pinhole pictures in high altitude

Does anybody have experience of or knowledge about taking pinhole pictures in high altitudes? Is a UV-Filter necessary, as it is with a lens to capture distant views, and/or does the size of the pinhole have to be adjusted (theoretically at least, it occurs to me it should be, as the light in mountainous area contains, as far as I know, more blue)?
Any advices?

I wouldn't worry too much about resizing the pinhole. While it is true that the "optimal" size varies with the wavelength of light, who's going to actually see the difference? The optimal size is usually set to something in the green part of the spectrum.

Filters are difficult with pinhole because if they aren't squeeky clean, the dust or whatever will show up as really ugly blurry dark spots in the image. If you are going to use one, I would suggest keeping it moving during the exposure. It would be necessary to keep it close to the hole so that reflections from the back of the filter don't appear in the image. If you are trying to cut through the blue haze, the uv filter may help some, but probably not a lot. A strong filter in the orange to red region will have much greater effect. Of course, if you really want to be picky about your "optimal size" the use of a filter will influence that as well. Again, I just wouldn't worry about that.

I'm assuming Black and White here. With color, you might have to settle for the uv filter, skylight filter, and/or polarizer, depending on what you want. I think there would be a significant faction of the pinhole community which would find filter use antithetical to their aesthetic (would these be the pinholier than thou?). Myself, I'd just do it. Might learn something.

You can get some amazing long distance penetration of haze using color or b&w infrared film and an infrared (dark red or ca. 600 nm and longer) filter.

Any lens or pinhole should be optimized for the colour of the object of interest, not for the colour of lighting.

AgX said:

Any lens or pinhole should be optimized for the colour of the object of interest, not for the colour of lighting.

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I don't think that's the point.

"Optimal diameter" in the pinhole is a compromise between the resolution and diffraction. Resolution "improves" when the hole gets smaller, but as the hole gets smaller the diffraction increases. The reason they use green is that since red and blue diffract differently (blue more, red less) they are going for an average so that the extremes will be accommodated in an intelligent compromise. It works.

When I make pinholes, I sometimes deviate from the "optimal" intentionally. I tend to prefer greater diffraction and better resolution. The "experts" seem to think that greater diffraction and less resolution result in the same "degradation" of the image. I disagree. They aren't the same thing, and they look different. I try to make the pinhole for the image I want, not for some abstract ideal value that nobody can really see.

Glass blocks some UV. A pinhole will not block UV. Therefore, UV becomes more important in pinhole exposures. As you go up in altitude you need more and more UV filtration. In my work on this, I used the Kodak series HA-1, 2 and 3 filters for High Altitude work to relieve the problems introduced by higher UV as altitude goes up.

PE

Glass blocks some UV. A pinhole will not block UV. Therefore, UV becomes more important in pinhole exposures. As you go up in altitude you need more and more UV filtration. In my work on this, I used the Kodak series HA-1, 2 and 3 filters for High Altitude work to relieve the problems introduced by higher UV as altitude goes up.
PE

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Good point. Knowing the pinhoids as I do, being myself a pinhead, it is very hard to imagine most of them being willing to deal with esoteric filters like that but who knows? I probably will have to order some immediately. But I'm on the lunatic fringe, to be sure.

The idea of putting !GLASS! at all in the path of a pinhole is anathema to some. I suggested etching a pinhole with farmer's reducer in a front surfaced silver mirror up here somewhere awhile ago, and even that wasn't acceptable to somebody!

Now, do that, and maybe the filter issue will disappear. Front surface mirrors in scanners are sometimes really thick.

I get a plastic infrared filter from Edmund Sci, which works great down here on the ground. Optically plane, it's made of a plastic so hard that I can't score and snap it; it must be cut on the bandsaw. An added advantage is that it is cheap. It doesn't seem to screw up the imagery, either. Even with the Super Angulon. Do you think that any UV could get through that stuff?

Larry

Thank you for the suggestions. The reason for my asking is, by the way, that I am in the initial stages of planning a trip into the Hindukush in Mai or June. You should have very little haze there, but you may go up to altitudes of maybe 10.000 feet (3.500 m) or even higher. I would very much like to make some pinhole pictures there, even get an 8x10 pinhole camera built for this purpose, so some research here seems appropriate.

There is one thing that puzzles me: the pinholes I have made so far, most of them somewhere in Germany's lower areas, regularly gave me very good skies, if I am not very mistaken, distinctly less blown out than with a lense. In fact, monochrome (that's what I am talking about) skies seem to have a luminescence and texture you approach with a lens only with an orange filter.

Considering that any lump of glass in front of a film, that is a lens, takes away quite an amount of UV light, should the rendering of a sky with pinhole not be worse rather than better? So I suspect there might be some other factors involved, like the relation of the size of the hole to the wavelength of the light.

Also, I found the following picture of the Mount Everest here:
http://www.slowlight.net/blog/index.php?paged=2
Would be worth finding out whether this was taken with a filter in front of the lens?

Lukas Werth said:

...you may go up to altitudes of maybe 10.000 feet (3.500 m) or even higher. I would very much like to make some pinhole pictures there

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I've used pinhole as high as 9400 feet. You may have a bit of uv but I suspect that it might not be obvious unless you did a controlled comparison. Since you are going that far, it might be good to test first, but I'm not sure I'd go to the trouble. I think I'd just do it. And I'm one who tests a lot; this would be under the threshold.

Lukas Werth said:

There is one thing that puzzles me: the pinholes I have made so far, most of them somewhere in Germany's lower areas, regularly gave me very good skies, if I am not very mistaken, distinctly less blown out than with a lense. In fact, monochrome (that's what I am talking about) skies seem to have a luminescence and texture you approach with a lens only with an orange filter.

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There is a very strange thing about pinhole images. There is a limit to how abrupt a transition can be. Where a lens might show a very hard contrast between two different values, the pinhole cannot do that. I have noticed what you mention also, and I'm not sure whether the contrast limit is the reason for it or simply that most of my camera designs are extremely wide angle, and so there is a very strong tendency for the skies to be underexposed, or a combination of both. I suspect both as a sort of opposing pair. Underexposure darkens them; the contrast limit softens the transitions.

Lukas Werth said:

I suspect there might be some other factors involved, like the relation of the size of the hole to the wavelength of the light.

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Art there any physicists in attendance here? One thought that occurs to me is that since UV will diffract more abruptly across the edge of the hole, the image that it projects would most likely be quite blurry, and could produce an affect of a hazy surround if you could see it at all. Most likely this would appear as simply a further diminution of local contrasts and softening of edges, much of which could be corrected by printing the negatives to a higher contrast. The image may look somewhat different because of some obscuring of the edges in areas of greater contrast. Of course, I really am out on a limb here, because a physicist, I am not.

Lukas Werth said:

Also, I found the following picture of the Mount Everest here:
http://www.slowlight.net/blog/index.php?paged=2
Would be worth finding out whether this was taken with a filter in front of the lens?

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Checking the text, I'm sure it was a pinhole image, not a lens. I would doubt that he's used a filter. He's inside the camera meditating, it seems, and during a long exposure, the filter would need periodic attention and cleaning, at least, if not to be kept moving.

Seriously, the use of a filter with pinhole is a really problematic thing. Eric Renner had asked me to write an article for the first edition of his book about it, but I got very discouraged with it when I tried it, so it never got done. I was on the desert in Eastern Washington, and the wind blew dust on the filter, which appeared as HORRIBLE BLOBS of dark fuzziness in the prints. Now, I'd probably go for it, because I've had so 15 years to mull it over. However, the substance of the article would definitely suggest that if you can possibly avoid using a filter, do so. I think that you will get some great images, but using the filter, the chances of your ruining them are much increased.

Bowzart,
one point first: of course I meant that the everest picture is a pinhole, I just accidently typed "lens" for "hole". Sorry for that.
Yes, you are right, I use wide-angle pinhole cameras, and considering the fact that I also apply perspective correction, you may well have a point that the sky tends to get comparatively underexposed.
You are absolutely right, filters may be a problem with pinhole (but you got zone plates, for instance, which need to be printed on a substrate). An idea would be to place a filter inside the camera, behind the hole, and fit along with it a device to blow some air over it before an exposure (like a rubber tube with a bulb attached). Then it also would not need to be directly on the hole, but keep a little distance, probably also somewhat alleviating the problem with those fuzzy spots.
I think what I will do is get a pinhole camera made and take it with me, make one trial exposure and get it developed over there (there must be a photographer with a darkroom somewhere there).

bowzart said:

I get a plastic infrared filter from Edmund Sci, which works great down here on the ground. Optically plane, it's made of a plastic so hard that I can't score and snap it; it must be cut on the bandsaw. An added advantage is that it is cheap. It doesn't seem to screw up the imagery, either. Even with the Super Angulon. Do you think that any UV could get through that stuff?

Larry

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Hello Larry,

IR filters, just like UV, are lowpass filters. The ideal lowpass filter will cut frequencies above a certain threshold. So, since IR is quite lower than UV, it will probably cut out any UV radiation. Of course, you can never be sure about how effective it is, unless you have a look at it's spectral response graph.

But I'm curious. What kind of film will you use with that? Is it an opaque filter, or does it let some red light pass?

Lukas Werth said:

Then it also would not need to be directly on the hole, but keep a little distance, probably also somewhat alleviating the problem with those fuzzy spots.

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That will make them smaller, but sharper.

Good luck. I'd like to hear what you discover.

bowzart said:

That will make them smaller, but sharper.

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Yup, you are right, of course. Anyway, I will try it without filter, first.