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Old Dec 10, 2006, 3:09 AM   #1
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Hi
Any body tried both here?

and what do u think is a better buy. How badly one will need the f2.8 at this focal length over the IS.

Thanks
Vj
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Old Dec 10, 2006, 8:25 AM   #2
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I don't care much about IS; However the 24-70 is pretty long in the tooth in design...
The new 24-105 is a much sharper lens (even more so @ the borders)!!!
Except for thoses few sunrises/sunsets would that 1-stop difference really matter? :idea:
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Old Dec 10, 2006, 3:54 PM   #3
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Also, if you were thinking about depth-of-field, consider that the extra focal length more than compensates for the loss of stop.

For example at 3m focus distance.

70mm @ f2.8 => 31cm DOF.
105mm @ f4.0 => 19cm DOF.

Though I agree with NHL that IS is not the most important factor, consider that most manufacturers claim ~3 extra stops of "hand-holdability" from IS, and you are only losing 1 stop from f2.8 - f4.

Combine it with extra range, the extra sharpness, the fact that it is lighter and quite significantly cheaper.

It seems that the 24-105 wins on just about every criteria that you care to mention.
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Old Dec 10, 2006, 5:57 PM   #4
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I agree for the most part with the others - although here in the states the two lenses are about the same price - around $1000 - $1100

The only reason I can think of to select the 24-70 is for low light action shots. No amount of IS can replace that stop. If you're not shooting low-light action than the 24-105 is the way to go.
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Old Dec 10, 2006, 9:37 PM   #5
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peripatetic wrote:
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Also, if you were thinking about depth-of-field, consider that the extra focal length more than compensates for the loss of stop.

For example at 3m focus distance.

70mm @ f2.8 => 31cm DOF.
105mm @ f4.0 => 19cm DOF.
Except... you have to shoot from further away to get the same subject framing with the longer lens, cancelling out the differences in DOF. With the same framing (shooting from further away with the 105mm lens), the shorter lens would actually have less DOF at f/2.8 compared to the longer lens at f/4. ;-)

At most distances you'd be concerned about D0F, you'll have the same DOF regardless of focal length, if the aperture and subject framing is the same.

Here is an article on the subject, and you can check it with a DOF calculator (works, unless your focus distance gets close to the hyperfocal distance).

http://www.luminous-landscape.com/tutorials/dof2.shtml

IOW, if you shoot with a 100mm lens, you'd need to be twice as far from your subject for the same framing as you'd need to be shooting with a 50mm lens. So, you have to take framing into consideration calculating DOF.

Although, I'll admit that the perspective difference you get from shooting from further away with a longer lens gives the illusion of a shallower depth of field (due to the more compressed background).


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Old Dec 11, 2006, 3:20 PM   #6
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I have to admit that that particular article I find very unconvincing.

I don't think the DOF formulae support his assertions, and I don't find the test setup convincing either. The toy is on a pedestal isolated from its near and far surroundings, and even so I find the DOF differs somewhat between the pictures.

I don't deny that adjusting for field of view mitigates the effects somewhat.

In general I'm a pretty big supporter of MR, and in fact I subscribe to the LLVJ, but that particular article leaves me very unconvinced. It simply doesn't take focal distance into proper account.
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