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FAQ or Answers to Frequently Asked Questions Section 20
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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 20 and its contents are listed below.
20.01 -< Flash Sync Speed Question and Answer >-
20.02 -< Kodak Lenses - characteristics and applications >-
20.03 -< Masking to change contrast esp. for Ilfochrome use >-
20.04 -< 3D FAQ or Frequently Asked Questions about stereo >-
20.05 -< Making Color out of B&W! >-
20.06 -< Variable Contrast Filter Settings and Color Heads >-
20.07 -< Tech Pan Exposure/Processing Info >-
20.08 -< Sound Synchronizers - Cheap and Simple >-
20.09 -< Convenient Pulfrich Effect 3D Viewing >-
20.10 -< What is EV (Exposure Value)? >-
20.11 -< Info on Film and Video Resources on the Internet >-
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Note 20.01 -< Flash Sync Speed Question and Answer >-
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reply on a question on sync speed
by Andrew Davidhazy andpph@ritvax.isc.rit.edu
Rochester Institute of Technology
>Sorry for the stupid question, but can someone explain exactly what
>"flash sync speed" is? Everyone's talking about it and I'm in the dark...
With Focal Plane shutter equipped cameras (typical of SLR cameras) the shortest
exposure time with which an electronic flash can be practically used is that
with which the distance between the leading and trailing curtains of the
shutter is equal to, or greater than, the full film gate dimension of the
camera measured in the direction in which the curtains move.
The problem arises because the electronic flash is a very short duration light
source.
At exposure times shorter than the X-sync speed the distance between the
curtains is less than the width of the image gate and thus one could only make
a partial frame exposure (limited by the distance between the curtain edges)
when an electronic flash is used as the light source. There was (is) only one
camera/flash combo that overcame this limitation and it's the Olympus OM-4T
with a special (F-280?) electronic flash that transforms itself into a very
high frequency stroboscope when used in the FP mode.
Since the exposure time with an FP shutter is equal to the distance between the
curtain divided by the speed at which they move past the film it is obvious
that given a particular distance between curtains (such as 36mm) one can
achieve shorter exposure times with curtains that move at a fast rate.
Actually the "flash sync speed" refers to the shortest exposure time that a
short duration electronic flash can be used without loosing part of the frame.
This exposure time includes not only the time it takes the curtains to move
from one side of the gate to the other but also an appropriate time for the
flash itself to burn plus possibly a bit of "manufacturing tolerance".
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Note 20.02 -< Kodak Lenses - characteristics and applications >-
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Kodak Lenses
Here is a less than exhaustive, yet not too shabby explanation of some of the
lenses found on Kodak cameras through the years. Information from a 1953 Kodak
Data Book called "Kodak Lenses" and from a small book published in 1959 called
"Photographic Lens Manual and Directory."
KODAK EKTAR LENSES
Kodak Ektar lenses simply referred to Kodak's finest lenses. They never
referred to any particular lens formula (tessar type, gaussian type, etc.), so
it is easy to find Ektar lenses that differ in design and construction. There
were Ektar lenses made for still photography, for enlarging, for cine work and
for projection. All Kodak Ektar lenses for still photography focused as a
unit. They were supplied integral to cameras, separately in shutters and in
barrels (lens tubes without shutters)
Kodak Ektars for Small and Medium Format:
101mm f4.5 in Synchro-Rapid 800 Shutter (4 element)
105mm f3.7 in Flash Supermatic Shutter (5 element)
127mm f4.7 " " or Supermatic-S Shutter (4 el.)
152mm f4.5 " " (4 element)
44mm f3.5 on Kodak Signet 35 Camera (4 element)
Kodak also sold Ektars, Commercial Ektars, and Wide Field Ektars in various
focal lengths mounted in various shutters for use on large format view cameras.
KODAK ANASTAR (Anastigmat Special)
These lenses were especially designed for use on amateur cameras like the Kodak
Tourist II and Kodak Flash Bantam. They employ simple front element focusing
and usually consist of 4 elements. These lenses approached Ektar quality at
generally used apertures and lens-to-subject distances. They included a 48mm
f4.5 (Bantam) and a 101mm f4.5 (Tourist II).
KODAK ANASTON (Anastigmat)
Kodak Anastons were also front cell focusing anastigmats usually having 3
elements. They were even more "amateur" than the Anastars. Anastars included
lower priced lens for:
Kodak Tourist II (f4.5 or f6.3)
Kodak Pony 135 and 828 (f4.5 or f6.3)
Only the f4.5 models were "Lumenized" (Kodak name for Mag. Flouride
coating)
KODAR and KODET anastigmats
Cheap lenses mounted on Duaflex and Tourist cameras. Typically these were f8
lenses. The Kodars were focusing lenses and the Kodet were fixed focus.
EKTANAR and EKTANON
These were 3 element lenses for 35mm cameras. They include:
Ektanar 44mm f2.8
Ektanar 50mm f2.8
Ektanon 46mm f3.5
From: pcotnoir@wpi.WPI.EDU (Paul D. Cotnoir) @ Worcester Polytechnic Institute
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Note 20.03 -< Masking to change contrast esp. for Ilfochrome use >-
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Masking 101
by Barry Sherman of Amdahl Corpration
What is a contrast reduction mask?
---------------------------------
Put very simply, a contrast reduction mask is a b/w negative which is produced
from an original and is sandwiched with the original to alter contrast. Being
a negative it will be dark where the original is light and light where the
original is dark, thus lowering contrast.
Masking can get quite sophisticated, however. You can take a negative
contrast reduction mask, contact print it onto another sheet of film, getting
a positive, and use this as a contrast-increasing mask. You can use either
type of mask with b/w and color negatives as well as with color transparencies.
I have done contrast masking with color negatives and, while I haven't done
it, have the idea stored away for use with difficult b/w negatives. Why
mask with b/w negs when we have different contrast grades available? With
a little care it should be possible to produce masks which are clear except
for certain areas, where they'll affect contrast. Localized contrast control.
To date I've been able to do so using variale contrast papers and buring
different areas with different colors of light. But it's an example of
a potential use in b/w printing.
You can vary the overall density of the contrast reduction mask so that it
reaches down to the mid-tones or even to the shadows, thereby varying
where contrast will be altered.
In addition, you may at times make a mask which is used in making the final
mask. Several generations can be involved. More on this later.
Masking equipment
-----------------
Equipment can be simple or fancy. Basically, the equipment, if any, is
used for registering the original and the mask.
* Light box and loupe. After producing the original you lay them on a
light box and use a loupe to line them up, taping them together when they're
right. Mylar tape, available in better photo shops works well for this.
This can just about drive a person crazy.
* Condit Pin registration equipment. This is a set of equipment comprising
a punch, contact print frame and negative carrier. The punch punches
little 1/16" holes in the edges of 4x5 or larger film. These holes are
used to align the original and the masking film in the contact print frame
and in the negative carrier.
Quite expensive. A typical setup costs about $1000 purchased new. I got
mine for $400 from a Shutterbug ad. It is without doubt the most useful
darkroom accessory that I've ever had. You can take the color analyzer,
Jobo, print washer, compensating developing timer, you name it. I can
improvise around these losses. Just leave me my Condit Pin Registration
setup.
Condit Mfg: U.S. (203) 426-4119
* Wess Plastics makes some equipment (a duper and a registration punch/slide
mount system) that people have used with good success for working with
35mm.
Materials
--------
* Film. Kodak Pan Masking Film is the standard. Comes in 4x5 and larger
sheets. How to use with 35mm or medium format? Cut a hole in a sheet of
junk 4x5 film and use mylar tape to attach the smaller original in the hole.
Kodak Pan Masking film is somewhat slower than Tmax 100 (mentioned for
comparison) I'd guestimate its speed at around 25 or so. While it's
reputed to be a low contrast material, testing has shown it to be about
the same as Tmax 100, except that it's developed for a short time in
dilute developer, thereby lowering contrast.
What's different is that it has no anti-halation backing. This allows light
to bounce around, softening the edges of the image. This is desirable,
producing what are called "unsharp" masks. Such masks are easier to register
and show errors in registration less than would sharp masks. Unsharp masks
are also reputed to increase the apparent sharpness of the print.
Pan Masking Film is usually a special order item and is not cheap. I buy
mine from B & H or Adorama for about $75 per 50 sheet box.
Because of the expense I've been trying Tmax 100. It requires different
handling to produce the unsharp masks, but I think that it works just
fine. Only problem is the amount of effort required to remove the purple
stain, which is pretty tedious. Why Tmax 100? Because I have it lieing
around so it's handy.
Roll film can be used for masking 35mm or medium format. Tmax 100 is
certainly an option here. FP4, both in sheets and rolls, is popular as well.
Kodalith. Kodalith high contrast film is used for highlight protection
masks. More on this later. Very useful stuff to have around. Very
cheap. Something like $40 for 100 sheets of 4x5.
Kodak LPD4. This is a litho type positive film. Dunno how it works but
developed in any standard developer it yields a high contrast *positive*
image. Yup. Positive. Useful in making highlight bump masks. More on
that later. This can be difficult to get hold of. Apparently it's
classed as a graphic arts item and most photo shops won't know what you're
talking about.
I ordered mine through the
Aperture Film Center
127 Main St.
Los Altos CA 94022
(415) 941-1500
I believe that they do mail order. The smallest size of LPD4 available is
8x10 in 100 sheet boxes. I paid $100 for mine and figure that what with the
400 sheets of 4x5 that it'll be cut up into, it's dirt cheap and that's
enough for most of the rst of my life.
Both Kodalith and LPD4 can be used with a red safelight. Nice convenience.
I use one of the little "painted light bulbs" for this.
* Devlopers.
For developing contrast reduction masks using Pan Masking film or Tmax 100
I use HC110 diluted 1:11 from stock.
For developing Kodalith, used in highlight protection masks, I use either
HC110 diluted 1:11 if I want relatively low contrast, D11 undiluted for
most work and occasionally Kodalith RT (two part litho) for very high
contrast.
* Bleach
Often a highlight protection or other type of mask will have density in
unwanted areas. The answer is to bleach with Potassium Ferricyanide. I
just pour some in a 35mm film cannister, add water and apply with a cotton
swab. Several applications, alternating between applying the ferricyanide
and dunking in fixer to remove the bleached silver will completely remove
all silver from the areas being bleached, leaving clear film there.
* Diffusion material.
This is used either above the original or between the original and the
masking film when exposing the mask and increases the unsharpness of the
mask. I use some stuff called Duralene, which I believe to be used for
drafting purposes. It's like a sheet of plastic frosted on both sides. I get
mine at a local art store. I've tried tablets of "frosted acetate" but
found them abominable. One side was glossy and they attracted dust like
nothing I've ever seen. The Duralene doesn't. Duralene cost around $1.50
per 8x10 sheet but I've been using the same 4x5 piece for several months
now.
Condit Mfg also sells "Herculene" which I gather is similar.
Making a mask
-------------
* Exposing the material.
Exposure is done as a contact print. I use one of two different
"sandwiches".
Layers from top to bottom, top being closest to the light source:
diffusion material
transparency, emulsion up
masking film, emulsion up
or
transparency, emulsion up
diffusion material
msking film, emulsion up
I use the former sandwich when using Pan Masking Film with its inherent
unsharpness and the latter when using Tmax 100. I'm not completely
satisfied with the degree of unsharpness that I'm getting with the latter
sandwich and may try putting a layer of diffusion material between the
transparency and the light source or may try putting the masking film
smulsion down.
* Determining exposure and development.
Exposure is easy. Just experiment. With time you'll develop the ability
to guess exposure based on the appearance of the transparency. Don't forget
that these contrast reduction masks are developed to a low contrast. This
means that variations in exposure don't have a huge effect on density.
Bob Pace teaches a technique based on equating development time and exposure:
less development means more exposure and vice versa. I haven't found this
to be necessary. He also adjusts exposure based on the average density
of the original. I find that three exposure times suffice: one for a
thinner mask, one for an average mask and one for a heavy mask. The
thinner mask will have density only in the highlight areas. The average
one will have a little density in the mid-tone areas. A heavy mask will
have density going down to the lowest of the mid-tone areas.
For my enlarger and working conditions these are:
With Tmax 100 With Pan Masking film
Thin 2 seconds at f32 8 seconds at f32
average 4 seconds at f32 8 seconds at f22
heavy 8 seconds at f32 8 seconds at f16
Yours will vary, probably greatly. This is offered as a sample only.
Obviously I adjust based on how dense the original is, overall. I get the
mask right on the first try about 75% of the time.
Development can be more complicated. The basic term used is "gamma" where
gamma is defined as:
density_range_of_transparency - exposure_scale_of_printing_paper
----------------------------------------------------------------
density_range_of_transparency
The calculated gamma will typically fall between 0.0 and .6 or so. The
rule of thumb taught to me by Charley Cramer is that:
transparency contrast gamma developing time in HC110 1:11
low contrast .1 1 minute
average .2 2 minutes
average .3 3 minutes
higher .4 4.5 minutes
high .5 5.5 minutes
really high .6 7 minutes
... ... ...
Exposure scale of the paper is defined as the density range of an original
which will print with slightly less than total black (Dmax) and slightly less
than total white (Dmin). Two ways to determine the exposure scale of the
paper. Print a step tablet. Find the steps which are just lighter and
darker than Dmax and Dmin. The difference in density between the
corresponding steps in the original tablet is the exposure scale of the
paper.
Or you can just accept that Ilfochrome high contrast material has an
average exposure scale of ~1.75 when developed in P3 chemistry. Somewhat
higher if developed in P30P.
With a given transparency you can:
1) Learn to judge the gamma required in the mask and to develop accordingly.
This is Charley's usual technique. He does stunning prints.
2) Measure the lightest and darkest areas using a densitometer or a
baseboard light meter, calculate the gamma required and develop
accordingly. I use this approach, using my color analyzer as a
baseboard densitometer.
I've gone one step further. Having determined the density range of the
slide, I look at the step tablet print and decide which step represents
how I'd like the highlights to look and which step represents
how I'd like the shadows to look. Then I use the difference in
density between these steps in the original step tablet as the exposure
scale of the paper in calculating gamma. This has significantly
increased the number of masks that are right on the first try.
* Developing the mask
I just use 4x5 film trays and agitate constantly. Stop bath and fix as
normal. I give a quick rinse (often just dropping the mask in the Jobo
water bath for a minute or two), dip in distilled water with wetting
agent added and dry in a closet with an electrical space heater running.
I've tried blow drying masks but they seemed to shrink somehow as they
never registered quite right when dried this way.
Printing with masks
-------------------
Very simple. Just register the mask with the original and print. The
mask goes on top of the original, closest to the light source. Expect
exposure times to go up significantly. Probably around 1-2 f-stops.
Additional masking
------------------
Ilfochrome has a fairly pronounced toe to its characteristic curve. I.e. not
a lot of contrast. And transparency films have the same. So highlight
contrast, or lack thereof, can be a problem even without masking. This can be
exacerbated when a mask is introduced which decreases contrast in the
highlightss. Also, sometimes a sense of "sparkle" is lost when specular
highlights are increased in density by a contrast reduction mask. One answer
to either of these problems is to make a "highlight protection mask".
The highlight protection mask is made using Kodalith film. It's made sharp.
I.e. Emulsion to emulsion with the original in the contact printer. It's
exposed so that only the brightest highlights in the original show any density
in the highlight protection mask. Sometimes ferricyanide bleach is used
to remove unwanted density from it.
This mask is then laid on top of the original when exposing the contrast
reduction mask. I.e. it goes between the original and the light source. It
"increases density" in the highlights so that they result in less density in
the contrast reduction mask and print brighter in the final print.
I know one person (Charley Cramer) who has gone so far as to make a pre-
highlight-protection mask which was used when exposing the highlight
protection mask. The effect was to darken a small area in a highlight in the
final print. I haven't gotten quite this far into it yet.
An alternative is to use Kodak LPD4 positive litho film to make a "highlight
bump mask". This mask is exposed such that it's all black except for little
clear "holes" where the brightest highlights are. This film can show
significant chemical fog so it may be helpful to lightly bleach the
entire mask in dilute ferricyanide to clear the highlight areas.
After exposing the print with the contrast reduction mask, the negative carrier
is removed from the negative stage and the highlight bump mask is laid on top
of the original and an additional burn or "bump" exposure is made to brighten
the highlights. Obviously this type of technique can only be used if one
has a full pin registration setup. (You'll have to pry mine from my cold,
dead fingers - to take a page from the NRA. :-)
Once the registration equipment is available and some experience has been
gained there are lots of other possibilities. Contrast increasing masks.
Area masks - evenly toned masks which "dodge" an entire area of the print.
Kodalith area masks which are all black or all clear and allow printing
different parts of the print completely separately from the others. Lots
of new worlds to explore!
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Note 20.04 -< 3D FAQ or Frequently Asked Questions about stereo >-
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Question:
I was wondering if there's a FAQ list that would cover some of the basics of
3d photography...... What kind of equipment is most frequently used for 3d
photography? I've heard a lot about beam splitters and Realists and stuff,
but I don't know where to buy them; none of the camera stores around here have
any 3d equipment.
Answer:
There IS an ftp site and it has a couple of files which may interest you.
One is the FAQ list and the other is the 3D products and services list.
To get there:
% 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:
2002 Jun 29 1.index
45512 Mar 29 3d-faq.ps.Z
83542 Aug 17 3d.prod.serv
32467 Aug 17 3d.prod.serv.Z
203292 Mar 11 ES.CTD.ACHR.PS.Z
3537 Jun 18 ISU
2694 Jun 28 NSA
501655 Mar 18 archive_1.Z
201485 Mar 25 dpthfld.ps.Z
184006 Jun 29 ortho.mag.ps.Z
184207 Jun 17 ortho.sep.ps.Z
12041 Mar 9 photometry
423407 Mar 17 raytrace.ps.Z
2324 Mar 5 tc.expl
19890 Mar 5 tc1.25.ps.Z
20205 Mar 5 tc1.6.ps.Z
6040 Mar 9 wratten.filters
"1.index" gives a description of the other files, as you might suspect.
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Note 20.05 -< Making Color out of B&W! >-
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HOW TO MAKE HIGH CONTRAST BLUE, CYAN OR MAGENTA COLOR IMAGES
STARTING WITH A HIGH CONTRAST B&W ORIGINAL
by Dr. Lothar Engelmann
1) Use a high contrast black & white film (e.g. lith film, microfilm or
Tech Pan) and develop in C-41 or E-6 color developer to which you
have added a color coupler solution. You would have to experiment to
establish the right amount (I would start with 10ml of the coupler
solution given below for 500ml of color developer). After development
you have to bleach, wash, fix and wash again before drying. This method
would give you a negative.
2) Use a black & white high contrast image and change it to a color image.
Your image has to be well fixed and washed. This method involves the
following steps, which are all done in light:
a) Bleach your image in C-41 bleach, E-6 bleach, or the bleach
formula given below, until the silver image is fully converted
to a silver-bromide (yellowish white).
b) Wash thoroughly and make sure your film is well exposed to the
light to form a latent image in the silver-bromide formed in
the bleach step.
c) Develop in C-41 or E-6 color developer to which you have added
coupler solution (I would use about 10ml per 500ml developer).
This may take 3 to 5 minutes. Since development goes to
completion there is no danger of overdevelopment. In this step
the silver bromide is developed to silver while the color
developing agent is oxidized. The oxidized color developing
agent reacts with the color coupler to form a dye.
d) Short stop for a few seconds. (see formulation below)
e) Wash for about 30 seconds.
f) Bleach again to convert the silver back to silver bromide.
The dye is not affected.
g) Wash until all bleach is removed.
h) Fix in any common film fixer for the time recommended for your
film.
i) Wash and dry. You are left with a monochromatic color image
which has replaced your original silver image.
Either of the two methods will work. The second converts the silver
image into a dye image. If you start with a negative you will get a
negative, if you start with a positive you will end up also with a
positive. If the cyan forming coupler does not give you the right blue
image, you could add a combination of cyan and magenta coupler solution
in a ratio of 3 to 2 to your color developer, rather than the cyan
coupler alone. You could also stop the process after the color
development and use the combination silver-dye image directly. In that
case you would simply have to wash after the development step.
PAGE 2
FORMULATIONS:
Caution: All the chemicals used in the suggested processes may be toxic and/or
staining.
Bleach:
Potassium Ferricyanide 30.0g
Potassium bromide 20.0g
Water 1000.0ml
Short Stop:
Sodium Bisulfite 10.0g
Water 1000.0ml
Cyan Coupler Solution:
2,4-Dichloro-1-naphthol (EK #3704) 750.0mg
Acetone 100.0ml
Magenta Coupler Solution:
p-Nitrophenylacetonitrile (EK #3495) 125.0mg
Acetone 100.0ml
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Note 20.06 -< Variable Contrast Filter Settings and Color Heads >-
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dichroic filter settings for illford multigrade papers
calibrated filter settings for Ilford Multigrade MG-III Rapid
paper using a color head filtration system.
Grade Filtration
------------------
0 80Y
1/2 55Y
1 30Y
1 1/2 15Y
2 0
2 1/2 25M
3 40M
3 1/2 65M
4 100M
4 1/2 150M
5 200M
If you need maximum contrast, dial in full magenta and full
cyan, so you get nothing but blue; if you want minimum
contrast, use full yellow and full cyan for nothing but
green. This will give you about a grade above/below the ends
of the above scale, at the cost of long exposure times.
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Note 20.07 -< Tech Pan Exposure/Processing Info >-
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Here is the data from Kodak data sheets: Exposure: the speed of this film
depends on the application, the type and degree of developement, and level of
contrast required. Therefore, no single speed value applies for all situations.
While you can use all the speed values given below as ISO (ASA/DIN) meter
settings, they are exposure indexes(EI), Not IS0 (ASA/DIN) speeds. The table
below is for scientific, technical, photomicrography, and electron-micrography
applications, use the table as a guide to obtain the required contrast. This
assumes you start with a subject of average contrast.
high contrast Kodak DEV. DEV time Exposure index
-2.50 Dektol 3 min 200
2.25-2.50 D-19 2-8 min 100-200
1.20-2.10 HC-110(Dil B) 4-12min 100-250
1.00-2.10 D-76 6-12min 50-125
0.80-0.95 HC-110(Dil F) 6-12min 32-64
low contrast
0.50-0.70 Technidol Liquid 5-11min 16-25
For pictorial applications, use an exposure index of 25 and process the film
in Kodak TEchnidol Liquid Developer. To prepare a working solution empty the
contents of one bottle of dev. concentrate in a suitable 1-qt. container. Then
add water at 68-77F degrees(20-25C) to make one quart of dev. solution. This
dilution of developer(for 4x5 sheets) is one-half the working strength used
for roll film. Presoak film for 2-1/2 min in water of 68 degrees. Dev. for
8min. BE SURE the dev. is at 68 degrees. Rinse in Kodak stop bath SB-1a, SB-5
for 15 to 30 sec. or running water for 30 sec. Fix for 2 to 4 min. and wash
for 5 to 15min save water by using kodak hypo clearing agent.
PICTORIAL PHOTOGRAPHY: Because the sensitivity of this film extends further
into the red region than conventional panchromatic films, the recording of red
objects will be slighty lighter than normal in print. In some cases this
characteristic may be desirable. For example, it helps reduce the effect of
some types of skin blemishes and in many cases produces a luminous quality to
skin tones which many observers consider quite pleasing.
FILTRATION is usuall not required in either portrait or scenic pictorial
photography. However, in some cases filtration may be required. In particular,
Caucasian flesh tones in full sun may look too light and possibly pasty. This
effect is less evident in shade portraits outdoors because there is less red
light present. In some cases, a Kodak Wratten filter #38 or Kodak CC filter
CC40C used without a filter factor, may be sufficient to lessen the excess red
sensitivity. Because of variations in circumstances and tastes, experimentation
is in order. Kodak Technidol LC Developer is available in a 3-pack each pouch
holds enough powder to make 1 US pint. This is sufficent to process 2 35mm 36exp
rolls.
EXPOSURE INDEX: 25 for trial exposures. This is based upon the formula EI=.81E
where E is the 1/25 second exposure in lux seconds required for a density of
.1 above Base plus Fog.
PS: You can contact Kodak at 800-242-2424 and ask for publication P-255 or
write them at Customer Technical Services, Eastman Kodak 343 State Street,
Rochester, New York 14650.
From: nmyers@novell.ur.utk.edu (Nick Myers)
Subject: Re: Using Techinal Pan
Organization: University of Tennessee
================================================================================
Note 20.08 -< Sound Synchronizers - Cheap and Simple >-
--------------------------------------------------------------------------------
For high speed photography the problem generally centers around triggering the
camera or flash at the right time and how to do it. For this photographers
rely on various synchronizers. Below are two schemes designed to trip an
electronic flash by detecting sound waves. The very simplest sound sensitive
synchronizer one could make might be the one described below:
You obviously have to figure out how to connect the
flash sync cord to this device which looks like this:
To Flash
.....................................
_______:
-_-----------------------_- |: <- thin strip of aluminum foil
|: taped to tightly stretched
|: rubber membrane with 2-sided
|: tape.
|:
TIN COFFEE CAN |:--. <- tip of wire _almost_
both ends removed |: | touching aluminum foil
| |
rubber membrane from balloon or such -> | |
covering one end of coffee can | |
_-_______________________-_ | |
------ | <- wire insulated to here
=========================================
To Flash
point open and of can towards source of loud sound ... if you set everything up
VERY carefully flash will go off when aluminum foil comes in contact with tip
of wire located VERY near, but NOT touching, it.
Here is another simple sound sync which is much more sensitive but is also a
bit more expensive. It consists of one electronic part plus a common, hopefully
already available, casette tape recorder. The idea is to simply couple a SCR to
the EARPHONE jack of the casette tape recorder and hook up the flash sync
contacts to the SCR.
First, get a SCR that can handle 250 or 400 volts between Anode and Cathode such as
C106D. Radio Shack has them or similar, I believe.
Use a plug that fits into the earphone jack and connect the CATHODE and GATE
leads to the two, normally open, connections on the plug. Then, connect the
CATHODE and ANODE leads on the SCR to the flash sync contacts. Make sure plug
is now UNPLUGGED from the EARPHONE jack.
Now, put a tape in Tape Recorder and activate the Tape Recorder so it is now in
RECORD mode. Make sure it is very quiet in the room. Now plug the jack into the
EARPHONE jack. The flash should fire. It should also fire each time you make a
tiny sound assuming the flash has recycled.
If it does NOT do fire the flash it is possible the connections between the
flash and the SCR are hooked up "backwards". Try moving sync cord connections
to opposite SCR leads. Now the synchronizer may or may not work.!!!!
The IDEA here is that the VOLTS generated by the recorder when recording and
which would drive the earphone can be used to turn on a SCR which in turn
triggers the flash upon sensing a sound. CHEAP, quick, dirty and unfortunately
somewhat unreliable. But so what did you want for nothing?
================================================================================
Note 20.09 -< Convenient Pulfrich Effect 3D Viewing >-
--------------------------------------------------------------------------------
The Pulfrich 3D effect and Switchable Glasses
The Pulfrich effect allows you to get a 3D effect from normal television
sometimes, by wearing glasses with one dark lens and one clear lens (such as
sunglasses with one of the lenses missing). If the dark lens is the left one,
then anything on the screen that's moving right-to-left in relation to the
background scenery will appear to be in front of it. Likewise, if the dark lens
is the right one, then objects moving left-to-right will appear closer than the
background. Ice skating is a good type of program to watch in order to be
guaranteed of some good side-to-side motion shots, and Mike Watters has pointed
out that the introduction to the "Star Trek: The Next Generation" has a good
shot in which the Enterprise moves left-to-right in front of a background of
stars.
But how do you switch the dark/clear side of your glasses in a hurry, when a
motion-shot comes on the screen that's in the wrong orientation for your
glasses? After months of detailed and painstaking research, I've discovered a
good answer. The company whose address appears below sells something called
"flip-up glasses". They're cheap plastic sunglasses whose lenses flip up
_individually_. They're certainly not intended for use as Pulfrich glasses,
but I have a pair, and they work great for that purpose. You can instantly
flip one dark lens up and the other one down when necessary, without even
taking the glasses off. They cost $1.95 per pair (plus postage).
The rest of their free mail-order catalog is quite wonderful! They sell cheap
novelties and other weird things that apparently didn't sell very well in
stores. For instance, there's an inflatable buffalo, a plastic monkey that
blows smoke rings, and a glow-in-the-dark water gun shaped like a squid. Other
3D-related items include various cheapo holograms of eyeballs (some mounted in
glasses), and a vinyl card (presumably lenticular) which shows a portrait of
Jesus when you look at it one way and a picture of the Shroud of Turin when you
look at it another way. Truly a smorgasbord of essential items. Here's the
address...
Archie McPhee
Box 30852
Seattle, WA 98103
U.S.A.
order desk and info line: (206) 782-2344
From: Tim Klein
================================================================================
Note 20.10 -< What is EV (Exposure Value)? >-
--------------------------------------------------------------------------------
>Can someone tell me what the relationship is between LUX and EV and ASA?
>For example can I determine LUX from F number, Speed and ASA and vice versa?
Well, according to ANSI PH 3.49-1971 (R1976) [American National Standard for
General Purpose Photographic Exposure Meters (Photoelectric Type), thing's are
related thusly:
2^EV = BS/K
where
EV = exposure value.
B = Field luminance.
S = ISO/ANSI film speed
K = exposure constant (reflected light); the luminance units
which B must be expressed in must be identified for any
given K value to be meaningful since B and K change
proportionally.
If B is in candelas/meter^2 K=12.5
footlamberts K= 3.65
candelas/ft^2 K= 1.30
And:
2^EV = A^2/T
where
A = f-number of aperture
T = shutter time in seconds
In other words, EV = log2(A^2/T) = log2(B*S/K).
Note that EV is a measure of *EXPOSURE*, not of illumination. EV0 is *by
definition* an exposure of 1 sec at f/1, or any equivalent *exposure* (2
sec@f/1.4, 4 sec@f/2.0, etc, etc). When people refer to a given brightness
level as EV1, they usually mean "EV1 for a film with an ISO speed of 100".
>So does an EV number stand for an absolute amount of light?.
Again, EV is a measure of *exposure*. It is, by definition, log2(A^2/T), where
A is the aperture (f/ number) and T is the exposure time in seconds. That's why
it's an EXPOSURE Value and not a LUMINANCE Value.
The usage of EV by itself to express a light level seems to have originated
with advertising copywriters who were too damned lazy to write "EV at ISO
100", which is typically what they mean.
>Since you normally measure EV or LUX, and then, using ISO or ASA compute the
>F number and shutter speed, can you do the conversion in the other direction
>using any light meter and find the amount of light falling on a scene?.
Actually, you really normally measure light level, and then, using ISO or ASA
compute the EV (which is a neat way of referring to all possible combinations
of aperture and shutter speed which produce the exposure you want).
Contributed by Steve Gombosi, sog@craycos.com
================================================================================
Note 20.11 -< Info on Film and Video Resources on the Internet >-
--------------------------------------------------------------------------------
Guide to Film and Video Resources on the Internet
This guide includes information on many resources such as listservs and
USENET news groups on topics related to film and video, as well as film
review databases, filmographies, etc.
Our intention in compiling this guide was to locate as many resources
as possible in the subject area of film and video which are available
on the Internet. While it is not a definitive source, it is a good
place to start if you are looking for information about film and video.
We intend to maintain this guide as an ongoing project and would
encourage any comments you have.
The guide is now available but since it is 72K we chose not to post it
on the listservs and news groups. While we will be happy to send a copy
(absolutely free) through e-mail to anyone interested, we wanted to
warn everyone that it is a very big file and that people are better off
accessing it in the following ways:
anonymous FTP:
host: una.hh.lib.umich.edu
path: /inetdirsstacks
Gopher:
via U. Minnesota list of gophers
menu: North America/USA/Michigan
Gopher .link file:
Name=Clearinghouse of Subject-Oriented Internet Resource Guides (UMich)
Type=1
Port=70
Path=1/inetdirs
Host=una.hh.lib.umich.edu
Uniform Resource Locators (URLs) for WWW/Mosaic:
http://http2.sils.umich.edu/~lou/chhome.html or
gopher://una.hh.lib.umich.edu/11/inetdirs
_Film and Video Resources on the Internet_ was created during the fall
semester, 1993 at the School of Information and Library Studies. It is
the final project for the course ILS 606 Internet: Resource Discovery
and Organization. This guide and numerous other subject -oriented
Internet resource guides are available from the Clearinghouse for
Subject-Oriented Internet Resource Guides using the methods described
above.
Once again, thank you to everyone who provided information and
assistance with our guide. If you have any questions about the guide,
please feel free to send us a message.
Thank you,
Lisa R. Wood
~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~ ~*~
Lisa R. Wood School of Information and Library Studies
lrw@umich.edu University of Michigan
(313) 763-1614 Ann Arbor, MI USA 48109
----------------------------------------------------------------------------------
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