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Tamron 70-300 VC exposure issues


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#1 mst

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Posted 16 September 2010 - 09:01 AM

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:

Posted Image

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
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#2 Klaus

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Posted 16 September 2010 - 09:11 AM

Even though I'm repeating myself - a mechanically controlled aperture sucks.
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#3 mst

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Posted 16 September 2010 - 09:20 AM

Even though I'm repeating myself - a mechanically controlled aperture sucks.


Yes, it's not that precise. However it works well enough for me in the field and in addition it's not the issue here. Plus: it doesn't explain the metering errors, which are done with wide open aperture.

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#4 wim

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Posted 16 September 2010 - 10:05 AM

Yes, it's not that precise. However it works well enough for me in the field and in addition it's not the issue here. Plus: it doesn't explain the metering errors, which are done with wide open aperture.

-- Markus

Actually, it does. It means that the mechanical control is not very good, that's all, not even for wide open at different FLs.

Kind regards, Wim
Gear: 5D Mk II, 1D Mk III, with a solitary zoom, a gaggle of primes, an accesory plague, and a Panasonic GF-2 with 3 primes, 3 zooms, and some alternative lenses ....

#5 mst

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Posted 16 September 2010 - 10:12 AM

Actually, it does. It means that the mechanical control is not very good, that's all, not even for wide open at different FLs.


Sorry, no, it doesn't. The mechanical lever pulls the aperture wide open when mounted to the camera, regardless of the focal length (and of course I checked that visually, too). Works with almost any lens I have, only two exceptions: the Tamron Di 60 (currently at Tamron Europe again) and now the 70-300 VC.

And even if the lever was the reason: since the lever is not moved during exposure for wide open shots, the metering should at least be correct in this case.

Edit: actually, the metering should be correct in any case. Moving the lever to stop down might lead to under- or overexposed shots (see 70mm/f8 above), but the metered values should be correct. Unfortunately, they are not.

Another Edit: forgot one lens, that has expsoure issues on Nikon, too: the Voigtländer 20 SL II.

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#6 joachim

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Posted 16 September 2010 - 04:14 PM

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:

Posted Image

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



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

#7 mst

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Posted 16 September 2010 - 04:33 PM

Did you try different bodies?


Not yet, but I will. I also posted this in two German forums with the intention to find out if this is an issue of my lens only or a general issue.

The underexposure of the Di 60 was independent of the camera used (tried several).

Just an idea. From your reports on the 60/2 it seems that Tamron doesn't understand what they are doing.


Well, maybe they (finally) do. There have been reports of Di 60 lenses which no longer show underexposure, either purchased new just recently or repaired by Tamron. That's why I just sent mine in again.

-- Markus
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#8 Bare

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Posted 16 September 2010 - 07:49 PM

Even though I'm repeating myself - a mechanically controlled aperture sucks.


I must disagree because many Canon failures are conected to electonic controled aperturture and was verry often in the '90-is.

#9 Klaus

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Posted 16 September 2010 - 08:53 PM

I must disagree because many Canon failures are conected to electonic controled aperturture and was verry often in the '90-is.


I was referring to the exposure accuracy not reliability.
Canon & Olympus have both an electronically controlled aperture and they are, by quite a margin, the most accurate here.
Actually I've never experienced a failure here anyway throughout the years.
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#10 Brightcolours

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Posted 16 September 2010 - 08:58 PM

I was referring to the exposure accuracy not reliability.
Canon & Olympus have both an electronically controlled aperture and they are, by quite a margin, the most accurate here.
Actually I've never experienced a failure here anyway throughout the years.

I have, with the Tokina 12-24mm f4. But that hardly has to do with the fact that Canon implemented electronically controlled apertures, it is a systematic fault from that particular Tokina model.

#11 Koulang

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Posted 17 September 2010 - 05:35 AM

I am looking for anyone who Tamron 70-300 VC. I plan to purchase this lens but really hesitate between the new Canon 70-300L with this one. Can you let me know the image quality between this one and your Nikon 70-300 VR?

I am sure the new Canon will be sharper, but the price will be 3-5 times more expensive.

#12 Bare

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Posted 17 September 2010 - 11:33 AM

I am looking for anyone who Tamron 70-300 VC. I plan to purchase this lens but really hesitate between the new Canon 70-300L with this one. Can you let me know the image quality between this one and your Nikon 70-300 VR?

I am sure the new Canon will be sharper, but the price will be 3-5 times more expensive.


I doubt Canon will be sharper. Also im sure it has better build quality and better AF than Tamron.

#13 sth

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Posted 21 September 2010 - 11:57 PM

Any first impressions on this lens so far?

#14 Vieux loup

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Posted 23 September 2010 - 03:15 PM

I just bought the latest Tamron 70-300, but have not used it a lot so far. I have not seen any obvious exposure problems and I am really impressed by the optics, but I have not shot enough for it to be an opinion in the real sense. With my body (D300s) it behaves well, maybe apart from a little AF gearing some times. If I were living closer to you Klaus, I would gladly give you the lens for testing. I could of course ship it by UPS. Let me know if you want me to! :) Kindly Tele Wolf
Kind regards, Vieux Loup

#15 Vieux loup

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Posted 24 September 2010 - 11:58 AM

Here is a link to a test done by the French magazine LE MONDE DE LA PHOTO on September 24. http://www.lemondedelaphoto.com/Prise-en-main-et-formule-optique,5058.html
The results were excellent and notably better than the Nikon at 300mm. The piqué is excellent or very good at all focal lengths and the only possible negative is some chromatic aberration , which however is taken care of "in camera" by my D300s :D The test confirms my own opinion, which of course is both non scientific and not yet based on a lot of shots, but reassures me in my choice. I bought mine at Cameratools.com at a very good price. Kindly Vieux Loup
Kind regards, Vieux Loup

#16 Sammy

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Posted 26 September 2010 - 07:31 AM

The results were excellent and notably better than the Nikon at 300mm.


If we can take these MTF charts for real, the Tamron 70-300 VC is a clear winner indeed, and probably class leading right now.

http://www.tamron-us...p/a005/mtf.html
http://imaging.nikon...6g_if/index.htm

You mentioned some AF issues, how bad is it in this regard?

Cheers

Sammy

#17 Vieux loup

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Posted 27 September 2010 - 03:20 PM

Not bad at all, it geared a couple of times for me in very poor light, but for the most part it was excellent. You can take those charts seriously. The tool (DxO) is very good and the people doing the tests are real pro's. Kindly Vieux Loup
Kind regards, Vieux Loup

#18 William9

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Posted 06 October 2010 - 05:41 PM

I'm new to this forum, and came here because of my interest in the Tamron 70-300 VC. I'm looking forward to reading a photozone review of this lens. When will one be done with the Nikon version?
William9

#19 mst

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Posted 19 October 2010 - 11:43 AM

Welcome to the forum, William, and sorry for the late reply.

All I can say for now is that I'm working on it, but I don't know when it's done.

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#20 mst

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Posted 19 October 2010 - 11:46 AM

Well, maybe they (finally) do. There have been reports of Di 60 lenses which no longer show underexposure, either purchased new just recently or repaired by Tamron. That's why I just sent mine in again.


While we're at it, just a quick update on this one: the lens is back from Tamron, repair report says aperture has been adjusted, but it seems unchanged to me.

-- Markus
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