Zoom ranges

Just wondering, why does most zoom lenses start and end at "standard" focal

lengths? For instance why don't we have a 15-75mm (or 10-50 APS-C) lens? Is

this because there's no demand for them or is it more difficult to make them?

 

I often find it frustrating while using the Sigma 10-20, trying to zoom out a

bit more... A 10-50 would be so nice for indoor use. Does anyone share this

sentiment?

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It's likely more out of law of the nature. It's not easy to combine ultra wides with (even moderate) telephoto, as such a zoom lens will need more glass construction inside, wider diameter to use in order to get an acceptable speed (nobody would want to buy a 10-50mm f/5.6-8, right?), more things have to be done to prevent flare, distortion, abberations etc. caused by this complex construction. By the time they finally succeed to do it (after years of research and all that), the price is already exorbitantly high nobody's going to buy except a few for whom money doesn't seem a blockage. From economical point of view such a lens isn't interesting to sell.<BR>

 

<BR>I'd rather buy another (cheaper) second back-up body and mount something like 28-135mm lens and have it with you all the time beside the one with 10-20mm mounted in your bag. That way you're flexible enough to shoot almost anything photographable.  | <A HREF="http://www.photo.net/photodb/user?user_id=332699" TARGET="_blank">JRa</A><P>

Marketing? I suspect it's done out of habit duplicating fixed focal length lenses at both

ends to get buyers with comparable focal length. Why would someone carry a set of lenses

from 28mm to 135mm when a 28-135mm zoom will replace it? And what would you do if

you had one that didn't end on a common focal length? It may seem awkward to use when

it ends between common focal length lenses, and force the photographer to carry that lens

with the zoom.

 

In the "old" days, zoom lenses had 2:1 ratios and were eventually extended to higher

ratios, where 3-4:1 or more is common now. I don't have any zoom lenses, never got used

to them, and don't plan to own any. In the "old" days there weren't as good optically as

fixed focal length lenses, and most still aren't, with few exceptions (eg. Nikon's 200-400

f4 zoom).

 

But it's a personal choice and zoom lenses have some advantages. Just my thoughts on it.

Quality and price. It is not possible to make a good quality zoom lens that has a large range. This becomes especially difficult when you combine very short fobal lengths (below 20mm) and then try to extend it further. That is why the good wide angle zooms only have 17-35 type ranges. There are some lower quality lenses that offer wider ranges (18-200) but these do not have very good image quality. Really good zoom lenses are difficult to make even if their zoom range is small and that adds to the cost and size. To achieve similar image quality with larger zoom range would make the lens much bigger and more expensive, limiting its usefulness.

I've got a 70-150mm zoom for my 35mm SLR. Neither end of the zoom range is what I'd call "standard". It's a useful lens though.