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PostPosted: Thu Oct 07, 2010 9:55 am 
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Apologies for my ignorance but how does a telephoto lens relate to the magnification as described on a compact ?

compacts say stuff like "10x optical zoom" whereas proper lenses are described using mm's

e.g. what is the 'optical zoom' (in laymans terms!) of a Canon EF-S 55-250mm f/4-5.6 IS ?

I Hope this post makes sense!


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PostPosted: Thu Oct 07, 2010 10:04 am 
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Roughly 4.5x optical zoom. As far as I know, optical zoom shows the multiplication factor between the widest and most zoomed view through the P&S lens.

Meaningless comparison, of course, as you don't really know what the minimum focal length on the 10x zoom you're talking about is, in 35mm film terms.

For DSLR lenses, generally the higher the 'optical zoom' the more compromises there are. The biggest I can think of off the top of my head is the Sigma 50-500mm (10x)


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PostPosted: Thu Oct 07, 2010 10:05 am 
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Ninja'd.

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Last edited by Eagle1337 on Thu Oct 07, 2010 10:06 am, edited 1 time in total.

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PostPosted: Thu Oct 07, 2010 10:06 am 
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D'oh - and then there are the 18-200mm which is 11.1x optical zoom.


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PostPosted: Thu Oct 07, 2010 10:06 am 
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Or the new 28-300mm Nikkor, which is 10.7x optical zoom

I'm putting my calculator away now!


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PostPosted: Thu Oct 07, 2010 10:51 am 
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One more :P

Tamron 18-270mm --> 15x zoom

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PostPosted: Thu Oct 07, 2010 11:22 am 
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Thanks for the replies, just wondering how you work it out ?!


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PostPosted: Thu Oct 07, 2010 11:28 am 
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its kinda easy: optical zoom= telephoto end mm / wide angle end mm

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PostPosted: Thu Oct 07, 2010 2:13 pm 
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And most or all compacts give you the widest angle equivalent in the specs - they'll usually tell you 24mm or 36mm...then have the optical zoom as '5x' or '12x'. So with the compact, just take that wide number, and multiply by the 'x' to get the maximum telephoto in 35mm equivalent.

It's one of those things I always tried to explain to friends with compact ultrazooms who didn't know better. They'd have a 12x camera, and were interested in picking up a 15x camera, because it could reach farther. When I'd tell them it couldn't, they looked at me like I had 2 heads. But their 12x camera was 36mm wide, while the 15x they were considering was 24mm wide. They didn't get the concept - they just saw 'more x' and assumed longer reach.

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PostPosted: Thu Oct 07, 2010 3:16 pm 
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zackiedawg

Is that 24mm or 36mm the equivalent of 35mm/full frame, or x1.5/1.6 for Nikon/Canon crop, or x2 for 2/3rd bodies?!?!?!?


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PostPosted: Thu Oct 07, 2010 4:24 pm 
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Silly, isn't it - all those crop factors and equivalents!!??

Though I take it you're joking...I figured I'd add a deeper explanation for some who might not know all this yet:
Those are from ultrazoom P&S cameras - they always give the 35mm equivalent when quoting wide end. Their actual crop is something like 6x - since they only use tiny 1/2.5 sensors (checking out the lens on the front of my old H5 ultrazoom, the actual focals of the lens itself were 6-72mm, which with the 6x crop factor were the 35mm equivalent of 36mm to 432mm. The newer superzooms added more wide end range, with 4mm lenses (24mm after crop factor), and upped the zoom multiplier to 15x...but at the long end they still maxed out at 360mm equivalent (24 x 15). So despite the big 'ol 15x, the zoom range of the newer 15x camera was actually quite a bit shorter than the old 12x camera.

Of course, Phil already knew that - but some might not...I certainly still routinely hear "how much zoom is that?" from people when I'm using a DSLR with a long lens, and if I answer in mm, they look at me funny - they're waiting for how much 'x' it is!

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Justin Miller
Sony DSLR-A580 / Sony 18-250mm / Minolta 50mm F1.7 / Sigma 30mm F1.4 / Tamron 10-24mm / Tamron 200-500mm / Tamron 90mm F2.8 macro / Minolta 300mm F4 APO
Sony NEX5N / 18-55mm F3.5-5.6 / 55-210mm F4-6.3 / Pentax K adapter / Konica K/AR adapter / bunches o' Konica & Pentax lenses!

Galleries:
http://www.pbase.com/zackiedawg


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