lens question - both P&S and DSLR related
So I'm not completely new to photography, but I have been away from it for a few years and am trying to make sure I understand things. In particular I'm wondering if I correctly understand how lens specifications work and such..

I understand that a fast lens is a lens with a lower f number or bigger/wider aperture. I have read that a lens with a single f-number has the same lowest f-number across all ranges of the zoom, where as a lens with two f-numbers listed has the first number as the widest at the wide end, the second as the widest at the long end, and may have some other lowest f-numbers at points in between. So, my current camera - an olympus C-4000 (soon to be replaced by a D40) - says 1:2.8 on the front. I take this to mean that it always has 2.8 available. I have read that in order to make a constant-aperture lens it's more difficult because you have to expand the diameter of the opening as the lens zooms..

My questions:Am I correct in my understanding of these facts?.

Are constant-aperture zoom lenses for SLRs more expensive because they are more difficult to make?.

Does this make the lens on my current camera better because although it's not terribly fast, it is faster at the long end than other p&s cameras may be?.

Sorry for being long-winded. Thanks for helping me to understand. Merry Christmas everybody!.



Comments (5)

Yes, I do believe your understanding is correct. And yes, zooms with constant apertures are more expensive. Does the fact your camera has a constant aperture make it 'better'? Well, for point and shoots like your camera, that's pretty much the norm. Making a zoom with a constant aperture for camera like yours (one with such a small sensor) is a lot easier to make (thus cheaper) than one for DSLR sized sensors. You might technically have a 'fast' zoom ranged camera but your still at a disadvantage due to senor size. If these specifications are important to you, you ought to invest in a DSLR....


Comment #1

They usually let in a lot of light (f2.0), brighter lenses are more expensive, plus quality.End of RantTim..

Comment #2

With the point and shoot you could try putting it in a aperture priority mode and seeing how large and aperture it'll let you use on the long end to be sure. Sound an awful nice feature for a point and shoot, all the ones I've used have had variable zooms making the long end only useful in bright conditions..

Image control:Zoom outZoom 100%Zoom inExpand AllOpen in new window..

Comment #3

Corona_drinker wrote:.

If these specifications are important to you, you ought to invest in aDSLR.... my two cents worth! Hope this helps..

Yeah, I'm working on that. My D40 is supposedly getting shipped today. .


Comment #4

BA baracus wrote:.

With the point and shoot you could try putting it in a aperturepriority mode and seeing how large and aperture it'll let you use onthe long end to be sure..

I mostly shoot in M, and the f2.8 is available all the way to the long end - still not great in low light, but at least I don't get slower...

Comment #5

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