09-16-2010, 03:14 PM
[quote name='mst' timestamp='1284624109' post='2821']
Remember the exposure issue of the Tamron Di 60? Well, it seems we have another one ...
I've been shooting in the field with both the Nikon 70-300 VR and the Tamron 70-300 VC for a few days. Some of the Tamron shots looked rather fishy to me, they were a bit bright. A lot brighter than what the Nikon delivered in the same situations.
I did some tests with both lenses yesterday and this is what I got:
![[Image: 70-300VC.png]](http://www.mst.cc/Images/70-300VC.png)
Left column is what the camera metered with the 70-300 VR (tried three copies, consistent results here). The center column is the 70-300 VC, manually set to the same exposure. As you can see, the results a very similar except stopped down at 70mm, where the Tamron either has higher transmission (unlikely IMO) or just does not set the aperture correctly (I did all these shots 10 times, so the possible variation in exposure due to the mechanical aperture lever is already ruled out).
The right columns shows what the camera metered with the 70-300 VC. Especially at lower focal lengths, the metering is way off. This matches what I saw in the field.
Currently, I have only one copy of the Tamron 70-300 VC. I'll try to find out if this is an issue of my copy only or a general issue of the lens (or more precisely the F-mount variant). Any help in this regard by owners of the lens is highly appreciated.
-- Markus
[/quote]
Did you try different bodies? I mean radically different, e.g. D3000 and D3. Collimation effects in the light path (including mirror, prism, screen,...) from the lens to the exposure meter can have a lot of effect on the metering. With my 1976 Minolta XE-1 I have to dial in exposure correction for WA (brighter) and for telelenses (darker) to get decent metering. The 50mm lens is spot on. All lenses are genuine Minolta MD. This matches what I see in the finder: the WA is darker the telephoto is brighter. Over the years I saw similar reports from other people.
I understand modern CPU lenses transmit data to the camera how to compensate for this. I see no reason why one set of data should fit all bodies (different prism, different screen, different exposure metering element). If Tamron doesn't understand (reads: license) the genuine Nikon protocol but reverse engineers the thing, that data could easily be fine on one body and messed up on a different one.
Just an idea. From your reports on the 60/2 it seems that Tamron doesn't understand what they are doing.
Remember the exposure issue of the Tamron Di 60? Well, it seems we have another one ...
I've been shooting in the field with both the Nikon 70-300 VR and the Tamron 70-300 VC for a few days. Some of the Tamron shots looked rather fishy to me, they were a bit bright. A lot brighter than what the Nikon delivered in the same situations.
I did some tests with both lenses yesterday and this is what I got:
Left column is what the camera metered with the 70-300 VR (tried three copies, consistent results here). The center column is the 70-300 VC, manually set to the same exposure. As you can see, the results a very similar except stopped down at 70mm, where the Tamron either has higher transmission (unlikely IMO) or just does not set the aperture correctly (I did all these shots 10 times, so the possible variation in exposure due to the mechanical aperture lever is already ruled out).
The right columns shows what the camera metered with the 70-300 VC. Especially at lower focal lengths, the metering is way off. This matches what I saw in the field.
Currently, I have only one copy of the Tamron 70-300 VC. I'll try to find out if this is an issue of my copy only or a general issue of the lens (or more precisely the F-mount variant). Any help in this regard by owners of the lens is highly appreciated.
-- Markus
[/quote]
Did you try different bodies? I mean radically different, e.g. D3000 and D3. Collimation effects in the light path (including mirror, prism, screen,...) from the lens to the exposure meter can have a lot of effect on the metering. With my 1976 Minolta XE-1 I have to dial in exposure correction for WA (brighter) and for telelenses (darker) to get decent metering. The 50mm lens is spot on. All lenses are genuine Minolta MD. This matches what I see in the finder: the WA is darker the telephoto is brighter. Over the years I saw similar reports from other people.
I understand modern CPU lenses transmit data to the camera how to compensate for this. I see no reason why one set of data should fit all bodies (different prism, different screen, different exposure metering element). If Tamron doesn't understand (reads: license) the genuine Nikon protocol but reverse engineers the thing, that data could easily be fine on one body and messed up on a different one.
Just an idea. From your reports on the 60/2 it seems that Tamron doesn't understand what they are doing.
enjoy