The Guide to Film Photography
Exposure = Intensity x Time (or E=It)
This
means that if you increase the intensity, you can reduce the time
proportionally and still achieve the same exposure. Let’s have a 2nd
look at our exposure triangle to better visualize:
If we use the triangle as a guide, we can see that film speed is
effected by aperture, and shutter speed. Shutter speed is effected by
ISO and aperture. Aperture is effected by ISO and shutter speed.
Meaning:
they are all related when it comes to exposure. Increase one
and you must decrease the other.
Some examples:
Say you’re shooting with an ISO of 100 and you know that your correct
exposure is 1/250 at f/8. Your correct exposure could also be 1/125 at
f/11 (1 shutter speed down, 1 stop up).
This is where knowing about all 3 elements becomes important. First off, if you are shooting 100 speed film, it’s because you have bright
light and you want fine grain. Now if you want
more depth of field (a higher f-stop) or selective focus (a lower
f-stop). Also your subject is moving, which
requires a fast shutter speed, or standing still, which does not.
These factors are the reason why there is no exact answer to the
question
“What’s the correct exposure?”
18% or “Middle” Gray:
Ansel Adams to open this semi-complicated subject:
“A
reading made from any uniform luminance surface used directly to
determine exposure will give exposure settings that will reproduce that
surface as a middle gray in the final print.”
It means that there is a middle gray. On a
geometric scale going from “Black” to “White,” 18% is the mathematical
middle. It also means that the middle gray is always the same. In fact,
light meters are calibrated to 18% “middle” gray -
for an intro to light meters, please head on over to my partner in film crime, The Photon Fantastic. You can use this gray to achieve more accurate exposures, with a maximum amount of information in the highlights and shadows.
A “uniform luminance surface” is referring to a gray
card. If you place a gray card into the scene you’re shooting and take a
meter reading, you are guaranteed to have a middle value. This
is important because, sometimes you don’t have a middle value… e.g: a
black and white checkerboard is only black and white. You need to take a
middle value to have sufficient white tones and sufficient blacks when
printing
Over- and Under- Exposure
Sometimes
we don’t expose correctly, even the best of us, and we finish with a
negative that is either underexposed or overexposed. An underexposed
negative did not receive enough light, and will appear light with a lot
of visible film base. An overexposed received too much light, it'll
appear black.
Each has it’s disadvantages, however underexposed
negatives tend to have less or no information in the shadow areas,
whereas an overexposed negative retains some information in the
highlight areas.
Different types of film have a different range of stops that can be over or underexposed while still retaining information:
- Black and white film: 5 stops (this means you
can over or underexpose by 5 stops and still retain information in your
negative… black and white film is very, very forgiving)
- Color negative film: 3 stops (slightly less forgiving, but still a little breathing room)
- Color slide film: 1 1/2 stops (here you
really need to be precise with exposure, which is often why slide film
is considered to be “professional” film)
Here is a
very very basic rundown of what
film is, in general, I will say
that once you've got a solid grasp of how paper and film are made and the
chemicals used to develop them, it’s easy to venture off into the world
of alternative processing… which is brilliant.
The 101 of how film works:
Film is composed of layers, these are different for
color, slide, black and white, and instant film but all contain millions
of light-sensitive silver halide crystals (what we call grain) that you
expose when you pop the shutter. While the other layers are crucial,
for our purposes we will be looking at the light sensitive layers. Color
film has three layers of silver halide: red, blue, and green.
Slide film has a few more layers than C-41:
Black and white paper is what we call “orthochromatic” which is
basically a fancy word for “red blind.” This is why you can print black
and white in a darkroom with the redlight on, allowing for minimal
vision, whereas when printing colour you must remain in total darkness.
Very weird, and kind of fun. Technically you can still buy
orthochromatic black and white film, but it’s not very common. Most
black and white film today is panchromatic, which means it is sensitive
to all colors of the visible light spectrum.
The layer composition of
black and white film is simpler:
You’ll notice they all have what we call an “antihalation” coating or
layer, which is basically applied to the back layer to absorb stray
reflecting light from the film emulsion.
To understanding aperture, easily is to go over the basics of film speed or ISO (formerly known as ASA.)
ISO
is the speed of the film, also known as; the number printed on the box
and the canister. FujiChrome Velvia 50 has an ISO of 50; Ilford Delta
400 has an ISO of 400. ISO or Film Speed is expressed as a number, which is generally
doubled as it gets higher.
E.G: 50, 100, 200, 400, 800, 1600,
3200.
There are several exceptions to this, such as; Ilford FP4 which has
an ISO of 125.
Photographic film is made up of millions of light-sensitive silver
halide crystals, which we call grain. The lower the film speed, the
finer the grain; the higher the film speed, the fatter the grain. Larger
silver halide crystals have more light sensitivity than smaller ones,
so a
higher ISO will be more sensitive to light than a lower one.
An ISO of 50 or 100 is not very sensitive and requires bright light,
which means that if your camera’s fastest f-stop is 3.5 or higher, you
would not have enough light to do interiors (for example) without a
flash. An ISO of 3200 is extremely light sensitive, but also has very
prominent grain and therefore a specific style. It’s also very easy to
overexpose if shooting in direct sunlight.
This is where fine
tuning the balance between f-stop, ISO, and shutter speed comes in to
achieve the desired result. When you look at a manual SLR, you’ll see a
little dial with all of the film speed numbers going from 25 or 50 up
to 3200 or 6400 (depending on make/model). Setting this dial is only for
the light meter and will not have an effect on your exposures. Ideally,
you would set the ISO, and use the light meter to balance between
f-stop and shutter speed. If you’re not sure what the light meter is,
it’s that little needle you see when you look through the view finder,
and you want it to be in the middle for a correct exposure. You need to have
batteries in the camera for the light meter to work. This is why manual
cameras take batteries; the batteries have nothing to do with the
shutter or any mechanical part of the camera.
Here’s a little film speed guide (these are just my personal recommendations):
- ISO 50 (or lower): Bright sunlight (the beach in the afternoon, for example), studio lights
- ISO 100: Bright sunlight, bright overcast, studio lights
- ISO 200: Sunlight, overcast, some shade, studio lights
- ISO 400: Outdoor (sunlight/overcast), indoor (during the day or very well lit)
- ISO 800: Outdoor (very overcast), dusk, interiors, motion/high speed
- ISO 1600: Night, interiors (day or night), motion/high speed
- ISO 3200: Night, interiors, motion/high speed
Again, there are always ways around this, such as using an external flash head at night with an ISO of 100.
Understanding Aperture and F-Stop
A lot of people ask me about where to start in
film photography, or what’s my advice for beginners. One of the things
that’s most important in photography (film and digital) is understanding
the basics of aperture and f-stop. So for all of you who asked me
questions on the subject, here’s a little 101:
Aperture is
basically the diameter of the lens opening; the aperture is expressed as
a fraction of focal length - that’s where the f-stop numbers come from.
For instance, f/4 means the aperture equals focal length divided by 4.
When we talk about a 1.8 lens or a 3.5 lens that refers to the largest
aperture of the lens; so a 1.8 lens would start at f/1.8. An opening of
1.8 is bigger than 3.5, I know that doesn’t seem to make sense, but
remember it’s fractions. As you slide the f-stop down, meaning as the number gets
bigger, you’ll notice the hole gets smaller.
Let’s look at the major stops:
f/1 1.4 2 2.8 4 5.6 8 11 16 22 32 When you look at an f-stop, the
numbers on either side represent either twice or half of the amount of
light. For example, take f/5.6: f/4 is twice as much light, while f/8
is half as much. Many lenses have numbers in between to represent half
and third stops.
The f-stop you choose will have an effect on your depth of field;
the way to control this is by using a combination of ISO (film speed)
and shutter speed to provide the correct exposure while achieving the
depth of field desired. I will explain more on this when I do a post on
depth of field, but for now it’s important to note that larger f-stops
have a smaller depth of field. Meaning, at f/1.4 you will have to use
selective focus and choose either the foreground or background whereas
at f/32 you would have much more of the image in focus.
What is Shutter Speed?
In the simplest of
terms, shutter speed is the amount of time that light hits the film. The
shutter is the little curtain that opens and closes when you push the
release button (when you make an exposure).
Exposure is effected
by both the time and the intensity that light hits the film. In general,
the correct exposure for all film is about the same amount of total
light energy absorbed. Since we know that film sensitivity to light
varies with ISO (formerly ASA), and that we can control the amount of
light that reaches the film with shutter speed and aperture, we can use
this formula to express total exposure:
Exposure = Intensity x Time (E = It)
In
complicated photography/optics terms, intensity has other factors but
is partially controlled by aperture settings. This
formula basically means that if you increase the aperture, you need to
decrease the shutter speed (or film speed) or that if you increase
shutter speed you need to reduce aperture or any mix n’ match of the
three. Hence the exposure triangle of aperture, shutter speed, and ISO:
Each
element effects the others and must be adjusted accordingly but more
on that in “Exposure.” For now, let’s get back to shutter speed:
On most cameras, shutter speeds increase by a ratio of 1:2 (w/ several rounded values), e.g:
1/2 1/4 1/8 1/15 1/30 1/60 1/125 1/250 1/500 1/1000 1/2000 1/4000
1/60 is one sixtieth of a second. 1/1000 is one one thousandth of a second.
Most
shutters also have a B and or T function; “B” stands for “bulb” and
leaves the shutter open as long as you press it. “T” stands for “Time”
and you press the shutter once to open, and again to close. “T”
obviously makes more sense if you needed to do an exposure that was
minutes or more.
1/60
is the lowest you can go without a tripod before you will have camera
shake; and even at 1/60 you need to be standing still.
For flash
sync: the majority of cameras made before the 90’s sync with an external
flash at 1/250; newer cameras can also have a flash synch at 1/200.
Types of shutters:
Leaf Shutter- a leaf shutter has overlapping blades that are controlled by a rotating ring. It looks not unlike a star:
A leaf shutter is located at the base of the lens, near the
diaphragm. For those of you who are familiar with focal plane shutters,
opening up the back of a camera with a leaf shutter will look like a
focal plane shutter that is stuck on open.
Focal
Plane Shutter - a focal plane shutter is mounted near the film plane
and features a horizontal curtain. Actually, older focal plane shutters
feature one curtain, most new focal plane shutters now have two
curtains:
Both have their
drawbacks, and for the focal plane shutter this mainly has to do with
fast moving subjects and image compression. Basically, when you’re
subject is moving really, really fast (for example, a car) it'll
probably be in a different place at the end of the exposure than it was
at the beginning, which results in the image being either stretched or
compressed. Depending on whether your focal plane shutter is horizontal
or vertical, this stretching or compressing with take place either (you
guessed it) horizontally or vertically. Because a leaf shutter exposes
the entire film area at once this distortion will not occur, however, leaf shutters are not without flaw because a leaf shutter exposes the entire film area at once (versus the
small slits of the focal plane) very high shutter speeds are not
possible. There are not very many leaf shutters manufactured today.
Depth of field refers to the part of your photograph that is in focus.
If all or most of your photograph is in focus, you have a deep depth of
field (also called deep focus.) If only a part of your photograph is in
focus, you have a shallow depth of field (also called shallow focus and
selective focus.) And that’s what depth of field is. Seriously.
The tricky part is figuring out how your aperture relates to your
depth of field, and your beloved (or hated) exposure triangle. Exposure 101,
has several factors affect depth of field, including your
distance to your subject, the focal length of your lens, your selected
aperture (f-stop) and the format you are shooting. This means that a
photo taken with a 50mm lens at f/1.8 from the same distance will not
have the same depth of field when taken with a 35mm camera and 4x5 field
camera.
A general rule to guide you: the smaller the f/stop number (so the larger the opening), the shallower the depth of field. F/1.2 has a shallower depth of field than f/1.8, which has a shallower
depth of field than f/2.8 and so on. F/5.6 and F/8 tend to give medium
focus, depending on your distance from the subject (and the format you
shoot, of course.)
Side-by-side examples:
{Selective Focus: F/2.8 - This is pretty
shallow, but not to the point where it creates a complete bokeh effect
and the background is indistinguishable. Both of these were shot at
F/2.8 with a 50mm lens in 35mm.}
{Deep Focus: F/16. -These two, on the other
hand, have deep focus - meaning that the foreground and background are
in focus. Both were shot at F/16, but the left image is medium format
and the right is 35mm.}
{Shallow and medium side-by-side: The background
in the left shot is completely blurry with zero detail. It was shot at
f/1.8, approximately 12 feet from the subject with an 80mm portrait lens
on 35mm film. The right shot has a blurry background, but you can still
tell what it is. It was shot at f/8, approximately three feet from the
subject with a 50mm lens on medium format film.}
F/32 is
most commonly the highest number on lenses that don’t cost, but you can definitely come across field cameras with an f/64.
In fact, in the early 1930s, a bunch of photographers got together to form Group F/64. Their principal belief was that
photographs should be perfectly exposed, profoundly sharp and
completely in focus. An aperture of f/64 was the best way to achieve
this, as far as they were concerned.
F/32 really doesn’t let a lot of light in, this is where if you absolutely have to shoot 100 ISO and need a very deep DOF,
you’ll have to lower your shutter speed. If you want to use a specific
shutter speed at f/32, you’ll have to pick a film with a high enough
ISO. For those who shoot digital, this doesn’t prove as much of a
constraint, considering you can change the ISO. Even if
you decide to push or pull to fit the situation, you still have to shoot
at that ISO for the entire roll.
Many SLR film cameras have a depth of field preview button; it’s
usually located on the front near the button to release the lens or the
self-timer. When you hold the depth of field preview button and look
through the viewfinder, you’ll notice it is significantly darker but
accurately displays your complete depth of field.
Let’s sum up the major points:
- Depth of field refers to the areas of the photograph in focus.
- Small f-stop numbers produce shallow depth of field, or
selective focus. This is when the background is blurry. Great for
portraits.
- Medium f-stop numbers produce a medium depth of field,
still with selective focus, but with significantly more definition in
the out-of-focus areas. Good for portraits and specific landscapes.
- Large f-stop numbers produce a deep depth of field, meaning the foreground and background are in focus. Ideal for landscapes.
Enlargers
An enlarger is a specialized transparency projector used to produce photographic prints from film or glass negatives using the gelatin silver process, or from transparencies.
Construction
All enlargers consist of a light source, normally an incandescent light bulb, a condenser or translucent screen to provide even illumination, a holder for the negative or transparency, and a specialised lens for projection. The light passes through a film holder, which holds the exposed and developed photographic negative or transparency.
Prints made with an enlarger are called enlargements. Typically, enlargers are used in a darkroom, an enclosed space from which extraneous light may be excluded; some commercial enlargers have an integral dark box so that they can be used in a light-filled room.
Types of Enlarger
Photographic Enlarger.
- A condenser enlarger consists of a light source, a condensing lens, a holder for the negative and a projecting lens. The condenser provides even illumination to the negative beneath it.
- A diffuser enlarger's light source is diffused by translucent glass or plastic, providing even illumination for the film.
- Condenser enlargers produce higher contrast than diffusers because light is scattered from its path by the negative's image silver; this is called the Callier Effect. The condenser's increased contrast emphasises any negative defects, such as dirt and scratches, and image grain.
- Diffuser enlargers produce an image of the same contrast as a contact print from the negative.
- Dedicated colour enlargers contain an adjustable filter mechanism - the colour head - between the light source and the negative, enabling the user to control the amount of cyan, magenta and yellow light reaching the negative. Other models have a drawer where cut filters can be inserted into the light path. These enlargers can also be used with variable-contrast monochrome papers.
Digital enlargers project an image from an LCD screen at the film plane, to produce a photographic enlargement from a digital file.
Enlarger physical arrangements
Most modern enlargers are vertically mounted with the head pointing downward and adjusted up or down to change the size of the image projected onto the enlarger's base, or a work table if the unit is mounted to the wall.
A horizontal enlarger consists of a trestle, with the head mounted on crossbars between two or more posts for extra stability. A horizontal enlarger structure is used when high quality, large format enlargements are required such as when photographs are taken from aircraft for mapping and taxation purposes.
The parts of the enlarger include baseboard, enlarger head, elevation knob, filter holder, negative carrier, glass plate, focus knob, girder scale, timer, bellows, and housing lift.
Principles of operation
Enlarger lens: using the diaphragm - aperture ring the photographer adjusts the iris.
The image from the negative or transparency is projected through a lens fitted with an adjustable iris aperture, onto to a flat surface bearing the sensitized photographic paper. By adjusting the ratio of distance from film to lens to the distance from lens to paper, various degrees of enlargement may be obtained, with the physical enlargement ratio limited only by the structure of the enlarger and the size of the paper. As the image size is changed it is also necessary to change the focus of the lens. Some enlargers, such as "Autofocus" enlargers, perform this automatically.
An easel is used to hold the paper perfectly flat. Some easels are designed with adjustable overlapping flat steel "blades" to crop the image on the paper to the desired size while keeping an unexposed white border about the image. Paper is sometimes placed directly on the table or enlarger base, and held down flat with metal strips.
The enlargement is made by first focusing the image with the lamp on, the lens at maximum aperture and the easel empty, usually with the aid of a focus finder. The lamp is turned off, or in some cases, shuttered by a light-tight mechanism.
The image is focussed by changing the distance between the lens and the film, achieved by adjusting the length of a light-tight bellows with a geared rack and pinion mechanism.
Electronic timer: photographers choose exposure time.
The lens is set to its working aperture. Enlarging lenses have an optimum range of apertures which yield a sharp image from corner to corner, often around f8. The lens is normally set to this aperture and any color filtration dialed in, if making a color print or one on variable-contrast black-and-white paper.
The enlarger's lamp or shutter mechanism is controlled either by an electronic timer, or by the operator - who marks time with a clock, metronome or simply by counting seconds - shuttering or turning off the lamp when the exposure is complete. The exposed paper can be processed immediately or placed in a light-tight container for later processing.
Digitally controlled commercial enlargers typically adjust exposure in steps known as printer points; twelve printer points makes a factor of two change in exposure.
Paper processing
After exposure, photographic paper is developed, fixed, washed and dried using the gelatin silver process.
Automated print machines
Automated photo print machines have the same basic elements and integrate each of the steps outlined above in a single complex machine under operator and computer control.
Rather than project directly from the film negative to the print paper, a digital image may first be captured from the negative. This allows the operator or computer to quickly determine adjustments to brightness, contrast, clipping, and other characteristics. The image is then rendered by passing light through the negative and a built-in computer controlled enlarger optically projects this image to the paper for final exposure.
As a byproduct of the process a Compact Disc recording may be made of the digital images, although a subsequent print made from these may be quite inferior to an image made from the negative due to digitization noise and lack of dynamic range which are characteristics of the digitizing process.
For better images, the negatives may be reprinted using the same automated machine under operator selection of the print to be made.
Advantages
- The image may be printed to a size different from the negative or transparency. Without an enlarger, only a contact print would be possible, and large images would require large size negatives and hence very large cameras.
- Local contrast and density of various parts of the print can be easily controlled. Changing the amount of light exposing the paper in various areas will change the image density in those areas. A mask with a hole can be used to add extra light to an area "burning", which will have the effect of darkening the regions with additional exposure, while the use of a small wand to reduce the total exposure to a region is called "dodging" and has the effect of lightening the regions with reduced exposure. The tool is kept moving to avoid producing a sharp edge at the region boundary. Using these techniques it is possible to make significant changes to the mood or emphasis of a photographic print. Similar methods are available with contact printing, but it is more difficult to see the image as it is being manipulated.
- It is also possible to make composite photographs by overlaying the print with a hand-cut mask, performing an exposure, and then using the inverse of that mask to perform another exposure with a different negative. This is much more difficult to do well using photographic methods than it is now by using the methods of modern digital image manipulation.
Image enlargement limits
The practical amount of enlargement (irrespective of the enlarger structure) will depend upon the grain size of the negative, the sharpness (accuracy) of both the camera and projector lenses, blur in the image due to subject motion and camera shake during the exposure, and the intended viewing distance of the final product.
For example, a 5 by 7 inch print intended for viewing in a scrapbook at 18 inches may be unsuitable for enlargement as an 8 by 10 inch print to be hung on a hallway wall to be viewed at the same distance, but usable at a larger 5 by 7 feet (twelve times larger) on a billboard to be viewed no closer than eighteen feet (twelve times more distant).
How to Develop Photo Negatives in a Dark Room
Developing photo negatives is not a hard task to conceive, and it’s fun to open the developing tank at the end of the process to see what images you have captured. Fewer chemicals are required for developing negative film, and the tolerances for maintaining times and temperatures are looser, than for colour transparency (slide) film.
Instructions in Developing
- 1
- Place your measured chemicals in glass or plastic containers in a water bath that is at the correct processing temperature. A plastic dish washing tub works well for this. Consult the developing chart that came with your film. There is usually a combination of time and temperature, e.g. a development time of 7 minutes at 20 degrees Celsius, or 5 minutes at 23.9 degrees Celsius.
2
- Turn off the lights to load film onto the developing reel. Before opening the undeveloped film, let your eyes adjust so you can make sure there are no light leaks which can strike and fog the film. Open 35-mm film canisters with a bottle cap opener, or carefully remove the protective paper around a 120-mm roll of film.
3
- 4
- 5
- Pour the water out of the tank and pour in the developer solution. Start a timer for the correct developing time, and continue to agitate the film at consistent intervals during processing. Consult your film’s development instructions for the correct agitation interval. When you’re not agitating the tank, keep it in the water bath to maintain the solution temperature.
- 6
7
- 8
Open the developing tank at the end of the fixer cycle and let clean water at the correct processing temperature run through the tank for five minutes. Carefully unroll the film from the reel and gently dip the film through a shallow dish filled with a soapy solution called Photo-Flo. This will help the film surface dry without residue on it. Hang the film with film clips or clothespins in a clean environment where it will not be disturbed while drying, such as a bathroom after you’ve run the shower to fill the air with moisture.
Tips and warnings
- You can sacrifice a roll of film and practice with the lights on, and then with your eyes shut, to get the feel for loading the film correctly. Film that is crooked on the developing reel can touch adjacent layers in the spiral and ruin your images.
- You can develop colour negative film using the same procedures, but you’ll have several more chemicals, depending on the chemistry that you use. For example, some developing kits combine a bleach and fix solutions. You’ll also need to pay closer attention to maintaining the chemicals at the indicated processing temperature when working with colour film.
