By GEI staff with coaching from Gary Peck

Modern automatic cameras take care of the details for you, and give generally good pictures for most conditions.   But what happens if your general settings don’t give you the results that you want?   Then you may want to manually adjust your settings.   For that, you need to know some basic terms and principles of how cameras work.   Here are some of the basic principles of cameras.

Camera type basics:

Modern cameras come in two types, those that use film and those that are digital.   Within these, there are two types, point and shoot and single lens reflex (SLR).   The SLR and its digital brother (DSLR) both allow the photographer to view the scene through the same lens that the camera will use to take the photograph.   The point and shoot cameras provide a separate view finder window for the photographer to compose their shot (which is cheaper to manufacture).

Digital basics:

The quality of a digital camera photograph will depend on the size of the photo expressed in megapixels.   Ignoring the professional level cameras, five years ago a five megapixel camera was state of the art.   Currently ten to fifteen megapixel cameras are available for under a thousand dollars.   For comparison, cell phones currently have built-in 1.3 to 5 megapixel cameras.   Roughly speaking, a 35 mm film photograph is comparable to a 20 megapixel photo (available to those with sufficient funds).   The tradeoff on digital photographs is image size versus resolution.   Most magazines require 300 dots per inch for “photo quality” publication.   Given that resolution, you can generate a 5” by 7” print from a 3 megapixel camera, and an 8” by 10” print can be made from an 8 megapixel camera. A 16” by 20” print would require between 24 and 30 megapixels for comparable quality.

Film basics:

The original cameras used photographic film that had a layer of light sensitive chemicals (grains of silver halide) on it.   Exposure to light darkened the film.   Areas of the film that got less light remained clearer.   The size of the grains is controlled in the manufacturing process to be larger or smaller.   Larger grains are more sensitive to light than smaller grains.   Films with larger grains are called faster films, films with smaller grains are called slower films.   This is where the ISO number comes in.   For everyday use, the general purpose film speed to use is ISO 100.   This is good for still portraits and outdoor shots taken in the sunshine.   But what if you want a picture in the shade, where there is less light?   Then you move to an ISO 200 film.   What if you need a picture in low light conditions without a flash?   Then move to an even faster ISO 400.   ISO films of up to 1600 (for very low light situations) are commercially available.   What is the tradeoff?   The faster the film, the larger the grain size.   For a given area, if you cover the film with many small grains, you get much detail (like ISO 64 or 100), and if you cover it with only a few large grains, you get less detail (like ISO 400).   An enlargement or blowup of a fast ISO photograph tends to be grainy and will lack the detail of an identical photograph taken with a slower ISO number.   The comparison would be like a postage stamp covered with 100 large grains of sand (ISO 1600), versus a different postage stamp covered with a thousand small grains of sand (ISO 64).   This effect is best seen when a digital photo is displayed on a computer monitor and enlarged to the point of losing detail.

Connecting Film to Digital:

ISO numbers are still very important with the advent of the digital camera, where sensitivity and resolution are physically and electronically controlled by the quality (translation: cost) and "computer brain" of the camera.   As noted in the Digital Basics section, megapixels are important to clarity.   But, you need to be aware that in most fully automatic digital cameras the camera is adjusting the sensitivity for you.   In film, grain size is truly a physical aspect, but in digital, the manufacturer uses computer wizardry to give you more sensitivity, but at the loss of resolution.   This can be seen as “graininess”, loss of sharpness, and loss of color vibrancy.   Fortunately the camera industry did a really smart thing by using the film ISO scale to indicate sensitivity, and thus resolution  and degradation.   In a DSLR you have the option of manually setting the ISO or using the "Auto ISO" function.   In a digital Point and Shoot you need to refer to your owner's manual to see if a single ISO is referenced or, as in most, an ISO range.   Why is this important?   Your camera will reduce your clarity to "help you out".   This is especially true in Sport and Scenery modes (most cameras have a few options).   Again, here is another tradeoff because these modes sacrifice clarity to maintain higher shutter speeds (prevents blur from movement), or greater depth of field (again, prevents blur from out of focus).   In Point and Shoot cameras your best bet is to use the standard or portrait settings.   Fill flash modes can also help in short distance shots.   For DSLR cameras you will get better results if you set your ISO manually, forcing the camera to give you higher resolution.

Lens basics:

Camera lenses are shrouded in both mystery and hype.   They range from the simple to highly complex, costing thousands of dollars.   The camera lens is basically a curved piece of glass, held in a tube, carefully polished and coated for special reflective properties.   Remember as a child how you would use a magnifying glass to look at the end of your finger?   You moved it closer and farther until your subject came in focus.  The camera lens does the same thing, focusing your photographic composition onto the film or pickup surface.   Most cameras come with a non-removable lens, which is a middle-of-the-road compromise in terms of lens choices.   The alternative is to allow you to change your lens to custom suit the occasion.   We have now entered the era of DSLR camera bodies that accept lenses manufactured for film cameras, which really opens up a new world of reasonably priced choices for the DSLR user. The magnification power of a lens is described by its focal length and simple mathematics can tell you how much magnification you have.   A 50mm lens has a magnification of one on a 35mm film camera, meaning it does not either magnify or shrink an image.   On a digital camera, the exposure surface (or chip or pickup area) is smaller than the area of a 35 mm film camera, so the “one” magnification point is roughly a 35 mm focal length lens (not 50 mm), depending on the chip size (which is not industry standardized).   A 50 mm lens on DSLR thus creates about a 1.4 magnification.   A 200 mm lens would have significant magnification for your distance shot, (4 times for film and 6 times for a DSLR).   Zoom lenses allow you to adjust between the focal lengths.   A typical DSLR camera comes with an 18-55 mm zoom lens, which provides from one half to two times magnification.   Another side note: since the digital pickup size is smaller than the typical 35mm for film, it is not suitable for extreme wide angle lenses (greater than .5 magnification).   If you use your film camera extreme wide angle lens on your DSLR you will experience a noticeable edge clarity loss which can only be compensated for by paying an extreme price for a specialty lens.

Shutter speed basics:

The shutter speed is the period of time that the shutter is open to expose the film to the incoming light.   This is the next area of tradeoff.   Generally speaking, you want the slowest shutter speed possible to get the maximum amount of light for the most detail possible onto your slowest possible ISO film.   A still life is easy, but what happens if your subject is a moving child? The image will be blurred. Therefore you need a quicker shutter speed (less time of open shutter) to “freeze” the subject. A typical shutter speed for a non-moving object may be 1/60 of a second.   A moving racecar may need a 1/500 of a second to “freeze” it without blurring. Again the tradeoff is that at 1/500 of a second, not much light will get in, so an ISO 100 film will be underexposed (dark), except in bright sunlight.   Therefore, if you are going to be taking action shots, you need to also go to a faster ISO film (more sensitive to that lesser amount of light).   If you do not enlarge the photo, it will look fine, but if you enlarge it, it will be grainy in comparison to an ISO 100 film enlargement of the same shot.

(Side note from Gary: As a long time race fan photographer, I shot almost all sunny day race photos at 100 ISO or 64 ISO with a 200 mm lens, or a 500mm lens using a shutter speed of 1/125 and a polarizing filter.   I found that 1/125 is preferable as 1/500 removes all blur.   Most people enjoy the photos taken with the car sharp, but background and wheels blurred which is done at 1/125 as you smoothly pan along with a car passing at speed.)

Aperture basics:

The size of the hole that is opened to let the light into the camera body (the aperture) is also changeable.   Typically there are six overlapping metal blades or plates that form an iris diaphragm.   This is similar to the iris in your eye.   When the iris is open wider, you get more light, when it is not opened as wide, you get less light.   The ability to change the aperture adds another adjustment to getting the optimal amount of light to the film or pickup surface.   If you were using a slower film, but wanted a fast shot to “freeze” that moving car, the ability to use a larger aperture could allow you to still get a fully exposed photograph.   Aperture also determines the depth of field, or how much of the photograph is in focus.   A numerically large “F stop” means a small hole which allows both the foreground and background to be in focus.   A numerically small “F stop” value means a large opening which will allow the objects at the point of focus to be clear, but objects in the foreground and background will be out of focus.   Again, we have another tradeoff of light admitted versus focus.   Most DSLR cameras now come with small zoom lenses with a maximum "F stop" of f/3.5 to f/5.6.   If you wish to optimize your natural light capabilities, a 50mm lens can be purchased very inexpensively ($25-$75) used with maximum "F stop" of f1.8 or less for most cameras (remember small number equals big opening).   This will allow you to shoot indoors without a flash in many situations without changing to really high ISO settings.

(Side note from Gary: I still use my Minolta 50 mm f1.4 all the time, it gives me 4 F-stops greater light input for low light shots.   So if you shoot ISO 1600 at f3.5, I shoot ISO 100 at f1.4.   This also extends the maximum flash distance by up to 70%, which is a big deal with smaller flashes.  Using the Minolta 50 mm f1.4 with my big flash has extended my usable flash range out to 100ft.)