Leica advertises their R extenders for use ONLY on lenses of f/2 or smaller. Is there a physical/optical reason why you can't use the 2X APO extender with the latest 80mm f/1.4 ROM lens? I can see why the 1.4 extender might physically not fit because of its forward bulge but don't see why the 2X wouldn't work. Thanks for info. LB

-- Luther Berry (lberrytx@aol.com), November 23, 2001

Answers

Nikon has a similar limitatiom on their 2x converters. It is the size of the converter's optics that limit it to f/2.

-- John Collier (jbcollier@powersurfr.com), November 23, 2001.

As long as it doesn't physically damage the glass, give it a try. You may get some corner fall-off, and/or degraded sharpness or contrast, but only you can say whether the results are good enough for you.

-- Ken Shipman (kennyshipman@aol.com), November 23, 2001.

And try some shots stopped down to f/2 or smaller, that may "cure" whatever ills (if any) are present at f/1.4.

-- Jay (infinitydt@aol.com), November 23, 2001.

FWIW, if you test this and it fits, there are several possible operating reasons why it won't perform perfectly with an ultrafast lens.

1. The optics of the 2X may not be able to 'see' the full f/1.4 lens area. This could lead to vignetting, as mentioned above, or simply that the combination acts as a 170mm f/4 even with the aperture set to 1.4, because the TC never 'sees' more than f/2 or thereabouts.

2. Even with Leica, there may be some play in the stop-down actuating mechanisms, which gets multiplied by 2 (lens-to-TC and TC-to-camera). This can lead to uneven exposures at SMALLER apertures and fast shutter speeds - the aperture has a long way to move and is still in the process of closing down from 1.4 to (say) f/11 when the shutter opens. In this case the first part of the frame uncovered gets more exposure than the rest. Nikon warns about this with its TCs.

In addition, TCs sometime just work differently with different optical designs. Nikon's standard manual-focus 2x vignettes significantly more with the AF 180 f/2.8 than with the MF 180 f/2.8 - just something to do with how the glass and the tube designs interact.

-- Andy Piper (apidens@denver.infi.net), November 24, 2001.

I suspect it is not recommended because the Summilux is a speciality lens with no doubt plenty of aberrations left which will cause poor quality with a teleconvertor. What Leica are saying is that they do not feel "responsible" for the resulting image quality (i.e. in their opinion it is not good enough to be up to Leica spec). You can use it and see what you think though.

-- Robin Smith (smith_robin@hotmail.com), November 26, 2001.