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    FAQ or Answers to Frequently Asked Questions                  Section 25
    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. For complete table of content
    send message to   ritphoto@rit.edu   with  FAQ$txt  in the Subject: line
                      These files are available in SECTIONS. 
             This is Section 25 and its contents are listed below.
      25.01  -< Daguerreotype Info from 1858 available on-line >-
      25.02  -< List of Photo/Imaging Books, Magazines, etc.  >-
      25.03  -< Basic Photo Lesson w/pinhole camera >-
      25.04  -< Tips for use of PhotoFlo >-
      25.05  -< Remote Camera Triggering Discussion >-
      25.06  -< More on Polarizing Filters! >- 
      25.07  -< Kodak 2481 HS Infrared Film Data Sheet >-
Note 25.01    -< Daguerreotype Info from 1858 available on-line >-
    as seen on PHOTOHST mailing list:
           "American Hand Book of Daguerreotype" available online
    I have prepared a digital edition of the "American Hand Book of the
    Daguerreotype," by S. D. Humphrey, 5th edition, 1858.  I have
    contributed the ASCII text version (with GIF images of the
    illustrations to Project Gutenberg.  You can fetch the files via
    anonymous FTP from:
    mrcnext.cso.uiuc.edu   in directory  /pub/etext/etext94
    The files are:
    amdag10.zip (or .txt) -- ASCII text
    amdgf10.zip           -- GIF files of the illustrations
    Any comments or suggestions are welcome.
    A second text that I have prepared will be one of the October releases.
    Greg Walker       gwalker@netcom.com
    Digital Daguerreian Archive Project --
    Electronic texts from the dawn of photography.
Note 25.02     -< List of Photo/Imaging Books, Magazines, etc.  >-
    This is a partial list of magazines, newsletters, and books relating to
    photo/imaging being compiled by  Jerry Courvoisier of Southern Illinois
    University's Photographic Production Technology Department.  He is also  
    trying to keep the list current and asks that if you know of additional 
    publications you please email the info to him at GA4216@siucvmb.siu.edu
    Larish, John, Digital Photography Pictures of Tomorrow
    Micro Publishing Press, Torrance CA 1992
    Larish, John, Photo CD - Quality Photos at your Fingertips
    Micro Publishing Press, Torrance CA 1993
    Adobe Photoshop Classroom in a Book
    Adobe Press /Hayden Books
    Rich, Jim and Bozek, Sand  
    Photoshop in Black and White 
    Peachpit Press Inc. Berkeley CA 1994
    Linnea Dayton & Jack Davis 
    The Photoshop WOW Book 
    Peachpit Press Inc. Berkeley CA 1993
    Weinmann, Elaine and Lourekas, Peter 
    Photoshop for the Macintosh
    Peachpit Press Inc. Berkeley CA 1993
    Sally Wiener Grotta/ DanielGrotta
    Digital Imaging for Visual Artists 
    Windcrest/McGraw-Hill 1994
    Mark Beach
    Graphically Speaking
    North Light Books 1992
    Biedny, David,  Monroy, Bert
    The Official Adobe
    Photoshop Handbook Bantam Books 1991
    Breslow, Norman 
    Basic Digital Photography 
    Focal Press  1991
    McClelland, Deke 
    Macworld Photoshop 2.5  Bible
    IDG Books  Worldwide, Inc. 1993
    Arlington TX 76012
    Adele Droblas Greenberg & Seth Greenberg 
    Fundamental Photoshop
    Osborne McGraw-Hill 1994
    Electronic Photography News
    EPN Publishing Div.
    Photofinishing News Inc.
    10915 Bonita Beach Rd.
    Bonita Springs, FL 33923
    Fractal Design Gallery
    P.O. Box 2380
    Aptos, CA 95001-9973
    Photo/Imaging Education Assocation (PMA)
    3000 Picture Place
    Jackson, MI 49201
    Association of Texas Photography Instructors
    P.O. Box 121092
    Arlington, TX 76012
    Photo Imaging In The Year
    2000- The Future of the Photo/Imaging Industry,1991
    Photo Marketing Association International
    3000 Picture Place 
    Jackson, MI 49201
    Omura, Dr. Glenn,
    Imaging Technology Trends Transition to a New Industry,1991    
    Photo Marketing Association International
    3000 Picture Place
    Jackson, MI 49201
    Studio Photography
    Div. Of PTN Publishing
    445 Broad Hollow Rd
    Suite 21
    Melville, NY 11747
    Photo Lab Management
    P.O. Box 1700
    Santa Monica, CA 90406-1700
    T.H.E. Journal
    (Technological Horizons in Education)
    150 EL Camino Real Suite 112
    Tustin, CA 92680-9833
    PC Graphics and Video
    P.O. Box 7708
    Riverton, NJ 08077-8708
    Integrated Media Inc.
    501 Second St.
    San Francisco, CA 94107
    PC Magazine
    Ziff-Davis Publishing Company
    Computer Artist
    P.O. Box 2649
    Tulsa, OK 74101-9632
    Photographic Processing
    900 Haddon Ave. Suite 326
    Collingswood, NJ 08108-2101
    Advanced Imaging
    445 Broad Hollow Road
    Melville, NY 11747-4722
    Photo Electronic Imaging
    1090 Executive Way
    Des Plains, IL 60018
    Photo Marketing
    Photo Marketing Association International
    3000 Picture Place
    Jackson, MI 49201
    Minilab Developments
    2627 Grimsley Street
    Greensboro, NC 27403
    P.O. Box 191826
    San Francisco, CA 94119
    Photo District News
    49 East 21st Street
    New York, NY 10010
    New Media
    Hypermedia Comm. Inc.
    901 Mariners Island  Blvd.
    Suite 365
    San Mateo, CA 
    Mac User
    P.O. Box 52461
    Boulder, CO 80321-2461
    Mac World
    P.O. Box 51666
    Boulder, CO 80312-1666
    Mac Week
    525 Brannan St.
    Suite 309
    San Francisco, CA 94107
    Communication Arts
    410 Sherman Ave.
    Palo Alto, CA 94306
    News Photographer
    1446 Conneaut Ave.
    Bowling Green, OH 43402
    Step By Step Electronic Design
    6000 N. Forest Park Drive
    Box 901
    Peoria, IL 61656
    5783 Park Court
    P.O. Box 501100
    Indianapolis, IN 46250
    (317) 849-6110
    Industrial Photography
    PTN Publishing Co.
    Div. Of PTN Publishing
    445 Broad Hollow Rd
    Melville, NY 11747
    Presentations Magazine
    Lakewood Publications Inc.
    50 S. Ninth St.
    Minneapolis, MN 55402
    TV Technology
    P.O. Box 1214
    Falls Church, VA 22041-9808
    Association for Information and Image Management
    1100 Wayne Ave. Suite 1100
    Silver Spring, MD 20910
    Imaging World
    P.O. box 1358
    Camden, ME 04843
    Silicon Graphics World
    P.O. Box 399
    Cedar Park, TX 78630-1285
Note 25.03          -< Basic Photo Lesson w/pinhole camera >-
        What follows is offered for public school teachers who may wish to 
introduce photography on a basic level in their classrooms.  What is 
presented is written on a -very basic- level, not to insult anyone's 
intelligence, but to be as complete as possible.  Further, this is not 
intended to be "the last word" on the subject - It's only one approach 
among many.  For instance, those familiar with graphic arts will 
immediately see that Ortho film could be easily substituted as the negative 
        Yours in teaching,
        Carroll Hale
        (Chair/Professor - Art) Eastern Kentucky University
-----------------------------CUT HERE--------------------------------------
                    BASIC PHOTOGRAPHY FOR THE
                     PUBLIC SCHOOL CLASSROOM
                    (USING THE PINHOLE CAMERA)
The prime goal of this project is to teach the basics of classic
Positive/Negative photographic technique.  Secondary goals are to
make the project interesting to students from many grade levels,
keep the need for special materials-equipment-facilities to a
minimum, hold down costs as much as possible, and avoid
technically complicated processes. 
To achieve these ends, the photographic process chosen is of
extreme simplicity.  However, because the depth of the student's
involvement may be varied from the level of simply making the
exposure, to that of starting with the construction of the camera
and continuing through printing, students of markedly different
photographic sophistication should find the project stimulating.  
The process chosen is about 150 years old.  It was developed by
the photographic pioneer Henry Fox Talbot.  The name he chose for
it, Calotype, means "beautiful picture".  The reason Calotype was
chosen for this project is that it is a very simple and
"forgiving" process which requires a minimum of materials and yet
contains all the basic steps of standard photography.  In this
process the negative is made on translucent paper rather than a
transparent substrate.  The negative is then "contact-printed" on
a second piece of the same sort of paper.  The resulting positive
image is soft by current standards (that is, it's slightly blurred 
by the pinhole "lens" and the light scattering properties of the 
paper negative).  Further, these images cannot readily be enlarged 
or reduced.  This last shouldn't be a drawback in most public school
classrooms since enlarging equipment would needlessly complicate
the project.  The camera used in the project is one of absolute
simplicity, a pinhole type, that may be made for less than a
dollar.  The negative-print size is 4"X 5".  This is large enough
for the print to be a desirable acquisition on the part of the
student while remaining small enough to keep costs down.  Paper
size is modular in the sense that it divides evenly into the 8" X
10" sheet of photo printing paper which is standard and readily
available (you can also buy 4"X 5").
The camera is a cardboard box of approximately 4"X 5"X 6" outside
dimensions.  It is most readily made of black matboard with the
black surface in the interior.  If black matboard is not
available, another heavy opaque cardboard (approximately 1/8"
thick) may be used providing the interior is completely
blackened.  One 4" X 5" end is covered with a removable cap while
the other has the pinhole centered in it.  The removable cap
serves as the negative holder.  The pinhole is made in a piece of
aluminum foil and is taped to the inner surface of the box
centered in a cut-out about 1/4" square. (The smaller the
pinhole, the sharper the picture, but the longer the exposure.) 
When making the pinhole, press through the foil into a piece of
cardboard then pull the pin straight back to make a clean, round
hole. Check to make sure the edges of the hole are clean and flat
for the sharpest possible image.  An opaque flap on the outer
side of the front cap serves as the pinhole's shutter.  Cover all
possible light leaks (especially seams and scored edges) with
opaque tape.  The cap and the shutter are easily secured by
rubber bands.  
I hope the construction is clear from the diagrams below (it's
not too easy doing them in ASCII!)
Cut matboard to the dimensions shown and score on the side 
AWAY from the direction of fold.
           BASIC BOX (make one)           END CAPS (make two)
                                          Bend the 1"W flaps
    <--            19"            -->      <-   6"   -> 
     --------------------------------        ________ 
^   I      |       |      |       | I      I-I------I-I  ^
|   I      |       |      |       | I      I |      | I  |
6"  I      |       |      |       | I      I |    5"| I
|   I      |       |      |       | I      I |      | I  7"
v   I      |       |      |       | I      I |      | I
     --------------------------------      I_|__4"__|_I  |
     <-4"-> <-5"--> <-4"-> <-5"--><1">       I------I    v
          ASSEMBLE TO LOOK LIKE THIS (below)
      /--------/I         _______________
  6" /        /II     4" / /----------/ /I
    /________/ II       / /          / / I
   I--------II II      I-I-----------I-I I    FRONT CAP 
   I        II II      I I           I I I    GLUED-ON
   I  flap  II II      I I           I I I
 5"I  I--I  II II    5"I I           I I I    REAR CAP
   I  I__I  II II      I I           I I I  LEFT REMOVABLE
   I        II /       I I           I I I
   I        II/        I I           I I /
   I--------I/         I-I-----------I-I/
       4"                     6"
 FRONT 3/4 VIEW         SIDE 3/4 VIEW
in the center of the front cap.  The flap that covers the pinhole
may be hinged with a piece of tape - a second piece of tape may
be use to make a tab so that the flap can be easily opened.  it's
a good idea to blacken the outer surface of the camera, under the
flap and rear cap, to cut-down on light leaks.  Also making the 
rear cap deeper than 1" helps cut down on light leaks (don't make
the cap too deep or it will act like a piston when it is put on
and will blow-out the foil).
                   I.   CAMERA CONSTRUCTION
The decision as to whether the student is to construct the camera
or him/herself or use one already made can only be made by the
classroom instructor.  If one is to be made, a complete
demonstration and close guidance are practical necessities.  Four 
cameras may be made from a single sheet of matboard.  Some matboard 
is left over, but little is wasted.  Making a camera should take 
about one class period if the parts are precut and -IF- all goes well.  
                    II.  LOADING THE CAMERA
The camera is loaded under safelight conditions.  The safelights
used for this paper must be amber.  Three or four sheets of RC II
paper may be cut at a time.  The 8" X 10" sheets are easily cut
on a guillotine type paper-cutter into four 4" X 5" pieces per
original sheet.  Since the safelights put out little light it is
best to mark the paper cutter ahead of time at the 4" and 5"
marks with tape that strongly contrasts with the cutter board. 
Cut all sheets for the project at one time.  Remember, each photo
takes at least two sheets, one for the negative and one for the
print.  This is probably not a job for young or careless
students.  Even under safelight illumination, photo paper will
fog if it is left out for a few minutes.  Only a few sheets
should be out to be worked on at any one time.  When the paper is
not in use it should be stored in a light-tight box.   The cut
sheets are loaded singly into the camera with the shiny surface
facing the pinhole.  Place the sheet in the back cap and put the
cap on the camera.  Secure it with two rubber bands and make sure
the shutter is closed (taped or held by a rubber band).  Check
the area to be sure all light sensitive materials are put away
and turn on the room lights. 
Exposures are made in full/hazy sunlight.  The camera is placed on 
a solid object that isn't subject to motion.  It's a good idea to
hold the camera down with something that weighs a pound or two
if there is any chance it might be moved by wind or whatever
during the exposure.  A book works well for this.  The shutter is
opened and secured by a rubber band.  Thirty seconds are allowed
to elapse and the shutter is closed and secured.  THAT'S ALL
THERE IS TO IT!  If the camera is joggled accidentally when the
shutter is opened or closed it doesn't matter since the exposure
is so long a second or two of upset is unimportant.
Prepare the chemicals as per instructions on the packets for
stock solutions.  Stock solutions should be kept in plastic
bottles so that the obvious problems brought on by broken glass
in a dark room can be avoided.  The developer (Dektol) is used at
a ratio of one part stock solution to two parts water.  The stop
bath and fixer are used in stock solution.  Prepare one tray each
of developer, stop bath, fixer and a running water bath.  The
trays should be large enough to hold a 4" X 5" sheet easily.  
4"X 5" trays will do but are cramped.  5" X 7" trays are better. 
The "chemical" trays should be filled to a depth of an inch or
so.  Tongs must be used to avoid possible dermatitis.  The wash
tray should be at least 8"X 10" since there will usually be
several negatives/prints washing at any one time.  A siphon
circulator is a great aid to washing.  If one isn't available,
use a tray that has a drain hole or two set about 1/2" below its
edge or the prints will keep washing over the edge of the tray.
What follows is done under SAFELIGHT.
1.   The camera is unloaded
2.   The negative is placed (shiny side up) in the developer for  
     1 to 2 minutes.  It is a good idea to slightly dog ear a
     corner the so the tongs will slide under.  Agitate the       
     solution gently at approximately 10 second intervals.
3.   Remove the negative from the developer by one corner and     
     allow the  developer to drain off the diagonally opposite    
     corner.  Place the negative in the stop bath for 5 to 10 
     seconds.  Agitate continuously.
4.   Remove the negative from the stop bath by one corner etc...
     Place in the fixer for 2 minutes.  If no other light   
     sensitive materials are out, the remainder of the negative  
     processing may be done in ordinary room light.  Use a 10    
     second agitation cycle as above.
5.   Remove etc... place in the wash for 5 minutes.
6.   Remove etc..  squeegee both front and back and dry with the
     hair dryer.  Dry the front (emulsion) side first.  (If the 
     wet emulsion  is allowed to dry in contact with another 
     surface it will be permanently glued to it.)  
What follows is done under SAFELIGHT.
1.   Place an unexposed sheet of the Rapid RC II paper shiny side
     up on a black background. (A piece of matboard is      
     excellent.)  Place the negative face down on the fresh      
     paper.  Make sure the two pieces are  evenly aligned. Put a 
     sheet of clear glass over the  paper to hold them in firm 
     contact with each other.
2.   Expose this "sandwich" to the light from a 15 watt household
     bulb in a reflector (clamp-lamp) at a distance of 3 feet for
     about 5 seconds.  If other wattages are used the time will 
     vary.  Make sure that no other light-sensitive material is 
     inadvertently fogged during the  exposure.  If the print is 
     too light, more exposure is needed.  If it is too dark, use 
     less exposure.  This negative may be used to make many prints.
3.   Process the print just as the negative was above (IV. steps 
     1. through 6.).
Used chemicals should be dumped in an environmentally approved
fashion.  Do not return them to the stock solution bottles as
they will weaken the fresh chemicals.  If the used chemicals must
be saved, put them in bottles reserved for the purpose and
clearly marked as such.  The trays should be rinsed and drained
and left to dry.  Any spills should be sponged up and the area
washed with clear water.  Store chemicals and paper in a cool,
dry, dark place. 
Photo Printing Paper - Kodak Rapid RC III, "F" surface
Developer, Paper - Kodak Dektol
Stop Bath - Kodak, With Indicator (optional but recommended)
Fixer (Hypo) - Kodak, General Purpose
Running water of potable quality
Jugs, Plastic, 3 ea., (to hold chemicals)
Trays, 3 ea., Plastic, Min. 4" X 5" X 1 1/2"Deep (may be larger)
Tray, 1 ea., Plastic, Min. 8" X 10" X 1 1/2"Deep (may be larger)
Tongs, Photo Print, 2 ea.
Contact printing frame or a Min. 5" X 7" sheet of glass and black 
surface to print on
Timing device (watch with seconds display)
Light, 15 watt, in reflector (Clamp-lamp)
Safelights, Amber, Min. 2 ea.
Squeegee, Photo Print (optional)
Extension Cords, as needed
Posterboard, Black, strip 6" X 33"
Glue, White
Tape, Black-Opaque (electrician's tape will do)
Foil, Aluminum, 1/2" square
X-Acto knife
Pin, Ball-Headed Straight, (J. & P. Coats size 20)
Bands, Rubber, 3" or 31/2" X 1/8", 3 ea.
Date: Fri, 23 Sep 1994 16:00:11 -0400
From: "E. C. HALE" 
Note 25.04               -< Tips for use of PhotoFlo >-
    > I would like any tips on removing and/or preventing water spots on
    > dried negs. Even though I always use photoflow, I have a problem with
    > spots from time to time.
    The problem could be many things...
    1. Check your water source, excess minerals in the water will cause
    spots. Try mixing your Photo-Flo with DI, or distilled water and see if
    the problem persists.
    2. Mix the Photo-Flo a bit weaker than recommended and keep it changed
    often. The spots you're seeing may actually be Photo-Flo sludge marks -
    a common ailment when the solution is too strong or too old.
    3. Lightly squeegie the film before drying. Sometimes the Photo-Flo
    dries before the suds slide off the film and leave marks accordingly.
    Also, check your film dryer temperature, rapid drying of the film also
    prevents the suds from sliding off the film before drying.
    4. Even though this is highly unlikely the problem, and I don't mean to
    insult anyone's intelligence, but I have known of students who, until
    corrected, thought that they should rinse the film off in water !after!
    the Photo-Flo, thus spots.
    Hope this helps.
    Barry Snidow, 
    North Lake College 
    Irving, Texas
Note 25.05          -< Remote Camera Triggering Discussion >-
Subj:   RE: remote nighttime photography
There are several commercial IR (beam interrupt) and sound detectors available
on the market. A fairly popular one is the Dale Beam. It costs around $500 as
do most of the others.
These devices allow you to set up an invisible beam of IR and when something
interrupts the beam it causes a switch to close thereby tripping a camera
capable of being tripped by the closure of a switch.
To set up the system so that the camera will ONLY fire when the subject is in a
specific location in space an "X" beam set-up must be set up. This can be
arranged by splitting a laser beam (if you don't mind a light spot to possibly 
show up on your subject you could use a red, visible, AV laser pointer) with a 
beam splitter and using a few mirrors directing each 1/2 beam so that they
recombine on the tripper's sensor but traveling through space in such a manner
that they cross at the desired location.
The sensitivity of the device is adjusted so that when either half of the beam
is broken the sensor's response is still high enough that the switch does not
close. But when both halves are interrupted, bingo, the device trips the
This type of synchronizer would be called a "dark" activated synchronizer.
BTW... you could also use a device built into several modern cameras called a
"trap" shooting mode. Meaning that when the subject is in focus the camera
trips. I don't know which specific cameras have this feature but I am sure our
colleagues on the list will let us know. 
If your camera does not have the capability of being fired by the simple
closure of a switch your problems are magnified manyfold. It is also useful to
have a winder or motor drive on the camera. I think some of the simples cameras
to trip with simple switches are Canon and Olympus cameras since they use a
2 mm (or maybe it is 1.5mm0 or subminiature plug available at most electronic
stores (such as Radio Shack). Nikons use "special" connectors but you can
circumvent this with a bit of ingenuity. I have simply slipped short lengths of
household extension wire, after appropriately expanding the plastic, over the
bottom two of the pins if a three connector Nikon plug or over both is a two
pin type and then a simple connection of the stripped ends should cause the
motor to fire the camera. (I can not accept responsibility for damage to pins
or camera due to installation of "improvised" cables).
Anyway, we routinely build such synchronizers in my photoinstrumentation class
with students learning the basic function of the circuit's "building blocks",
making the  printed circuit board, buying the components, and assembling the
final product. The cost if they scrounge for surplus parts is around $25. For
this they get a Light, Dark and Sound activated synchronizer with delay
capability and operable also as an intervalometer.                    
The electronic basis for the device is a 556 integrated circuit double timer
chip. The output is either independent SCR's, independent relays or a single 
relay switchable from timer one to timer two.
We also use this device to make milk splash photographs ala Doc Edgerton. (sort
of as illustrated in my signature file appended below) There are I am sure more
refined designs and designs built on digital rather than analog circuitry but
for us the 556 works well.
If anyone would like to have a copy of the circuit, as well as other circuits
that friends have sent me,I would be happy to mail you a copy if you send me
private mail and include your snail mail. 
      o o  0 0 o   o
       \/\/\/\/\/\/   Andrew Davidhazy, at RIT's Imaging and Photo Tech Dept
        |        |    andpph@rit.edu              High Speed Photography Lab
_______/          \_________________________________________________________
    The Dale Beam can be obtained from the manufacturer, 
    Protech, Inc.
    You can also obtain a similar device called the Shutter Beam from:
    Woods Electronics
    c/o Steve Yankey
Note 25.06              -< More on Polarizing Filters! >- 
>I would like to know how a circular polarizing filter works.
This is a subject which could really use a chalkboard to
explain.......Or, if you remain confused, try an optics text in a college
bookstore.  The description in the first paragraph below might be tough
to visualize, so you might want to skip to the second paragraph. 
The first element in a circular polarizer (CP) is a regular polarizer. 
So, light entering the CP is first filtered by a polarizer--reducing
reflective glare and all the things a polarizer normally does.  The next
element (actually binded to the polarizer) is a "quarter wave plate".  
This is made of a material that is birefringent--light polarized one way
has a different index of refraction (and, hence, speed) than light
polarized in the perpendiclar direction.  What this does (and what a
blackboard is needed to explain) is take the light which now is
polarized, say, up-down, and convert it to light where the polarization
vector rotates around in  a circle with time.  I.e. the light comming out
of the CP will be polarized up-down one instant, then polarized 45! off
an instant later, then polarized 90!!off another intstant later and so
What does this do?  It takes light and filters it into polarized light by
the first element.  Then it converts this polarized light into light
which is a combination of two polarizations.  Some cameras pick off one
polarization for the light meter and/or autofocus.  So, if you had used a
linear polarizer, you could filter out all the light that your meter
would see, so your meter would think it was very dark outside and would
overexpose your image.  Or, you might not be able to use your camer's AF
capability.   By using a circular polarizer, you take the linearly
polarized light from the first element and convert it into light which
has both componenets of polarization--just as "natural" light does.  This
allows light to pass the filters in front of the meters/AF.
Do you need a circular polarizer?  Only if your camera body requires it
for some purpose.  I have a Nikon N2020, which a camera store owner was
convinced needed a CP (he was wrong) and an N90 which does need it.  Will
it change the look of your pictures?  No, unless it is made poorly (the
bonding of the quarter wave plate and gettin all surfaces optically flat
is what makes these things cost more.  There is more possibility for
something to be done wrong with them).
From: Matt Carey 
Subject: Re: how does a circular polarizer work?
Organization: UCSD
Note 25.07          -< Kodak 2481 HS Infrared Film Data Sheet >-
                         Kodak High Speed Infared Film 2481
                                    (Estar Base)
          * A high-speed, infared-sensitive black-and-white film on
          dimensionally stable .004-inch (0.10nm) Estar Base.
          * Sensitive through the visible region of the spectrum and in the
          infared to approximately 90nm, with maximum sensitivity from 750nm
          to 840nm.
          * Used in scientific, medical, biological, industrial and
          questioned-document photography.
          HANDLING: Handle only in total darkness. No safelight should be
          FILTERS: For most applications, a filter must be used over the lens
          (or light source) to absorb the blue light to which the film is
          sensitive. For general photography, a KODAK WRATTEN Filter No. 25
          is recommended for this purpose. If only infared is to be recorded,
          use a KODAK WRATTEN Filter No. 87, 87C, 88A or 89B or its
          equivalent. Under very low light conditions and when infared
          rendition is not important, the film can be exposed without a
          FILM SPEED: Exact speed recommendations are not possible because
          the ratio of infared to visible radiation is variable and because
          photoelectric meters are calibrated only for visible radiation. Use
          a hand-held meter rather than a through-the-lens type.
          It is recommended that trial exposures be made to determine proper
          exposure for the conditions under which photographs will be made.
          Under average conditions, the following speeds can be used as a
          basis for determining exposures when meters marked for ASA speeds
          or exposure indexes are used.
          No. 25, 29, 70, or 89B              50             125
          No. 87 or 88A                       25              64
          No. 87C                             10              25
          Without a Filter                    80             200
          FOCUSING: For best definition, take all infared pictures at the
          smallest lens opening that conditions permit. If large apertures
          must be used and the lens has no auxiliary focusing mark, establish
          a focusing correction by photographic focusing tests. A basis for
          trial is the extension of the lens by 1/4 of 1 percent of the focal
          length of the lens.
          DAYLIGHT EXPOSURES: -for subjects in bright or hazy sunlight
          (distinct shadows):
          Distant Scenes       Nearby Scenes               Distant Scenes
          1/125 sec at f/11    1/30 sec at f/11          1/125 sec at f/16
          PHOTOLAMP EXPOSURE TABLE: For use with a KODAK WRATTEN Filter No.
          25 over the camera lens. Use two 500-watt reflector-type photolamps
          or two No. 2 photolamps in 12-inch reflectors giving comparable
          light output. Place one lamp on each side of the camera at an angle
          of 45 degrees to the camera-subject axis.
          Lamp-to-Subject Diatance          3 feet       4 1/2 ft   6 1/2 ft
          Lens Opening at 1/30 Sec.         f/11           f/8        f/5.6
          FLASH EXPOSURE: To obtain the lens opening for electronic flash or
          flashbulbs, divide the guide number by the distance in feet from
          flash to subject.
          87 over the camera lens:
          Output of Unit     350 500 700 1000 1400 2000 2800 4000 5600 8000
          (BCPS or ECPS)
          Guide Number for    20  24  30   35   40   50   60   70   85  100 
          Distances in Feet
          Guide Number for     6   7   9   11   12   15   18   24   26   30
          Distances in Meters
          1. Develop:
          Approximate Developing Time (in minutes)
          Kodak Dev    Aprox     SMALL TANK-(agit at    LARGE TANK*-(agit at 
                     Contrast    30-sec intervals)      1-min intervals)
                                 65F 68F 70F 72F 75F    65F 68F 70F 72F 75F
                               18.5C 20C 21C 22C 24C  18.5C 20C 21C 22C 24C
          D-76         0.70      13  11  10  9.5  8     14  12  11  10   9
          HC-110       0.80       7   6   6  5.5  5      7  6.5  6  5.5  5
          (Dilution B)
          D-19 (max-   1.65       7   6  5.5   5  4     8.5  7.5 6.5  6  5 
          imun con-
          *Development times of less than 5 minutes in a large tank may
          produce poor uniformity and should be avoided.
          2. Rinse:
             At 65 to 75 F (18.5 to 24 C) with agitation.
          Kodak Indicator Stop Bath - 30 seconds.
          Kodak Stop Bath SB-5     -  30 seconds.
          A running-water rinse can be used if an acid rinse bath is not
          3. Fix:
             At 65 to 75 F (18.5 to 24 C). Agitate films frequently during
              Kodak Rapid Fixer      -2 to  4 minutes    
          OR  Kodak Fixer            -5 to 10 minutes
          OR  Kodak Fixing Bath F-5  -5 to 10 minutes
          4. Wash:
             For 20 to 30 minutes in running water at 65 to 75 F (18.5 to 24
          C). To minimize drying marks, treat in Kodak Photo-Flo Solution
          after washing, or wipe surfaces carefully with a Kodak Photo
          Chamois or a soft wet viscose sponge. To save time and conserve
          water, use Kodak Hypo Clearing Agent.
          5. Dry:
             in a dust free place.
          Keep unexposed film in a refrigerator or freezer at 55 F (13C) or
          lower in the original sealed container. If the film is stored in a
          refrigerator, remove it four hours before opening the package. If
          stored in a freezer, remove it about eight hours before opening. A
          sufficient warm-up time before opeing the package is necessary to
          prevent condensation of atmospheric moisture on the film.
          Keep exposed film at 40 F (4 C). Process the film as soon as
          possible after exposure to avoid undesirable changes of the latent
          image. If it is necessary to hold exposed but unprocessed film for
          several days, it should be resealed and refrigerated. Before
          unsealing and processing exposed film that has been stored in a
          refrigerator or freezer, follow the moisture prevention and
          handling procedures for raw film as described above.
          FOR MORE INFORMATION: see the following Kodak Publications
          No. M-28, Applied Infared Photography
          No. N-1,  Medical Infared Photography
          No. N-17, Kodak Infared Films
          This film will be replaced if defective in manufacture, labeling or
          packaging. Except for such replacement, the sale or any subsequent
          handling of this film is without warranty or liability even though
          defect, damage or loss is caused by negligence or other fault.
          Eastman Kodak Co, Rochester, NY  14650
          Kodak, Estar, Wratten, D-76, HC-110, D-19 and Photo-Flo are
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