20D - Manual Mode: I can't adjust the Aperture - Why?

When I have been using manual mode I am able to adjust the shutter speed using the quick dial just fine. But, when I try to adjust aperture with the Quick Dial (the big wheel on the camera back) nothing happens. The viewfinder shows the aperture as 5.6 and nothing I do can change it. Yes, my power switch is set to the second "on" position, with the white line.

It's driving me crazy. I've checked the manual. Checked online help with Canon. No help anywhere.

Please let me know if you have an answer. FYI my firmware version is 1.1.0

Much thanks,

--gmaize

Obvious question, what lens is fitted ? Presumably its is not a fixed aperture lens.

Secondly are you not able to change it at all or can you only get smaller apertures? For some lens 5.6 is the maximum, you should be able to get 6.7, 8 etc but not 4.5 or 2.8.

Thirdly does this lens work normally in P mode on the 20D?

Finally do other lenses work ok and does this lens work ok with other bodies?

Sorry for obvious questions, but you already know that the rear wheel should work in these circumstances so we need more info.

Mark,

The rear wheel seems to work in all other modes and when scrolling menus and photos.

The lens is not a fixed aperture. I have a 28-80 USM, 75-300 USM and the 100 Macro 2.8. Just before I wrote this original post I tried bothe the 28-80 and the 100 Macro and had the same problem.

I get no change in aperature at all. Even if I set the speed to a point where the graphic exposure scale in the viewfinder is deadcenter I can't get the exposure settings to move in either direction.

The lenses work fine in all other modes....as best as I can tell. I have done a complete check through all modes. But the lenses were used today in Av, Tv and P just fine.

Good question about whether it works OK on other bodies. I'll check it out on my Elan II.

Thanks for your feedback. Let me know if you have any further ideas.

--gmaize

Mark,

I just check the 28-80 on my Elan II in manual mode and the rear wheel does worked just fine as I would have expected.

--gmaize

Check if you have switched the power to the On (Wheel Mode On - 2nd on notch), if you have it on the first On notch, the wheel is disabled. THe wheel is used to adjust the appeture.

Just something to try.

Khiem.

The power switch was indeed set to the second "on" position with the white line....and still not aperture control.

Ideas anyone???

--gmaize

Hmm, none at the moment..., sorry i couldn't help more.

M mode, the front dial controls shutter speed, and the rear dial controls aperture.

---Bob Gross---

Robert,

Yes I agree. The problem I am having is when using the rear wheel in an attmpt to adjust the aperture, nothing happens. I can't increase or decrease the aperture setting at all.

Still stumped.....

--gmaize

Can you change the exposure time?

It really sounds like either the on switch isn't turned all the way around, or the switch is faulty. Does the rear dial change the exposure compensation when you're in Av mode?

Tim,

Thanks for checking in. I always find your thoughts and advise very useful. I tried to adjust the exposure compensation in Av mode and was not able to do it. Interesting, now I have two faults. I did notice that if use the rear wheel to adjust the AF-WB, Drive-ISO, Metering and Flash compensation, I am able to perform those adjustments just fine. So I think the rear wheel is working, it just does not in certain instances....the manual mode exposure control and Av mode exposure compensation control.

Really strange!!!

Any other ideas??

--gmaize

You're sure you've got the on-off-extra switch in the right position? It's a 3 position switch, not a 2 position. It could be it's faulty.

One more thing to try - set all the custom functions to normal or default.

Some of these change the control actions, though I can't remember if any affect the rear wheel.

Also clean the lens and camera body contacts just to be sure they are making a good connection.

Tim,

Yes indeed, the power switch is in the third position. Checked it several times. I even tried to hold the switch with some extra pressure into the higher position. You may be right, it could be a faulty switch. Are there any other functions I could check that require the switch in position number 3?

Thanks for the feedback!

--gmaize

Must be the switch. Can you take it to where you got it from and see what they say? That way you can compare with another camera and see what you rekon.