Digital Photography/Pre-Processing

From Wikibooks, the open-content textbooks collection

This section deals with the decisions you need to make before you take your first shots.

• The choice of compression and resolution
• the choice of manual or automatic mode

[edit] Choice of Compression and Resolution

The primary choice you must make when choosing resolution/compression is how often do you want to change memory cards.

You should always take photos at your camera's highest resolution and with minimum compression (normally known as superfine), even if you just want photos for the web, you never know when you might take the perfect photo you want to print for posterity. With some cameras, you can store the photos in raw format. While these allow for maximum flexibility, you're unlikely to need this level of flexibility unless you want to use advanced post-processing techniques.

Memory cards have very high amounts of storage and even at high resolution, they can hold hundreds or thousands of digital images. On top of that, they are cheap and plentiful. Given that, there isn't much need to shoot photos at anything less then your highest resolution settings. If for some reason you need low resolution photos for a particular circumstance (web, e-mail, etc), it is best to crop and down-sample your images in post-production. You will end up with much better results and have a lot more flexibility in how the final product will turn out.

[edit] Choice of Manual or Automatic Mode

The purpose of this guide is to help you understand what setting your camera handles when it is in automatic mode and how, by taking control of these settings, you can improve your photos.

The three most important items your camera's automatic mode controls are the flash, aperture size and exposure time (usually called shutter speed). These three all affect the lighting of images.

• The flash affects the lighting in an obvious way, but in some situations a flash will be inappropriate (for example when there is something in the shot that will reflect the flash or if you are photographing animals that will be scared by the flash).
  • Specific conditions under which you would want to use a flash are:
    • Indoor photographs not requiring natural light
    • Portraits
    • Night Photography where natural light is again not important.
    • Daylight Photography when shadows are not desired on the object or person.
  • Conditions under which using a flash would spoil your photographs are:
    • photographs in which you want to capture the effect of dim lights on objects, portraits, landcapes, etc.
• The aperture can be thought of as the "iris" of the camera. When the aperture is wide open lots of light gets through, so the image will be brighter. However, having a larger aperture will mean you get a narrower Depth of Field, which means a limited range of focus.

• The exposure time is the amount of time the aperture is "held open". The longer the time, the more light can be received, so the image will be brighter. However having a long exposure time has one major disadvantage, a long exposure time means motion (either on the part of the subject or on the part of the person holding the camera) is more likely to cause problems (i.e. blurring).