Zone focus takes advantage of the apparent DOF from a small aperture.
Simple, or sometimes not so simple cameras that have smallish apertures,
and only use Zone focus will make a number assumptions about film size
print size and the users tolerance for out of focus images and supply
usually either two, three or four zones focus settings.
It actually seems to me that you're talking about using the hyperfocal
distance. Which once again makes assumptions about those three things
but attempts to produce an image that's in acceptable focus from some
near distance to infinity. This doesn't quite work the way you are
trying to use it. Old Pentax WA lenses give the recommended hyperfocal
settings as red settings on the aperture ring and the distance scale in
red, (for f8), assuming 35mm film, and an 8x10 print.
Now you're using a 15mm lens on an APS-C sensor. f/Calc(tm), assuming a
circle of confusion of .016mm gives a near focus distance of ~1.7 meters
at f8 or ~0.9 meters at f16.
The usual technique for using this information is to set the near
focusing distance to the near dof marking for the set f stop, but that
doesn't work for APS-C sensors using full frame lenses. The assumed
acceptable circle of confusion diameter is less than 1/2 the size the
DOF markings assume. So if you use the f8 distance with the aperture
set to f16 you'll come close.
And yes a flange distance error could cause the problem but only if you
observe it using the modified settings.
On 10/3/2013 12:50 PM, Steve Cottrell wrote:
Okay folks here's a question I'll throw to the floor.
I've finally been able to mount a fully manual wide angle lens onto my
Fuji X-E1 and I was testing with it this afternoon.
For the curious, this is what the combo looks like:
<http://pdml.posthaven.com/fuji-and-wide>
BUT if I try and 'zone' focus with it, the background is out of focus.
Facts: lens is M39 mount and mates to camera via a M39-to-Fuji X (FX)
adaptor. Camera set to Auto so you offer it some light through the lens
and it will correctly calculate the exposure. This is flawless. Lens set
at (say) f/16, and infinity mark on focus barrel is moved to the f/16
mark so that everything between the two f/16 marks should be in focus
according to depth of field.
Result: foreground is sharp, everything from about 20 feet away to
infinity is soft.
However: if I leave the infinity mark at maximum focus (eg lens set to
infinity focus), and stop down to (say) f/16, then everything from about
2 feet away to infinity is in sharp focus!
Supplementary question:
To mount an M39 lens onto an FX body, apparently there are two routes:
just by using a M39-FX adaptor. OR by using an M39-Leica M (LM) adaptor
AND a LM-FX adaptor as well. Wouldn't the two methods produce differing
lens flange - to - sensor plane measurements? I appreciate this question
really needs to be addressed to something like the Fuji forum, but
thought I would put it past the ,might PDML collective first.
Would an incorrect lens flange-to-sensor measurement create the zone-
focus issue above?
Many thanks
--
A newspaper is a device for making the ignorant more ignorant, and the crazy,
crazier.
- H.L.Mencken
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