Hopefully someone can help me out here.

I've been using MF lenses with chipped adapter rings from big-is and happypagehk on a Canon XT for about two years, and never had a problem with the accuracy of the stop-down metering being within two stops and usually being absolutely spot on. Then my XT recently died, and I took advantage of the Canon Loyalty Program to upgrade to a 50D.

I could have sworn when I first put some MF lenses on the 50D that I was getting stop-down metering. But now I seem to have lost it. Wide-open, with the chip programmed with the correct max. aperture, metering is spot-on. The more I stop the lens down, the farther off the metering gets. It's as if the body's doing wide-open metering, not stop-down. These are the same lenses and rings that I was using just fine on the XT, with two exceptions, one of which is a new big-is EMF-chipped ring (Contax->EOS), which does the wide-open metering and sets the aperture in the EXIF. (The other exception is a programmable happypagehk Contax-> EOS ring).

Does anybody know of a way to force the body to perform stop-down metering again? (I tried snapping off a few shots without a lens mounted, and that didn't work). And has anybody else had this happen to them after using one of big-is's EMF chipped rings? Or is it just that my 50D always did this and I just need to get used to it?

I find it very annoying that I was getting better metering out of my XT.

Is it possible that your 50D is in one of the auto modes (e.g. landscape), instead of the "Creative Zone" of Av, Tv, M and etc. ?

Nope. I never go below the P, and usually shoot in M or Av--with an MF lens mounted, I'm always in M.

Well, for me, it always tends towards overexposure with my cameras the more you stop down...I've just learned to compensate with some EC.

Well, that's what I'm doing now. It just becomes a true PITA when I go beyond f/8 and I need to compensate more than two or three stops and I go off the end of the scale. I'm adjusting quickly, but it's annoying that I have to do this now when I didn't have to before.

I have a 50D and don't have any of the problems you are having. How do you have it set up to do metering? Is it set to a half shutter press or the star button on the back. Perhaps you are not reactivating metering after you stop down. Check you custom functions and make sure that you are in fact metering the scene again after stopping down. I have found metering to be excellent with the 50D and chipped adapters from the same sources, so I don't think it is the camera. I hope this helps.

I think it's set to half-press? Not sure. I don't think I've ever used the * button, honestly.

C.FnIV: 1 is set to 0: "Meter + AF start"
C.FnIV: 2 is set to 0: AF/ON/AE lock button switch: 0 Disable.

Is that what you mean?

The metering mode I'm using is Evaluative (I'm still getting used to the idea of having spot metering ).

It sounds like you have metering set to a half press of the shutter button, so if you hold the half press just a bit before you press the button fully you should get metering again before you shoot. Also keep in mind that if you are using M mode all the metering will do is tell you how far off you shutter speed is and the metering won't affect your shutter speed--you will have to change this manually. If you have it in Av mode metering will reset the shutter speed to what the camera thinks is the right exposure. I find that the camera in Av mode does pretty well. You say you shoot mostly in M mode, but you might want to try shooting more in Av mode. You might also want to set metering to center weighted, which I tend to like with alt lenses. I hope this helps.

Have you changed the focus screen?

Nope. Still the original one it came with. I tried messing with the focus screen settings to see if it made any difference, but the effect is the same with any of the settings.

Are you leaving the "in camera" aperture setting at max and then just rotating the aperture ring to stop down?

I would try three things. First, cover the eyepiece before you shoot. When the lens is stopped down a disproportionate amount of light is metered from light entering through the viewfinder, relative to the lens, and affects exposure, especially if you pull your eye away from the eyepiece during metering.
The next thing I would try is live view while stopped down and see if the camera meters properly that way.
As a last resort put some tape over the contacts on the chipped adapter. I've had problems with chipped adapters before.
Dan
www.danbrownphotography.com

pengland wrote:
Are you leaving the "in camera" aperture setting at max and then just rotating the aperture ring to stop down?

Yes. The chipped rings don't allow the aperture setting to be changed from the camera.

DanPBrown wrote:
I would try three things. First, cover the eyepiece before you shoot. When the lens is stopped down a disproportionate amount of light is metered from light entering through the viewfinder, relative to the lens, and affects exposure, especially if you pull your eye away from the eyepiece during metering.

I always have my eye to the eyepiece, so I don't think this is what's going on, but I just tried it, and I'm still getting the biased metering.

The next thing I would try is live view while stopped down and see if the camera meters properly that way.
Bingo! Works fine in liveview. Thanks! That takes care of most of the issues, since I'm likely to be using smaller aperture with a tripod anyway.

As a last resort put some tape over the contacts on the chipped adapter. I've had problems with chipped adapters before.
Actually, I don't think it's the chips, which is the weird part. I tried a Hartblei Super-Rotator (one of the old Russian-glass ones) on the camera this morning. It's essentially an adapted manual focus lens with no chip on the adapter. My aperture read "00", and I was still getting the unwanted metering bias.

Thanks, though, for the liveview tip. That's a good workaround. And thanks everybody for taking the time to help me with this. I don't feel so dumb about this, now.

Steve Spencer wrote:
... I find that the camera in Av mode does pretty well. You say you shoot mostly in M mode, but you might want to try shooting more in Av mode. You might also want to set metering to center weighted, which I tend to like with alt lenses. I hope this helps.
Thanks, I'll try it!

I've never had accurate metering with my alt lenses on my 40D, when stopped down. The deviations are different on each lens though.
I can confirm it doesn't depend on the AF-confirm chip. It does depend heavily on the focusing screen though. I used the Ef-s screen for some time and suddenly I needed to apply a heavy overexposure instead of underexposure...
(Now back to Ef-a because the Ef-s is way too dark when composing with a stopped down macro lens.)

Maybe I have to try center-weighted metering as well...

Thanks for the warning about the Ef-s screen, as I'm about to get one.

I also found that with Live View, I can't judge the exposure by the brightness of the picture on the LCD. When I increase the exposure time to be able to focus properly, I have to dial shutter speed back to what it was to get a proper exposure. Of course it's quicker to focus wide-open, but then you can't take focus shift and field curvature into account.

By the way: if you often compose with a stopped down lens, I wouldn't recommend using the Ef-s screen. Especially longer focal lengths (>100mm) get dark quickly. I think the Ef-s is mainly useful if you shoot at large apertures (under 2.8) very often and want to be able to accurately judge the DoF. I thought the Ef-s would also be useful for macro use, because the Ef-a often shows too much DoF, but the Ef-s just gets too dark in too many situations.

This hasn't been my experience with the Ef-s. I have no trouble using it with f/4 lenses and I have no trouble with metering. Aham, did you set the custom function to indicate you were using the Ef-s? In my case this did a great job of correcting for metering difficulties. With macro I almost always use live-view and have no trouble with any aperture. I really like the Ef-s screen and have found it to be wonderful for composition.