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05-12-2015, 04:55 PM   #1
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Minimum focus distance

According to the posted specs, the FA 75mm has a minimum focus distance of 23.6". However, mine will focus down to about 15". Are all of the posted minimum focus distances that conservative, or do I just have an oddball copy of the lens? This is currently my only 645 lens (though another is in the mail) so I don't currently have the ability to test another. Has anyone tested the 80-160mm? That one is next on the purchase list for me.

05-12-2015, 04:59 PM - 1 Like   #2
dms
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Min distance is from sensor to object--so that would account for several inches if you measured from lens objective.
05-12-2015, 05:11 PM   #3
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While the 645z is a bit of a beast, it's not THAT big (and the lens is puny). If I'm being super generous, I'm still less than 20" from sensor to subject. That's a decent variance from the posted specs.
05-12-2015, 05:40 PM   #4
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I'm not entirely certain how accurate those specs are. I was puzzling this same issue the other day with the SMC M 150mm.
The Lens Database reports the close focus distance as 180cm, which just happens to coincide with the last digit (1.8) written on
the metric scale on the lens barrel. However, the barrel can be focused just a little beyond that mark, effectively closer than
1.8 meters. I just took a quick measurement and it would appear that the minimum focus distance for the M150 is about
172cm, not 180cm. I'm now guessing that many lenses show this 'anomaly'.

---------- Post added 05-12-2015 at 07:49 PM ----------

And to be sure, I just measured the distance when the M150 is focused to the 1.8m mark. Sure enough, it's
180cm, so the actual close focus is indeed less than the minimum marked and the specs in the database.

05-13-2015, 09:25 AM   #5
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It's possible that in calculating this spec manufacturers build in the eventuality of lens adjustment: if you need to adjust for maximum front focusing, it would be closer to the official minimum.
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