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will kirchoff
12-02-2007, 09:24 PM
Hello all-

I am building a 7 x 17 inch camera that I would like to create a zone plate for. There is a zone plate generator on the site Mr. Pinhole, but I do not know what I should enter as the proper focal length. Can anyone suggest a "normal' focal length for this size format? Thanks for any help- Will

Murray@uptowngallery
12-02-2007, 10:13 PM
nominally (7^2+17^2)^0.5 (square root of sum of squares of the side dimensions = nominal diagonal...the actual is a miniscule bit shorter, but insignificantly).

If you have zone plate making capability, great...otherwise go back to f295 and email user POB (Pierre-Olivier) & tell him your project.

sanking
12-02-2007, 10:56 PM
Hello all-

I am building a 7 x 17 inch camera that I would like to create a zone plate for. There is a zone plate generator on the site Mr. Pinhole, but I do not know what I should enter as the proper focal length. Can anyone suggest a "normal' focal length for this size format? Thanks for any help- Will


Normal focal length for a 7X17" camera might be in the 450mm - 600mm range. However, many people prefer wide angle lenses for this format, and 305mm is very popular. Bear in mind that with a zone plate you have to be concerned about depth of field, since unlike a pinhole the zone plate lens focuses.

If I were you I would have the zone plate lens made in the 270mm to 350mm range.

Sandy

TracyStorer
12-04-2007, 11:35 AM
Hey Will,
don't I know you from Boston?
Many folks like to use the "normal" lens for the "normal" format on which the pano format is based, which in this case might be the defunct 7"x9" format, which would make between 270mm and 305mm a focal length to look at, or in other words, "what Sandy said"
Best,
Tracy

Deckled Edge
01-09-2008, 04:03 PM
[QUOTE=Murray@uptowngallery;553225]nominally (7^2+17^2)^0.5 (square root of sum of squares of the side dimensions = nominal diagonal...the actual is a miniscule bit shorter, but insignificantly).

QUOTE]

Nominally I would agree, where the aspect ratio is roughly equivalent to human vision, ie: 1:1.25 or 1:1.5. With a panorama however, it seems to me that the vertical is cut down somewhat and the horizontal is greatly expanded from our usual conception of the visual field. Accordingly, I wonder if Pythagoras should be invoked for a 7x17 to actually consist of an imaginary 7x9, or 8x10, or 9x12 (choose your own) field of view. If you choose 7x9, for instance, you get 11.4 in. or a 290 mm lens. If you choose 9x12 you get 15in. or 380mm.
Personally, I shoot a 355 when I want "normal" and it looks "normal" to me, but then again, I'm not normal.