S80 AutoFocus Problems

Started Dec 5, 2005 | Discussions thread
imbsysop
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Re: Thanks Vincent!
In reply to Nikolaj, Dec 5, 2005

Nikolaj wrote:

In low light is recommendable to use the center autofocus point
(AIAF=OFF) witch is more sensible to light,or...use the Hyperfocal
distance!

'...The concept of hyperfocal distance is easy to understand: focus
a lens at the hyperfocal distance and everything in the photograph
from some near distance to infinity will be sharp.'
'...When the lens is focused on the hyperfocal distance, the depth
of field extends from half the hyperfocal distance to infinity.'
'...The hyperfocal distance is the point of focus where everything
from half that distance to infinity falls within the depth of
field.'

For S70/S80 - 28mm f/2.8 = 2 meters is the hyperfocal distance-
ergo:from 1 meter to infinity falls within the depth of field...
;-)))

For S70/S80 - 100mm f/5,3 = 13,49 meters is the hyperfocal
distance- ergo:from 6,74 meters to infinity falls within the depth
of field... ;-)))

http://www.dofmaster.com/hyperfocal.html

the definitions you give for "hyperfocal" are a bit weird and controversial

and to use the DOF calculater at the dofmaster site you need to input the actual focal lengths not the 35mm equivalents .. The S70 being 5.8-20.7mm

Although yr "28mm" equiv (actually 5.8mm) seems to be more or less correct, the "100mm" F/5.3 is rather erratic

The closest I can get (S70) for a 21mm FL & F/5.6 and a subject at 18 meters (54ft!) nearest focus 7.55meters up to infinity and Hyperfocal point at 13 meters, not to mention that one has to give a "subject" distance in the equation. Setting subject distance = to hyperfocal the figures are 6.5m nearest hyper at 13m

Shifting F from 5.6 to 5.0 shifts hyperfl to 14.6m which just proves that using hyperfocal settings to compensate for low light (if yr cam doesn't focus properly in normal light you'd better toss it out :-)) is not very usefull for indoors when not usuing WA focal lengths even if the subject at half that length is still in focus ..
FWIW
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