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[OM] Re: Tele Football shots, was: Re: Chuck's 'round-the-country tour

Subject: [OM] Re: Tele Football shots, was: Re: Chuck's 'round-the-country tour
From: "Jez Cunningham" <jez@xxxxxxxxxxxxxx>
Date: Tue, 29 Jul 2008 17:00:18 +0200
I think you're using a good rule-of-thumb - but maybe for the wrong reason!

If a person walks at about 3mph, that's 4.4 ft/second.  His foot is
stationary for half each step and moving at double that (on average) for the
swing - lets say at peak 10ft/sec.
So in your 1/250th of a second, the foot moves 10ft x 12 inches-to-a-foot  /
250 = a half-inch. A half-inch blur on a foot-long foot is probably just
about tolerable to be considered a sharp rendition of the foot.

But none of the above has any consideration for the lens focal length or the
amount of magnification for the print.  For sure on a 4x6print of a
full-sized body the tiny blur on the foot is not going to be seen.  But if
you zoomed on just the foot it would be another story.

I think we end up with having to define what is an acceptable
circle-of-confusion or some such stuff.

I find it all much easier to do the simple math for how fast an object is
moving and setting the shutter speed for the amount of blur I want.

Concerning camera shake, now we're talking more complex math and I like the
"1/focal-length rule of thumb for 35mm format".

Jez
On Tue, Jul 29, 2008 at 4:33 PM, Chuck Norcutt <
chucknorcutt@xxxxxxxxxxxxxxxx> wrote:

> I beg to differ.  It very greatly affects angular velocity across the
> image plane... in other words, subject motion from the camera's
> perspective.
>


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