RE: Building my first serious pinhole

Hi Trevor,

On 18x24cm format, the equivalent focal lenght that gives the same
perspective of a 24mm lens on 35mm film is something around 160 - 165mm.
The diagonal length of 35mm format is 43.27mm, the diagonal length of 18
x 24cm format is 293mm (image size was assumed as 17.5 x 23.5cm -
thinking you will be using some sort of holder). So the equivalent focal
length in 18 x 24 mm would be 35mmFL * 293 / 43.27 = 18x24cmFL... Of
course, this doesn't take into account the image width / height
proportion difference between each format. If you need a specific
horizontal or vertical coverage, you have to make the calculations
accordingly...

Regards,
Loris.

-----Original Message-----
From: owner-pinhole-discussion@spitbite.org
[mailto:owner-pinhole-discussion@spitbite.org] On Behalf Of trevor
cunningham
Sent: Wednesday, December 01, 2004 9:06 AM
To: pinhole-discussion@spitbite.org
Subject: [pinhole-discussion] Building my first serious pinhole

Hey all...been lurkin' for some time. But now I need a few questions
answered. I've recently come into availability of B/W sheet film that
is 13cm x 18cm (this is a feat in Cairo). I'm going to get a set of
holders and will have a carpenter (my skills were heavily discouraged by
my high school wood shop teacher!) build a box to suit. My goal is to
achieve the effect of a 24mm lens on a 35mm camera and wish the image to
cover my entire piece of film with as little loss of image out of frame
as possible. I've tried a pinhole calculator on the internet and am
getting a focal length of approximately 100mm to achieve such an image
diameter...is this right? If I want that really wide angle look, do I
have to compromise my image size? My intention is making contact negs
for cyanotypes and gum bichromates. At a point, size becomes an issue.

Enjoy...Trevor Cunningham

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Received on Wed Dec 1 00:28:08 2004