Overexposure with 60D and manual M42 lenses

Hi guys,

I've noticed a strange problem and would appreciate any help or suggestions.

I recently upgraded from 300D to 60D. With the 60D, when I use any of my four manual M42 lenses (with an adapter), I notice that the smaller the aperture, the more overexposure I get. I'll give an examples:

I set the mode to Av
I set the camera to f/1.8

I set the lens to f/2.8, the camera sets the shutter speed to 1/320

When I change the lens to f/4 (close one stop) the speed changes to 1/125 (instead of 1/160)
When I change the lens to f/5.6 the speed changes to 1/40 (instead of 1/80)
When I change the lens to f/8 the speed changes to 1/13 (instead of 1/40)

All this time the ISO and the Av on the camera are constant.
This happens with all metering modes.
On my 300D this works fine with the same adapter and lenses.

Has anyone else seen this?
Is this a knows issue? Can it be fixed somehow?

Thanks!

http://forums.dpreview.com/forums/read.asp?forum=1029&message=38769947

are you always using the same M42 to EF adapter, or each lens
has its own? and what is the reported f-number??

jpr2
--
~
street candids (non-interactive):
http://www.flickriver.com/photos/qmusaget/sets/72157609618638319/
music and dance:
http://www.flickriver.com/photos/qmusaget/sets/72157600341265280/
B&W:
http://www.flickriver.com/photos/qmusaget/sets/72157623306407882/
wildlife & macro:
http://www.flickriver.com/photos/qmusaget/sets/72157600341377106/
interactive street:
http://www.flickriver.com/photos/qmusaget/sets/72157623181919323/

Comments and critique are always welcome!
~

I had this exact problem with adapted Contax lenses until I switched to the Ef-S focusing screen, which has rock-solid stable metering (at least with Center-Weighted Average) with manual lenses.

Others say they have no problems with cut-down Ec-A focusing screens, which have true ground matte (as well as microprisms) and thus are easier to focus than the rather grainy Ef-S screen, but I've never used one.

If you want an OEM solution for a low price (35 USD), get the Ef-S focusing screen.

Thank you both!

I read some more on this topic and decided I want the cut-down Ec-A focusing screen from http://www.focusingscreen.com .

However, for 40D, 50D or 60D they only have the K3 focusing screen in stock, and they haven't responded to my email asking them about that.

Does anyone have any experience with them? Is there another way to contact them? Phone number? Can I get cut-down Ec-A from another source?

Thanks!

all the info about the K3 I was able to gather so far:

http://search.dpreview.com/index.php?q=jpr2+K3&page=0&scope=Forums&forumid=Equipment&age=All&field=All&results=Default&sort=Date&view=Default

as to the Ec-A - if you're with some gumption and good at precise works
it is possible to cut Ec-A yourself, the shape needed is pretty simple. The
original substrate costs about $35, so even if you'd use two for trial
and error (it is rather easy to scratch the surface if one is not very
thorough and careful) it will be lass than the one from Taiwan (they
do it in batches, so after a while their supply jumps from zero, but
you'd need to watch their site daily),

jpr2

yniq said:

Thank you both!

I read some more on this topic and decided I want the cut-down Ec-A focusing screen from http://www.focusingscreen.com .

However, for 40D, 50D or 60D they only have the K3 focusing screen in stock, and they haven't responded to my email asking them about that.

Does anyone have any experience with them? Is there another way to contact them? Phone number? Can I get cut-down Ec-A from another source?

Click to expand...

--
~
street candids (non-interactive):
http://www.flickriver.com/photos/qmusaget/sets/72157609618638319/
music and dance:
http://www.flickriver.com/photos/qmusaget/sets/72157600341265280/
B&W:
http://www.flickriver.com/photos/qmusaget/sets/72157623306407882/
wildlife & macro:
http://www.flickriver.com/photos/qmusaget/sets/72157600341377106/
interactive street:
http://www.flickriver.com/photos/qmusaget/sets/72157623181919323/

Comments and critique are always welcome!
~

I got tired of waiting for focusingscreen.com and I wasn't going to cut down a focusing screen myself, so I finally got the canon EF-S focusing screen. Metering finally seems fine now. Thanks everybody!

What? I think you are missleading some concepts here. Focus screen has nothing to do with metering system. Light reflected in the main mirror goes trough focusing screen and then through pentaprism to reach finally you eye. Metering system, located on the bottom of the body, get their own light from a secondary mirror. Please look at this picture:

yniq said:

...

I recently upgraded from 300D to 60D. With the 60D, when I use any of my four manual M42 lenses (with an adapter), I notice that the smaller the aperture, the more overexposure I get. I'll give an examples:
...

Click to expand...

It is a known problem with lenses without a rom chip.

Read here:
http://nemeng.com/leica/002f.shtml
at the paragraph "Canon EOS snafus" about at the end of the article.

Also here:
http://www.bobatkins.com/photography/eosfaq/manual_focus_EOS.html
at the paragraph "Exposure and Metering" about at the end of the article.

I have the same problem with 50d camera.
I don't try with 300d.

A work-around is to shoot in live view mode.
In this way there are no more metering errors.

ciao

Bruno 0.5

UPS, Forget what I said before. I had a lapsus, that is the AF system not the metering system! Light meter sensor is located in the pentaprism, therefore focusing screens may affect exposure. MY MISTAKE!