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Old Jan 8, 2007, 9:19 PM   #11
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NHL wrote:
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It's already @ ISO1600 (with 1/800s & f/2.2)!
Yep - that would mean an f4 lens is a poor choice as you'd have to shoot at ISO 3200 to get acceptable shutter speeds and I'm guessing autofocus would be poor.

If you can shoot from the floor - go with the 85. If you have to shoot from the stands, save up for the 70-200 2.8 otherwise you're throwing money away, IMO.

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Old Jan 10, 2007, 11:53 AM   #12
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JohnG wrote:
* Even if possible, it might force you to ISO 3200 AND you'd likely see poor autofocus performance.* And poor autofocus is one of the things you're trying to correct.[/quote]

JohnG: Would you please explain the rationale for poor auto focus using ISO 3200...if given the choice, from an auto focus response point of view, should I avoid shooting at ISO 3200 and instead use a slower shutter speed (assuming the slower shutter speed is fast enough to stop action.
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Old Jan 10, 2007, 12:07 PM   #13
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Coachjerry - the poor focus isn't BECAUSE OF using ISO 3200. Sorry if I was misleeading. The need to use iso 3200 and the poor autofocus are both results of there being low light. In a given environment, a given camera and lens will focus just as good or bad regardless of what ISO you are using. The rationale behind my statement was this: Based on the exif information of that shot, an f4 lens would require ISO 3200 to get necessary shutter speeds. That is low light. An F4 lens is going to have trouble in low light. Even 2.8 lenses will have some issue in low light. Heck, if the lighting is really bad, even 1.8 or 1.4 lenses have trouble.

So, using a lower ISO and lower shutter speed won't make a difference - you still have the same poor amount of light and thus autofocus performance will suffer.

Or put another way: for the same gym, and assuming the same quality focus mechanism on each lens, a 1.4 lens will focus better/faster than a 1.8 lens which will focus better/faster than a 2.0 lens which will be faster than a 2.8 lens, etc. etc. etc. When lighting is good there may not be a difference. But when lighting is poor there is definitely a noticable difference.

Also remember, a lens always focuses at max aperture - a 1.8 lens always focuses at 1.8 - if you set the lens to f11, it will focus at 1.8 then close down to f11 when the shot is taken.

As a general rule, when you get up to needing ISO 3200 to get a 1/400 shutter speed, expect there to be focus issues. There just will be. Note this isn't an exact cut-off, but a guideline. While those focus issues may be negligible for still shots they mean the difference between success/failure for sports shooting.
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Old Jan 10, 2007, 12:13 PM   #14
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JohnG

Great response--thanks for the clarification.
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Old Jan 10, 2007, 2:01 PM   #15
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JohnG
Here a several photos I took yesterday that illustrate the focus difficulties in lighting environments that need ISO3200.

The focus is soft in some of the shots and the noise level is very evident even though I use noise ninja to help with that.

These are with a 20D 70-200 f2.8 and most were shot at 1/400th. I believe all the photos were taken using center point and AI Servo.

I think on most if not all I had the flash on in hi speed sync to help if it could.

Please free to critique.

Thanks
Jerry

PS apparently I wasn't ablew to attach the photos-sorry
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Old Jan 10, 2007, 2:08 PM   #16
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Can anyone give me info on properly attaching a photo including exif data?

Thanks
Jerry
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Old Jan 10, 2007, 3:04 PM   #17
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Maybe this will work. But apparently only one photo at a time.
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Old Jan 10, 2007, 3:06 PM   #18
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here is one with softer focus
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Old Jan 10, 2007, 3:07 PM   #19
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and one in a dark portion of the field
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Old Jan 10, 2007, 3:23 PM   #20
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The second shot is the soft focus problem I am having in low light also. Although I can't use a flash. Is there anything we can do for it?


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