[LRFlex] Re: David's 20D tests

David -

Thanks for your detailed report on your own specific findings.

Baffling, indeed.

By the way, Canon did come back with the all-too-predictable "...the camera does not support non Canon lenses, so go away" kindof thing.

I'll get back to y'all after my next round of digging.

Bob Palmieri



On Jul 31, 2005, at 2:22 PM, David Young wrote:

Good Mornin' Bob!

I've just taken my 20D outside, with a 90 Summicron and fotodiox adapter, to take the series you requested.

BTW, it's a bright, but overcast day... very even illumination... great for such tests.

And the results are in!

At f2, and f2.8 the LCD (top) display shows a blinking 8000, indicating that 1/8000th of a second is still too long, and I need to stop down.
That being said, the exposure for the white wall (lucky for you, it's still white! I'm painting it pale green, next week!) is an even grey (gray?) at f2, and a slightly darker grey at f2.8

At f4, the meter cannot decide if it wants to indicate 1/8000th, or 1/6400th of a second. No matter, the wall is a bit more underexposed at f4.

At f5.6 and below, the indicated shutter responds, as it should, going down by one stop, with each stop closed on the lens.

However, the images get evenly darker, f-stop by f-stop, until by f11 it is just possible to make out the grain in the wood siding. At f16, the image is not 'black', but it is so dark that it is no longer possible to make out the siding's grain.

With the exception of the first two shots, which should be overexposed (they weren't!) the shots would indicate that the shutter speed has remained constant, despite indications on the display, to the contrary!

I discovered this phenomenon last week, when I was attempting some close ups with the 50 Summi and an Elpro. I'd focus, wide open, and then close down to f11 for max DOF. The photos came out black! Shoot 'em again, near wide open, and they were fine.

All this aside, I've taken thousands of shots with my 20D, using the 50 Summi, 90 Summi, 80~200/f4 Vario and the 400 Telyt. The last two have seen extensive use with the 2x converter as well. In these 'real world' shots, nearly all shot at no more than 1 or 2 stops below wide open, there has never been a problem exposure.

However, like you, I remain baffled by these, and your, test results.

Do let us know, if you find the answer!

Cheers!





David Young,
Logan Lake, BC
CANADA.

Personal Web-site at: http://www3.telus.net/~telyt
Leica Reflex Forum web-page: http://www3.telus.net/~telyt/lrflex.htm

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