Nikon lens

[Dexter-1]

I've heard that conventional wisdom is that an 85mm lens is a great lens for portraits. So what, if any are the differences between a single focal length lens like a Nikkor 85mm F1.8 AF and say the 18-200mm F3.5-5.6, other then the obvious f-stop range? What I'm really asking is there any difference in the lens sharpness between these telephoto lens & single focal length lens?

Also, there is a large difference in price between say a Nikkor 50mm F1.4 & 50mm f1.8 lens or the 85mm F1.4 & 85mm F1.8 lens. Does the '.4' really make that much difference? thanks

 

[tirediron]

As a general rule, primes are sharper than zooms, simply by virtue of their simpler construction. The 18-200 you mention is a 'Swiss Army' lens, and like any tool meant to do a lot of different jobs, it doesn't do any of them very well. The wider apertures also produce significantly less DoF which is often needed for portrait work.

As far as the 50mm, yes, that .4 does make a big difference, but it's not all about the aperture. There's a huge diffence in build quality between the 1.4 and the 1.8. The 1.8 has an all-plastic barrel, plastic lens mount, and is essentially a consumer lens; the 1.4 while not quite 'gold ring' glass, is of a much higher standard both optically and mechanically.

 

[Dexter-1]

So is it reasonable to assume that photographers who do portrait work usually use prime lenses vice zooms?

I get the part about using better materials and construction but I guess your also saying the the F1.4 lenses have better glass then the F1.8 of the same length? Can you give me some feel on a relative basis for how much 'better' those lenses would be (WRT optical quality)? And in what kind of work are you going to notice this difference in?

 

[tsaraleksi]

There are differences in the sharpness of the lenses, their depth of field capacities, perhaps in autofocus quality or speed.