Do I have a bad lens? 50mm 1.8 overexposure issues.

[toner]

OK, I have a 20D. I bought a 50mm 1.8 and just started playing around with it. I'm a bit concerned I might have a bad copy. Once in a while I get the classic Err 99 with this lens (which I don't get with my other lenses), but today I was surprised at some real overexposure in P mode. If I put the camera into full Manual mode I could get a decent exposure. Am I missing something, or is something wrong here? Thanks in advance for any help you can all give.

First pic: ISO 100 P Mode
Shooting Mode Program AE
Tv( Shutter Speed ) 1/800
Av( Aperture Value ) 7.1
Exposure Compensation -1
http://cliffromig.smugmug.com/photos/57351246-M.jpg

Picture #2
Manual Exposure
1/2000
14.0
ISO Speed 100

http://cliffromig.smugmug.com/photos/57351236-M.jpg

[bolantej]

what did you meter off of? if it was the lens, then manual shot would be lousy as well.

[toner]

what did you meter off of? if it was the lens, then manual shot would be lousy as well.

I'm unclear on what you mean by "meter off of", sorry... Newbie here. I have a 100-400L, a 24-70L and a kit lens and none of those lenses have these issues. The 50mm 1.8 is the only lens that produces overexposed images or Err 99 messages. Shouldn't the camera automatically produce the image I shot on full manual?
(If I metered off of anything, it was off of the white building in the center of the picture. )

Cliff

[Specialhawk]

The thing is that this is just overexposed because of poor metering, which indicates more of a problem with your camera (since they are in auto modes). **Disclaimer** My camera doesnt have P mode so i'm not sure how it works.

In the properly exposed shot you are at ISO 100 f/14 1/2000 of a second
In the over exposed shot you are at ISO 100 f/7 1/800

Photography is all about balance between the three key components of capturing light:

Sensitvity to light (ISO)
Amount of light (f/stop)
Duartion of light (shutter speed)

Since your ISO is the same in each that has little effect in the difference

Going from f/14 to f/7.1 lets in twice as much light, which would mean your shutter speed would then have to be twice as fast, instead what happened in the over exposed shot is that it is actually twice as slow, which means that it is going to be roughly two stops brighter then it should be.

[cdifoto]

Just don't use the lens in P mode. ;)

[aparmley]

Lets assume your lens is fine for the time being. Why the obvious total over exposure of the scene? You could have inadvertantly locked the exposure - IE hit the exposure lock button while the camera was aimed elsewhere, ie the ground, dark grass something of that nature. . . pay attention to your meter next time, in the first photo it should have been all the way to the right and blinking telling you that you are going to severly over expose the image. . . that way you'd know if it was a metering problem.

[cdifoto]

Good call Andy. Very easy to hit that EL button without even realizing it when you have no flash mounted. At least with flash it becomes FEL and you see a pop of light hit the ground at your feet and you have a very visible warning to say "oh sh*t" and correct your booboo.

You also have some negative exposure compensation dialed in your first image there (which I didn't notice before). That's a stop of overexposure by itself.

[Specialhawk]

Good call Andy. Very easy to hit that EL button without even realizing it when you have no flash mounted. At least with flash it becomes FEL and you see a pop of light hit the ground at your feet and you have a very visible warning to say "oh sh*t" and correct your booboo.

You also have some negative exposure compensation dialed in your first image there (which I didn't notice before). That's a stop of overexposure by itself.

Indeed, i didnt even think of that, my EL button focuses so that didnt even cross my mind, but i remember when i had a 300D i did it all the time.

[toner]

The thing is, i took a whole bunch of pictures, not just two... I tried all kind of settings and the only way I could get a decent exposure was full manual. If I tried to take a picture of a less bright subject the camera did fine in P mode... It just couldn't handle anything sunny... My question really hasn't been answered, but perhaps I just don't know the right way to ask the question. If I'd had my 24-70, or 100-400, or even my kit lens, this would not have happened...
T.

[aparmley]

The thing is, i took a whole bunch of pictures, not just two... I tried all kind of settings and the only way I could get a decent exposure was full manual. If I tried to take a picture of a less bright subject the camera did fine in P mode... It just couldn't handle anything sunny... My question really hasn't been answered, but perhaps I just don't know the right way to ask the question. If I'd had my 24-70, or 100-400, or even my kit lens, this would not have happened...
T. Not to be short, but do you constantly get over exposed images with the 50? if yes then I'd say send it in for repair if not I'd say that the body controls the exposure, then lens doesn't if you over exposed its because of the camera. For me today I was shooting at 1.4 at ISO 100 and overexposed everything because the camera could not compensate for the amount of light at 1.4 and high noon, it tapped out at a SS of 1/4000. There is one senario where it is sorta the lens' fault. But you weren't wide open and you weren't using the fastest shutter speed, so all things point to metering here. I know exaclty what your asking and I suppose it isn't completely impossible that your lens is the issue if you feel that it happens enough with this lens and it always over exposes then I think you can be sure it IS the lens. The only thing I can come up with is faulty aperture reporting - if you were at say 1.8 would this be a problem. You say this was 7.1 - exif data is not intact, are we 100% sure it was at 7.1 - sounds right for auto mode but I want to be sure. . . We'd like to help you out believe me. we aren't saying its impossible. . . there are just a few other likely senarios that are little bit more likely. . .

[TheSteveMadden]

I suspect a faulty lens. It looks like the aperture blades are not stopping down and everything is being shot at 1.8 (wide open) regardless of body settings. If you look at your shots exposures as being 1/800@f1.8 and 1/2000@f1.8 ISO 100 the exposures are about what I would expect.

Try setting Av mode to f/11-22 and use the DOF preview button to see if the image gets darker in the viewfinder. This will test the aperture blade stop down capabilities of the lens.

s

[toner]

Thanks for that! If anything, I think it might be faulty aperture reporting... That's the exact EXIF data from the camera... Shouldn't the shutter speed should be much faster than 1/800 for a fairly open aperture of 7.1? This lens is so cheap, I don't know why I'm bothering to make a federal case out of it... Pluse there are the ERR 99 issues with this lens... Oh well, thanks for all the input...
T.

[mebailey]

Not heard of an err 99 with a Canon lens. I suspect a problem with the lens. I would return it if you can....

[TheSteveMadden]

If anything, I think it might be faulty aperture reporting... That's the exact EXIF data from the camera...

The lens doesn't report the actual aperture value back to the body. EXIF data contains what the camera told the lens it wanted, not what the lens acually stopped down to (or didn't stop down to, in your case).

Shouldn't the shutter speed should be much faster than 1/800 for a fairly open aperture of 7.1?

Nope, that seems just about the right exposure. Off the top of my head, the Sunny 16 rule for ISO 100 and f/7.1 should be within one stop of correct at 1/800s.

[aparmley]

Steve has a good case as well here. I guess I was speaking incorrectly about the bad reporting - camera says lens stop down to 7.1 and the lens' blades don't move - makes sense to me. . . except when he shoots in M. The blades would still get stuck but in this senario it was used to make the proper exposure - shoot f8 and look for DOF if you got a fair amount of bokeh I'd say steve nailed it on the head.

[Tee Why]

Your case sounds a little unusual. Mine works well. Error 99 detects lens incompatibility if I remember right. If you bought this new, I'd exchange it, if used, first clean the electronic contact points on the lens and see if that makes any difference.
Good luck

[toner]

A little follow up... I called Canon and described the problem... They asked if it happened with other lenses and I said "no". They told me to send it in. I just got an email saying they'd received the lens and that they'd be repairing it under warranty. A fair amount of effort for a $75.00 lens, but I'm looking forward to having it back in working condition.
T.

[Jackal]

Make sure to let us know what the fixed and if the problem went away. :)

[Jman13]

Yeah, there's no way 1/2000 at f/14 ISO 100 would yield a usable image in sunlight. A proper image at f/14 would be around 1/125 or so. Almost certainly your aperture was stuck. (you could have checked this yourself by seeing if the lens stopped itself down when you pressed the DOF preview button.)

[toner]

I did clean the contact points before calling Canon... I thought that might have solved the problem, but that was just wishful thinking as the Err99 came back after a few frames... Anyway, I'll let ya'll know what the problem was, that is, if they even bother to tell me when they send the lens back... Thanks for the feedback.
T.

[toner]

For anyone who cares...
I got the 50mm lens back today and here's what the repair ticket said:

Service Details
Replaced power diaphragm unit, checked projection, lens centering and all functions to factory specs.

Lens is working perfectly...

T.

[Tee Why]

Hey congrats,
I had a feeling it was the lens.

[RuggerJoe]

For anyone who cares...
I got the 50mm lens back today and here's what the repair ticket said:

Service Details
Replaced power diaphragm unit, checked projection, lens centering and all functions to factory specs.

Lens is working perfectly...

T.

Alway good to hear a happy ending.

[Livinthalife]

Congrats on your repair T.

[toner]

Thanks, folks! That ends that little Canon adventure... I remain a happy Canon junkie...
T.