large format lens installed on a zero image pinhole?

[northeast16th]

wondering if anyone has done this or knows if it is even possible. or i suppose it wouldn't even have to be large format, but it would have to be smallish and with the shutter in the lens for obvious reasons.

here is a link to the 6x12 that i thought it might be fun to try it with:

http://www.zeroimage.com/web2003/ProductPage/612B/Zero612B_2006.htm

the pinhole focal length is listed as 40mm, so which lens focal length would be the best so that stopped down you could get all in focus? i suspect it would have a pretty narrow range of lenses. i'm not familiar enough with the tech aspects to know this, but my wild guess is that if you have a 40mm lens, that would be focused to infinity installed on this camera.

i'm most curious to know if anyone has ever tried to mount a lens on a zero image pinhole so you could get quicker shutter speeds and sharper images.....

thanks for any info!

[Lachlan 717]

You'd probably need to mount the lens in a helical mount, and then get the extension frame that brings this close to the film to flange distance.

Being timber, you will possibly be able to sand the frame down to suit.

All in all, too much hassle for me. I'd prefer to buy a cheap P&S 4x5 (DaYi et al) and get shooting...

[Nathan Potter]

Waste of time. Resolution would be wholly determined by the pinhole aperture which would define the resolution limit and the amount of light reaching the film. Thus the shutter would be nonfunctional for any sort of speeds less than say a few minutes. Pinholes have an infinite depth of field so the optical advantage of an additional lens would be to change the image magnification at the film plane so I suppose that would be one advantage.

But to wax philosophical though; does a pinhole have an infinite depth of field if one cannot capture infinity in a physical sense?

The thought is making my head hurt a bit though. Coffee time.

Nate Potter, Austin TX.

[vinny]

Nathan, he's not talking about adding a lens over the pinhole aperture but in lieu of. Check ebay for helical focus mounts.

[rknewcomb]

A 40mm lens that will cover 6x12 might be a little hard to get and harder to pay for.

[BetterSense]

I have a box camera (made with a cigar box) with a graflok back, and 90mm Angulon. I used to have it fixed focus and it worked OK that way (75mm would probably be better for fixed-focus) but now I have the angulon in a helical I took from a junk 35mm lens. It makes a very handy camera, but I don't know if it makes sense to start with a zero image camera as a host.

[Dan Fromm]

I have a box camera (made with a cigar box) with a graflok back, and 90mm Angulon. I used to have it fixed focus and it worked OK that way (75mm would probably be better for fixed-focus) but now I have the angulon in a helical I took from a junk 35mm lens. It makes a very handy camera, but I don't know if it makes sense to start with a zero image camera as a host.The economy ZI is priced below most 6x12 roll holders. I wonder whether it holds the film flat enough to be used with any lens but a pinhole.

[Jim Jones]

[QUOTE=Nathan Potter;715661]. . . But to wax philosophical though; does a pinhole have an infinite depth of field if one cannot capture infinity in a physical sense? .[. ./QUOTE]

Philosophy aside, pinhole cameras are sometimes said to have infinite DOF. Wrong! There is a distance for any accurately made pinhole where the image is sharper than at a moderately closer or further distance. This phenomena is hardly noticable in most practical photography. However, it should be considered when maximum sharpness is desired in pinhole photography. I have read, but not convirmed through experimentation, that adding a lens of the correct focal length to an optimally sized pinhole does not significantly improve sharpness.

[rdenney]

A 47mm f/5.6 Super Angulon (not XL) is the shortest inexpensive lens I know of that will (barely) cover 6x12. A 38/5.6 SA XL will also cover, but it's obviously far pricier, and will probably be too short, especially after adding a helical. Both will require excavating a large hole, and then mounting the focusing helical.

I'm with Dan, though. A pinhole shows as much sharpness as it is capable of showing at all distances, so pesky details like film flatness are not hard requirements. And you would be limited to scale focus--these cameras don't have a focusing screen, which is superfluous on a pinhole camera.

I'm contemplating a similar project using a Shen-Hao 6x12 back, the rear standard for my no-longer-used Cambo view camera, a reversed recessed board, additional spacers as needed, and a focus helical. If I didn't already have most of those bits gathering dust, I would spend more than the cost of one of these pinhole cameras to put it together--maybe three times as much with poor luck. But it would hold the film flat and provide a focusing screen (and a Graflok).

Rick "sorta impressed by the design of the 4x5 camera--as a pinhole camera" Denney

[Nathan Potter]

Nathan, he's not talking about adding a lens over the pinhole aperture but in lieu of. Check ebay for helical focus mounts.

Vinny, rereading I see that now. Wholly a nice home project if one can find the appropriate focal length or a focusing helical mount.

Jim, as far as infinite depth of field with a pinhole, I hadn't considered that it might not be infinite. That would suggest that the diffraction function from a pinhole is not linear or otherwise variable with subject distance. Sounds like this is sort of "in the know" among pinhole users and builders. Dunno. What's the physics of that?

Nate Potter, Austin TX.

[JoeV]

Ignoring diffraction completely, pinhole's DOF is limited strictly because of geometric "ray tracing" optics. Consider what happens when the subject gets very close to the pinhole; the "blurr" effect caused by the size of the hole (again, ignoring diffraction) gets larger, because rays of light from each point on the subject are no longer parallel, but are diverging toward the film plane. At the distance in front of the pinhole equal to the focal distance, the blurr effect is double that at infinity. That is, for subjects near infinity, with parallel light rays, the blurr effect should be equal to the diameter of the pinhole. But for objects very close to the pinhole, the blurr effect is larger. So, if you intend on doing lots of close-up diorama and still-lifes, it helps to use a pinhole smaller than otherwise.

Of course, the reason why I don't worry about focus at infinity is because, due to the inverse square law, objects at infinity can't be seen at all, therefore you just can't focus on them. And, again because of the inverse square law, exposure times for objects at infinity are ... (wait for it) ... infinitely long. ;P

~Joe

[Jim Jones]

For one formula for correcting pinhole diameter in macrophotography, go to http://www.huecandela.com/. Near the bottom of the page click on PinPLUS Pinhole Cameras. On that page click on "Click here to enter PinPlus directory page. A link to the Prober-Wellman Formula for close-up and Macro pictures is on the left of the page.

When we do consider diffraction, it gets interesting. The image from an optimal size pinhole has less blur than the pinhole diameter. Also, as the pinhole diameter decreases below optimim, there is a size where the blur is like a donut; dark in the center.