1207 – Framed

Photozone.de has finally published a lab review of the Tamron 17-50/2.8 VC. It’s for the Canon version, but that should not make much of a difference. The review sparked off a thread in the Nikon forum of Photo.net, where the review was regarded as almost devastating. The original poster concluded with “If you value your photography, stay away from this lens!

Well, regarding distortions at 17mm, yes, it distorts badly, and apart from the brick wall, this original shot, provided for you in all glory of its full size, is as bad as it may get. For the Image of the Day I have applied PTLens, but that could only remove part of the barrel distortion. I’ve removed some more with Photoshop’s Lens Distortion filter, cropped, and you see that what I’ve got is pretty perfectly rectangular. Just frame a little less accurate, leave room for correction. That’s for distortions.

The other thing is, that down in the Photo.net thread Eric Arnold tried to compromise:

essentially,it comes down to this: if you need corner sharpness but constant aperture isnt important, i.e. for landscapes, get the 16-85 VR.

if you need a fast constant aperture and want stabilization at the expense of losing some corner sharpness, get the 17-50 VC.

I think my answer is relevant, and I don’t want it to be buried in an off-site thread, so please allow me to quote it as well:

I think this is wrong. The reason to get the 16-85 VR can only be the extended range.

Yes, it is sharper in the corners at f3.5 than the Tamron at f2.8, so what? Would you take landscape images at f2.8 or f3.5? Most of the time I wouldn’t. And even if:

I’ve just tried the Tamron at f3.5, tried it with book shelfs (detail!), tried it with flash (it’s still night here), and I can see a subtle sharpness falloff, only in the extreme corners, and I can only see it because I look for it. Even at f3.5, you would have a hard time seeing it, and for the 16-85 VR this is still wide open.

No, I suppose with the 16-85 you would shoot normally at at least f5.6, and by that the Tamron is stellar across the range. We’re speaking of 50/1.8 sharpness here. And that’s only at 17mm. Think of 24mm: the 16-85 just begins at f4, from 35mm at f4.5, and by 50mm it is at f5. At none of these focal lengths and at starting aperture it is a match for the Tamron.

Now take it the other way: Imagine a situation where you do want to take a scenic image at f2.8, for instance because it is night. Let it be architecture, for instance in a city, or let it be within a cathedral. It’s quite a typical situation, and it’s quite typical for situations where you either have no tripod or may not be allowed to use it.

In such situations the shot is frequently repeatable, thus I may go down from my normal 1/15s (auto ISO lower speed limit) to 1/8s or even 1/4s. With VR I have a sharp image, it may take me two or three attempts though, especially standing without support and shooting portrait format. Even in low light I may get away with ISO 200.

With the 17-55/2.8 at twice the price I may be lucky to get the shot at 1/15s, but I suppose 1/30s will be more likely, especially in portrait format. We’re talking two to three stops, i.e. ISO 800-1600 here. Do you believe that the added corner sharpness of the 17-55/2.8 will still be there at these ISOs? And if were not talking extreme corners but center or off-center, for instance a typical “rule of thirds” composition? The Tamron will be much better than in the extreme corners. The Nikon may or may not still have a slight edge on the charts, but you would have a hard time seeing it, and, remember, that would be at the same ISO. But what with our fictual but not so unrealistic situation in the church or at night in the city? With an advantage of ISO 200 vs ISO 800-1600 across the frame and the main subject where main subjects typically are, don’t you believe that any theoretical sharpness advantage of the Nikon, even if it were there at that point in the frame, would be hopelessly buried in noise?

Now say you accept some added noise because you need depth of field. You go to f5.6. That’s two stops, we are at ISO 800 with the Tamron. We may need two or three attempts to hold the shot at 1/4s, but we would need the same with the Nikon at 1/15s or even 1/30s. Both lenses operate at maximum sharpness now. Under ideal light and in the lab, you may still be able to measure a slight sharpness advantage in the extreme corners for the Nikon. Our subject is not in the extreme corners though, and the light is low as it is. Where is the Nikon now? ISO 3200-6400, right? Forget about any theoretical advantage it may have. At that light it is severely hampered by sensor noise. ISO 800 vs ISO 3200-6400? This is an almost too easy win for the Tamron.

I may sound like being biased, I may even sound like being affiliated with Tamron, but that’s not the case. I just own this lens and have used it for three months in the darkest time of the year. Really, I wouldn’t so easily dismiss this lens 🙂

Here we are. The Image of the Day was taken at 1/15s and f2.8. The extreme corners of the original shot are about 10cm in front of the focal plane. They are mushy because they are clearly out of focus. If they were in focus, they might be still mushy but less mushy. That’s how bad it can get. Could be worse, huh?

And, given the example in the quote, had I taken my time, I could have gone down to 1/4s and ISO 200. With non-stabilized lenses you’d still hover at ISO 800 or maybe at ISO 1600, look at the noise and console yourself with the fact that it’s not the lens, it’s only the light that’s so bad 😀

Oh yes, “Rahmen” means “frame” or “frames” in German. Thus the Song of the Day is “Framed” from The Sensational Alex Harvey Band’s 1972 album “Framed”. See them in a fine live performance on YouTube.

2 thoughts on “1207 – Framed”

  1. I just found the points here on this blog that convince me again to buy this lens …soon.

    If the fact wasn’t wrong and I wasn’t wrong, wouldn’t it f/2.8 will be soft due to DOF? …even the subject is a Landscape. Things will be even softer when below f/1.8 (ofcoz that the center is SHARP)

    I do think it is sensible when we inspect corner sharpness below f/4 on any lens would more or less produce the same result. I had tested f/3.5 on my kitlens … under low light in the evening with hand held. It will be a bit blur when shot on 17mm at 1/4 speed, ISO 3200 with Image Stabilizer Off.
    It was hack a lot of difference when IS is switch ON …. on the same setting. Hence, VC is very helpful on low light environment.

    Indoor low light, ISO 1600 only gave me 1/80 on f/4 … but it will be double as 1/160 with f/2.8 (it will be less different when speed drops to 1/30 on very low light)

    I strongly support your findings and verdict here ^^

    Cheers n God bless~

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