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05-12-2009, 09:44 PM   #1
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DA★ 60-250mm Focal length and focus observation

It seems to me as if the difference between 200mm and 250mm is virtually negligible.

Does anyone else have any observations or comments regarding this?

Also, the infinity symbol goes well beyond the focus indicator (about 3 or 4mm). Anyone else experience this? The focus is still fine though.

After a few test shots I can say I'm really happy with the image quality and the sharpness. I look forward to using it in the field.

05-12-2009, 10:31 PM   #2
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QuoteOriginally posted by kcmadr Quote
It seems to me as if the difference between 200mm and 250mm is virtually negligible.

Does anyone else have any observations or comments regarding this?

Also, the infinity symbol goes well beyond the focus indicator (about 3 or 4mm). Anyone else experience this? The focus is still fine though.

After a few test shots I can say I'm really happy with the image quality and the sharpness. I look forward to using it in the field.

Think about it this way.
The standard lens is ~28mm.
That makes 200mm about 7x magnification, and 250mm about 8x magnification.
That's not a lot of difference.
05-12-2009, 10:56 PM   #3
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I'm not sure about the DA* 60-250 but zoom some lenses only reach their longest focal length when focused to infinity. Maybe try focusing on something far away.
05-13-2009, 07:51 AM   #4
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Actually, it's more like 9x (250/28 = 8.92). 250mm is actually closer to 300mm than it is to 200mm, based on ratios. You're increasing your focal length 25% moving from 200 to 250, but only 20% moving from 250 to 300. For what that's worth.

QuoteOriginally posted by Wheatfield Quote
Think about it this way.
The standard lens is ~28mm.
That makes 200mm about 7x magnification, and 250mm about 8x magnification.
That's not a lot of difference.


05-13-2009, 12:51 PM   #5
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Lenses often have focusing capability past infinity to allow for changes in lens length with temperature changes. This is particularly true of long lenses.
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