This might be a really late response, but really the brand doesnt really matter much, unless you go for the carl zeiss ones, which have the best lens material. If you choose either nikon, canon or other brands, what matters most is the maximum aperture of the lens and glass built quality.
For Example
A.
http://www.adorama.com/CA5018AFU.htmlB.
http://www.adorama.com/CA5014AFU.htmlC.
http://www.adorama.com/CA5012AF.htmlBoth A B C Canon lenses have the same focal length of 50mm, but due to the lens quality, Lens C has max aperture of 1.2 f-Stop which permits to shoot with less light, while the cheaper lens (A) has a maximum aperture of 1.8 f-stops.
Its amazing how 2 f-stops increases the lens price for over 1,000 bucks. Its not the brand, but the lens built quality...
In other words, the wider the aperture of the lens, you require less light and have a shallower DOF (more blurry), but with the f1.8 lens would be enough to get your look.
I try to evade any lens which maximum aperture is 3.5 or over, to get descent results Id try a lens with a maximum f-stop of at least f2.8
Also take into consideration, the longer the focal length of the lens (or higher amount of zoom), it will be exponentially more expensive to get the lens with a low maximum aperture, its cheap to get a 50mm lens with f1.8 aperture, but really expensive to get a 200m lens with f2.0 (lens E below) aperture. So when choosing telephoto lens on a budget, you donīt have much of a choice.
See for yourself what I mean:
D.
http://www.adorama.com/CA20028AF.htmlE.
http://www.adorama.com/CA2002AF.htmlPlus the second lens, has an image stabilizer, which is useless if you are only using the lens with a 35mm adapter.
To conclude, With a 3.5 to 5.6 Aperture lens you still get descent looking results, but anything above that, DO NOT GET NEAR IT, it would be a sin to try using a Telephoto lens with an f8 aperture, you will start to harm the quality of your footage with the letus and any lens with an aperture over 5.6...
Post edited by: migueltb, at: 2008/10/08 02:38