Underexposed LCD screen query

[DeanB72]

Hi,

I have just bought a used 5d and have a question that I hope someone may be able to help with....

I have an old manual focus lens with an EOS adapter that I have used on my other camera (450D) and everything works fine, but when I fit this lens to my newly acquired 5D (using same adapter as on 450D), the LCD image is very very underexposed.  I haven't had chance to check whether the saved image is also underexposed or if it's just the LCD image.

I have found one similar issue on another forum and will try that but wondered if anyone here had come across this issue before ?

Thanks

[ebiggs1]

"I have just bought a used 5d ..."

Are you sure the 5D works properly.  If you are, there is something wrong with your old lens.  Using them on a DSLR is not recommended by me.

[DeanB72]

Thanks for the reply ebiggs1,

Yes, the camera seems to work ok having first mounted my 50mm f/1.8 ii.  If the old lenses don't work then I'll just put them on ebay.  Seems a bit strange how one of the adapters doesn't quite want to fit the 5D when it does the 450D.  I also experienced a similar problem trying to mount to a D60 a while back.  Makes me wonder if Canon changed the body recess very very slightly at the mount position before the 450D came out in 2008.

[ebiggs1]

The 5D has a EF mount but the Rebel also has a EF-S mount.  Maybe that is the issure.

It's just not a good idea to use those old film lens on new DSLR's.  Even though we used to love them.  I know.  

[RobertTheFat]

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@DeanB72 wrote:

Hi,

I have just bought a used 5d and have a question that I hope someone may be able to help with....

I have an old manual focus lens with an EOS adapter that I have used on my other camera (450D) and everything works fine, but when I fit this lens to my newly acquired 5D (using same adapter as on 450D), the LCD image is very very underexposed.  I haven't had chance to check whether the saved image is also underexposed or if it's just the LCD image.

I have found one similar issue on another forum and will try that but wondered if anyone here had come across this issue before ?

Thanks

---

Is it possible that your old lens isn't a preset lens, and that therefore the image presented to the LCD doesn't reflect the lens's maximum aperture? If, for example, the lens was intended for a rangefinder camera, there would be no need for a preset diaphragm. If that's the explanation, the brightness of the image in the viewfinder should vary with the aperture setting. Did you notice such an effect on your 450D? (I'm guessing that the 450D didn't have live view; my 400D didn't.)

[DeanB72]

Thanks for the replies. I investigated further last night and after looking at the photos properly I found that half of the image was obscured by the mirror hitting a protrusion from the back of the old lens (28mm Petri) which was causing only a fraction of the light to get to the sensor. I was able to unscrew and remove the offending obstruction and then everything works properly.

Robert.....Once I had resolved the issue, the brightness of the image in the viewfinder did change with aperture which I do not remember noticing on my 450D, which has got live view.