obi-wan-yj

I have a couple of manual lenses (a brand new, cheapo 500mm f/8 and a 40-yr-old

Pentax Super-Takumar 50mm f/1.4) that I mate via different adapters to my

XTi/400D. Neither adapter has a focus confirmation chip, but I plan to get one

soon for the Takumar. Shooting in Av mode with either lens, my XTi wants to

overexpose the shot by roughly a full stop. I have to forcibly tell the camera

to underexpose the shot by -0.7 to -1.3 stops (depending on aperture, it seems)

in order to get a reasonable exposure. This isn't a huge deal when I want a

normal exposure, but I fear that someday I'm really going to want to underexpose

a shot by two stops, and I won't be able to because I'm already starting out at

-1. This also makes it hard for me to let anybody else use the camera (manual

focus & aperture not withstanding).

The exposure is set perfectly when using any of my EF lenses.

Is this a common problem when using manual lenses on EOS bodies? I've never

heard of it in any of the web pages I've read. With the 500mm, which I've had

for a few months, I used to just write it off as being an artifact of the cheap

lens. Now that I'm seeing the same behavior with my recently acquired Takumar,

I think it must be more than that.

Is there a good way around this? Will a focus confirmation adapter affect this

at all on the 50/1.4? I'm at a loss here.

I get the same effect on my XTi, but not quite as bad, regardless of the exposure time I use. It occurs even at small fractions of a second, so I doubt the automatic noise reduction is the issue. They occur in the same place regardless of which lens I use. Here's a full-res example shot of the inside of my lens cap (it's slow):

http://tatooine.jedi.com/digicam/2007/20070618/IMG_8618.JPG

I showed these to my only local dealer, and they said they'd never seen the problem before, but that I should definitely send the camera in to Canon for warranty repair, which would take 4-6 weeks. I'm probably going to do that once my summer traveling is done with.

I've seen posts from several other people who have the same problem, but I've never heard from anybody after they've had it fixed to know what the solution was. A coworker who bought an XTi just a couple weeks after I did doesn't have any of these hot pixels on his sensor.