[LRflex] Re: Z + N = ? OT (maybe)
- From: George Lottermoser <imagist3@xxxxxxx>
- To: leicareflex@xxxxxxxxxxxxx
- Date: Mon, 06 Jun 2011 16:31:30 -0500
On Jun 6, 2011, at 4:10 PM, Richard Ward wrote:
> tied that argumentally well with theses regarding the confluence of
> challenges presented by the utterly flat plane of digitalimage sensors, those
> sensors having reached a combination of small enough pixel sites and/or pixel
> counts which make detecting quite minute variations in alignment of any optic
> used with them a straight forward proposition, and theoretical and ancedotal
> information regarding the cause of one customer exchanging a rented lens as
> unusably soft and the exact same copy of the lens being extolled by the next
> renter as being stunningly sharp.
I totally understand the discussion Richard
re: sensor plane alignment to optical system focusing on it.
Though again consider a TS (tilt shift) lens where one can readily alter the
parallel relationship.
This same issue of absolute critical placement of the sensor to the focusing
ground glass, mirror/ground glass, or range finder system
has been discussed in view camera circles when using digital backs;
and at Leica with the M8, M9 and S2.
In those cases and I suspect any other SLR cases
it's much more about shimming the sensor to achieve absolute, precise
relationship to the focusing system
than having anything to do with a lens mount.
.01 mm out at sensor will affect the image
.01 mm out at the ground glass will affect the image
.01 mm out at the mirror will affect the image
.01 mm out at the lens mount will not affect the image
(because you'll compensate for it when focusing - as if using a .01 mm
extension tube)
unless there are alignment problems at the mirror, ground glass or range finder.
Point being: You can hang any lens at all in front of the box;
with or without extension tubes, bellows, swings, tilts, shifts - whatever
— but what ever you're using to focus that lens
(ground glass on a view camera, mirror and ground glass in an SLR, rangefinder)
must be absolute critical relationship to the sensor plane
to achieve focus accuracy.
Regards,
George Lottermoser
george@xxxxxxxxxxx
http://www.imagist.com
http://www.imagist.com/blog
http://www.linkedin.com/in/imagist
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