Friday, 1 March 2013

Camera Cheat sheet - part 1 - The basics

Originally published: 2010-05-14 on my old blog

I've put this brief intro together in the hope that it will explain the basics
of some of the jargon you'll encounter around digital cameras, and how to make the
most of your photos. It's part one in a series of posts, the size of which I haven't decided yet.
Enjoy!


Aperture or f/number

Relates to the size of the circular hole through which light enters the camera. A wider aperture means more light will enter the camera.
A higher f/number gives a smaller aperture (less light), a lower f/number gives a wider aperture (more light).
Aperture controls depth of field, which is the amount of an image which is in focus. A wider aperture (smaller number) gives a smaller depth of field, meaning
less of the area in front of and behind the object you have focussed on will be in sharp focus. Use wider apertures for portraits (such as f/11), and narrower ones (such as f/2.8) for landscapes.


Larger aperture lenses tend to be more expensive as they use higher-quality and more glass elements in their construction.

Shutter Speed

Controls how many milliseconds the shutter remains open, capturing light for your image. The longer the shutter is open, the more chance there is that you will either shake the camera,
or the subject you are photographing moves, blurring the image.
You will usually need a tripod for any exposure longer than 1/60 of a second. For fast-moving objects you will need faster
shutter speeds to capture them without blurring the image. (1/200 or faster). Cameras with vibration reduction or steady-shot technology will allow longer exposures without blurring the image through
camera shake, but will not affect motion-blur from fast-moving objects.

White balance and colour temperature

Often left on auto. A higher "K" (Kelvin) value, the higher the colour temperature, and the warmer (redder)
an image will look, a lower temperature results in a cooler (bluer) image.


For example you may have to change this to reduce the orange tinge you often get under tungsten lighting, by setting a lower colour temperature in post-processing, or selecting the correct temperature preset in the camera.

Focal length

Our eyes' natural focus length is around 50mm, anything lower than this is called wide-angle (17 - 50mm), anything higher than this (50mm+) is called telephoto. Wide angle lenses allow you to see a larger
field of view (more objects), but those objects will look smaller. Telephoto lenses will show you a smaller field of view, but the objects in that field will look larger (more "zoomed in").
Typically telephoto
lenses will have a higher f/number (thus let in less light) than wide-angle lenses.

Exposure Compensation

In certain circumstances, you may find that the exposure that your camera has picked for an image is too dark or too bright, in this case you can re-take the image and adjust the exposure compensation to correct it.
For example by
default a camera will underexpose snow, making it look grey, rather than white.

ISO

This number relates to the sensitivity of the camera to light. The default is normally 100 ISO. The higher the ISO the more sensitive to light, but the more noise (speckles) you will get on the image.

In digital cameras it will simply amplify the signal. Useful in low light, or at night, to increase the shutter speed you can use and reduce blur, but at the cost of slightly increased noise.

RAW vs JPEG

An image saved as RAW saves the un-processed information straight from the camera's sensor. It means that you will have to process the image before you can see it on screen or share it with friends. However it also means that the camera
hasn't decided for you what the image should look like, and things like the colour temperature can be set correctly.
It also allows you to make bigger changes to the brightness and colour of the image than you would by re-processing a JPEG
image that's already been saved by the camera.

Modes

Full Auto (AUTO on most camera dials) - Camera controls everything for you, including ISO and Flash


Program (P) - Camera controls Aperture and Shutter speed to give correct exposure, may or may not control ISO


Aperture Priority (A or Av) - Camera determines shutter speed to use, based on the aperture you have chosen to give a correct exposure


Shutter Priority (S or Tv) - Camera determines aperture to use, based on the shutter speed requested to give correct exposure


Full Manual (M) - All settings can be changed simultaneously, up to you to work out correct exposure (maybe using a light meter).




Try to use your camera in Aperture priority, Shutter Priority, and Program modes, rather than leaving it on Auto, to learn more about how these affect your image.