Lesson 4 Quiz

SLR cameras, digital or film, take interchangeable lenses, so you can swap between a wide angle, a telephoto or a macro lens for different jobs. Smartphones, disposable cameras and basic compacts have a fixed lens built in.

A wide-angle lens in the 20mm to 35mm range takes in a broad angle of view, so a whole valley, coastline or skyline fits in the frame. A telephoto does the opposite, magnifying a small part of the scene, and a fisheye covers so much that it bends straight lines.

At the same aperture and subject distance, a short focal length gives more depth of field than a long one. That is why wide-angle lenses keep both near and far objects looking sharp, and why landscape shooters favor them. Telephoto lenses are the ones that give shallow focus.

An 85mm to 135mm lens lets you stand a comfortable distance from the person, which keeps facial features in natural proportion instead of enlarging the nose as a close wide-angle does. Its narrower view and shallower depth of field also blur the background, isolating the subject.

A fisheye is an extreme wide-angle lens that can cover around 180 degrees. To fit that much in, it bends straight lines into curves, especially near the edges of the frame, which exaggerates the wide-angle look. It does nothing special for color or background blur.

In black and white, a colored filter passes light of its own color and blocks its opposite. A red or orange filter, for example, darkens a blue sky so white clouds stand out, while a green filter lightens foliage. The filter changes the tones, not the color, because the final image has none.

Light reflecting off non-metallic surfaces such as water, glass or wet leaves becomes polarized. Rotating a polarizing filter blocks that polarized glare, so you can see into water or through a window. A neutral density filter only darkens the whole scene and does nothing about reflections.

A graduated gray (graduated neutral density) filter is dark on one half and clear on the other, with a gradual transition. Placed with the dark half over a bright sky, it holds back the sky so the darker land and the sky can both be exposed well in one shot.

A higher ISO amplifies the signal from the sensor more, so the camera can make a usable picture in less light. In practice it works like greater sensitivity, at the cost of more visible noise.

Raising the ISO amplifies the sensor's signal along with its noise, so high ISO pictures look grainier and lose fine detail. That is why the lowest ISO the light allows gives the cleanest image.