multiple apertures - any insights?

I've been crawling around the threads here and getting increasingly curious about pinhole cameras. Recently a link was posted to the work of Jeff Korte, whose work I very much liked. One of his galleries is of images made with multiple-pinhole cameras. Probably not everybody's cup of tea, but I found the whole idea to be very very intriguing.

Any ideas how this is done? I think I can picture the obvious bits (custom made camera, an array of aperture holes selectively opened and closed), but I'm wondering about things like - would each exposure be timed as you would a "normal" exposure in those conditions, or for shorter periods (as when you compensate for purposeful double-exposures)? In such a camera, is the distance from aperture to film plane dramatically shorter, or longer, and by how much? I'm having trouble picturing how one controls the area of film (or paper) that gets exposure from each individual pinhole.

I looked at his gallery on his website and those pictures are cool! Here's my guess on the how.... You have a grid of evenly spaced pinholes, each with it's own shutter. You can open say, one row of holes to get one image, another row for another, etc...
He has a picture of 3 fish that comes to mind. You could open each shutter individually with each lens centered on the subject like his owl picture. As for exposure, as with any careful photographer he probably does a lot of testing. However, it looks like the images for each lens do not overlap by much so I think he uses the same exposure for each lens. Give or take. I'm guessing he has more than one camera as well in different configurations.
Just my guess.

hey bruce -

i can make a guess, a pretty bad guess
maybe he is using a grid of very short focal length pinholes, so they do not cover the whole film/paper (whatever ... ) kind of like using a non-covering 2x3 or 3x4 focal length lens in a 8x10 camera ... you will get a small image on a big paper/film. if you get short focal length laser holes from http://www.pinholeresource.com -- you might look for one that is the right focal length for a matchbox &C.

oh, the ones that are laser-drilled have a known diameter & fstop relative to f64, so you can take a light meter reading multiply by a # and get a good exposure every time ...

good luck!

- john

Yeah, what he said. jnanian said what I meant to say about the multiples.

Hi guys.

It's the overlap (or actually, lack thereof) that had me stymied. From what I've read, you basically have two physical variables that define "focal length" with pinhole cameras - the size of the hole and the distance between said hole and the film. I think, Surly, that you're right about the exposure times - consistency between exposures and then, John, as you said - use a small focal length (or actually combination fo factors that give you a small focal length and:

jnanian said:

... you will get a small image on a big paper/film.

Click to expand...

Put a bunch of those together and voila. So I'm thinking now an array (or several arrays) of particularly tiny apertures, and a significantly short distance between those and the film plane.

That's what I got so far.

Thanks for that link, John!

Focal length of a pinhole is solely determined by the pinhole to film (or paper) distance. Aperture is determined in the regular way: focal length divided by pinhole (aperture) diameter. Aperture has no role in determining focal length.

I haven't checked the photos you mention, but Renner has a number of examples of multiple pinhole images in his books, and many are made by putting multiple pinholes in a line or grid, spaced so that they project images that overlap to the desired degree.

Lee

Surly said:

Yeah, what he said. jnanian said what I meant to say about the multiples.

Click to expand...

surly - great minds think alike!!

Bruce said:

Thanks for that link, John!

Click to expand...

no prob!

i just remembered that lomo makes a 9-image camera ... 50 bucks!
http://shop.lomography.com/shop/main.php?cat=&pro=pop

i wonder if it done the same way

-john

Lee, you're right - this is still new to me and I'm getting my terms confused. I found the following in an article by Jon Grepstad which exists in a couple of places on the web (I'll paraphrase):

Technically, pinhole cameras have no focal length. They have infinite depth of field. But from a practical standpoint, focal length is defined as the distance between the pinhole and the film or paper.

For any given distance, one can calculate an "optimal" aperture size, (although there appear to be a few different formulas in use and this is not as critical to image quality as getting a good clean hole.) Generally as the distance gets greater, optimal pinhole diameter gets smaller.

Short distances from pinhole to film/paper result in wide-angle views, long distances result in telephoto views.

Your f-stop is this distance, divided by your aperture (pinhole diameter). From there you calculate exposure times.

I'm just guessing that multi-image pinholes are a combination of short (wide-angle) distance with small (telephoto) apertures. Thanks for the Renner reference - I'll definitely be checking this out.

John - I had no idea there were so many different Lomo cameras! Holy apertures, batman, this place is wild!

Surly - I like that fish image too, reminds me of a good (old) friend who did some similar sculptures. Got me thinking...

i think the only modification i'd make is that as the distance from pinhole to film plane gets greater the optimal pinhole diameter also gets greater.... though, you can use any size hole with any focal distance - it just effects the effective fstop (smaller hole + greater distance = larger fstop = slower exposures)

cheers and welcome to pinhol'ing
Tom
f295.tompersinger.com

Looking at the national street rod pic (the one with the cars) you can see Korte uses some apertures one after the other. Otherwise he would not be able to have rotated images on the same plane. So he made one shot, tilted the camera 90 degrees, took another one, etc. etc.
Focal distance must be very short, judging at the extreme wide angle effect on some of the images. I suspect you have to do some experiments yourself to get the right distance to the film plane, where overlapping is reduced to the desired effect.
Those were my two pennies for the day.
Norm

Hi,

Been thinking about this a fair amount lately. There is an optimum pinhole size per focal length (film to pinole distance). That said, any size pinhole will give you an image given enough exposure time. But... and this is a consideration with multiple pinhole systems, the length from pinhole to film is greater as you get away from the perpendicular of the pinhole to the film plane. If you look at good pinhole calculators, they will give coverage information. Now coverage info is just the size of image circle that you can expect a reasonably well exposed image at the edge of the circle without overexposing the center.

So what does that mean? If you know the image circle for a particular aperture pinhole and space several pinholes that far apart on the lens (?) board of your pinhole camera, you should have one image run into the other, with no sections of over (or under) exposed image between them. A photomontage blend. Calculate your exposures as if you had just one pinhole and expose either simultaneous or serially.

tim in san jose

Yep, I think you nailed it there. Seems to me that using sheet film would afford the best use of space for multiple "lenses".
One other thing - for me understainding the film to aperture ratio made immensley more sense when I found out the f in f stop stood for factor.
I think I need to start building one of those.....

Coverage - that's the ticket. Thanks Tim, good insight.

Surly - I'm thinking the same thing, but since I haven't even tried a single pinhole yet, it may take me a while to get there. Happy Trails!

I made one that has three close together in a row. You just make a single exposure at the standard time and the results are very abstract; doubling like something an insect might see. Color film looks cool.

I've almost completed a three-pinhole-array panoramic camera. I'll post a sample when I have one.