Photos overexposed

snapper8v

snapper8v

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Lawrence CLIFT
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Having been out in the snow today, a few of the images are way overexposed even though the same settings (1/250 f7.1 ISO 400 aperture priority evaluative metering)were used and the photos were taken with a quarter of a second or so of eachother. Am I doing something wrong with some settings or (as I fear) will it be a fault with the camera (1D MK111). Thanks.
LAWRENCE

1553_1764645.jpg


1553_1764646.jpg
 
I had this once and it was sticking aperture blades in the lens.

Have you tried another lens?
 
Probably nothing wrong with the settings and probably nothing wrong with the camera.

Are they the same shutter speed? If they are the same shutter speed, aperture and ISO then yes something may be wrong with the camera. As you are in AV mode I would assume the shutter speed has probably changed between the first and second image.

If the shutter speed has changed then dark jacket is confusing the metering. Metering is designed around an 18% grey (typical monochrome Caucasian skin tone). The metering is compensating for the dark jacket in the second image and trying to expose for 18% grey.

Where you have a large light or a large dark surface then you could change to manual exposure and spot metering and meter off the face or something which looks to be about 18% grey. You can also meter off the dark jacket and then underexpose by a stop or so.

In situations like this I tend to look for the dominant shade of light or dark and use partial metering and then adjust the exposure reading to compensate for the lightness or darkness of the area I metered from.

By the way, you can test this at home by changing to partial metering and then metering off the fridge (usually mainly white so should underexpose) and then off the floor (usually dark so should overexpose).

Hope this helps.

John
 
To John/All,
I shall go out again tomorrow and try different lens combinations, but I reckon the camera will be going bnack to canon, just to be on the safe side (I did have an error99 show up a few weeks ago?!?!).

What I don't get is that the images were taken a split second between eachother and the 2nd is way overexposed, even though the information shows that a 7.1 aperture was used along with a 1/250th shutter speed on both images. I've restored the factory settings just in case I've over ruled something, but I doubt it. Just getting paranoid now!
 
snapper8v

did you have a flash fire ?

As you say the shutter speed, the ISO and the aperture was identical between the shots then the only other thing (apart from a fault) is the light itself. This could easily be caused by light coming back off the snow clumps in the air. The snow seems to be far denser and closer in the second shot. If a flash fired it would reflect back off the snow.

John
 
Have you actually studied all the exif data from the files? THey are not the same exposure settings.
 
I would like to see the files WITH the EXIF data. I do not believe they are actually the same.
 
can't be the same exposure on the two shots, the metering must have picked up the black jacket and metered according to that.

No idea what so ever about your camera, but is there a chance you were using spot or very narrow centred weighted metering and you focus point has shifted from say the skin tone of the girl in #1 to teh jacket in #2. as the jacket in #2 has a lot more clearly visible details and the shadow is completely gone from the folds.

anyway, you need to use AE-L button when in priority settings for same compositions
 
Thanks for the replies. John, no flash was used. I went out in teh snow again today and used the 28-135mm with no problems! Below is the exif data, please bear with me here as this is the 1st time that I've used it and had to download it off the net:-

Photo;Date and Time;Exp. Time;F/Stop;Exp. Program;Exp. Bias;Metering Mode;Light Source;Flash;Focal Length;Focal Length (35 mm);ISO Speed;Orientation;Dimensions;File Size;Path;Tags

LOZ_0168;07/02/2009 12:45:14;1/250;7.1;Aperture Priority;0;Pattern;-;Not fired;70.0;-;400;Normal;3888 x 2592;4706 KB;H:\DCIM\101EOS1D\LOZ_0168.JPG

LOZ_0169;07/02/2009 12:45:14;1/250;7.1;Aperture Priority;0;Pattern;-;Not fired;70.0;-;400;Normal;3888 x 2592;4335 KB;H:\DCIM\101EOS1D\LOZ_0169.JPG

As you can see, both photos taken at the same time with the same setting information. I have 4 similar images all taken with the same settings, the 1st would be properly exposed wheeras the 2nd would be over exposed. My wifes got me paranoid now as the photos that she took (using the same equipment) were spot on. Maybe she should go out and shoot the weddings????
 
OK, so they've got the same EXIF data, which means something somewhere is wrong. I've had a play with the two shots in Lightroom, and it looks like #2 is over-exposed by about 2 stops.

It could be the camera - it thinks it's giving you 1/400th both times, but in #2 it's actually giving you about 1/100th.

It could be the lens - the camera is telling it to stop down to f/7.1 both times, but in #2 it's staying stuck wide open at something like f/3.5.

Or it could be the communication between the camera and the lens - the camera is telling the lens to stop down to f/7.1 both times, but in #2 the lens isn't getting the message properly and thinks it's been told f/3.5.

If #1 has been shot at 1/400th and #2 at 1/100th, we'd expect to see more motion blur in #2. I don't think I'm seeing that, but I can't be sure.

If #1 has been shot at f/7.1 and #2 at f/3.5. we'd expect to see a shallower DOF in #2. I think I could persuade myself that I am seeing that - the snowflakes are more OOF in #2 than in #1, I think - but I'm not sure.

Does that analysis give others some information to help with the diagnosis?
 
Hello all, just a quick update. I've just been speaking to a very helpful man at Sigma and he reckons that it's the lens. Upon his advice, I've been pressing the depth of field preview button and the results are inconsistent (@ f7.1 I was getting 4/10 then 1 second then 3/10 with the Sigma lens) whereas the Canon 28-135 was consistent every time. I've e-mailed a selection of images to Sigma at their request but I think I'll be sending the lens back to them tomorrow. Stewart, any chance of sending me a lens up to compare please??? ;-). Thanks.

LAWRENCE
 
I suggested the lens, as, like I said, I've had the same problem and with Sigma lenses.

In fact I've had three different Sigma lenses do the same thing (sticking aperture blades)
 
Just before I put this thread to bed, a quick update. I e-mailed Sigma a selection of images and 3 technicians all agreed that the lens was at fault. If I remember correctly, they reckoned that an electrical flex was the culprit. Apart from the cost (it's recently just come back from Sigma with a new motor installed) they couldn't guarantee that it would be completed by next Thursday (I've weddings on Friday & Saturday) so I've gone and bought a Canon 70-200 f2.8 non IS. I was intending purchasing one in the Summer, but hey.................Thanks to everyone for their input :clap:.

LAWRENCE
 
Interesting read... Something new I've learnt. :) Glad you managed to figure out the problem.
 
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