For the fwiw department, a casual comparison of two old lenses on 6x7, the 105 f2.8 Xenotar (first purchased by a user in South America in 1956) and a 90 f6.8 Angulon. Subject was film boxes in a row, photographed from about 10 feet away.

The first "decent" aperture for the Xenotar was f8, with the center getting pretty crispy while the outer thirds were progressively soft. Sides improved at f11, then decent overall at f16.

In case you're wondering, performance is horrible at f2.8 with a _very_ slight improvement at f4, but focusing at f2.8 is wonderful.

For the Angulon, it lagged behind by a stop.

An unintended part of this test involved film flatness. I'd shot a series of six on HP5+ in a Graflex RH-10 leverwind back, the let the film sit overnight. The next day I shot some infinity-focus shots with the Xenotar; there were no apparent flatness defects in either the frame that was flat across the pressure plate overnight or the following four. Infinity remained at infinity, at least at f16.

-- John Hicks (jbh@magicnet.net), August 06, 2000

Answers

I love reading stuff like this. I wish more people would submit their test results. Of course you can never take another person's results as gospel but this kind of thing gives you a really good place to start with your own queries. Thanks very much for posting it. If anybody is interested, I posted a result of a lens coverage test of the 90 mm angulon on www.gnushack.com. Barely gets to the corners of a 5x7 and is pretty soft when it arrives there.

-- Erik Ryberg (ryberg@seanet.com), August 07, 2000.

Hi John. Your test report makes my glad that you outbid me for that lens. But are you sure that you don't have an imcorrectly located focal plane? I once bought a used camera where the ground glass had been reversed -- drove me crazy! Regards, Mitch

-- Bill Mitchell (bmitch@home.com), August 07, 2000.

> imcorrectly located focal plane

I don't think so; there's no sign of the plane of sharpest focus being ahead of or behind where it's supposed to be.

-- John Hicks (jbh@magicnet.net), August 07, 2000.