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Photo Forum / Film Photography / Large Format / May 2004another newbie question
Hello all, I don't see a newsgroup for "pinhole" cameras, so I hope y'all don't mind: The question is; Should I be able to see a preview image on "ground glass" thru' a pinhole camera? I'm assuming from my web research that with a smaller pinhole the image, if there is one, on the glass will be sharper and darker, and as the hole gets bigger, the image will get brighter and fuzzier?  Signatureregards from :: John Bartley 43 Norway Spruce Street Stittsville, Ontario Canada, K2S1P5 ( If you slow down it takes longer - does that apply to life also?) > I don't see a newsgroup for "pinhole" cameras, so I hope y'all don't mind: I don't mind. > The question is; > > Should I be able to see a preview image on "ground glass" thru' a > pinhole camera? It's not likely, but remotely possible with a large format camera if you have good, young eyes: for example an 8x10 or larger camera with a relatively large aperture (pinhole) might give you a faint image, but for smaller cameras it's highly unlikely. To see an image in a small camera with the typical pinhole you need rather ideal conditions: subject in daylight-bright circumstances when your eyes have become accustomed to total darkness. You can see how that combination is hard to come by. If you could ever go into a walk-in pinhole camera (camera obscura) you would see an image. Quite fun. That said, a bit of experimentation will show you how your camera frames and then you can fashion a wire-frame viewer. You really don't need anything more than that. Your experimentation will show you the typical DOF and view. Then you can take pictures and enjoy. For a great deal of very good information, please see: http://pinholeresource.com/ The site may not answer all your questions, but it is owned and authored by the experts who have decades of experience. >For a great deal of very good information, please see: >http://pinholeresource.com/ >The site may not answer all your questions, but it is owned and authored by >the experts who have decades of experience. > > Thank you, The "lack of light" idea had crossed my mind, but I was unsure of how major a problem it would be. Having had my curiosity piqued by the idea of large format cameras, I thought maybe I would start with a large format (8 x10) pinhole camera with the idea being that I could always subsitute a "lens and shutter" front board for the same body that I use for the pinhole. I sense some experimentation and learning ahead :-) ! cheers Signatureregards from :: John Bartley 43 Norway Spruce Street Stittsville, Ontario Canada, K2S1P5 ( If you slow down it takes longer - does that apply to life also?) > [...] I sense some experimentation and learning ahead :-) ! And it will be heartening and fun! Somtimes I wish I could start all over, or at least experience some of the early "new eyes" wonder and energy. Best, jjs > >For a great deal of very good information, please see: > >http://pinholeresource.com/ [quoted text clipped - 11 lines] > > cheers First, your signature: Not necessarily. When you get over the hill you speed up. Second, Why not? An appropriately sized pin hold for an 8x10 should compensate somewhat for the "loss" of light to the film. "dr bob" <rsmith@dmv.com> wrote in message > > ( If you slow down it takes longer > > - does that apply to life also?) > > Not necessarily. When you get over the hill you speed up. The slower you go the faster everything else goes - and when you stop it all races away, leaving you behind. SignatureNicholas O. Lindan, Cleveland, Ohio Consulting Engineer: Electronics; Informatics; Photonics. Remove spaces etc. to reply: n o lindan at net com dot com psst.. want to buy an f-stop timer? nolindan.com/da/fstop/ Your thinking is correct. A technique some pinholers use with view cameras is to use a rather large pinhole (about the diameter of a 10 penny nail) for compositional purposes. Then the smaller, working pinhole is substituted for the exposure. The larger pinhole does create a much brighter image on the ground glass, but it is definitely less sharp. KB > Hello all, > [quoted text clipped - 8 lines] > if there is one, on the glass will be sharper and darker, and as the > hole gets bigger, the image will get brighter and fuzzier? > Your thinking is correct. A technique some pinholers use with view cameras > is to use a rather large pinhole (about the diameter of a 10 penny nail) for > compositional purposes. Then the smaller, working pinhole is substituted > for the exposure. The larger pinhole does create a much brighter image on > the ground glass, but it is definitely less sharp. Ken, does the coverage change with the different sized aperture? My sense tells me it does not - that only the COC changes. >Ken, does the coverage change with the different sized aperture? My sense >tells me it does not - that only the COC changes. > If I may jump in with some speculation here; I hadn't thought at all about Mr. Burns suggestion for using two sizes of pinhole plates. That is a quite a good one, and one that I'll certainly try. Now for the speculation: My thinking is that the factors that would affect the coverage would be 1) the distance from the pinhole to the negative and, 2) the thickness of the pinhole material. I'm thinking that the thinner the material is, the smaller the hole can be and still be closer to the negative for a given field of view. This, to my way of thinking would also allow more light to hit the negative with a smaller hole? I don't know what COC means, I wonder if you could educate me on some of the short-form terms used in this hobby? cheers Signatureregards from :: John Bartley 43 Norway Spruce Street Stittsville, Ontario Canada, K2S1P5 ( If you slow down it takes longer - does that apply to life also?) On 5/22/2004 10:01 AM John Bartley spake thus: >> Ken, does the coverage change with the different sized aperture? My sense >> tells me it does not - that only the COC changes. [quoted text clipped - 11 lines] > field of view. This, to my way of thinking would also allow more light to > hit the negative with a smaller hole? Um, not really: so far as the brightness of the image goes, the crucial factor is the diameter of the hole. You're correct, of course, that thinner material is better in that you get closer to the ideal hole (which is two-dimensional) rather than the 3-dimensional tube you inevitably get in the real world. But so far as getting a brighter image goes, you need a bigger hole. > I don't know what COC means, I wonder if you could educate me on some of > the short-form terms used in this hobby? Circle of confusion. I won't go into the full explanation, which is a complex aspect of optics and could generate a miles-long thread here. Suffice to say that it's a theoretical construct that supposes a circle on the image plane (film in this case) corresponding to a point on the subject. The smaller the COC, the more in focus the image is. The smaller the pinhole, the smaller the corresponding COC; therefore, smaller pinholes give sharper images. (Until, of course, one hits the dreaded diffraction limit as the hole gets smaller, which then works against sharpness. But that's a whole 'nother can of worms. Which is why there are pretty well agreed-on optimal pinhole sizes, depending on focal length.) Don't worry, you'll grasp all this and figure it out eventually. Direct experimentation is the best guide (and the most fun). SignatureI was quickly apprised that an "RSS feed" was not, as I had naively imagined, some new and unspeakable form of sexual debauchery practised by young persons of dubious morality, but a way of providing news articles to the cybernetic publishing moguls of the World Wide Wait so they can fill the airwaves with even more useless drivel. - Cynical shop talk from comp.publish.prepress > (Until, of course, one hits the dreaded diffraction limit as the hole gets > smaller, which then works against sharpness. But that's a whole 'nother can of > worms. What diffraction limits are there in pinhole photography? Or rather, what aside from diffraction is there in pinhole photography? On 5/22/2004 9:45 PM MikeWhy spake thus: >> (Until, of course, one hits the dreaded diffraction limit as the hole >> gets smaller, which then works against sharpness. But that's a whole >> 'nother can of worms. > > What diffraction limits are there in pinhole photography? Or rather, what > aside from diffraction is there in pinhole photography? I don't know the answer to the first question, but I should, and the answers are somewhere out there on the web. But no, a pinhole of the optimum size has minimal diffraction distortion. Diffraction becomes pretty evident in pinholes that are too small. SignatureI was quickly apprised that an "RSS feed" was not, as I had naively imagined, some new and unspeakable form of sexual debauchery practised by young persons of dubious morality, but a way of providing news articles to the cybernetic publishing moguls of the World Wide Wait so they can fill the airwaves with even more useless drivel. - Cynical shop talk from comp.publish.prepress > My thinking is that the factors that would affect the coverage would be > 1) the distance from the pinhole to the negative and, Right. Some people say that 3.5 times the distance pinhole to film plane is the maximum coverage of a pinhole. >2) the thickness of the pinhole material. Exactly. If the material is too thick, you get faster light fall off than the one predicted by cosine^4 law. In other words the 3.5 times the distance pinhole to film plane for the maximum coverage gets reduce substancially as the tickness of the material increases. > I'm thinking that the thinner the material is, > the smaller the hole can be and still be closer to the negative for a > given field of view. For a given field of view you have to place your pinhole at a fixed distance from the film plane. Pinhole is just one of the so called lensless techniques, zoneplates and pinhole sieves are 2 other techniques that usually give lenses 3 stops faster at least, that an equivalent pinhole for a given focal length. If you google "zone plate" and "pinhole sieve" you'll find information on those techniques. I wrote couple of articles on those 2 techniques, here are the links, if interested: http://members.rogers.com/penate/zoneplate.html http://members.rogers.com/penate/sieve/photonsieve.html Guillermo Toronto/Ontario In article <KU9sc.129049$0qd.60056@twister01.bloor.is.net.cable.rogers.com>, "f/256" <askme@my.email.pls> wrote: > > My thinking is that the factors that would affect the coverage would be > > 1) the distance from the pinhole to the negative and, > > Right. Some people say that 3.5 times the distance pinhole to film plane is > the maximum coverage of a pinhole. You know, there are perfectly well researched papers which describe the physics of pinholes, give apertures and difraction limits for various focal lengths, and so forth. Speculation is unneccessary. > You know, there are perfectly well researched papers which describe the > physics of pinholes, give apertures and difraction limits for various > focal lengths, and so forth. Speculation is unneccessary. You suggested http://pinholeresource.com/ and I'd suggest you tell Eric Renner about the "unnecessary speculation", in your own words, he is "the expert who have decades of experience" and he is the owner of that speculation. BTW, what you call speculation, is not, Eric Renner has based the 3.5X factor on the physics of pinholes and a fall off criteria. I could have given further explication to the factor but basic and simple geometry and algebra is not digested well by most of artistic minded people, if we add some basic trigonometry, it would make it even harder, fortunately they (I am not artistic minded) don't need to know that stuff to make good images, so a factor like the "3.5 times the focal length" as the circle of coverage for a pinhole should be good enough. If you need more info about the physics of pinhole and its application for mundane photographic uses, pls ask me and I'll be glad to help you, Mr.JJS. Guillermo > > You know, there are perfectly well researched papers which describe the > > physics of pinholes, give apertures and difraction limits for various [quoted text clipped - 4 lines] > expert who have decades of experience" and he is the owner of that > speculation. I was not refering to that specific statement, but the tone of conjecture. If you have a source and you are that terribly sensitive and inclinded to the victim reflex, then you might consider citing the source. > [...] If you need more info about > the physics of pinhole and its application for mundane photographic uses, > pls ask me and I'll be glad to help you, Mr.JJS. I would be most happy to find a sense-of-humor donor for you, "f/256". Not large format, but on topic otherwise: I've built two two-pinhole lenses for my Mamiya TLR, where one pinhole replaces the taking lens and another larger one replaces the viewing lens. The image on the fresnel is very dark, but better than nothing and it sometimes helps me frame an image. In one of the lenses I've offset the pinholes vertically to give me some front rise. > Hello all, > [quoted text clipped - 8 lines] > if there is one, on the glass will be sharper and darker, and as the > hole gets bigger, the image will get brighter and fuzzier? |
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