[pure-silver] Re: Aha! Scan This....

  • From: Bogdan Karasek <bkarasek@xxxxxxxxxxxx>
  • To: pure-silver@xxxxxxxxxxxxx
  • Date: Sun, 04 Feb 2007 23:49:52 -0500

HI, Juat a question below:

Laurence Cuffe wrote:

On Sunday, February 04, 2007, at 06:14PM, "BOB KISS" <bobkiss@xxxxxxxxxxxxx> wrote:

  He reported a strange form of digital
chromatic aberration when the rays strike the surface at more than a slight
change from the perpendicular. CHEERS!
                        BOB

Somebody please correct me if I'm wrong (I don't know anything about digital photography; I do LF film and plates)

The implication of Bob's statement is that you could not use digital photography in the field of architectural photography (are there any others fields???) One of the problems in architectural photography is the phenomenon of convergence at top of the structure in question. So, you use the rise on the front standard to compensate, if you will, for the convergence phenomenon. Then in the darkroom, you fine calibrate the parallel lines of the structure.. tilting the easel etc..

This seems to suggest that digital sensor is useless in this field since it cannot compensate for the convergence. If true, then it is encouraging because it implies that there will be a professional need for film.

Can software correct the convergence, and if so, do it as well as the rise on a film View camera?

Any ideas on the matter?

Cheers,
Bogdan



Interesting, 1) I think I probably wasn't aware of the effects of tilt in the 1980's and so didn't recognize it! 2) The digital probably puts this OT but I can visualize this as being an effect of chromatic aberration in the IR cutting filter above the sensor dropping parts of the image into the wrong set of color sensors. This could be something which software corrects for correctly with short focal length lenses when used in a symmetrical fashion at small F stops on digital cameras, but I wonder does it become a problem at large F stops with such lenses when opened up?
All the best
Larry Cuffe (prepared to take this discussion off list if it a) continues and b) annoys any one.)

-----Original Message-----
From: pure-silver-bounce@xxxxxxxxxxxxx
[mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of Laurence Cuffe
Sent: Sunday, February 04, 2007 3:30 PM
To: pure-silver@xxxxxxxxxxxxx
Subject: [pure-silver] Re: Aha! Scan This....


On Sunday, February 04, 2007, at 12:09PM, "Bob Randall" <bob@xxxxxxxxxxxxxx>
wrote:

On 2/3/07 6:07 PM, "Stein" <rstein@xxxxxxxxxxxxxx> wrote:


I used the technique of a camera on a tall tripod looking down on the

rows of

subjects with a very small tilt of the front standard ( Try THAT on your

Canon

10D

I loaned the use of my studio to a fledgling photographer yesterday. He was
shooting a digital Canon of some sort with a most unique lens, 35mm focal
lenght with swings and shifts. You simply must read more!

Bob

A long time ago I bought a black and white digital camera sensor for
astronomy and mounted it in the back of a crown graphic press camera, which
made limited tilts, swings and shifts possible.  It was fun to play around
with. At the time I wondered if anyone had used tilts and swings
cinematographically, and I still wonder about it. Does anyone know of any
such work?
All the best
Larry Cuffe

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--
________________________________________________________________
  Bogdan Karasek
  Montréal, Québec            e-mail: bkarasek@xxxxxxxxxxxx
  Canada

                  "I photograph my reality"
__________________________________________________________________


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