Tamron 24-70 2.8 VC - issue

Started Aug 3, 2012 | Discussions thread
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inasir1971
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Tamron 24-70 2.8 VC - issue
Aug 3, 2012

(Previously posted on Canon forum - but about lens in general and issues with Nikon)

I am using the Tamron 24-70 2.8 VC on Nikons and some of us have noticed issues with the VC. As the Canon mount version has been out longer, am seeking feedback on how your units are doing. Also question about aperture performance.

Optically and in terms of build it seems to be a very good lens. However these two issues exist.

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. The issue is that the aperture lever is mis-calibrated by approximately 2/3 stop. Wide open the lens is at f2.8. However, it doesn't start stopping down at all till somewhere just before f4 on some units. (i.e. an indicated Av of f10 is actually f8). The effect on shooting is overexposure at apertures smaller than wide open and requiring an exposure compensation of around -0.7 EV. I think on a Canon you would take shots in 'M' mode with Tv, and ISO fixed at all apertures between wide open at f2.8 and f4 - there should be a change in brightness between each shot. Anyone with the lens care to try?

The second issue is with the VC system.

At normal shutter speeds VC degrades the image. I have checked two samples with a D800 and they both displayed the same behavior - at shutter speeds faster than 1/40s the image is degraded by having VC on. Even at 1/FL speeds turning off VC consistently provides better images than with VC on if Tv is above 1/40s.

This seems to be body dependent. Testing with a D4, the image was degraded at shutter speeds above 1/20s with VC enabled.

Testing IS/VR/VC is always tricky as there are so many factors and it must be handheld. Under ideal conditions: seated, 2-3m from a target, good technique but no elbows on the table (the human body is an excellent vibration damper) shots were taken starting from 1/6s at 70mm. Time was allowed with shutter half pressed for VC system to become operational.

With a D4, images were perfect at shutter speeds below 1/20s. Effects start to appear at 1/20s and get progressively worse till 1/80s and only get better again when shutter speed starts to exceed 1/320s (not really checked as it was well over 1/2xFL and VC should be switched off by this stage anyway).

With the D800 (tested on two bodies) the images were good till about 1/40s.

Any experience from Canon users with the lens would be most appreciated as the Canon variant has been around for longer and the VC system should be common.

Thanks.

Nikon D4 Nikon D800
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