Problems With Under Exposure

kjonnnn wrote in post #14636651
The data in Bridge says..

Created 6-25, 9:41pm
15.0s at f1.4 +5 ISO 100
Focal length 505mm

BOTTOM PHOTO
Created 6-25-2012, 9:43pm
15.0s at f1/4 +5 ISO100
Focal length 455mm

Go Figure.....

Where does one buy a lens that goes into 455mm-505mm range, especially one which is capable of f/1.4 ?!

Diagnosis: Sick camera. Send to Canon for emergency surgery.

Wilt wrote in post #14639075
Diagnosis: Sick camera. Send to Canon for emergency surgery.

I would not yet give up...we obviously don't have valid EXIF information as a start. Perhaps this is from the PNP file format, perhaps the lens isn't communicating properly with the camera, but so far we haven't had good information that we can use for helping the OP.

John from PA wrote in post #14639181
I would not yet give up...we obviously don't have valid EXIF information as a start. Perhaps this is from the PNP file format, perhaps the lens isn't communicating properly with the camera, but so far we haven't had good information that we can use for helping the OP.

Agreed. And the issue might be with the lens, and its communication of bogus information to the body.

If the camera is receiving bad lens information then it might not be surprising that the exposure is wrong, but the flower image in post #5 was shot with manual exposure according to the EXIF. How can the camera be blamed for bad exposure under those circumstances? According to the EXIF, the XSi image in post #8 was also made using manual exposure.

What could be going on with the camera? Here are a couple possibilities that might account for these strange results. Either the camera has lost its marbles or some of the settings are out of whack.

• If the cameras processor has lost its marbles, some of the functions are apparently still functioning correctly and there is no error code. That seems to rule out the processor.
  
• I am wondering if possibly the Mode dial can slip on its shaft so that it appears that one mode is selected, but in actuality another mode is the true setting (such as Manual is selected while it appears that Av is the setting). The PNG format might be responsible for all of the garbled EXIF data especially if it was edited in Paint Shop Pro (for example, I don't believe the 15 second exposure reported in EXIF s well as the phenomenal 500+ mm f/1.4 lens).

Bill,
If the lens information is bogus, the camera might have correcly commanded f/8 but the aperture actually closed to f/16.

OP needs to verify if a different lens behaves correctly or not. If the camera is at fault, exposures would be bad with both lenses. If the lens is at fault, changing lenses will resolve the problem.

Also, the issue might be with a bad meter, or the issue might be with an improper shutter speed or aperture, where the selected value is not the actual value used...for example, meter correctly says ISO 100, 1/100 f/16 (per Sunny 16), but the shutter speed or aperture or ISO used was not matching those values.

Wilt wrote in post #14639701
Bill,
If the lens information is bogus, the camera might have correcly commanded f/8 but the aperture actually closed to f/16.

OP needs to verify if a different lens behaves correctly or not. If the camera is at fault, exposures would be bad with both lenses. If the lens is at fault, changing lenses will resolve the problem.

Also, the issue might be with a bad meter, or the issue might be with an improper shutter speed or aperture, where the selected value is not the actual value used...for example, meter correctly says ISO 100, 1/100 f/16 (per Sunny 16), but the shutter speed or aperture or ISO used was not matching those values.

Bad communication with the lens sounds plausible to me. I wonder if it's just a dirty or corroded contact? I'd try scrubbing the contacts with a pencil eraser to clean them up.

Wilt wrote in post #14639701
Bill,
If the lens information is bogus, the camera might have correcly commanded f/8 but the aperture actually closed to f/16.

OP needs to verify if a different lens behaves correctly or not. If the camera is at fault, exposures would be bad with both lenses. If the lens is at fault, changing lenses will resolve the problem.

Also, the issue might be with a bad meter, or the issue might be with an improper shutter speed or aperture, where the selected value is not the actual value used...for example, meter correctly says ISO 100, 1/100 f/16 (per Sunny 16), but the shutter speed or aperture or ISO used was not matching those values.

I agree. Being a very complex electromechanical device, it is actually pretty amazing how long a DSLR goes between failures.

I found that Photoshop does not save EXIF data in PNG files so I am a bit surprised that the OP's PNG images show EXIF when viewed using Bridge, but not when using other applications. My take is that any EXIF data that I see is probably some corrupted vestige of the original and that the PNG format does not officially support EXIF data.

Alright, looks like it may be lens related. Hopefully the EXIF is still intact with these. I uploaded them to photobucket, straight from the card. Yes they were shot in Manual, so I could be sure it would have the same settings in each photo. The goal wasn't to get perfect exposure, the goal was to rule out variables for a test. Sorry the first one is blurry, that's what I get for just free holding with a 300mm lens haha.

Canon 450D with 300mm lens
http://i127.photobucke​t.com …rokenChainsX/IM​G_1668.jpg

Canon 450D with 105mm lens
http://i127.photobucke​t.com …rokenChainsX/IM​G_1669.jpg

Canon Power Shot SX130 IS
http://i127.photobucke​t.com …rokenChainsX/IM​G_2461.jpg

EsotericForest wrote in post #14641756
Alright, looks like it may be lens related. Hopefully the EXIF is still intact with these. I uploaded them to photobucket, straight from the card. Yes they were shot in Manual, so I could be sure it would have the same settings in each photo. The goal wasn't to get perfect exposure, the goal was to rule out variables for a test. Sorry the first one is blurry, that's what I get for just free holding with a 300mm lens haha.

Canon 450D with 300mm lens
http://i127.photobucke​t.com …rokenChainsX/IM​G_1668.jpg

Canon 450D with 105mm lens
http://i127.photobucke​t.com …rokenChainsX/IM​G_1669.jpg

Canon Power Shot SX130 IS
http://i127.photobucke​t.com …rokenChainsX/IM​G_2461.jpg

OK, 105mm underexposed at 1/100 f/8 on your camera, yet 300mm was fine at same 1/100 f/8 exposure on your camera. And your wife's camera exposed just fine at 1/100 f/8, too.
Therefore, I blame the 105mm lens, since your camera performed fine with the 300mm lens and your wife's camera was fine with same indicated exposure.

The connectors on my 105mm lens look clean, so wonder what the problem is.

A test...

1. Zoom the lens to max FL
   
2. Put the camera on Av mode, and set aperture dial to wide open
   
3. Press in on the DOF Preview button while looking in the front of the lens...
   
4. ...and (while continuing to press DOF Preview) turn the control dial to select successively smaller apertures
   

Wilt wrote in post #14641852
A test...

1. Zoom the lens to max FL
   
2. Put the camera on Av mode, and set aperture dial to wide open
   
3. Press in on the DOF Preview button while looking in the front of the lens...
   
4. ...and (while continuing to press DOF Preview) turn the control dial to select successively smaller apertures

Watch to make sure that, for each smaller f/stop, you see the visible change in aperture diameter shrinking in size.

Perhaps a bit easier to see ... rather than looking through the viewfinder is to look straight into the objective lens while holding down the DOF preview button and rolling the thumbwheel next to the shutter. You can easily see the iris size stepping from one value to another if the lens is working correctly. Since you saw the same problem in Manual, do the same test in that mode except roll the large thumbwheel on the back of the camera. Oops -- just remembered that Rebels are configured differently -- use whatever the buttons are for adjusting the aperture setting in those two modes. I suspect that the mechanism that moves the iris blades is hung up at the smallest opening on the 105 mm lens.

Bill Boehme wrote in post #14642325
Perhaps a bit easier to see ... rather than looking through the viewfinder is to look straight into the objective lens while holding down the DOF preview button and rolling the thumbwheel next to the shutter. You can easily see the iris size stepping from one value to another if the lens is working correctly. Since you saw the same problem in Manual, do the same test in that mode except roll the large thumbwheel on the back of the camera. Oops -- just remembered that Rebels are configured differently -- use whatever the buttons are for adjusting the aperture setting in those two modes. I suspect that the mechanism that moves the iris blades is hung up at the smallest opening on the 105 mm lens.

My test instruction was

Wilt wrote in post #14642418
My test instruction was

Press in on the DOF Preview button while looking in the front of the lens...

Duuuh! It was way past my bed time. I guess that is why I thought that you said to look through the viewfinder. Sorry for exposing my non-functioning brain cells.

Bill Boehme wrote in post #14644840
Duuuh! It was way past my bed time. I guess that is why I thought that you said to look through the viewfinder. Sorry for exposing my non-functioning brain cells.

That's OK, I sometimes have brain flatulence, too. I later come back and fix the posted evidence of brain flatulence in posts, when I later return to my senses.