This is a complete list of Pinhole information I've accumulated from "The Net", mostly rec.photo. Contents: ============ =1= General information =2= More General Info =3= Primer =4= Book List =5= Optimum Diameter =6= Coke can pinhole =7= Polaroid Zoom Pinhole =8= Paint Can Camera (more silver) =9= Making round pinholes =10= Silver Foil & Diameter (no defraction problems?) =11= Precision Parts available =12= Distance vs image quality Other files available: School Project (requires lots of safelight work.) =1= General information ======================= From: bercov@bevsun.bev.lbl.gov (John Bercovitz) Newsgroups: rec.photo Subject: Re: Pinhole camera question Date: 25 Jan 1994 21:02:49 GMT Organization: Lawrence Berkeley Laboratory, California Here's my standard post on the subject: This is a brief? 8-) note from a NON-expert for those who haven't used pinholes as imaging devices before. My camera is an adaptation of an old 4x5 camera. The resolution (and I realize most pinholers aren't striving for resolution) is easily better than what you would expect from a dinky format (say Kodak Disc). Nevertheless, the pinhole gives a really unique softness. The depth of field, of course, is astounding. I have a picture of my son with his face nearly pasted to the pinhole and with a tree 1/4 mile away in the same shot. The face and tree limbs both have good resolution. Very exciting for me. According to an article by a fellow named Connors in the _Pinhole_Journal_, optimum resolution under average conditions is achieved when the diameter of the pinhole is related to the distance of the pinhole from the film as follows: diameter of pinhole in inches = .0073 (approx.) times the square root of the distance from pinhole to film in inches The reason that there is an optimum pinhole diameter is that as the pinhole diameter is decreased, the resolution on the film gets better due to the obvious geometric effects but at the same time it gets worse due to diffraction effects. As a result, there is a fairly broad range of acceptable pinhole diameters but the best resolution is found when the pinhole is sized by the formula given. There is also another effect, which I'm not sure I can prove rigorously so I won't attempt it, and that is that the larger the film format, the higher the resolution. Basically, as the film size goes up, one uses a greater distance from pinhole to film, but the size of the pinhole goes up as the square root of that distance so it's not increasing very fast hence resolution goes up. Leastaways, that's how I heard it! 8-) I'd love to have an 8x10 pinhole camera, but I can't afford the less common and hence more expensive film, film holders, etc. I have an old 4x5 camera, a Crown Graphic, which can be had cheaply anywhere. Someone gave me a messed up Wollensak "Alpax" shutter which I restored to more or less working order. I mounted the shutter on a lens board which fits the 4x5, mounted a pinhole on the front of the shutter and a Polaroid 545 film holder on the back of the camera and presto, I've got a pinhole camera. I use Polaroid ASA 400 black and white film. Obviously, one doesn't need all this stuff to make a pinhole camera, but I sure think the Polaroid back is a really nice thing to have as a starting point. The shutter is just a convenience; an old felt hat will do just as well. I wanted a few different pinhole sizes to use with the 4x5. I decided on three pinholes; the optimum distance from the film plane for the middle hole is about twice and half the distance of its smaller and larger mate, respectively. I decided the middle pinhole should be for around 6" operating distance. By the formula: diameter = .0073 SQRT 6 = .018 inches. I found I had a drill with a diameter of .018" so that was the middle-sized drill. Similarly, I used drills of .0135 and .024 inches. These drills are easy to get. They are members of the American number drill series. The .024" drill is a #73, the .018" drill is a #77 and the .0135" drill is a #80. They're available at machine shop supply stores. Drilling the holes is really not too tough. I got some.001" brass shim stock (available at machine shop supply houses and some automotive supply houses). I clamped the shim stock between two 1/16 inch thick layers of aluminum. I put the drill bit in a Sears "Lil Crafty" (a Moto Tool or Dremel tool would work as well) and drilled through the assembly. There was a barely perceptible burr on the hole which I removed with 600 grit wet and dry abrasive paper (available at the same places as those which have shim stock). I then painted the interior of the hole black by daubing it with a felt pen. Larry Bullis has another way of making pinholes which is less equipment intensive but I'll let him explain his method. Exposure is not too difficult either. Just remember that the definition of f/number is merely the distance from the pinhole to the film plane divided by the diameter of the pinhole. For my .018" pinhole used at a distance of 6", the f/no is 333. For my first exposure, I just read my Luna Pro F light meter and figured what the exposure would be for f/333. It turned out to be 3/4 second for ASA 400 so that's what I set the shutter for. I got a perfect exposure on the first try! The "Sunny 16" exposure rule would work just as well if you have negative film and hence a little latitude. The upshot is that if you haven't tried a pinhole camera, it's easy and yuh oughta! John Bercovitz (JHBercovitz@lbl.gov) =2= More General Info. ====================== Newsgroups: rec.photo From: pls9235@ultb.isc.rit.edu (P.L. Steppic ) Subject: Re: Pinhole success Organization: Rochester Institute of Technology Date: Tue, 19 Oct 1993 16:47:53 GMT In article news@butch.lmsc.lockheed.com writes: > >In article <1993Oct19.033724.13913@henson.cc.wwu.edu> adam@henson.cc.wwu.edu (Adam C. Epp) writes: >> >>After reading Popular Photography's "How to Make a Pinhole Camera" a while >>back I thought I'd try my hand at it because I really liked the effect. >>The only problem is that you need to do your own film processing which I >>haven't gotten around to learning. It occured to me that it might be >>possible to turn a standard SLR into a pinhole camera by stretching a >>piece of tinfoil across the lens mount. This would allow several >>advantages such as a built in film transport system. I've never heard of >>anybody doing this before, will it work? (I currently lack the funds to >>blow off a role of film in the name of science, so I figured I'd ask >>before I tried.) If does, it should be possible to use extention >>tubes to change the focal length, as well. >> >>Thanks, >>Adam >>adam@henson.cc.wwu.edu >> As a matter of fact, this was one of our first assignments in one of my Photography classes here--making pinhole cameras out of our SLR's. Yes, it does work, although you have to make *ABSOLUTELY CERTAIN* that you make it light tight (as I found to my dismay). You can increase the "focal length" by taping a piece of tinfoil to an empty roll of toilet paper and taping that to your lens mount (again, make sure it's light tight--you can buy black masking tape at most photo supply stores, or electrician's tape works well). If you have any way to measure the diameter of your pinhole, the optimum pinhole width is calculated by taking the square root of the focal length (i.e. the distance, in mm, from the pinhole to the film plane) and divide by 44. For example, if you had a tube that held the pinhole 10 cm (100 mm) from the film, you optimum pinhole diameter would be about 1/4 mm. One caveat: since the pinhole lets in so little light, you'll be hard pressed to see an image in your viewfinde unless you're looking at a relatively bright object; your f-stop is (I seem to recall) the focal length divided by the hole diameter, so in the above example, you're shooting at f400; a tripod is imperative. I guess the short answer to your question is "yes, you can make a pinhole camera out of an SLR." How much did the article you read cover? We actually did quite a bit of experimentation with the concept, and if you're interested, I could tell you some more... Pat =3= Primer =========== ================================================================================ Note 17.04 -< Pinhole Photography Primer >- -------------------------------------------------------------------------------- SOME ASPECTS OF PINHOLE PHOTOGRAPHY From: bercov@bevsun.bev.lbl.gov (John Bercovitz) Organization: Lawrence Berkeley Laboratory, California >When building a pinhole camera, what is the optimum size for the pinhole? >I thought I read once that it was about 1/200th of the focal length. There was an article in the "Pinhole Journal" by a fellow named Connors who did picture quality tests with various pinhole diameters. Connors found that the best resolution resulted when the diameter of the pinhole in inches was = SQRT(.000054 * "focal length" in inches). As I recall, he did his tests with the subject at fairly ordinary distances. As an example, for a "focal length" of 6", you have a diameter of SQRT(.000054*6) = .018 inches. If you like your formulae with bigger constants, you could also say diameter in inches = .007*SQRT("focal length" in inches). The bigger the film format, the better the angular image resolution. Here's a table for the 3 focal lengths I use on my 4x5 with B&W Polaroid film: Focal length Focal length hole diameter drill size f/no in inches in mm in inches 3.375 86 .0135 #80 250 6.000 152 .0180 #77 333 10.666 271 .0240 #73 444 I like the 6 inch focal length best - I leave it on an old shutter on a lens board. Many others like the shorter focal lengths. As the astronomer said, an old felt hat is often the best shutter. Don't worry too much about the focal length; just get the pinhole _approximately_ the correct focal distance from the film. +/- 25% would't be noticeable, I'm sure. There are many methods of making pinholes; here's mine: I sandwich a piece of .001 inch thick brass shim stock between two 1/16 inch thick pieces of sheet aluminum and drill through with the drill size from the above table using a high speed drill motor body such as a Dremel tool or a Moto tool or a Sears' Lil' Crafty or whatever. The aluminum backing pieces (the "bread" of the sandwich) keep the burrs to a minimum. After the brass is drilled, I take off the remaining burrs with 600 grit abrasive paper. Then I ink in the inside diameter of the hole with a black "Magic Marker" type of thing - whatever's black and sticks to brass and isn't clumpy so as to leave junk in the hole. Just be sure to inspect your pinhole with a magnifier when it's done to make sure you have a good round hole - irregularities decrease image sharpness considerably. Irregularities can be dirt particles inside the hole so I keep my pinholes in dust-free environs. You blacken the interior of the pinhole to cut out reflections off the short cylinder which is the hole's inside diameter. f/no is always just focal length divided by pinhole diameter, the equivalent of a lens' diameter of aperture. So the f/no of the 6" focal length pinhole is 6/.018 = 250. I really shouldn't be calling this length the "focal length" of the pinhole as focal length is a property of a lens, not a pinhole. Pinholes are afocal, that's their charm, but they do have a distance from the film or image plane at which they give their best resolution. Maybe I should call this "optimum length" instead of "focal length". ============================================================================ =4= Book List ============== ================================================================================ Note 16.03 -< PINHOLE Photography Book List ^- -------------------------------------------------------------------------------- I would recommend the following books and article on Pinhole Photography: "The Visionary Pinhole" by Lauren SMITH, Salt Lake City, 1985, Gibbs M. Smith, Inc., Peregrine Smith Books. A history of pinhole cameras, beautiful black and white photographs, with examples of various types of cameras. It cost $14.95 when I bought it a few years at the San Diego Museum of Photography "The Hole Thing: A Manual of Pinhole Fotografy(sic) by Jim SHULL, Morgan & Morgan, Inc, Publishers, Dobbs Ferry, New York "The" how-to-do-it-yourself book. Paperback full of useful illustrated information, with some black and white photographs. Probably "the" book. "The International Pinhle Photography Exhibition" Published by the Center for Contemporary Arts of Santa Fe, a book full black and white and color photographs from 22 photographers. "Pinhole Journal" Used to be published three times a year, by the Pinhole Resource, San Lorenzo NM te. 505 536 9942. A journal devoted to the theory and practice of pinhole photography--I don't know if it is still published. Popular Photography, January 1988, Volume 95, No. 1 had an extensive article on the subject with good practical tips on how to get started, how to make the pinholes, etc. The small "KodaK camera with 126mm film was actually made (I think) by Time-Filed Co, Newark, Delaware 19711 and called the PinZip 126 and used Kodak Instamatic Cartridge, Kodacolor II, Kodachrome 64, and Verichrome Pan. It cost $11.95 in 1987 and was available then through the Pinhole Resource. Again, I don't know the current status of the camera, or Pinhole Resource. If it is still around, that is probably the best source of information on the subject. ++++++++++++++++++++++++ CUMMINGSR@RFERL.ORG RFE/RL Inc Munich,Germany This information may have already appeared on this newsgroup, but for those who don't know, there is a new book out on pinhole photography, entitled Pinhole Photography, by Eric Renner. It is a gem of a book, one that I knew I had to own as soon as I saw it. It is truly amazing what people have done with the pinhole concept, often with alternative printing processes. The book is by Focal Press and it will give you a lot of pleasure. Sandy ------------ Eric Renner was here at Clemson this week as a visiting artist. Here's the info on his book. It came out in Jan, a press run of 3000, sold over 1000 the first month so he figures the run is about half gone. It's available through Light Impressions, Photo Eye, Barnes & Noble, and others. Retails for $29.95. I can second Sandy's remarks, it is a book of great value on pinhole. Pinhole Photography Rediscovering a Historic Technique Eric Renner, Focal Press ISBN # 0-240-80231-4 Order the book direct from Eric, and help the artist out. $32.95 including shipping from: Pinhole Resource Star Route 15, Box 1355 San Lorenzo, NM 88041 (505) 536-9942 **************************************************************************** Shane Patterson Dept of Visual Arts College of Architecture patters@hubcap.clemson.edu Clemson University Home (803) 287-5320 Office (803) 656-3924 WWW-- http://agno3-si.clemson.edu/cc/clearcreekhome.html **************************************************************************** From: ben@lonestar.jpl.utsa.edu (Ben A. Fairbank) Newsgroups: rec.photo.advanced Subject: Re: Pinhole expertise needed Date: 9 Apr 1995 03:47:28 GMT Organization: University of Texas at San Antonio In article <3m6she$a1a@grape.epix.net> lowenbur@news.epix.net (Async User) writes: >I'm very interested in getting into low-tech photography after years and >years of precision... There is an excellent semi-techical book that goes into a little detail on pinhole cameras. It is called "Optics, Painting, and Photography," and is by M. H. Pirenne, published by Cambridge University Pess in 1970. Pirenne is a physiologist specializing in vision (if you have ever studied human vision you have probably read of the great experiment on the sensitivity of the human visual system, published in 1942 by Hecht, Schlaer, and Pirenne -- it is the same Pirenne). The whole book IMHO should be required reading for Serious Photographers; it is a true classic. On the pinhole camera you will find such statements as (p. 17) "Whereas each luminous point sends divergent rays into its surroundings, the pinhole camera does select certain cones of rays (Fig. 2.3) from among all the rays which fill the whole of space, so that the __main rays__ of these cones do now __converge__ toward the centre of the pinhole. These main rays are shown in Fig. 2.2 as the lines AH, BH, and CH." Anyway -- it is a good read. Ben Fairbank =5= Optimum Diameter ============================ OPTIMUM PINHOLE DIAMTER From: andpph@ritvax.isc.rit.edu "andrew davidhazy" Organization: Rochester Institute of Technology A couple other formulas related to determining optimum pinhole diameter: From Applied Photography, by Arnold, Rolls and Stewart: ______ D = V 3.6vL where v = pinhole to film distance L = wavelength of light used all in same units From Seeing the Light. by Falk, Brill and Stork _____ D = 2V vL where units same as above From Materials and Processes of Photography by Stroebel, Compton, Zakia, Current ___ D = V v / 141 where D = pinhole diameter in inches v = pinhole to film distance in inches From Ilford Manual of Photography ___ D = V v / 125 where units same as in M&P book From Handbook of Photography by Henney and Dudley (1939) ________ D = V .00007v where v = pinhole to film distance in inches > . > . > . > . > . > . > . > . > . > . > . > . > . > >From John Bercovitz, bercov@bevsun.bev.lbl.gov, Lawrence Berkeley Laboratory quoting experiments by Connors: "found that the best resolution resulted when the diameter of the pinhole in inches was = SQRT(.000054 * "focal length" in inches)..." ....... this message posted by andrew davidhazy, andpph@rit.edu .......... < . < . < . < . < . < . < . < . < . < . < . < . < . < From: Larry Newsgroups: rec.photo.advanced Subject: Re: pinhole photography Date: 27 May 1995 03:50:23 GMT The Pinhole Camera Spot Size Focal Length Microns l/mm in Inches 400 * 2.5 16 350 * 2.8 11 300 3.3 8 250 * 4.0 5.6 200 * 5.0 4 150 * 6.6 2 100 * 10.0 1 250 500 750 1000 f stop I hope this helps. Graph is based on diffraction limits. LJM ================================================================================ =6= Coke can pinhole ==================== Last night my camera club had a talk from Justin Quinnell on pinhole photography and the fun that can be had with an infinite depth of field in a cheapo container. Here is a summary of his description on how to turn a drink can into a camera. 1. Get an Aluminium can (non magnetic). These are preferable to steel because they are thinner and safer to cut. 2. Cut the top off using a pair of sissors. 3. Spray inside with matt black paint (essential if you are going to put film in the camera not so important if you are going to load it with paper - he suggested using paper with children to make the process simpler). 4. The hole should be one third of a millimetre in diameter and as circular and smooth as possible. 5. Before making the hole file the area in which you are going to put the hole down to make the metal as thin as possible. 6. Take a very fine pin and gently create an indentation my smoothly turning the pin - do not go through and make a hole. 7. Use very fine sandpaper on the inside to gently smooth away the indentation and create your hole. (For children he suggested not being so fussy and going for a larger hole which will decrease the exposure times.) 8. Make up a cover for the top of the can using cardboard and black insulation tape. 9. Use a piece of black insulation tap over the pinhole as your shutter (and lens cap!) 10. Load with either 5x4 paper or film. 11. If you use paper try exposing (in bright sunlight) for 30 seconds Contact print the paper negative into a positive. 12. If you use film expose for about 15 seconds (in bright sunlight) Colour film has such incredible latitude that you can usually get a workable print from it. Slide film tends to be odd. 13. Don't point the pinhole directly into the sun unless you want real flare! 14. You can also use a flash gun very close to the pinhole camera to freeze action and get pictures of things that won't stay still. 15. Take a clean changing bag with you to reload the camera. He also gave directions on how to make a pinhole camera based on a 126 cartridge which has the advantage of providing a wind-on film! The exposure times for this are 4 seconds sunny, 10 seconds cloudy and 1 min+ indoors. Or use a flash. Mathematical relationship between f-stop, aperture and focal length ------------------------------------------------------------------- f-number = focal length/aperture diameter So a Coke can 100mm long with a 0.2mm pin hole will be f500. It is because pinholes are so slow that we all use lenses! Caroline Knight HPLabs Filton Rd Stoke Gifford Bristol BS12 6QZ =7= Polaroid Zoom Pinhole ========================= Get an older Polaroid pack film camera. They can be had for $20. Remove the lens assembly and toss it. Replace the lens board with a brass plate ($1 at the hobby store) in which you've made a pinhole. MIne were usually .2 to .5mm. Add a shutter- I used tape, or a hinged door. Now, by varying the bellows length, you have a zoom pinhole! To compute exposure, divide the focal length by pinhole size. With 4 inches of extension (102mm) and a .25mm pinhole, you've got a 102mm f/408 lens. But with polaroid's high-speed b&w films, you can get very reasonable exposure times, even in available light. ----------------------------------------------------------------- Caroline Knight HPLabs Filton Rd Stoke Gifford Bristol BS12 6QZ FAX: 0272 228796 cdfk%hplb.uucp@ukc.ac.uk Tel: 0272 228040 cdfk@hplb.lb.hp.co.uk Switchboard: 0272 799910 cdfk@hplb.hpl.hp.com ----------------------------------------------------------------- =8= Paint Can Camera ==================== **************** From alt-photo ************************ I currently have been experimenting with a paint can, with the hole in the side and the paper neg. wrapped along the inside the can. I have been using 4x10 inch format (half an 8x10 sheet) and will be trying 5.5x14 soon. The characteristic stretch one gets with rectangular boxes is removed (reduced?_) and the only distortion is this pincushion or barrel divergence of lines. Very cool. Anecdotally, other pinhole cameras used by others around here: U-haul van, and a hotel room (the pinhole really is the door peephole, not a view into the next room). chico Seay cseay@TUred.pa.utulsa.edu Chico et al: > - Is my brass shimstock thinner than your silver > sheet? I can't remember the thickness of the brass > stuff, but it is foil-like, from the auto parts store. Maybe, maybe not. Can't know without measuring. Probably doesn't matter much because since you are removing metal, the foil will be thinner at the edge of the hole anyway. I use .003 because it is easier to work. No point in having it so thin it crunches up on you. > Also, I know that aluminum makes for bad holes because > of the tendancy for the foil to tear and burr and crumb Right. Aluminum is brittle and work hardens so badly that it is pretty useless for pinholes. However, the first camera I made had aluminum holes, and it worked surprisingly well. Don't try to go beyond the initial poking however. The metal won't tolerate any working. > up. Is silver superior to brass? I would think it > behaves similarly to aluminum... Not at all. Working with brass is horrible compared to silver. Silver is malleable, ductile, a dream to work with. That's why it has been used for jewelry for so many centuries. (I did my MA work across Photography/Jewelry. I learned to absolutely love silver. The fact that silver is so important in photography is a coincidence that has intense meaning for me.) You can work silver a lot longer before it gets nasty. Maybe gold would be better, but hey, silver's cheap, too. For about $35, you can make a pinhole a day for the rest of your life. Maybe. Anyway, an ounce of silver rolled out to .003 in a 1/2" roll is one heck of a long strip. Have the dealer supply it annealed (heat treated). This softens it, makes it even easier to work with. Remember, as you work it, the metal becomes harder. Work it long enough, and you can either re-anneal it, or it will be so messed up you ought to be happy to throw it away and start over. > - Also my experience has shown that there is an optimal > hole size, (no measurements; i don't have access to a > microscope) and if I try to make a hole smaller, the image > i get is suddenly fuzzy. Is this diffraction, or just > imperfect hole results? I would bet lunch that if you look at the hole with a microscope, you won't believe the junk in it! Junk adds incredible horrible diffraction; look, every edge makes diffraction. When you've got measurements, let's talk about optimal hole size. Otherwise, we're just guessing, and I don't like to comment when there are wildcard variables. Your can cameras sound like a lot of fun. My first camera was a two holed semi-quaker. Glad to hear the enthusiastic comment on Eric's book; I think it's a classic. I hope I'm not too blatently self-promotional if I mention that the cover is one of my images. Larry Bullis Shoreline Community College From: Larry Bullis -------------- =9= Making round pinholes ========================= Path: genmagic!decwrl!decwrl!tribune.usask.ca!skyfox.usask.ca!holtslander From: holtslander@skyfox.usask.ca Newsgroups: rec.photo Subject: RE: Pinhole camera question Date: 26 JAN 94 15:11:08 GMT Organization: University of Saskatchewan Lines: 32 Message-ID: <26JAN94.15110818@skyfox.usask.ca> References: <1994Jan24.211354.21843@cobra.uni.edu> NNTP-Posting-Host: sask.usask.ca In a previous article, williamj@wehner.cs.uni.edu ( Jonathan Williams ) wrote: >I am going to attempt to make my own pinhole camera. I was wondering about the >metal used for the pinhole. What is the best metal to use, and what thickness >is recommended? What is the best way to bore the hole to achieve maximum >smoothness? Finally, how do I determine the focal length for the camera? to get the best resolution the pinholes need to be perfectly round. The method most often used to to get a sewing needle and some brass shims. The brass is soft enough that you can slowly push the needle through by sticking the needle in the eraser end of a pencil and slowly twist it around. A bulge is make in the shim on the oppposite side of the needle. Using fine sand paper you sand away the bulge and press the needle in repeatedly until you have a nice round hole. A quicker method would be to go to a tool supply shop and buy a very small metal drill bit and drill a hole in any thin strong metal (spring steel strapping) The focal length is simply the distance between the pinhole and the film. If you know the diameter of the hole (by the pinsize or drill size) you can figure out the what the f stop equivalent of your pinhole is. The f stop number is the recipricol of the ratio of the aperature diameter to the focal length. ie f 2 means that the diameter of the aperature is 1/2 the focal length, f 4 is 1/4 the focal length. You can get reasonable results simply by poking a hole in aluminum foil with a pin. I would reccomend doing this before you try anything elaborate. you should be albe to make a pinhole camera in a few minutes. gord Holtslander Holtslander@skyfox.usask.ca =10= Silver Foil & Diameter =========================== On Sat, 11 Mar 1995, Chico Seay wrote: > Larry: > How do you make your pinholes? > My methods have changed somewhat since the article I wrote for _Pinhole Journal_ in 1987 ("Pinhole Crafting", _PJ_ Vol 3 #2, August, 1987), but the object is the same. The best pinholes are "poked" rather than drilled. Drilled holes are miniature tubes, where a carefully made handmade hole is knife-edged inside and perfectly round. The appropriate tool is a needle, preferrably held in a pin vise. I use a cork block and puncture a piece of pure silver foil, which I have rolled out for me by a precious metals supplier to .003". Then I turn the foil over and dress the protruding metal with a very fine jeweler's file. >From that side, the original back side, I again work the hole with the needle. Whenever metal appears on the backside of the hole, I again dress the hole (there will be a dimple in the silver surrounding the hole). This process continues back and forth with frequent microscopic examination of the hole for size and quality. To measure the hole, I use a microscope that projects an image enlarged 100x on a ground glass screen. This makes measuring very easy. If there are any burrs on the inside of the hole, I can spot them and remove them by gently inserting and turning the needle. That's basically it, but the other night we had a pinhole making session and after making a hole myself in about, I'd guess, half an hour, I watched two other persons work for a couple hours and not quite get the right dimension and not quite get the inside clean. The message is that my experience in making holes (I have made hundreds) is part of the answer to your question. So don't get discouraged! Like anything else, skills are acquired by practice. Oh yes. It helps to darken the silver to diminish flare inside the hole and from the surface of the silver. Selenium toner is what to use for that. DON'T use PAINT! Toner leaves the hole clean and does not change the dimension. Not so paint! As far as the diameter to shoot for, that depends. The original formula I used I got from the photo lab index. d for diameter, f for "focal length" (since pinhole does not focus, this is a faux term): d=the square root of .00007f (values in inches) This gave me very good results, but I have since gone to much smaller values than .00007, and don't know where I will stop. The experts say that there is a point of diminishing returns, that diffraction will begin to cancel improvements in resolution achieved by reducing the hole size. I have yet to find this point, and have come to believe that the quality of the hole itself is of paramount concern. At the present time, I think I am approaching commercially acceptable standards for architectural imaging. Of course, if we are making pinhole cameras for reasons of simplicity (they have a terrific virtue in that dimension, to be sure), this may not be a desirable quality. I am currently working in the f/300 - f/400 range on 4x5 materials using extremely wide field cameras. Anyway, give it a try. IMHO there is nothing more fun than this. To think I did photography for more than a decade before I got around to building my first pinhole camera! If you can find the _PJ_ article cited, it still has a lot of other information you might find useful as well as some assignments I gave my students to develop an understanding of perspective. Enjoy. Larry Bullis Shoreline Community College ------------------ RFC822 Header Follows ------------------ Sender: alt-photo-process@vast.unsw.edu.au From: Larry Bullis Subject: Re: Pinhole Photography =11= Precision Parts =================== Note 15.06 -< Precision Pinhole Parts for Pinhole Photographers >- -------------------------------------------------------------------------------- Do you need precision pinholes and plans for your pinhole camera? Read on. I now have precision pinholes in brass which have been laser diffraction tested for size and uniformity. Prices are $5.00 for one, $7.50 for two or $10.00 for three. Matched sets (+/- 1/4 f-stop) are available for panoramic pinhole cameras. Prices include plans for three pinhole cameras including a panoramic one. The panoramic camera can use three or more pinholes. Add $2.00 for each additional pinhole over three. Large quantities available for photography classes. Send email requesting info on the quantity you need. Pinholes come with data stating hole size so you can make preliminary f-stop approximation and all instructions. Send orders to: Jim Michael, Box 941124, Atlanta, GA 30341 e-mail: 70304.3567@compuserve.com - this was posted on rec.photo on the Internet Netnews - (Posted to alt-photo-process list) One possible source for premanufactured pinholes would be condenser apertures used in electron microscopes. As they are part of a high resolution imaging system they are *very* accurate. Hole sizes available range from 1mm (0.039 in.) down to 0.010mm (0.00039 in.). The holes are either made in metal strips or in metal discs which range in outside diameter from 2mm to 6mm. The metals that they are made in are usually gold, platinum, or molybdenum. They are not cheap and prices vary according to the size and material but they average around $40 to $60 (Canadian). They are available from a number of electron microscopy supply companies. ----------------------------------------------------------------------------- John Hudak hudakjm@mcmaster.ca Electron Optics - Institute for Materials Research McMaster University Hamilton, Ontario, Canada ----------------------------------------------------------------------------- Supplies for Pinhole Photography, Supplies for lensless imaging for sale: Minute Aperture Imaging W. Joseph Christiansen 7586 County H Maplewood, WI 54226 (414) 856-6842 e-mail: wjchrist@mail.wiscnet.net =12= Distance vs image quality ============================== Date: Thu, 30 Mar 95 03:34:35 -0500 From: hardy@sweng.stortek.com (Steve Hardy) Replying to ³?² from Tom Whitmore There is no focal length of the pinhole itself. However, there is an effective focal length which is the distance from the pinhole to the film (let's call this F). If the diameter of the pinhole is D, then the f-ratio is F/D. The pinhole should not be too large or too small. A point light source is smeared out to a spot on the film roughly equal to the size of the pinhole, for large pinholes. For very small pinholes the spot size becomes larger than the pinhole due to diffraction. There is an optimum size of pinhole which trades off these conflicting phenomena. When I go home tonight, I will look up the formula. Similarly, for a fixed pinhole size, there is an optimum imaging surface position. This time the tradeoff is between speed and sharpness. If very close to the pinhole, the ratio of spot size to overall picture size is bad (low resolution). Moving the image surface further away improves things at the expense of speed. Moving really far away may cause NO improvement in resolution, because of the diffraction effect. It's really quite complicated! Compiled by Bruce Barrett E-Mail: bruce @ earthreflections.com