On Oct 17, 2007, at 9:49 AM, Cotty wrote:

> On 17/10/07, [EMAIL PROTECTED], discombobulated, unleashed:
>
>> And less than 2.8 is frequently the stop of choice for portraiture.
>
> or even 1.4  ;-)))

Huh? I dunno about anyone else, but I need about 1-1.5 feet DoF as a  
minimum at 7' focus distance for a conventional H&S portrait to  
obtain razor sharp eyes and acceptably sharp nose to shoulders, with  
a nicely soft backdrop.

With an 75mm lens on a 35mm film SLR, that requires f/8.
-
Subject distance 7 ft
Depth of field
Near limit 6.43 ft
Far limit 7.67 ft
Total 1.24 ft
In front of subject 0.57 ft (46%)
Behind subject 0.67 ft (54%)
-

With a 43mm lens on a Pentax DSLR, it presents a somewhat wider FoV,  
but f/4 works well to produce a very similar image:
-
Subject distance 7 ft
Depth of field
Near limit 6.42 ft
Far limit 7.7 ft
Total 1.28 ft
In front of subject 0.58 ft (45%)
Behind subject 0.7 ft (55%)
-

Shooting with either at f/2.8 or larger lens openings creates  
unsharpness in the foreground (at the nose) of a H&S portrait, which  
is distracting and looks bad.

Godfrey

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