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30/11/2010

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hannes

Hey!

Nice article. One remark: Focal lenght has nothing to do with DX vs full frame.
Even though the 55-300mm lens is a DX lens, it should still give you the same field of view as the tamron 70-300 if both are at the same focal length. (except for inaccuracy introduced by the manufacturer)

On a DX camera both will give you at the long end the equivalent FOV of a 450mm lens on a full frame.

Regards,
hannes

Kim Brebach

Thanks Hannes.
The focal length is indeed the same, and never changes regardless of camera, nor does the angle of view. However, the FX Tamron lens on a DX camera will have its image cropped. That is equivalent to the digital zoom on digicams, and in this case results in a 50% magnification compared to the 50-300 DX lens.
Is that a more accurate description?
Kim

hannes

Hey Kim!

Sorry but this is still wrong. The crop is due to the DX Sensor, so no matter which lens, it will always give you 50% magnification on a DX sensor as compared to an FX Sensor.

The 55-300 DX also is a "real" 55-300 lens (and not a 55-300 FX-equivalent). So it will also give you 50% magnification of an image from a DX body, as compared to a FX body with a 300mm lens.

The mm focal length is a quality of the lens independent of the sensor. The size of the sensor then determines the crop. On small sensors a given image of an object produced by the lens will cover a relatively larger fraction of the sensor and the object will thus apperently be magnified on the final image.

Sorry but I struggle exlaining this in English.

The DX specification just says that the lens might not cover the whole image circle of a FX camera. But on a given camera, a 300mm lens always gives you the same magnification, no matter whether it is a DX or FX lens.
However, it is true that for comact cameras the focal length is sometimes given in "equivalent to full frame", but not for Nikon DX lenses.

Regards,
hannes

Kim Brebach

Thanks a lot, Hannes. You are right in saying that all lenses, whether designed for DX or FX, are affected by the crop factor of the smaller sensor. This results in an effective 50% magnification of their physical focal lengths. I've corrected the error in the text.

Frohe Weihnachten
Kim

Patrick Francis

First of all, fantastic article. This is the kind of in-depth information that I appreciate. It looks like it might have been a while since you last made a blog entry, but I really appreciate the focus you had on image stabilization, as it's critial to catch the shot!

Kim Brebach

Thanks for the feedback, mate. In a way, I regret selling this lens but I found the size and weight a bit too much. I'm a 'lite' kind of shooter and eventually settled for the Nikon 55-300 which is the right size if not in the same class as the Tamron other respects.

I'm puzzled by your comment about it being a while since my last blog entry, since I've made dozens of them since the article you hit on.

http://briard.typepad.com/get_the_picture/

Kim

Clint

Which is much faster, nikon(70-300mm VR) SWM or USD of tamron(70-300mm VC)? thanks!

Kim Brebach

From what I've read, the Tamron is at least as fast as the Nikon, and accurate too

Clint

Thanks, I'm confuse on which one will I buy, the VC or the VR 70-300mm. I have the budget for the both lens though.

Kim Brebach

I reckon the Tamron is the better lens, and better value.

Clint

Got the Tamron just today. It's really good! Thank you for the advice. :)

Kim Brebach

Good choice, mate! Happy to have been of help.

Clint

Hi, have you tried using teleconverters on the Tamron 70-300 VC? How was its performance?

Kim Brebach

No I haven't Clint. Without TC, the performance was all you could ask for. I would've kept it if it weren't so big.

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