================================================================================
FAQ or Answers to Frequently Asked Questions Section 21
--------------------------------------------------------------------------------
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 21 and its contents are listed below.
21.01 -< A DOF program written in C FYI >-
21.02 -< Polaroid batteries and accessories >-
21.03 -< Infrared Ektachrome Processing in E-6 chemicals >-
21.04 -< New f# when using bellows extension >-
21.05 -< Data on Wratten Filters by the Numbers >-
21.06 -< CHEAP IR Filters - experimental quality >-
21.07 -< UV and IR Technique Basics >-
21.08 -< Solarization Tip >-
21.09 -< Create-a-Print used for B&W printing >-
21.10 -< Decoding De DX Code >-
21.11 -< IR Ektachrome Processing in cool E6 chemicals >-
================================================================================
Note 21.01 -< A DOF program written in C FYI >-
--------------------------------------------------------------------------------
From: bjthomas@cisco.com (Bill J. Thomas)
Subject: depth of field c code
Organization: cisco Systems
the following is a Depth of Field program written in C
*******************************************************************
%dfield
enter focal length in mm's 135
enter Y for 35 mm N for roll or sheet film Y/N? n
enter focal length in mm's for depth of field f ratio scale 135
Enter plot scale increment e.g., 0.4 now 0.4
Feet f3.5 f4 f5.6 f8 f11 f16 f22 f32
f scale 0.130 0.148 0.207 0.296 0.407 0.593 0.815 1.185
Focus in Feet 4.921 Scale is 9.000
Focus in Feet 5.150 Scale is 8.600
Focus in Feet 5.401 Scale is 8.200
Focus in Feet 5.678 Scale is 7.800
Focus in Feet 5.985 Scale is 7.400
Focus in Feet 6.327 Scale is 7.000
Focus in Feet 6.711 Scale is 6.600
Focus in Feet 7.144 Scale is 6.200
Focus in Feet 7.636 Scale is 5.800
Focus in Feet 8.202 Scale is 5.400
Focus in Feet 8.858 Scale is 5.000
Focus in Feet 9.629 Scale is 4.600
Focus in Feet 10.546 Scale is 4.200
Focus in Feet 11.656 Scale is 3.800
Focus in Feet 13.027 Scale is 3.400
Focus in Feet 14.764 Scale is 3.000
Focus in Feet 17.035 Scale is 2.600
Focus in Feet 20.132 Scale is 2.200
Focus in Feet 24.606 Scale is 1.800
Focus in Feet 31.637 Scale is 1.400
Focus in Feet 44.291 Scale is 1.000
Focus in Feet 73.819 Scale is 0.600
Focus in Feet 221.457 Scale is 0.200
Compute Depth of Field Table Y/N? n
End computations ? (Y/N) n
enter focal length in mm's 90
enter Y for 35 mm N for roll or sheet film Y/N? n
enter focal length in mm's for depth of field f ratio scale 135
Feet f3.5 f4 f5.6 f8 f11 f16 f22 f32
f scale 0.292 0.333 0.467 0.667 0.917 1.333 1.833 2.667
=====================plot depth of field slide rule=============
Lay out the "DISTANCE SCALE" using the numbers from the Focus in Feet
display.
Draw a vertical line (DISTANCE SCALE).
At the top print the symbol for infinity.
Next at 0.200 inches (2/10'ths of an inch) print 221.457 feet.
Continue with the rest.
At the bottom at 9.000 inches from the top print 4.921 feet.
Lay out the 135 mm lens "DEPTH of FIELD SCALE" using the numbers
from the 135 mm "f scale" display.
Draw a horizontal line with an arrow at the right end (FOCUS ARROW).
Draw a vertical line through the horizontal "FOCUS ARROW LINE".
On the vertical line print f11 "0.407" inches above and below
the "FOCUS ARROW LINE".
Repeat the above for the rest of the numbers in the "f scale"
display.
USAGE: Align the vertical line of the "DEPTH of FIELD SCALE" with the
"DISTANCE SCALE". Set the "FOCUS ARROW" at the focus distance
on the "DISTANCE SCALE" (say 17 feet). Now for a given lens
opening (say f11) read off the distance both before and after
the focus distance (14.7ft & 20.2ft). Everything between these
distances will be in focus (based on the "circle of confusion"
built into the code based on your answer to "enter Y for 35 mm
N for roll or sheet film Y/N?").
Lay out the 90 mm lens "DEPTH of FIELD SCALE" using the numbers
from the 90 mm's "f scale" display as was done for the 135 mm lens.
By running a series of different lens lengths less than in this case 135 mm,
you can construct a "DEPTH of FIELD SCALE" like the ones found on many
zoom lenses.
*******************************************************************/
#include
main(){
float F, H, u, c, dn, df, Hu, F_scale, H_scale;
char type_c;
#define MAX_u 1000
float u_range[MAX_u];
float v_delta;
float v_ratio;
#define max_f 8
short max_u;
#define TRUE 1
float temp[max_f];
short i, j;
/*float f_range[] = {3.5, 4.0, 5.6, 8.0, 11.0, 16.0, 22.0, 32.0};*/
float f_range[max_f];
f_range[0] = 3.5;
f_range[1] = 4.0;
f_range[2] = 5.6;
f_range[3] = 8.0;
f_range[4] = 11.0;
f_range[5] = 16.0;
f_range[6] = 22.0;
f_range[7] = 32.0;
printf("\n Lense Depth of Field Calculations");
printf("\n Copyright (C) 1992. ");
printf("\n All rights reserved ");
printf("\n Bill Thomas ");
printf("\n 43559 Southerland Way ");
printf("\n Fremont, CA 94539 \n");
while(TRUE){
printf("\n enter focal length in mm's ");
scanf("%f", &F);
if(F < 0.0) exit(0);
printf(" enter Y for 35 mm N for roll or sheet film Y/N? ");
scanf("%s", &type_c);
printf(" enter focal length in mm's for DOF f ratio scale ");
scanf("%f", &F_scale);
if(F > F_scale) {
printf("\n f ration length can't be less than focal length \n");
continue;
}
F *= 0.03937;
F_scale *= 0.03937;
if(type_c == 'Y' || type_c == 'y')
c = 0.001; /*for 35 mm*/
else {
if(type_c != 'N' && type_c != 'n'){
printf("\n ***ERROR*** enter Y or N!!! ");
continue;
}
c = 0.0019685; /*roll or sheet film*/
}
H_scale = F_scale/F;
/*compute feet depth scale so as to be plotted at v_delta increments */
v_delta = 0.4;
if(F_scale == F){
printf(" Enter plot scale increment e.g., 0.4 now ");
scanf("%f", &v_delta);
}
v_ratio = 9.0;
i = -1;
while(i++ < MAX_u && v_ratio > 0.00001){
u_range[i] = F_scale/(v_ratio*12)*100;
v_ratio -= v_delta;
}
max_u = i;
printf("\n\n Feet f3.5 f4 f5.6 f8 f11 f16 f22 f32");
printf("\nf scale ");
for(j = 0; j < max_f; j++){
H = F*F/(f_range[j]*c);
/*see v_ratio computation below*/
v_ratio = F/H*100*H_scale;
printf(" %8.3f",v_ratio);
}
if(F_scale == F){
printf("\n\n");
for(i = 0; i < max_u; i++){
u = u_range[i];
/*m = F/(u*12); */
/*v = F*(1 + m);*/ /*lens formula*/
/*v_ratio = (v/F - 1 )*10; */
v_ratio = F/(u*12)*100;
printf("\n Focus in Feet %7.3f Scale is %8.3f ", u, v_ratio);
}
}
printf("\n Compute Depth of Field Table Y/N? ");
scanf("%s", &type_c);
if(type_c == 'N' || type_c == 'n')goto EndTableComp;
printf("\f \n f3.5 f4 f5.6 f8 f11 f16 f22 f32");
printf("\n FOCUS");
printf("\nInfinity");
for(j = 0; j < max_f; j++){
H = F*F/(f_range[j]*c);
printf(" %8.1f", H/12);
}
printf("\n ");
for(j = 0; j < max_f; j++)
printf(" infinity");
for(i = 0; i < max_u; i++){
u = u_range[i];
printf("\n %7.1f", u);
u *= 12;
for(j = 0; j < max_f; j++){
H = F*F/(f_range[j]*c);
Hu = H*u;
dn = Hu/(H+u);
temp[j] = df = Hu/(H-u);
if(dn < 0.0)
printf(" infinity");
else
printf(" %8.1f", dn/12.0);
}/*end of for(j */
printf("\n ");
for(j = 0; j < max_f; j++){
if(temp[j] < 0.0)
printf(" infinity");
else
printf(" %8.1f", temp[j]/12.0);
}/*end of for(j */
}/*end of for(i */
EndTableComp:
printf("\n\n End computations ? (Y/N) ");
scanf("%s", &type_c);
if(type_c == 'Y' || type_c == 'y')
exit(0);
}/*end while(1) */
}
===============================================================================
Note 21.02 -< Polaroid batteries and accessories >-
-------------------------------------------------------------------------------
Are you looking for batteries to power up your old Polaroid camera? Do you need
accessories? Then the FREE catalog of the following outfit may interest you.
Graphic Center
P.O. Box 818
Ventura, CA 93002
1-800-336-6096
They carry batteries and various accessories. They also convert Polaroid 110A/B
to use standard pack film. They also carry refurbished plastic and metal pack
film cameras, electronic flashes designed to fit 100-450 seies cameras, EE-100,
Reporter, and others. Interesting accessories include PC-flash adapter cords,
cold clips, filters, cable releases, closeup kits, portrait kits, and filters.
As for batteries, the No. 532, are $7 each., the 4v No.531 batteries are $7.75.
===============================================================================
Note 21.03 -< Infrared Ektachrome Processing in E-6 chemicals >-
-------------------------------------------------------------------------------
Ektachrome Infrared processing in E-6
The simplest information on E-6 processing of film intended for E-4 was in
Darkroom & Creative Camera Techniques magazine, Nov/Dec 1989, page 2. They
had previously tried processing E-4 film in E-6 chemistry, but at 70F. This
took a lot of time and the results were questionable. They then recommended
using a prehardener and neutralizer before the first developer (such as is
used in E-4), and then doing the E-6 process as usual at 85F. There hasn't
been any follow-up comment about this since last year in the magazine. The
formulas below should work adequately.
E-4 Prehardener
Water 800 mL
Sodium Sulfate 140 g
Formaldehyde 38% 30 mL
Potassium Bromide 16 g
Water to make 1 L
E-4 Neutralizer
Water 800 mL
Hydroxylamine Sulfate 18 g
Potassium Bromide 20 g
Sodium Acetate 7 g
Glacial Acetic Acid 7 mL
Sodium Sulfate 50 g
Water to make 1 L
These two solutions may be reused.
Most of the chemicals should be available from: Lauder Photographic, 2650B
Mercantile Dr. Rancho Cordova, CA 95670, 916-638-1225,Zone V, Stage Rd, S.
Strafford VT 05070, 802-765-4508, Tri-Ess Sciences, 1020 W. Chestnut St.,
Burbank, CA 91506, 213-245-7685. Rapid Fixer should be available from your
photo dealer. Formaldehyde is available at most any drug store.
Schedule at 85F:
Prehardener 3 min
Neutralizer 1 min
First Developer and remaining steps per standard E-6
directions for a processing temperature of 85F.
The E-6 kit recommended in the article was the Kodak E-6 Hobby Pak Kit.
Obviously, these aren't official E-4 formulas, but they should work OK. The
biggest problem with E-4 film is that the emulsion isn't prehardened, and it
gets too soft at normal E-6 temperature (100F). There possibly could be some
color shift, but I would guess if you are wanting to do Ektachrome Infrared
how would you know a color shift if you saw it??? :)
I hope that this information works for you.
Ron Speirs, Evans & Sutherland Computer Corp., Salt Lake City, UT
===============================================================================
Note 21.04 -< New f# when using bellows extension >=
-------------------------------------------------------------------------------
How to adjust for bellows extension factor/stops
It's actually pretty easy to do the arithmetic for this computation in your
head. The effective f-stop is simply the marked f-stop times the ratio of
lens-to-film distance (bellows extension) to focal length.
For example, say I have my handy Schneider 210 mounted up, and I'm taking a
picture of something at a magnification of 1:1, and I need to set the lens to
f/22 to get everything adequately sharp. The lens-film distance according to
the tape will be 420mm, focal length is 210mm, f-stop is 22. My effective
f-stop will be 22 x 420 / 210 = 44. Call it f/45 and dial that into the meter.
That's all there is to it.
This formula provides an additional benefit - you can calculate a magnification
or distance for which you needn't bother getting out the tape measure.
If 1/6 stop is the largest error you find tolerable, that means that the
lens-film distance/focal length ratio must be 7/6 or less. Plugging that into
the formula for focal length (fl), lens-film distance (d_lf) and lens-object
distance (d_lo),
1/fl = 1/d_lf + 1/d_lo
1/fl = 1/(7/6*fl) + 1/d_lo
d_lo = 7*fl
which means if you are more than 7 focal lengths away from your subject, your
underexposure due to ignoring bellows extension will be less than 1/6 stop. If
you're willing to go to 1/3 stop error, 4 focal lengths is the threshold. In
general, if you are willing to set your error threshold at "err" f-stops, the
nearest you can get to your subject without compensating for bellows extension
is (1+err)/err focal lengths. In the case of my 210mm (aka 8 1/4") lens, if
I'm making life difficult for myself by using color transparency film, and I
think I can meter things accurately enough that 1/3 stop accuracy is crucial
(don't I wish!) I can see that if I'm closer than about 3 feet I need to get
out that tape measure.
Fortunately, since I mostly shoot b&w, and more often than not I'm doing
landscapes, I can see from the formula that I don't have to worry much about
the fact that I lost my tape measure a few months ago :-)
Bill
From: whp4@Csli.Stanford.EDU (Bill Palmer)
Organization: Stanford University CSLI
===============================================================================
Note 21.05 -< Data on Wratten Filters by the Numbers >
-------------------------------------------------------------------------------
This is a listing of Wratten Filters by number, their color and
applications. It was compiled from the CRC Handbook where more
filters and additional charactristics are also listed.
Wratten
filter
number color use
colorless
UV(0) none absorbs UV
0 clear thickness compensation
1 absorbs UV < 360nm
1A pale pnk skylight filter
1B lt. pink (skylight) cuts blue cast in shade and distance, absorbs UV
yellows
2A pale yel UV 405 nm
2B pl yel absorbs UV 390 nm
2E pl yel absorbs UV
3 lt yel
4 lt yel CCC - corrects outdoor scenes for panchromatic film
6 lt yel (aka K1) partial correction for outdoors
8 yel (aka K2) full correction outdoors for Type B panchromatic film
9 dp yel
11 yl-grn (aka X1) corrects tungsten light for Type B film
12 dp yel minus blue - haze cutting for aerial photography
13 yel-grn (aka X2) corrects tungsten light for Type C panchromatic film
15 dp yel (aka G) contrast control in aerial IR photography
16 yel-org blue absorbtion
18A transmits UV and IR only
oranges and reds
21 org blue and blue-green absorbtion
22 dp org yellow-orange (mercury yellow) increase contrast in blue
preparations for microscopy
23A lt red contrast effects
24 red for two-color photography
25 red (aka A) for tri-color separation, high contrast effect,
aerial IR haze
two-color general viewing
26 red stereo red
29 dp red high contrast, tungsten projection of tri-color, red sep. in
fluor. process
magentas and violets
30 green absorbtion
31 green absorbtion
32 magen minus green
33 strong green absorbtion
34A violet blue separation in fluorescence process
35 contrast in microscopy
36 dk violet
blues and blue-greens
38 red absorbtion
38A Blue red absorbtion, increasing contrast in visual microscopy
39 contrast control in printing motion pictures
40 green two-color photography
44 lt blu-grn minus red, two-color general viewing
44A lt blu-grn minus red
45 contrast in microscopy
46 blue projection
47 blue direct color separation, tungsten tri-color projection
47A lt blue
47B dp blu tri-color separation form transparencies
48 green and red absorbtion
48A green and red absorbtion
49 dark blue
50 very dark blue - mercury violet
greens
52 lt grn
53 middle green
54 very dark green
55 stereo green
56 very light green
57 green for two-color photography
57A lt grn
58 grn tri-color green for separations, contrast in photog & microscopy
59 green for tri-color projection
59A very light green
60 green for tungsten two-color photography
61 dp grn grn tri-color sep, tungsten projection
64 red absorbtion
65 red absorbtion
66 contrast effects in microscopy & medical photography
67A red absorbtion Two-color projection
narrow band
70 dk red IR photography 676 nm
72B dk or-yel 605 nm
73 dk yel-grn 575 nm
74 dk grn mercury green 539 nm
75 dk blu-grn 488 nm
76 dk vio (compound filter) 449 nm
Hg line filters
77 transmits 546 nm mercury line. glass plus gelatin 580 nm
77A transmits 546 nm mercury line. glass plus gelatin 582 nm
photometrics
78 bluish photometric filter (visual)
78AA bluish photometric filter (visual)
78A bluish photometric filter (visual)
78B bluish photometric filter (visual)
78C bluish photometric filter (visual)
86 amber photometric filter (visual)
86A amber photometric filter (visual)
86B amber photometric filter (visual)
86C amber photometric filter (visual)
light balancing
80A blue color correction for daylight film (5500) under 3200K (studio) lamps
80B blue color correction for daylight film (5500) under 3400K (photo) lamps
80C blue color cor. for daylight film (5500) under 3800K (clear flash) lamps
81 amber warming -100K
81A amber color correction for Type B tungsten film under 3400K (photo) lamps
warming -200K
81B amber to remove blue cast in shaded daylight
warming -300K
81C amber to remove blue cast in cloudy/rainy weather; Kodachrome Type A with
flash; warming -400K
81D amber Kodachrome Type A with flash; warming -500K
81EF amber Ektachrome Type B with flash; warming -650K
82 blue cooling +100K
82A blue color correction for Type A tungsten film under 3200K (studio) lamps
cooling +200K
82B blue color correction for Type B tungsten film under 2900K (100w incand.)
cooling +300K
82C blue to remove reddish cast in early morning or late afternoon
cooling +400K
83 amber 16mm commercial Kodachrome in daylight
85 orange color correction for Type A tungsten film in daylight (5500K->3400K)
85B orange color correction for Type B tungsten film in daylight (5500K->3200K)
85C amber converts 5500K (daylight) to 3800K lighting
miscellaneous
79 photographic sensitometry
87 for infrared photography; IR 770nm ->
87C absorbs visual, transmits IR 830nm ->
88A for infrared photography; IR 740nm ->
89B for infrared photography; IR 700nm ->
90 monochrome viewing (narrow-band for viewing scene brightness);
about 570->590 nm; 10% luminous transmittance
96 neutral filter for controlling luminance; 9% luminous transmittance
97 dichroic absorption
102 correction filter for Barrier-layer cell
106 correction filter for S-4 type photocell
FL-day purple converts daylight fluorescent light for daylight film
FL-W purple converts white fluorescent light for daylight film
K2 yellow improves contrast in B&W; absorbs UV and part of violet
G orange greatly improves contrast in B&W; absorbs UV and part
of blue-green
25A red strongest B&W contrast; absorbs UV and part of yellow;
"night filter"
also used as a color separation filter with #47 blue and
#58 green
X0 yel-grn natural rendition of skin and lips of female models B&W?
X1 green Absorbs more red than X0, good for green trees B&W?
Data on a very few narrower band filters:
Filter no. low l high l domin. l lum. transm.
Color separation filters:
47 blu 400 475 464 2.8
58 grn 490 600 540 23.7
25A red 590 700 615 14
Narrow band filters:
76 400 470 449 .046
75 460 530 488 1.3
74 510 570 539 4.0
73 560 600 575 1.3
72B 590 640 605 .74
70 660 700 676 0.31
This file was found in the photo-3D FTP-able archives at csg.lbl.gov.
================================================================================
Note 21.06 -< CHEAP IR Filters - experimental quality >-
--------------------------------------------------------------------------------
In case you did not know and might benefit from this information I had
some filters often used for Infrared photography, along with some unexposed
but developed Ektachrome sheet film, characterized with a spectrophotometer.
The films were obviously visually quite opaque. Especially if you stacked two
of these. It turns out that the dyes that make up the color layers in this
film (and I suspect all color films) are visually opaque but IR TRANSPARENT!
This means they can be used as cheap makeshift IR filters, especially to cover
a flash source to make unobtrusive flash photos by IR illumination. This info
is not totally new as I had already seen such curves at RMIT in Melbourne,
Australia, where I spent my summer vacation a couple of years ago. I also used
one and two layers of Ektachrome film as a filter in front of my camera's lens
and the images were not totally fuzzy and unusable. They had, in fact, a visual
quality all their own which you may (or may not) like if and when you
experiment in a similar fashion. andy - andpph@ritvax
3.0|......... .......... ....... -------
| \__/ :\__/ \ ; | : Wratten #25 (red)
| : \ ; |
| : \ ; | ; Wratten #87 (IR)
D | : \ ; |
E 2.0| approximate : \ ; | \ 1 layer Ektachrome
N | Density vs Wavelength : \; |
S | for : \ | | 2 layers Ektachrome
I | 2 Wratten Filters and : ;\ |
Y | Ektachrome Sheet Film : ; \ |
1.0| unexposed & developed : ; \ |
| : ; \ |
| : ; \ |
| : ; \ '- ________
| '.............> ;-...........
-------------|------------|-------------|------------|------------|------
400 500 600 700 800 900
wavelength (nanometers)
================================================================================
Note 21.07 -< UV and IR Technique Basics >-
--------------------------------------------------------------------------------
ULTRAVIOLET and INFRARED PHOTOGRAPHY SUMMARIZED
by Andrew Davidhazy
Imaging and Photographic Technology
Rochester Institute of Technology
A large part of the spectrum and its relationship to the world around us is
invisible because we are limited to seeing electromagnetic wavelengths which
extend only from those characteristic of violet-blues to those of the deep
reds. Photographic materials can extend our vision, especially when aided by
special light sources and various filters. The proper use of film, lights,
filters, exposure techniques and specific applications of the four basic
methods of photographing the invisible spectrum are discussed below.
The premise for photographing by REFLECTED ULTRAVIOLET or REFLECTED INFRARED
radiation is that we desire to "see" the interaction, by way of reflected
energy from our particular subject, of UV or IR rays as compared to the effect
on the same subject of visible light rays. The hope is that the subject may
appear differently by these rays than it does by "white" light or than it would
appear if seen through colored filters.
An analogy for the reason to apply these techniques is the lengths to which we
go to render a blue sky dark on a B&W print to contrast it against the white
clouds. This, of course, is accomplished by placing a yellow or red
(complementary colors to blue and cyan, the color of the sky) filter over the
camera lens. The filter does not allow the sky color wavelengths to pass on to
the film and thus the sky is rendered clear on the negative and dark on the
print. The point is that we can distinguish between two subjects of similar
tone, the sky and the clouds in this instance, but different color by filtering
out one of the colors with a filter of complementary color placed over the
camera lens. This principle applies also to the invisible areas of the spectrum
but we need films which can "see" in these areas in order for our own eyes to
see the differences if they exist.
Since UV and IR wavelengths are invisible to our eyes and thus can not be
assigned a "color" as such, B&W film is the most appropriate to use for both of
the above applications. Almost any B&W film can be used for reflected UV
photography although the slower emulsions seem to deliver somewhat better
negatives. To record the IR wavelengths Kodak High Speed Infrared film should
be used. It is also about the only IR emulsion readily available! Since the
film has no antihalation backing allowing light and IR to pipe into the
cassette it should be loaded into the camera in total darkness or under subdued
fluorescent illumination. Fluorescent tubes usually are very weak in IR output
diminishing the chance for fogging the film by IR rays passing into the
cassette.
When attempting either UV or IR photography the subject must be lit with lights
which emit the wavelengths by which we wish to photograph.Electronic flash is a
good source of both UV and IR wavelengths. Some flashes have a UV absorbing
filter incorporated in the flash head and this may need to be removed (if
possible) for best results. However, even if not removed, there is usually
enough UV that "leaks" through so that at close range they still serve as
useful UV sources. Then, placing a UV transmitting filter (Wratten 18A) or IR
transmitting filter (Wratten 87 or 87C)over the camera lens will effectively
expose the film only to the wavelenghths of interest.
Under certain conditions it is possible to previsualize the approximate
appearance of a UV scene by installing into the camera a groundglass covered
with a fluorescing substance. The UV energy passing through the lens causes
this substance to fluoresce and the UV scene becomes visible in the finder!
In order to continue to use a 35mm SLR camera for reflected IR photography even
when you use the visually opaque 87 filter for photography it is possible to
install the filter behind the camera's mirror mechanism and composition of the
IR picture becomes almost as easy as if you were using "light" for your
pictures. In some cameras with behind the mirror metering systems the filter
may need to be positioned just in front of the film between the film plane
guide rails. Metering off the film may be impossible.
While exposure is most appropriately determined in either case by making a set
of test exposures or by bracketing it may be possible to establish a UV or IR
"personalized speed index" by using one of the new ultrasensitive light meters
but metering through the UV or the IR filter and correlating the exposures that
seem to deliver negatives which you judge acceptable by your own standards with
those suggested by the meter. You should generally only attempt to establish
this personalized speed index metering in the reflected mode. Finally this does
not preclude bracketing but you may more consistently arrive at the proper
exposure with less waste.
The focal length of a given lens "changes" with wavelength and for this reason
its focus should be adjusted slightly when attempting to use it for other than
light wavelengths. The lens must be moved somewhat further from the film than
visual focus demands when photographing by IR and generally also when
photographing by UV. The reason for this is that most camera lenses are
achromatic in color correction (unless otherwise stated to be simple, very
unlikely, or apochromatic in correction) and thus curve the chromatic focal
plane about two visible (except in some cases with lenses intended specifically
for UV photography) wavelengths thus bringing both IR and UV to a focus further
from the film plane than visible wavelengths. Under normal conditions the use
of small apertures will in most cases diminish or eliminate the need to make
this focus adjustment. When using a fluorescing screen in UV photography the UV
rays are properly focused when the image on the screen is sharp.
I've already mentioned the term "fluorescence", and most of us are aware of the
term but may not be quite sure of what process is at work. When some subjects
are illuminated by certain wavelengths they reflect back not only the same
wavelenghts that they are illuminated by but they may transform some of these
incident wavelengths into usually longer ones. In a sense they change the color
of the light falling on them. When a subject behaves like this it is said to
FLUORESCE. Some subjects change short, ultraviolet energy into longer, visible,
wavelengths or colors. Others may change visible rays into yet longer, infrared
wavelengths. The former effect is, of course, visible while the latter is not.
This is the realm of FLUORESCENCE photography and to apply it you need to start
with a source that contains the wavelengths which the subject will transform
into longer wavelenghts. Usually over this source is placed an EXCITER filter
the function of which is to allow only those wavelenghts through which will
cause fluorescence. In UV work this is most commonly the Wratten 18A filter and
in the visible region of the spectrum the Corning filter #9788 can be used. To
photograph fluorescence excited by UV, which usually results in a visible
effect, color film can be used to good advantage with Kodachrome 64 being
paricularly suitable. Since not only the "new", visible, wavelenghts are
reflected from the subject but also some of the UV transmitted by the exciter
filter, a UV blocking filter, called a UV barrier filter, is placed over the
camera lens to allow the film to record only the fluorescence. For UV work this
barrier filter is the 2E or similar, pale yellow, filter. Exposure may possibly
be metered in the camera especially with the newer more sensitive in-camera
meters. No focus compensation is necessary.
To photograph IR fluorescence (or as H.Lou Gibson calls it: IR luminescence)
the B&W infrared film should be used. The exciter filter placed over the light
source must not allow any infrared rays through to the subject. The Corning
9788 is just such a filter and it can be obtained from the Corning Corporation.
It is a glass filter and since it will be used over the light source it can be
of low optical quality. Even so, it is almost as expensive as the 18A filter
(which should be of optical quality) although for a much larger size. Six
inches square vs. three inches square for the 18A, at a price of about $100 for
the 9788 and $150 for the 18A. The barrier filter should be a deep red or
infrared filter such as the 87 or 87C. Camera focus should be adjusted as per
previous discussion. Metering is not possible because the effect ocurrs in the
IR and most meters are designed to meter light, not infrared. Even meters with
IR metering capability would probably fail to detect the presence of IR
fluorescence because of the very low amounts of IR produced in this fashion.
The four techniques briefly summarized above have widespread application in
document investigations and forensic photography, in surveilance and in
environmental studies. Also in medicine, mineralogy, philately, art
history,etc. Generally one sets out on a voyage of discovery when faced with a
new subject. One tries each method in turn, hoping that one of them will yield
better information about the subject than that which the unaided eye can
perceive. Each new subject becomes a most exciting photographic adventure.
TO PHOTOGRAPH BY REFLECTED ULTRAVIOLET
The sample is illuminated by "white" light and an 18A filter is placed over the
camera lens, tightly fitted. If the subject does not fluoresce then you can
place the filter over the light but you need to work in a dark room.
This technique is useful for the photographic enhancement of rashes and other
skin disorders and also for detecting alterations in documents, etc.
Suggested light source: Electronic Flash (best if flash does not have UV
absorbing coating)
Filter on camera : 18A
Appropriate Film : Most any B&W film, especially slower emulsions
Lens : Should be able to transmit UV. Most camera
lenses are suitable for long wave UV associated
with use of 18A filter over lens.
Under special conditions, such as when a short wave UV source is available,
photography is done in the dark and the 18A filter is not used. Subjects that
fluoresce will be recorded as a mixture between reflected UV and visible
fluorescence. When photographing with short wave UV (around 254nm or less)
energy, typically provided by special sources, many standard camera lenses are
unsuitable because the glasses they are made of absorb such wavelengths. Quartz
or mirror lenses may need to be used although pinholes and some plastic lenses
are an alternative. Under very short wave UV conditions the gelatin of the
emulsion itself may absorb the incident rediation. In this case special
emulsions with silver halides deposited on the surface are used.
Exposure : Generally determined by trial.
Focus : Camera focus must be adjusted for critical use.
TO PHOTOGRAPH FLUORESCENCE EXCITED BY UV RADIATION
In its most common practice the sample must be irradiated with UV rays and due
to fluorescence it will "GLOW" in the visible region of the spectrum. The
sample will appear in various colors as a result of the effect the sample has
on the incident energy. Because samples also reflect some UV as well as
fluorescing, the unwanted UV is removed with a "barrier" filter opaque to UV.
The filter which limits the incident energy to a desired spectral region is
known as the "exciter" filter. This technique is particularly useful for the
identification of minerals and for "fingerprinting" documents such as stamps
and currency. It is also used in forensic work with fluorescing powders in
fingerprint visualization.
Light source suggested : Electronic Flash or UV emitting lamps
operating in a darkened environment.
Exciter filter suggested: with lamps it's built in so none needed
with electronic flash use 18A over flash.
Barrier filter suggested: Wratten 2A or 2E
Appropriate film : Color reversal daylight film seems best.
Effect is in color so B&W film less useful.
Exposure : Can often be determined with built in meter but light level
is much lower than it might appear visually.
Focus : Visual focusing on groundglass possible.
TO PHOTOGRAPH BY REFLECTED INFRARED
The sample can be illuminated by "white" light and an 87 or 87C 9or similar)
filter is placed over the camera lens, tightly fitted. In a darkened room the
filter may be placed over the light source. Sometimes a filter is not required.
For example, a flatiron may be used as a source of IR radiation and if
operating in a dark room no filters are needed.
Some photographers use a #25 filter over the lens of SLR cameras in particular
so that they can focus on the image in the groundglass. Alternatively, the
visually opaque IR filter may be inserted behind the camera's mirror.
This technique is useful for the recording of subcutaneous (below skin) veins,
for the detection of alterations or forgeries of documents, for
surveilance,etc.
Light source suggested : Electronic Flash, floodlights or daylight.
Filters suggested : 87 or 87C over camera lens.
Film : Kodak High Speed Infrared
Exposure : Determined by trial, use manufacturer suggested data,
or using CdS Luna Pro and metering through 87C filter
set ASA guide to a speed of 2400.
Focus : For critical results it must be adjusted.
TO PHOTOGRAPH FLUORESCENCE EXCITED BY LIGHT IN THE INFRARED (LUMINESCENCE)
As in fluorescence excited by UV certain samples transform shorter wavelengths
into longer ones which in this case are in the invisible IR region. This
effect is sometimes called "luminescence" and the sample is usually irradiated
with BLUE-GREEN light without any IR present in the beam. A barrier filter
which allows only the newly created IR wavelengths to pass into the camera is
placed over the lens. Best to work in a dark, IR free, environment.
This technique is particularly useful for the study of inks, hardwoods and
forgery detection in forensic photography.
Light source suggested : Tungsten or Electronic Flash.
Exciter filter suggested: Corning 9788 over light source plus Corning
3966 heat absorbing filter placed between
source and the 9788 if using tungsten source.
Certain blue-green lasers also may be used
without any filters.
Barrier filter suggested: Wratten 87, 87C or 88A
Film : Kodak High Speed Infrared
Exposure : Determined generally by trial. Expect it to
be extremely great.
Focus : Must be adjusted for critical results.
Note: when IR reflected light photography is done with COLOR INFRARED film,
then "white" light plus IR must fall on the sample, thus a Wratten #12 is used
over the camera lens to remove from the incident radiation the blue light to
which the three layers of the IR COLOR film are all sensitive.
================================================================================
Note 21.08 -< Solarization Tip >-
--------------------------------------------------------------------------------
There was an interesting suggestion posted on the Internet that I thought
might be of help if you are trying your hand at solarization (Sabattier).
writes:
> My students just finished using dektol and Ilford Multigrade rc with
> a #5 filter and a #5 filter in the white light source. They all seemed
> to get pretty good results.
That would make sense...under those conditions, a Variable Contrast
emulsion becomes essentially a single-layer graded emulsion. (The second,
green-sensitive, low-contrast layer is completely out of action.) I
had tried the #5 filter in the image light, but not on the fogging
light. I'll try that...
Richard Hosker
rph0470@tntech.edu
================================================================================
Note 21.09 -< Create-a-Print used for B&W printing >-
--------------------------------------------------------------------------------
> Has anyone figured out a way to use black and white negatives other than
> xp2 in the create a print? It doesn't seem to want to accept non-bar coded
> negatives, and i was wondering if there was a way to override this...
It's pretty easy. Right above the negative eject symbol is a number,
most often '1' but it depends on the last type of film inserted in the
Create-A-Print. Using the diamond key with the arrows (triangles) on
it, move the cursor on top of that number and rotate the zoom control
(one on the right) til the number gets to '40' .. turn it either right
or left until it gets to '40'. Then hit the button with the yellow
circle on it and the machine is now set for B&W film. You may need to
turn that up or down while you are using the machine, using 41 or
whatever (I think XP2 is 49) until you get the right color correction
on the screen. It will not be perfect at first, but make your own
color corrections. Good luck,
Robert E. Klimkiewicz, Jr. -- Communication Major
George Mason University Fairfax, Virginia U.S.A.
================================================================================
Note 21.10 -< Decoding De DX Code >-
--------------------------------------------------------------------------------
DX codes decoded
>1) Does any one have a clear view of the DX coding? What means what and how it
>is used. Especially interested in the meanings of each of the squares.
This info was transcribed from the June 1983 issue of "Modern Photography",
page 8, by Markus Wandel and he posted on rec.photo.
========================= <-- Light trap
+---+---+---+---+---+---+
+-| 1 | 2 | 3 | 4 | 5 | 6 |
Bottom --> | +---+---+---+---+---+---+ <-- view of the film cartridge
|_| 7 | 8 | 9 | 10| 11| 12|
+---+---+---+---+---+---+
-------------------------
The DX coding surface is divided up into 12 squares as shown. Squares 1 and 7
are ground, i.e. they are always bare metal. The remaining squares are encoded
as follows ("*" means bare metal, otherwise square has nonconductive paint):
FILM FILM EXPOSURE
SPEED 2 3 4 5 6 LENGTH 8 9 10 LATITUDE 11 12
---------------- -------------- ----------------
25 * 12 * +/- 1/2
32 * 20 * +/- 1 *
40 * * 24 * * +2/-1 *
50 * * 36 * +3/-1 * *
64 * * - * *
80 * * * - * *
100 * * 72 * * *
125 * *
160 * * *
200 * * *
250 * * *
320 * * * *
400 * *
500 * *
640 * * *
800 * * *
1000 * * *
1250 * * * *
1600 * * *
2000 * * *
2500 * * * *
3200 * * * *
4000 * * * *
5000 * * * * *
================================================================================
Note 21.11 -< IR Ektachrome Processing in cool E6 chemicals >-
--------------------------------------------------------------------------------
How to process Ektachrome Infrared in E6 chemicals
While it is true that E-4 chemicals should be used to process this
film, it can be processed with E-6. That is, if you can tolerate
somewhat weird colors.
To process with E-6 first all temps must be at 75 degrees fahrenheit
time(min.)
first developer 10
-wash 2
reversal bath 2
color developer 8
conditioner 2
bleach 10
fixer 10
-wash 6
stabilizer 2-3
I have developed the two rolls that i was able to find like this.
The results were fantastic, if only in an artistic sense.
From: tom@po.CWRU.Edu (Thomas O. Moore)
Organization: Case Western Reserve University, Cleveland, OH (USA)
---------------------------------------------------------------------------------
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