Same settings, same camera, same model lenses but different exposure.

dave_bass5

dave_bass5

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Dave
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At the weekend i was testing out two copies of the Tamron 24-70 f/2.8. Mine and my mates.
We set the camera up on a tripod, got the correct exposure for the test and locked everything down. AF was off, VC was off, full manual on the camera.
We took a couple of shots with each lens and viewed them in LR at 100%.
We noticed that one lens produced a slightly brighter image in all the tests. This was noticeable on the histogram in camera, by the different areas that were blinking to show blown highlights on the camera LCD and in LR.
It wasn't much, both produced good images, but having never done this sort of thing before im wondering if its normal.

Cheers.
 
No, like i said, everything was fixed before the first shot, plus i was using live view and thats fixed at Evaluative metering.
I can understand the histogram on the camera reporting slightly different readings, maybe the camera was moved very slightly when changing lenses, but it was noticeable looking at the full frame in lightroom.

Cheers.
 
So reading between the lines, the exposure details were the same for each shot with respect to aperture, shutter speed and ISO? So that puts metering out of the equation.

What was the source of lighting?
 
perhaps the aperture blade sizes on each shot were slightly off?

camera lenses are not build to as high standard as cinema video lenses.
 
gad-westy said:
So reading between the lines, the exposure details were the same for each shot with respect to aperture, shutter speed and ISO? So that puts metering out of the equation.

What was the source of lighting?
Click to expand...

Yes, everything was identical according to the Exif, and the camera settings weren't changed at all.
We did a few tests indoors first, then we went outdoors and set up in the garden.
We took about 3-4 sets in total and each set showed the same thing. Not really a scientific test but we could both see it, although because we were looking for differences in IQ anyway i suppose we were looking harder than normal at the images.

wuyanxu, thanks, this is what im thinking.
 
Theres an issue with this lens where the aperture doesnt stop down properly on affected batches, lots of info on dpreview forums.
 
twist said:
Theres an issue with this lens where the aperture doesnt stop down properly on affected batches, lots of info on dpreview forums.
Click to expand...

Thanks,
I thought i had read every current Tamron thread going, i must admit ive not seen this issue raised before.
 
Oh, and for what its worth the lens that was brighter had a later serial number than the darker one (mine).
Come to think of it ive had the camera lock up twice in the past week, with it reporting no lens (just 00 for f stop setting) so that seems to fit in with what you just said.
Its going back tomorrow anyway. This is my second and ive more or less had enough.
 
May or may not be the case but worth checking anyway incase its not the lever and to do with the blades.

As the aperture issue is simpler, that first. Some of the units are coming with mis-calibrated aperture levers in the Nikon mount version. I believe that Canon don't use an aperture lever so this may not be applicable.
 
twist said:
Here ya go....

One of many....

http://forums.dpreview.com/forums/post/42177958
Click to expand...

Ah, cheers. Yes, ive already posted in there a few times. I'd forgotten about that thread. I think at the time my copy was a newer model and that thread was quite old so i didn't feel it was applicable, but this current one is older so maybe it was part of that batch. Although it seems it just Nikon users that were suffering from it in that thread.
 
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