|"Balance" // D700, 1/250s at ISO720, Sigma 50-500OS at 500mm, f/8, monopod.|
Because I'm not really happy with the reach of the 70-300VR on the D700 and because I was curious, I rented the "Bigma" (Sigma 50-500 OS) for a whale watching cruise.
500mm on full frame? Sounds damn good. But to jump to the conclusion of this post right away: I'll rather use the 70-300VR on a crop sensor camera (namely, Shuwen's D90:) instead in the future if I need that reach.
Why? The Bigma is, well... big, of course. And heavy. The build quality is really convincing, and the sharpness at 500mm is good for the "low resolution" 12 megapixel sensor of the D700. But you can't really use it hand-held (and you shouldn't - I think the thing is heavy enough to cause serious strain on the lens mount of the camera, and when you're using that combination handheld, it will happen that you hold it on the camera body - if only for seconds, but still).
I've been using it on my monopod since I don't have a tripod head that suits these telezoom lenses. The monopod is also versatile and unobtrusive enough to use it on a boat, like on our whale watching cruise*. There would have been no way to set up a tripod on that boat.
When the cruise was over, some fellow photographer asked me about the lens. He had the 70-300VR on a D60. It was then that it dawned on me that he had a reach of 450mm (and the 50mm difference between 450mm and 500mm is really neglectible IMHO) with a fraction of the weight.
Yes I know, 300mm is 300mm even on a crop sensor, it's just the angle of view that equivalents 450mm, I could just crop my D700 image, yada-yada-yada... to which I reply: resolution. If I crop that D700 image, I probably end of with an OK 5 megapixel image (that's the resolution of the D700 if the sensor was DX size). Compared to a 12 megapixel image from the D90 that is maybe a little less sharp (at 300mm, the 70-300VR isn't that much of a performer) with some room for cropping, I'll end up with a rather good 6-8 megapixel image. See what I mean?
So for me, who only occasionally makes wildlife photos that need these long zoom lenses, it really makes more sense to use the slow and lightweight 70-300mm on the 12 megapixel crop sensor instead of the slow and heavy 50-500mm on the 12 megapixel full frame sensor. (And I didn't even mention the money.) Use the latest Nikon body like the D7000 with it's excellent high ISO image quality, and it's even less of a question for me.
*) it attracted enough attention for the captain of the boat to ask if I would share the photos with him.