Using Thrid Party Lenses for Nikon DSLRs

This is a very interesting topic indeed. Is using third party lenses a good enough alternative to using Nikon lenses? Well, the simple answer is yes it is a good enough alternative, but if you can afford to get a Nikon lens, go for it.

I have used a couple of third party lenses like SIGMA, TAMRON, and TOKINA for paid shoots (Carl Ziess ZF lenses are of course excluded from this discussion). They're actually very good at what they're supposed to do, they won't win in a pixel peeping side by side comparison with original NIKON branded lenses but at 1/3 the cost they do a good enough job that you might not even notice the difference. IMHO, sharpness is where the third party lenses have concentrated on, to the point that they are (almost) just as sharp as their NIKON counterparts. But there's more to lenses than their sharpness. Color, contrast and saturation are big factors as well, and here's where most third party lenses fall a bit short. BOKEH, or the appearance of the out of focus area is also important. And of course there's build quality and reliability, which is good for others and mediocre for some third party lenses.

To sum it all up, I have built a small pros and cons of each of the three third party lenses I have tried and used. (note: I have used; Sigma 28-70 f/2.8 EX, Sigma 28 f/1.8, Tokina 12-24 f/4 ATX PRO, Tokina 16-50 f/2.8 ATX PRO and Tamron 17-50 f/2.8 LD)

SIGMA
Sharpness - Very good, even at wide open and near excellent stopped down to f/5.6-8.0
Color - Has a slight yellow color cast, which oddly some people find pleasing
Contrast - A bit on the lower than what I would like, tends to smudge some detail on slight gradiations
Saturation - Very good saturation a bit too much on the reds and oranges, but overall very nice
BOKEH - nice and pleasing, great for portraits (due to the 70mm end)
Build Quality - Crinkle finish wears of very easily, lens cap is impossible to remove when the hood on the lens, made of (what feels like) very sturdy plastic and some metal parts. AF ring rotates and can be a problem if snagged by loose articles of clothing.
Reliability - Varies from sample to sample, my first Sigma had a back focusing issue but my subsequent copies have been spot on, it is also important to note that SIGMA has a lot of Quality Control issues, so if you're buying one be sure to give the sample a thorough testing before paying up.

TOKINA
Sharpness - Wide open its just good enough, stopped down it to f/5.6-8.0 its excellent
Color - Emulates the color produced by genuine NIKON lenses very well
Contrast - very good, does have the tendency to flare a lot and produce chromatic abberations under extremely high contrast scenes
Saturation - Good saturation all throughout
BOKEH - good but a bit lacking for portraits (due to the 50mm, not really a good range for portraits)
Build Quality - This is the forte of TOKINA, who recently is building a reputation of building tank-like lenses, very rugged and durable metal alloy with an excellent "armalite" finish, a pleasure to hold, really good double clutch mechanism that makes shifting from AF to MF really easy. It's in the same class as the NIKON in this department.
Reliability - Never had a problem with my now 3 yr old 12-24 but the 16-50 seems to have some focusing issues in the beginning, (my guess is that the mechanism was strung out too tightly from the factory) the focus was slow and erratic at best, I had to stop down to f/5.6 to ensure that subjects were in proper focus. After 3 weeks of use, it finally gave me the results I wanted and focussed accurately enough for me to be able to use f/2.8 which is the primary reason you would buy such a lens in the first place.

TAMRON
Sharpness - Probably the sharpest of the thrid party lenses I have used, even at f/2.8 it (looks to be) as good as my NIKON 17-55 f/2.8
Color - Produces Similar color to NIKON lenses but looks slightly cooler.
Contrast - great contrast, very high
Saturation - IMO a little bit lower than what I'd hoped for, easily fixed
BOKEH - good but a bit lacking for portraits (due to the 50mm, not really a good range for portraits), the TOKINA has much better BOKEH though
Build Quality - A lot of plastic, I think it is the lightest f/2.8 lens that I've used. The focus ring turns as the AF motor drives the lens. Looks and feels like a cheap lens, same build quality as the 18-55 kit lens of NIKON.
Reliability - I cannot comment on this as I only used the TAMRON for a month (had it together with the TOKINA, kept the TOKINA and returned the TAMRON). But for that month AF was spot on and very fast, contemplated on returning the TOKINA during the first 3 weeks, but then the TOKINA came good and its build quality won me over, sorry TAMRON.