Small Focal Length Question on Lenses

All,

This seems like such a dumb question, but I was looking through lenses and it occurred to me: why are lenses sold with relatively small focal length ranges? For example, in the 18-55mm range provided by my D3100's kit lens, I could buy the following from Nikon:

• 17-35 f/2.8
• 16-35 f/4
• 18-35 f/3.5-4.5
• 16-85 f/3.5-4.5

I'm certainly not asking for the pluses and minuses of each lens, but I don't understand why there are so many focal length choices in the same range. Yes, I realize that the apertures are different, but why would I want an 18-35 f/3.5-4.5 to supplement my 18-55 f/3.5-5.6, or why would I want two lenses when I could just use one?

Unlike prime lenses, where all lens elements can be utilized to maximize the image quality at a single focal length, zoom lenses have to make trade-offs between image quality, focus, and various optical aberrations. Smaller zoom ranges usually tend to have better IQ throughout the focal range, while lenses with larger zoom ranges often have a sweet spot where IQ is at its best, which falls off as you move towards the extremes.

That answer makes a lot of sense. I guess I just have a feeling most "people who like taking pictures" like me (I would not currently call myself a photographer :oops:) probably couldn't tell the difference.

You would be surprised. Once you start shooting with a decent lens, the IQ difference becomes extremely noticeable. I copied and pasted the above reply by the way. lol.

Quote:

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Originally Posted by smaeda

I copied and pasted the above reply by the way. lol.

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I thought it seemed a little too "by the book" :lol:

So basically it's a matter of IQ going up as the focal range goes down (in general), right? That said, lenses like the 24-70 exist because sometimes you just can't have 5 lenses in your bag at once and expect to catch the moment?

Also different ones are released at different times. Some of those are older lenses and some are newer..and some are DX only (crop sensor), others are FX (full frame compatible)

Good point. I didn't think about that.

Still, I was wondering why you'd have, say, an 11-16 for wide shots. Why do you need such a narrow focal length? It's not like 18-55, 55-200, 24-70, etc. where you're covering from wide to narrow-angle...wouldn't you be better served to just have a prime?