 25mm f/2 Photar which I am looking for data about. From my existing research it appears that it should offer around 3:1 to 7:1 reproduction on full frame 35mm (I use Canon 5D and 5D2 cameras) based on the Leica R bellows. From looking through posts it looks as though its optimum aperture for stacking is f/2.8? Does anyone know what the optimum bellows extension is for this lens? I intend to use it for field work and do have it securely attached to the camera via various adapters and would rather work with a rigid fixed reproduction ratio for the images that I have in mind. Any data would be much appreciated - I do have a copy of Leitz's "The Leica R in the near-focusing range" publication which is handy but no other information about this lens other than by repute it should be relatively versatile.

[enricosavazzi]

Hi pkg,

according to my notes, this lens is said by Leitz/Leica to be optimised for 6.3x to 20x. I am not sure where I got this information, but it should be reliable.

I have one, and depending on the magnification you should stop it down up to 2 stops below 5x, 1 stop between 5x and 7.5x and use it fully open at higher magnification if you want the maximum resolution. Diffraction visibly reduces resolution even when fully open above 10x (in the sense that the sensor of an average DSLR will outresolve the fully open lens above approximately 10x).

[mgoodm3]

f/2.8 is about the sharpest aperture for that lens. I have seen the mag range listed as 3:1 - 8:1. I have a Nikon PB-4 and can go from about 3:1 to 9.5:1 with it. If I put it directly on the camera with or without an extension tube, I can get down to about 2:1 on my D200. That may not work with a full-frame detector.

[dunksargent]

William White in his book "Photomacrography" published 1987 shows a matrix with "Magnification range - best performance" for Leitz Photars, Zeiss Luminars, Nikon Macro Nikkors, Olympus Zuiko Macro and Polaroid bellows lenses. The 25mm Photar listed is the f2.5 for which mag. 7x to 16x is shown.

In an article from a 1970s 'Leica Photography' magazine, date unknown, entitled 'Leitz lenses for the Leicaflex and Leica' by P. Holm, matrices show reproduction ratios for various Leitz lenses including the Micro Summars and Photars. The 24mm and 25mm are shown as having best performance at 7x to over 16x. But on the focusing bellows II and Bellows R , the 25mm is shown as having a maximum mag. of 7.3x which presumably is at maximum bellows extension. The article also includes a matrix showing Pupillary Ratios for various Leitz lenses ie "exit pupil diameter/entrance pupil diameter", with the 25mm Photar pupillary ratio shown as 0.91 (referred to as 'Pupil enlargement in the article) . Another matrix shows exposure increases necessary for various magnifications within pupillary ratios.

Cheers

dunk

Edit 20.45 hrs : Hi Paul, When I first posted this reply, I did not realise whom I was addressing!

Cheers

dunk