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 ``` ================================================================================ FAQ or Answers to Frequently Asked Questions Section 18 -------------------------------------------------------------------------------- This is a file containing answers, tips, hints and guidelines associated with recurring questions asked by photographers. If you would like to add a tidbit of knowledge to this list just send it to ANDPPH@rit.edu who will gladly add it to this collection. These files are available in SECTIONS. This is Section 18 and its contents are listed below. 18.01 -< Depth of Field Calculation >- 18.02 -< How to Dispose of Darkroom Chemicals Safely >- 18.03 -< Depth of Field in C >- 18.04 -< Basic Stereo and Parallax Concepts >- 18.05 -< More Advanced Stereo Concepts and Stereo FTP site >- 18.06 -< Photometry and Light Meters Primer >- 18.07 -< More on Polaroid Transfer Process >- 18.08 -< Tailflash Synchronizer Circuits >- 18.09 -< Some aerial photography Tips >- 18.10 -< Where to get film for SUBMINIATURE cameras >- ================================================================================ Note 18.01 -< Depth of Field Calculation >- -------------------------------------------------------------------------------- DEPTH OF FIELD Depth of field is to some extent an arbitrary matter depending upon what one deems to be "proper" focus. Given this, you can calculate depth of field, more-or-less. Near limit of focus = F[squared]S ---------------- F[squared] + SAC Far limit of focus = F[squared]S ---------------- F[squared] - SAC Depth of field = (far limit) - (near limit) C = diameter of "circle of confusion" in meters (e.g., .000033m) A = lens aperature or f-stop S = distance to subject in meters F = lens focal length in meters The depth-of-field result will be in meters. ================================================================================ Note 18.02 -< How to Dispose of Darkroom Chemicals Safely >- -------------------------------------------------------------------------------- DISPOSING OF DARKROOM CHEMICALS SAFELY The following is a chart from the article "Pollution Solution", "prepared by Peter Kolonia and Peter Krause, with technical information contributed by Krause". It was in Modern Photograph, but the pages it was on that I photocopied do not have the date on them. **************************************************************************** Disposing Of Common Darkroom Chemicals Chemical Disposal Method All film and paper developers Mix developer with acid stop bath, acid fixing agent, or vinegar until relatively neutral pH is reached and gradually pour in drain with wash water. Use pH indicating paper to determine level of acidity.* Stop Bath Mix with developer or borax until relatively neutral pH is reached and gradually pour into drain with wash water. Acid fixer (with or without Mix with developer or borax until relatively hardener), bleaches, and neutral pH is reached and gradually pour in bleach fixes. (Some fixers drain with wash water; or arrange with a are alkaline and essentially commercial lab to accept exhausted fixer; neutral. Check with pH paper). or purchase a silver recovery unit. Hypo clearing agent Pour into drain with wash water. Sulfur-type toners Pour into drain with wash water. (brown, sepia, Polytoner) Selenium, gold, Heavy metallic content. Use sulfur-type iron (blue) toners toners, if possible. Pour into drain with wash water. Wetting agent Dilute slightly with exhausted stop bath or fixer and pour into drain with wash water. Stabilizing bath Gradually pour into drain with wash water. Sulfamic acid tray cleaners Mix with developer or borax until relatively neutral pH is reached and gradually pour into drain with wash water. * Available through Edmund Scientific, 101 E. Gloucester Pike, Barrington, NJ 08007-1380 ================================================================================ Note 18.03 -< Depth of Field in C >- -------------------------------------------------------------------------------- The following two files (one called DOF.H, the other called DOF.C) will calculate the depth of field with various f-stops, focal lengths, and distances to subjects. Built in help. Here's how it works: 1 Extract the first file as DOF.H 2 Extract the second as DOF.C 3 \$ cc dof/c_opt/opt (on the VAXs, at least) 4 \$ dof == "\$user:[abc1324.subdir]dof.exe" (this is the path to your DOF.EXE file, must be defined in this fashion, note the \$ in the quotes) 5 DOF (help is given) -Eric ------------------------------------------------------------ #ifndef __DOF__ #define __DOF__ 1 #define C 0.000030 /* Fudge factor */ double doffront ( double f, double s, double l) { double x, y; x = C * f * s * (s - l); y = (l * l) + C * f * (s - l); return (x / y); } double dofrear ( double f, double s, double l) { double x, y; x = C * f * s * (s - l); y = (l * l) - C * f * (s - l); if (y <= 0) return (0); else return (x / y); } #endif ------------------------------------------------------------ #include #include #include "dof.h" int main (int argc, char *argv[]) { double f; /* F number of lens */ double s; /* Distance to center of shot, m */ double l; /* Focal length of lens, mm */ double x, y; /* Internal use in this procedure */ int z; /* Internal counter */ if (argc < 4) { printf ("Usage:\n"); printf ("\t%s f d l[...]\n", argv[0]); printf ("\nWhere\n\tf = f-number (ie, 2.8, 4, 8, etc)\n"); printf ("\td = distance to subject in meters\n"); printf ("\tl = focal length of lens in millimeters (ie 28, 50, 200)\n"); printf ("\tOptionally, a series of lengths may be given\n"); return (1); } f = atof (argv[1]); s = atof (argv[2]); for (z = 3; z < argc; z++) { l = atof (argv[z]); l = l / 1000; x = doffront (f, s, l); y = dofrear (f, s, l); printf ("\nUsing an f-stop of %g and a %2.3fm lens, ", f, l); printf ("a subject at %g meters:\n", s); printf ("\tD.O.F. front: %g m\n", s - x); if (y == 0) { printf ("\tD.O.F. rear: infinity\n"); printf ("\tD.O.F. total: infinity\n"); } else { printf ("\tD.O.F. rear: %g m\n", s + y); printf ("\tD.O.F. total: %g m\n", x + y); } } return (1); } ================================================================================ Note 18.04 -< Basic Stereo and Parallax Concepts >- -------------------------------------------------------------------------------- PARALLAX PRINCIPLES IN STEREO PHOTOGRAPHY John Berkovitz The subject is parallax or more specifically what we mean by same in stereography. Below are crude ASCII graphics which depict the situation. L x R A B L is the left eyeball R is the right eyeball A is a vertical rod at some distance B is a taller but otherwise identical vertical rod a little further away x is a dummy point so I can use small angle approximations later This is a plan or top view; we are looking down on the top of the viewer's head and at the upper ends of the rods. It may help if you draw lines between each pair of real points and also a line between x and L as well as x and B. Distances are designated by their starting and ending points. For example, LR is the interpupillary distance, usually around 65 mm. Angles are designated by three letters, the vertex in the middle. For example, the angles LRA and LRB are both 90 degrees. >From the point of view of R, objects A and B have a common left edge. >From the point of view of L they do not if L can detect angle ALB. The detection of angle ALB is the crux of the matter, the heart of the stereo effect. This is probably a good place to mention that there isn't only one kind of acuity associated with the human visual system. Normally when we speak of acuity we are speaking of the ability to, say, separate closely-spaced fine black lines on a white background. In this sense of acuity, the best eyes can resolve about half a minute of arc and not- so-good eyes, two minutes of arc. Usually one assumes the figure is one minute of arc. In stereo or vernier acuity (vernier acuity is the acuity associated with lining up split lines such as on a vernier scale) the figure is much smaller. Stereo or vernier acuity is assumed to be around six seconds of arc though there is at least one recorded instance of a person having three-second stereo acuity. You can see from the diagram that if the distance RA becomes greater, the distance AB must become much greater for the angle ALB to remain detectable. Assuming angle ALB is 6 seconds of arc, what is the relationship of AB to RA? First, we convert 6 seconds of arc to radians and find that it is 2.9E-5 radians. So ALB = 2.9E-5. ALB = ALx - BLx but ALx = RAL and BLx = RBL so ALB = RAL - RBL and we don't need the point, x, anymore. RAL = arctan LR/RA RBL = arctan LR/(RA+AB) IF RAL and RBL are small angles measured in radians, we can say, approximately: RAL = LR/RA and RBL = LR/(RA+AB) So: ALB = 2.9E-5 = LR/RA - LR/(RA+AB) solving: 2.9E-5 = [LR(RA+AB) - LR*RA] / [RA(RA+AB)] Since AB< >AB = 2.9E-5 [(RA)^2]/LR ------------------------------------------------------------------------------ If the approximation above regarding RAL and RBL is not made then: ALB = 2.9E-5 = (arctan LR/RA) - (arctan LR/(RA+AB)) Solving this we get, step by step: tan(2.9E-5) = (LR/RA) - LR/(RA+AB) LR/RA - tan(2.9E-5) = LR/(RA+AB) LR AB = -------------------- - RA (Where LR = 0.065m normally) LR/RA - tan(2.9E-5) In this relationship, AB goes to infinity when the bottom line goes to zero. ie: AB is infinte when LR/RA - tan(2.9E-5) = 0 Solving this for RA we get RA = LR / tan(2.9E-5) = 0.065 / tan(2.9E-5) RA = 2236 meters ---------------- In other words, normal vision should be able to perceive the parallax between an object A at range 2236m, and object B at a distance of "infinity". I think that this is a little more than the figures I have heard previously. It does of course depend on what you assume for the value of stereo acuity (6 seconds of arc used above) The only reason for working this through without the assumptions was that John Bercovitz's posting got me thinking about all this. Now I'll just put that final equation for AB into my spreadsheet and plot me a handing graph to show the neighbours..... Steve Spicer Melbourne, Australia (I hope my algebra is OK, I just don't have time to double check this before posting!) ================================================================================ Note 18.05 -< More Advanced Stereo Concepts and Stereo FTP site >- -------------------------------------------------------------------------------- MORE ON STEREO PARALLAX also, at end, instructions on FTP info on stereo stuff by John Berkovitz I also wanted to talk a little about the effects of not maintaining ortho conditions in stereo photography. I think an intuitive way into this may be to first discuss the effects of binoculars on stereo perception. The usual binoculars (the models which use Porro prisms as erectors) do two things: they magnify and they increase the separation of the eyes. Going back to our sketch: L R A B L is the left eyeball R is the right eyeball A is a vertical rod at some distance B is a taller but otherwise identical vertical rod a little further away >From this sketch I previously derived: AB = 2.9E-5 [(RA)^2]/LR where: AB is the smallest separation which can be detected at range RA. 2.9E-5 is the tangent of 6" of arc which is a figure for stereo acuity The first thing binoculars do is to magnify the angle ALB. This makes the eyes sensitive to a smaller angle. So the new angle which can be detected is ALB/M where M is the magnification of the binoculars. The second thing binoculars do is to increase the distance LR. For small angles, doubling LR doubles ALB. So let's say that LR is doubled and M = 7. How far away can you now see what separation? I suppose we need a new variable, S, which will be the separation of the binoculars' objectives divided by the separation of the eyes (65 mm). In the present case, then, S = 2. Taking these effects into account, our modified formula becomes: AB = 2.9E-5 [(RA)^2]/(LR*M*S) So we can see a separation which is 1/M*S or 1/14th of the separation which we can perceive with our unaided eyes. If we could in practice separate something which was at 350 meters from the infinite background, with the aid of binoculars we can now separate something which is at a distance of 14*350 = 4900 meters. The next questions are "What is the effect of the increased separation of the points of view when using binoculars?" and "What is the effect of increased angular magnification when using binoculars?". The increased separation of the points of view may be thought of as giving a giant's view of the world. A giant would see the world same as you or I but everything would appear smaller relative to his size. That's why when you take pictures of scenes with widely-spaced cameras, you get a Lilliputian version of the scene. I realize that wasn't terribly rigorous. 8-) I've drawn a sketch of how the geometry causes this. It's in the photo-3d ftp directory as "ortho.sep.ps.Z". You can see from the sketch that increased camera spacing gives an exact reduced model of the scene. The model is reduced in depth, width, and height. So the reduced-size objects appear nearer. This means that height & width of a reduced object subtend the same angles at the viewer's eyes as the full-sized object would. The other problem is that of magnification. Magnification causes an apparent decrease in the depth of objects in the scene and also of course a decrease in the distance from object to object along the line of sight. (Non-sequitur: Is this what would happen if you were looking along the line of motion if you were approaching the speed of light?) Sorry. 8-) There is a companion sketch in the ftp directory called "ortho.magn.ps.Z" which demonstrates the problem. Usually in stereo photography we have the opposite problem, demagnification, when we are viewing. This is because it is easier to find a camera lens which puts a wide coverage on the negative than it is to find a viewing lens which will cover that angle. The upshot is that most stereo cameras' taking lenses are 35 mm focal length while most viewing lenses are 50 mm focal length for a demagnification of 35/50 = 0.7. The effect here is to stretch the object along the line of sight from the viewer to the reconstructed object. The apparent size of the object in height and width does not change but the apparent distance to it changes. The actual angles subtended at the eye by the object's height and width do change, of course; that is the essence of magnification. The apparent depth increases by the factor 10/7. If you care to look at the sketches, you get to the photo-3d ftp directory as follows: % ftp csg.lbl.gov account : anonymous .., send ident as password... cd pub/listserv/photo-3d dir binary get will transfer file to your home directory.. quit At the present time the 3d directory looks like so: 1545 Jun 2 1.index 45512 Mar 29 3d-faq.ps.Z 54068 Apr 12 3d.prod.serv 21237 Apr 12 3d.prod.serv.Z 203292 Mar 11 ES.CTD.ACHR.PS.Z 2324 Mar 5 PStc.expl 19890 Mar 5 PStc1.25.Z 501655 Mar 18 archive_1.Z 201485 Mar 25 dpthfld.ps.Z 182768 May 4 ortho.magn.ps.Z 184272 Jun 17 ortho.sep.ps.Z 12041 Mar 9 photometry 423407 Mar 17 raytrace.ps.Z 6040 Mar 9 wratten.filters "1.index" gives a description of the other files, as you might suspect. John Bercovitz (JHBercovitz@lbl.gov) ================================================================================ Note 18.06 -< Photometry and Light Meters Primer >- -------------------------------------------------------------------------------- The Photometric System in General followed at end with specific photographic references re: light meters by John Bercovitz Light flux, for the purposes of illumination engineering, is measured in lumens. A lumen of light, no matter what its wavelength (color), appears equally bright to the human eye. The human eye has a stronger response to some wavelengths of light than to other wavelengths. The strongest response for the light-adapted eye (when scene luminance >= .001 Lambert) comes at a wavelength of 555 nm. A light-adapted eye is said to be operating in the photopic region. A dark-adapted eye is operating in the scotopic region (scene luminance - -------------------------------------------------------------------------------- Questions and Answers: Polaroid Transfer Process What is a polaroid transfer process ? This is a process that transfers a polaroid image from the polaroid film sheet to art paper. The procedure is to take a polaroid picture, start the processing, peel the backing paper after about 10 seconds, place the developing image onto damp art paper, rub / roll the image for 1.5 to 2 minutes and slowly peel the film. What is left on the paper is a color dye image. What kind of film can I use ? It's the color dye that makes the transfer work. B&W doesn't transfer. Use the "9" films such as 59, 669, ... for making transfers. For 3x4, it's type 668/669 or the new Polacolor 100. Polacolor 100 has more vivid colors than the other two. For 4x5, it's type 58/59 sheet film, or 558/559 4x5 pack film. The 64T also works, but it's a Tungsten film. For 8x10, the film to use is type 809. It costs about \$10 a sheet. Integral (600) films do not transfer. How long do I process before peeling the backing paper ? Time ranges from 5 seconds to 30 seconds. Polaroid seggests 10 seconds. The best time will be the result of your experimentation ! Some say the longer you wait before peeling the film apart, the more likely the emulsion will lift off. Of course, lift off could also be a desired effect. Choosing the time to pull apart the packet is quite critical, after 10 seconds most of the red is transferred to the backing paper. If the film develops longer than 10 seconds, colors in the transfer will be less saturated. Not necessarily bad. Some have gotten good images after a deliberate wait of 30 sec. What kind of paper should I use and what do I do ? Hot pressed watercolor paper is probably the best bet for a transfer surface. Warm temperature is claimed to be a help. Some people soak the paper in hot water. You could use a hot lamp over your work surface to keep the surface warm. Light tones are easiest to transfer. Hot press gives you a sharper higher quality image, naturally it's more expensive. Some use wet rice paper with good luck. Then you need just the right amount of moisture. Make sure your paper is not too wet. How about filters and color bias ? Many people use filtration to correct the imbalance; Polaroid suggests this in their literature. You can't expect perfect colors, or even close to perfect. It just doesn't work that way. The process has a built-in cyan color bias. Polaroid recommends a CC20R filter (I think) If you use a strobe flash, any kind of warm filter over the flash will help. If you are in a hurry and don't have filters, use incandescent lights (yeah, 60-100 watt household lights) This doesn't give true color, but if you want true color you shouldn't use the transfer technique. If you use incandescent lights, beware that reciprocity failure sets in quickly with this type of film, compensate accordingly if your exposures are longer than 1/15 sec. Tip: Use a 30 magenta filter on your lens. (it really helps the color) Magenta filtration will help the "whites" somewhat.. Some people use a 20cc magenta or red filter to correct the blue cast. You can also try to peel earlier. How do I peel, place, roll and lift ? When making the transfer, press the film snugly against the transfer sheet. You will find that repeated pressing with the palm of you hand can work fine. Transfer for about 1 1/2 minutes before peeling the film sheet away. ******************* 1. Place neg on transfer paper quickly and carefully (I use dry paper to transfer to, rather than wet, it tends to be sharper) 2. Use a rubber roller to bond the negative to the transfer paper. (it takes about a minutes worth of constant even pressure) You'll aquire the skills quickly. 3. Let the transfer develop for about two minutes, then pull the negative away VERY SLOWLY. ******************** Give a couple of rolls with a rubber roller (the type used for printing wood cuts) and then burnish with a wad of dry paper towel (you could use and soft ball of stuff). Peel apart very gently and slowly, and PRESTO! a transfer print. ******************** One trick I picked up from the Polaroid reps is to roll the roller 2-3 times, then turn the whole assembly over and rub the back of the paper with your hands in a circular motion. The heat from your hands supposedly helps the transferring process. ******************** Polaroid suggests that heavy pressure on dark areas is desireable, as it helps prevent the dark areas from peeling up. Polaroid even suggests rubbing those areas (with the back of a spoon?) to prevent peel up. It doesn't work, now what ? Don't be discouraged if you get part of the image lifted off in the first few tries, or not much transfered at all. Experiment ! The colors aren't correct, what did I do wrong ? Probably nothing. Don't use this process if you want perfect colors. Tips ? Have lots of paper towels and water to clean up with. Transfers can be real messy! ********************************** Compiled by: mcfarlan@eso.mc.xerox.com (Doug McFarland) from messages sent by: monson@hobo.ECE.ORST.EDU (Ty Monson) glp@fig.citib.com (Greg Parkinson) sinclair@nlbbs.rn.com (Dan Sinclair) bu890@cleveland.Freenet.Edu (Brian Segal) dsp@halcyon.com (Don Smith) helen@seismo.gps.caltech.edu (Helen X. Qian) ================================================================================ Note 18.08 -< Tailflash Synchronizer Circuits >- -------------------------------------------------------------------------------- Tailflash synchronizers permit firing an electronic flash at the end rather than at the beginning of an exposure as is usually the case. Their purpose is to make a sharp picture due to electronic flash exposure next to a blurred one caused by a relatively long tungsten exposure. Tailflash synchronizers make the blur appear in the correct position with respect to the sharp image. 4 PART TAILFLASH SYNCHRONIZER FOR LEAF SHUTTER CAMERAS -9 volt ----------------------------------------------------. .__________. | .--------------------------. .____| 180 ohms |__*_____> to shutter | 16 15 14 13 12 11 10 9 | | |__________| | | *------------------------> to flash | IC 4049 | | .-------------. | | '----| Cathode | | 1 2 3 4 5 6 7 8 | .----|-------------|-----> to flash '--|--|--|--|--|--|--|--|--' '----| Anode | | | | | | | | | | C106D SCR | | | *--|--*--|--*--|-------------| Gate | | | | | | |_____________| | | | | |____________________________*____> to shutter | | | | .__________. | +9 volt ___*__*_____*_____*___________________| 10 Kohms |___| |__________| Note: On IC 4049 pins 9-16 are not connected to anything. Use a 16 pin IC socket rather than soldering to IC leads directly. Note: SCR output is polarized and if flash does not work one way try reversing connections. SCR must be able to deal with 250 volts or so. Note: * signifies connection Note: When connecting flash to device it should fire. Wait a while and then close the connection between the two shutter contacts. Nothing should happen when you do this. When you disconnect them, however, flash should fire. Shutter speeds shorter than 1/15 second may not work. EDGE DETECTOR TYPE TAILFLSH SYNCHRONIZER CIRCUIT FOR LEAF SHUTTERS ............. ............. +9 volt ----| 6.8 Kohm |----*----| 6.8 Kohm |-------------------> to shutter |___________| | |___________| | .............. | | Anode|------------------> to flash | | Cathode|--------------*---> to flash ._____________________| |C106D SCR | | | | Gate|----. | | ............. |____________| | | *----| 1N4148 | |----. .________| | | |_________|_| | ........ | | | ............. | | | | ............. | :____| 470 Kohm |____*__| .1uF |___*__| 6.8 Kohm |___* |___________| | | |___________| | |______| | -9 volt ------------------------------------------------------*----> to shutter Note: SCR output is polarized and if flash does not work one way try reversing connections. SCR must be able to deal with 250 volts or so. Note: * signifies connection Note: Shutter speeds shorter than 1/15 second may not work. Note: Connect to flash with female PC cord, to camera with male PC cord. copyright 1993 - andrew davidhazy non-commercial uses permitted ================================================================================ Note 18.09 -< Some aerial photography Tips >- -------------------------------------------------------------------------------- AERIAL PHOTOGRAPHY TIPS Here are some tips from a photographer who posted them on rec.photo... 1. Use a high-winged plane. 2. Make sure the window on your side of the plane opens, some will, some won't. The glass adds too much distortion. 3. Keep the horizon horizontal. Even if the horizon isn't in the picture, by keeping it level the picture will make sense. (note: vertical is ok, too... I'm just saying the pictures where I held the camera at weird angles made me dizzy) 4. Shoot in the morning or evening. The additional shodows add depth to the picture. 5. Keep the camera out of the airflow, and ton't touch the aircraft with your upper body. It'll help you hold the camera steadier. 6. Carry lots of film... it's expensive to drop into your local grocery store to buy more. (pocket may be better than camera bag. 7. Discuss communications with your pilot. What works for us is for me to explain what I want to take a picture of and from what side. He then fly's by and I get a picture (only one is really good since only at an instant am I exactly perpendictular.) I usually then tell him to get farther from the subject, or closer and do it again. It is best for me to tell him what to do. I tried asking him and get "I'm not the photographer". The person I fly with uses the trips to learn better aircraft control. He enjoys my directions and practices to maintain them as exactly as possible. 8. Focus on infinity, and have the lens focused before the shot appears. You won't have time to focus and shoot when the decisive moment comes. 9. I like the 100mm range for focal lentgh. A zoom was helpful. 35mm lenses tends to get landing gear. My shutter speed was 1/2000, (100asa) and there is some blur. I wouldn't want to enlarge much over 8x10. 10. I find aerial shots not very creative, but extremely fun. Although the pictures might not be "artsy", people tend to look at them for a much longer time than they do for even the most expensive paintings. 11. Watch for fog, it is no fun, and the pictures show it! We have rescheduled many flights. 12. Hail Mary's can be fun ( hold the camera out and point it straight down and shoot) --- try one, but don't drop the camera. 13. Try pictures of your workplace or school. everyone is always interested in finding their car, of building 14. If you really enjoy it, you can make money with aerial photography. I've heard of several schemes, but havn't tried any yet. 15. If you want sharper pictures try renting a gyro-stabilizer. i've never done it, but have had recommendations to the effect. 16. Have fun! lee -- Lee McFearin. #include mcfearin@convex.com ================================================================================ Note 18.10 -< Where to get film for SUBMINIATURE cameras >- -------------------------------------------------------------------------------- If you happen to need film for tiny cameras (such as the Minolta 16) that use 16mm or Minox 9mm film here are two suppliers that may be of interest to you. 1) MicroTec Industries P.O. Box 9424 San Diego,CA 92109 (619) 272-8820 They do processing of color and B&W Minolta 16 and minox films. Also they have Minolta 16 bulk rolls (100ft) for \$50. Their 18exp B&W is \$5, color \$6. They also have lots of minox accesories, have then send you a catalog. 2) Minolta Processing Station P.O. Box 2919 Torrance CA. 90510 They do processing of Minolta films and sell them. B&W 100 ASA for \$3.50 with discounts on larger quanties. The nice thing aobut the film canisters is that you don't have to destroy them to get the film out. They just pop open. Once you have several on hand you could get a bulk roll and probably be set for life as far as film goes. ............................................................................... listserv@listserver.isc.rit.edu with this text in the BODY of the mail: subscribe photoforum your-name-here where it says your-name-here substitute your real name and then send message. Also, there are a number of articles available from this server. Get to them at the following URL: http://www.rit.edu/~andpph/articles.html For info on a global databank of schools offering photography instruction go to: http://www.rit.edu/~andpph/database.html FTP: You can also obtain most of these files also by Anonymous FTP from vmsftp.rit.edu under pub/ritphoto/photoforum WWW: You can access the PhotoForum Home Page on the WWW at the this address: http://www.rit.edu/photoforum ```