mm to Optical Zoom conversion?

[Adgjqetuo]

Hi Guys -

I'm new to the SLR world and I'm used to reading zoom in regards to optical x however i'm seeing SLRs measure in mm. Until I get my feet wet some more with the SLRs - does anyone know where I can find some kind of conversion chart as to what mm = ? optical zoom?

Thanks!

[Photo-John]

Welcome to PhotographyREVIEW.com, Adgjqetuo!

There isn't really a conversion for the optical zoom specs on compact cameras because that "times" is actually an accurate measure. You could have a 3x optical zoom that's equivalent to 28 to 85mm, and you could also have a 3x optical zoom that's a 100 to 300mm lens. Both are 3x zooms, but they're very, very different lenses. Most point-and-shoot zooms start around the 28 to 35mm wide-angle focal length and go up from there. A 28-85mm is a 3x zoom and a 28-140mm is a 5x zoom. But if the wide part of the lens is 35mm, then those numbers change.

The "times" spec is really just a marketing tool that's trying to tell camera buyers they're getting a certain amount of lens. But we don't really think that way with digital SLRs. Lenses with really big zoom ratios aren't usually very good. We choose a lens for the effect its focal length offers, not the zoom ratio. I don't really want a 10x zoom lens for my DSLR. The optical compromises required for such a lens mean that it probably won't have very good image quality. I'd rather have more than one lens and pick the right one for the job.

You probably got more than you bargained for with that answer. And I'm not so sure I explained it well. Maybe someone else will jump in and give it a shot. But this is a good place to start and we're here to help. If you are confused now, let me know what you don't understand and I'll try to explain it better

[ksbryan0]

Adgjqetuo, this doesn't directly answer your specific question, but I think it may help you understand how to look at the "mm" figures on a lens. The mm number refers to the focal length. This is the distance from the front of the lens to the camera's sensor. To help you visualize what this "looks like", Tamron has a page that let's you compare the impact of different focal lengths on a photograph. Check it out at http://www.tamron.com/lenses/learnin...comparison.php

[Liz]

This is may not be what you're looking for. However, I've always compared the film mm to dslr mm so I get an idea of what I'm going to be looking at. I do the "configuring for dummies" version that for me gives me a good idea what I'm going to get having been used to film for years.

Here is how I do it.....
If the lens I'm using is 50mm - I multiply it by .6 (50x.6=30) - then add 50+30 = 80. So I know (compared to film version) that the 50mm lens will be 80mm comparing it to film.

85mm = 136mm - this helps me to remember that for me 85mm is good for portraits - but 136 is a bit close indoors.
20mm = 32mm

However, if you haven't used film, PJ's version will help you out, especially if you're only used to a digital p&s.

All the techies can correct me if I'm wrong - or put it in a more intelligent language.

Liz

[Kag12]

Pj explains it well, have a look on the front of some point and shoot lenses, mine says 28-280 or a 10x. but if it said 50-500, then it would still be a 10x. but i would get much closer because of the 500mm instead of 280mm. basically 'times' the first number until you get the larger number and thats how many 'times' it is. all cameras use the mm method but the p & s use the commercialized 'times' for beginners to simplify it. hope that helps a little.