ULF Pinhole?

[john_kasaian2]

Every so often I start drooling over the prospect of shooting ULF, but fortunately I am in no danger of having enough disposable income in the foreseeable future to enable me to purchase a 12x20 and the requisite lens and holders. I was wondering if any of you knowledgeable people have ever tried building a 16x20 pinhole camera? There are lots of pinhole websites, and I found an excellent table at the Penultimate Pinhole Guide cross referencing film to plane distance, optimum pinhole size and f/no., but none of the sites I visited had any information on the image circle a given size pinhole would produce at a given distance. This seems like a cheap way to try ULF using 16x20 paper and a box. Does anyone out there know of a table for pinhole image circles or can give the specs for a 16x20 pinhole camera? Thank you!

[dmin-99]

The actual image circle is somewhat (totally actually) dependent upon

the thickness of the material used and the aperture cut (and how

cleanly it is cut). Under ideal circumstances you may be looking at

an acceptance angle of ~150 degrees. Just remember the Cosine law -

things will get darker toward the edges the wider the angle that you

use.

[bj_rn_nilsson]

I havn't seen any such table either, but judging from most cameras

I've seen pictures from (in 4X5"), the shortest "focal length" seems

to just shy of 2". For 16X20" that would be some 8". Now, you will

probably have severe light falloff and possibly some vignetting as

well, apart from the extreme wide-angle effect. Given that 25" is

the "normal" focal length for that size, I'd start with a camera 12"

deep. with a hole that is some 0.7 mm (slighty smaller than 1/32").

 

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As you've probably already figured out, this camera would just be a

box, which you can make as nice (or ugly) as you want, as long as it

keeps stray light out. You can spend one hour or one week building

it. (It will probably look much nicer in the one-week version.)

 

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The main thing it that you have fun doing it! (People who pass when

you take pictures with this beast will have fun looking at you. ;-)

[david richhart]

John... If you are building your own camera for pinhole why not

consider constructing a method to arc the filmplane around the

hole... keeping the center & the edges of the filmplane equidistant

from the hole. I would think that should produce a type of panoramic

camera...??? -Dave

[jnanian]

hi john

i am building a 8x20 pinhole camera for pretty much the same

reasons you are...

 

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from the research i have done -

you can get laser cut pinholes of any minute aperature from

pinhole resource or a place called "minute aperature" in wi.

the thinner the shim is that the hole is cut into, the better chance

of full coverage and the image circle is about 3x the focal lenght.

good luck!

- john

[john_kasaian2]

Thank you all for the great ideas! I think I'll try Bjorn's specs

and I like the idea of an arc to hold the paper/film as Dave

suggests.If I have trouble making my own pinhole, I'll contact

Pinhole Resource as John suggests. Thank you all!

[desmond_kidman]

Hello,

 

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Could someone tell me how to contact "Minute Aperture" or "Pinhole

Resource?"

 

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Could you also suggest some of the best pinhole camera forum sites?

 

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There is a book of Venice which has stricly pinhole images which has

sparked my curiosity about the practical use of these cameras.

 

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Thanks.

[bj_rn_nilsson]

Armando and all others

 

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Pinhole resource is at http://www.pinholeresource.com and one of the

users that have had his page up for a long time is Jon Grepstad at

http://home.online.no/~gjon/ (where you find a pinhole link, with

lots of info and links).

[guillermo_penate]

John,

You have already been giving you good suggestions. Risking

being redundant, allow me to add this: A flat film plane camera would

be affected by the "full" COS^4 law. It is said that "acceptable"

fall off (under pinhole imaging standards) is obtained with cameras

whose focal length is no more than 3.5 times the diagonal of the film

format, BTW, 3.5 times would give you a camera with an angle of view

of about 120 degress, equivalent to 12mm lens on a 35mm format

camera. If you really dislike fall off, use a focal length no more

than 2 times the diagonal, which still would give you a wide angle of

view (2 times would give you the equivalent to 21.5mm for 35mm

format).

 

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An ARChed film plane is a good way to reduce substancially the fall

off, so that is a good suggestion, just wanted to add that if your

camera is cylindrical, you would get distortion (something good if

that is what you want). If you don't want distortion, make your

camera a half cylinder and position the pinhole right in the center

of the the half-circle describing your arched film plane.

 

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Making pinholes is not that difficult, the difficulty most people

have is in measuring them. A microscope with measuring capabilities

is what I use, but also a scanner (flat bed or film scanner) could be

used, I wrote a small article (nothing fancy) on how to do that,

here is a link to a page that points to it:

 

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http://members.rogers.com/penate/pinhole.html

 

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Guillermo

[john_kasaian2]

Thanks for all the advice!I"m getting the thinnest brass shimstock I

can find for my pinhole and I've been trying to rig some kind of go

no go guage, either that or take it to the local University. I've

found that a box of Krispy Kremes on the desk of the right people are

an excellent way of tapping the their resources and getting things

done(like having a pinhole measured) I think following the directions

I've seen on the web---making a dimple and sanding it down until it

becomes a hole will be interesting. For a film/paper holder I think

I will get some soft metal like brass or aluminium, bend it to form

the semicircle and make a channel on each end to keep the paper from

slipping. With the paper/film holder and the pinhole finished, I

only need to find a box it will fit in to try my "proof of concept"

before attempting to build a wood body. Hmmm...I've got some redwood

from an old fence thats been replaced...Maybe I could take a picture

of a redwood with a redwood camera?? Thank you all!

[lbi115l]

Just for the record, In "The Camera" Adams talks about having pinholes cut in something very thin, I believe it was thin sheets of gold.

[jon_grepstad1]

<p>Please note that in October 2015 my webpages on building large format cameras move to: jongrepstad.com</p>

<p>Jon Grepstad</p>