Nikon Sigma Tamron

Nikon Sigma Tamron

For a Nikon d50 which brand of lenses is better: Sigma, Tokina or Tamron ?

Any lens is a compromise between cost, speed, and image quality. Rather than get into a Ford vs. Chevy debate, I would encourage you to look at what your need is and go from there. I would consider Sigma, Tokina, Tamron and Nikon lenses - it all depends on what your particular need is.

For example, I think the Nikon 12-24 is better than the Tokina 12-24. But I bought the Tokina. Why? It is almost as nice (very close) and was half the cost. If I was making the purchase today, I might buy the Sigma ulta-wide. Why? It is also very good and just a bit wider.

In other words, new brand is always the best. It varies by model. A great discussion of the trade offs is at http://www.nikonians.org/html/resources/nikon_articles/nikkor/af/wide_angles_shootout/super-wide_shootout_6.html

Some lens basics:
a) The "reach" of a lens is expressed in mm. For example, a 17-55mm lens is a wide angle to normal range zoom. It is crucial that the range of the lens matches what your need is. Think something under 30m for wide angle (scenic landscapes), 50mm to 85mm for portrait work and 100mm to 600mm as a telephoto (sports, wildlife, etc.). I think the best approach is to buy a lens or two and then wait. See what you always wished you had...
b) The speed of a lens is expressed as an f stop. A lower number means the lens lets in more light. That is a great thing -- it gives you more options (such as allowing faster shutter speeds), makes the viewfinder brighter and can help the autofocus work better in low light situations. Why doesn't everyone buy only fast glass? It is bigger, heavier and costs much more than a lens with a larger f stop.
c) Not all lens are created equal. Not all lens are equally sharp at all f -stops; they all have a sweet spot.

What to buy and where?
a) I would consider most brands of lens that are autofocus and work with the D50. Nikon, Tokina, Tamron and Sigma. While you almost always get what you pay for, some lenses are a better value than others. For example, a new Nikkor 50mm F1.8 is a great lens when shot at around f4 or 5.6. The built quality is a little flimsy but, hey, it only costs $110.
b) Think about what light you will be shooting in. Middle of the day? A fast lens is an expensive luxury. Low light with no flash -- a slow lens will be little more than a frustration inducing paper weight.
c) Consider used. Keh.com is very reliable. Many non-chain sellers also have a used department.
d) Try out the lens. Does it feel ok? How is the af? In some cities, you can rent upper end lenses (i.e., locally I can rent a 500mm f4 for about $300 a week. Sounds like a lot until you look up what the lens costs new!!
e) Research the lens via the internet. Great sources include:

http://forums.dpreview.com/forums/forum.asp?forum=1030

http://www.slrgear.com/reviews/index.php

http://www.bythom.com/nikon.htm

http://www.naturfotograf.com/lens_surv.html

http://www.nikonians.org/nikon/

http://www.nikonlinks.com/equipment_lenses_general.htm

Nikon 70-200mm VR Lens review part 2 The results and conclusion (dombower.com)