[mvheyst]

I am experiencing an under exposure problem with my new Tamron 17-50mm lens on a Nikon D300 body. The model (A16N II) is the SP AF17-50mm F/2.8 LS IF XR Di II

The lens is made in Japan.



I don't have the same problem with my Nikkor lenses or my Tamron 90mm Macro lens.



I need to adjust the EV to approx +0.7 EV to +1.3 EV to get a proper histogram on the D300.



The histograms on the D300 clearly shows the problem, as most of the bars are towards the left, and none towards the right.



Photographs taken in bright sunlight have a dark appearance, with properly exposed highlights.



The pictures have the appearance of low-key photographs. The highlights appear to be properly exposed, but detail gets lost in the shadows. Some of the photographs looks very good.



I noted a similair complaint of the Flickr website as well as on Amazon.com



Link to "Tamron 17-50 under-exposure?" in Flickr :



http://www.flickr.com/groups/tamron17-50mm/discuss/72157594571525532/

[joachim]

Hi,



welcome to photozone. Your issues might be the same as the one Markus is experiencing:



http://forum.photozone.de/index.php?/topic/355-tamron-70-300-vc-exposure-issues/



Hope this helps

Joachim

[Brightcolours]

[quote name='joachim' timestamp='1285173721' post='3098']

Hi,



welcome to photozone. Your issues might be the same as the one Markus is experiencing:



http://forum.photozone.de/index.php?/topic/355-tamron-70-300-vc-exposure-issues/



Hope this helps

Joachim

[/quote]

No, he experienced over exposure.

[mst]

[quote name='Brightcolours' timestamp='1285178157' post='3099']

No, he experienced over exposure.

[/quote]



But underexposure with the Tamron Di 60/2.



I haven't tried the non-VC Tamron myself, so I can't comment on this one.



-- Markus

[vc13130]

I have an exposure issue with my Tamron 60 f/2 as well. When I first got it, I saw no underexposure except when I set it wider than f/2.8. I ran some tests and found that the camera is misreading what aperture the lens is set to. When I set the f-stop on the camera to 2.8 the lens was actually at 2.2 (and the camera exposed correctly for f/2.2, when I first got the lens). When I set the lens to 2.2, it was still at 2.2 but the camera exposed correctly for 2/3 of a stop ABOVE 2.2, so I got underexposure. I never had problems at any other apertures, even wide-open at macro distances where the maximum f-stop is lower.



Recently I've had to set the exposure to +0.7 to get accurate metering, which is apparently a common problem. I think the aperture lever became loose.



What I think is going on is that Tamron is not good at calibrating the aperture lever on the mount to the camera. That's the problem with the mechanical aperture control on Nikon cameras, compared to electrical aperture control on Canon cameras. I've never read a report of Tamron lenses systematically underexposing on Canons. I hope that Nikon eventually makes aperture under electrical control to get rid of these ridiculous problems. That will give them one more reason to charge extra for higher-end bodies <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='' />

[mst]

[quote name='vc13130' timestamp='1285190524' post='3108']

I have an exposure issue with my Tamron 60 f/2 as well.

[/quote]



Are you sure this was really a aperture error? The Di 60 is a macro lens and it's common for F-mount macro lenses to report the effective aperture to the camera ... which increases with decreasing focus distance. So, what's wide open or f/2.2 at infinity becomes effectively f/2.8 (or even less) at close distances ... where closer starts at around 5 m, IIRC (sorry, can't test at the moment).



-- Markus

[vc13130]

[quote name='mst' timestamp='1285223977' post='3127']

Are you sure this was really a aperture error? The Di 60 is a macro lens and it's common for F-mount macro lenses to report the effective aperture to the camera ... which increases with decreasing focus distance. So, what's wide open or f/2.2 at infinity becomes effectively f/2.8 (or even less) at close distances ... where closer starts at around 5 m, IIRC (sorry, can't test at the moment).



-- Markus

[/quote]

Yes, it was an aperture error. The camera shows the correct maximum aperture: f/2 at infinity, f/2.2 starting at 5-10 feet, and so on. But I find no different in bokeh between f/2.2 (which is the widest aperture I can go under the conditions I test under) and f/2.8--the size of the OOF blurs and the "cat-eye" shape are the same. I even see the same vignetting, when I use appropriate exposure compensation. However, when I compare the bokeh of the Tamron 60 at "f/2.8" to my Tokina 50-135 at 60mm f/2.8, the size of OOF highlights in the Tamron is about twice as big as that in the Tamron as in the Tokina. So what I'm saying is that even though the camera is adjusting the aperture based on what it thinks is correct, there's a systematic 2/3 stop discrepancy between what the camera says and what the lens is actually showing. I think that explains why there is (more) underexposure at f/2.2 than at f/2.8.



I'll try to post some test results soon. I don't have a tripod so it won't be as good as it could be, but I think I can demonstrate the main point <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='' />

[mvheyst]

SOLUTION: An under exposure problem on my Tamron 17-50mm lens (Nikon) was fixed by an mechanical adjustment of the aperture controller of the lens. The lens under exposed by approx 1 EV in automatic.



I contacted Tamron Japan and they refered the lens to the local Tamron repair centre.



The repair must be done by an official Tamron repair centre. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='' />



I noted others reported the same problems with Tamron lenses. There may be a problem with the quality control at Tamron regarding the aperture control settings of the Tamron lenses.