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Old Jul 29, 2010, 12:13 PM   #1
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Default Focusing speed

Yeah, I know I'm asking a lot of questions, but thats just how you learn isn't it?

Ok so today the quesion is-

I hear a lot in comparison between lenses about the focusing speed, let's take for example the telephoto lenses-

1.Sigma 70-300
2.Canon 55-250
3.Canon 70-300 IS USM
4.Canon 70-200 NON-IS f/4

I wrote them in order of the focusing speed according to what I read, but i ask myself, how much faster are they one from another? are we talking seconds faster? half a second? a hundred of a second? and how will it really affect the pictures?

(Let's assume that i try to photograph a moving object to make the focus speed important.)

Thanks for answering all my questions
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Old Jul 29, 2010, 12:53 PM   #2
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Ishay

We are talking about, generally speaking, fractions of a second. If you are doing action shots that time can be critical. However, for general photography, it will be of less importance.

Have you gotten that need external flash for the wedding yet??

Sarah Joyce
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Old Jul 29, 2010, 1:07 PM   #3
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Hey sarah,

I was asking because there seems to be a quite big price difference, so i was wondering how much more do you really get in the focusing department.

About the flash, thanks for asking, haven't got it yet. Wish money would grow on trees...until it does, i'm saving penny by penny to get the amount needed...
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Old Jul 29, 2010, 1:12 PM   #4
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It's not the speed of the subject that will be the problem but the speed of the relative change of distance from the camera. If you shot a car going past at 70mph but you were say 100 yards from the road then for the portion where it passes the relative change of distance is no more than a couple of yards. Now if you are right next to the road shooting the car coming towards you that is a different matter.

Focus speed is not only helpful in shooting action though. I'm used to using the Canon 24-105mm f4 IS USM and 70-200mm f2.8 IS L USM which both focus very quickly. As I only have 2 of my camera bodies with me I've been using my Sigma 17-70 quite a bit and I really notice the slow down in work flow when shooting portraits on location where usually I like to work quickly so that the subjects don't get bored. Don't get me wrong, we are not talking an age, but it is very noticeable compared to the high speeds of USM.

Also the body will make a difference in focus speed too.
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Old Jul 29, 2010, 1:13 PM   #5
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Quote:
Originally Posted by Ishay View Post
Hey sarah,

I was asking because there seems to be a quite big price difference, so i was wondering how much more do you really get in the focusing department.

About the flash, thanks for asking, haven't got it yet. Wish money would grow on trees...until it does, i'm saving penny by penny to get the amount needed...
For most people the important thing is to get good sharp glass. In your list however the two sharpest/best performing lenses also have HSM, so you win both ways.
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Old Jul 29, 2010, 1:20 PM   #6
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Also, the price difference isn't just focus speed - although that's part of it. You're also paying for optical quality and BUILD quality. Go to a store that has those lenses - hold a sigma 70-300 and a canon 70-200 f4. You'll notice immediately a tremendous difference in the quality of the material used. Even between the cannon 70-300 and the 70-200 f4 there's a very big difference in build quality. There's also a difference in optical quality. Tremendous difference between the sigma and Canon f4. Less difference between canon 70-300 and canon 70-200 f4 but it's still there.
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