If you have switched to a DSLR, then you have a few choices to take photos. The fact that you switched to a DSLR is that you wanted to try out the capabilities of a camera than just point-n-shoot. A DSLR will very likely have a ‘mode dial’ or a knob that you can use to set various settings for different situations.
Auto – The Auto mode is your point and shoot mode, where the camera makes all the decisions about exposure. Exposure is basically the amount of light that the camera lets in. It is a combination of the size of the shutter opening and speed. With more opening, the shutter can close faster and vice versa. So, in theory, you can get the same amount of with a combination of these two. Also in Auto mode, cameras save the photo is a JPG format – i.e., the chip inside the camera processes the image as it sees fit and saves it. JPG format compresses the image and saves disk space. In auto mode, the camera also decides to use the flash when it sees the flash as necessary.
P – The P mode is the ‘Program’ mode. In this mode, the images can be saved in RAW mode. In RAW mode, there is no pre-processing and the size of the image is much bigger, depending on the pixel size you have selected. On my Rebel XS, I set the camera to use the maximum resolution, so an image in RAW mode is about 10 Mega bytes. In the P mode, you can decide to switch off the flash. A flash is needed for darker lighting, but it also takes away the detail on the subject unless it is controlled. Without flash, you can capture more detail and edit the photo in a photo editor and add light as you see fit. I use P mode when the lighting is ‘difficult’ or challenging to assess. In areas where there is much contrast such as sunlight and shadows, the P mode is a safe bet. A practical example is when you are in a garden with a lot of trees and plant and the subject is covered with both sunlight and shade.
A – The A mode, is called the Aperture priority mode. In this mode, you control the aperture i.e., the size of the opening. There will be a second dial to control this (along with speed). When you have the control knob in A mode, using the second dial you can only change the shutter opening. Shutter openings are dependent on the lens. If a lens has a rating of F1.8, then the maximum opening is 1/1.8; The more expensive lenses have a bigger opening i.e., a smaller F number. With a bigger opening, the depth of focus (DOF) is smaller. That means, the part right around where the lens has focus comes out sharper and the rest is blurred. This effect is great on portraits and wherever you want to isolate the subject such as a flower. The smaller the opening gets, the DOF increases – i.e., the area of the photo in focus increases. If you want to shoot landscapes, you want F8 or F11, etc. So the A mode can be used for landscapes (higher F) or isolation (smaller F)
T – The T mode is called the Shutter priority. In this setting, you select the amount of time the shutter needs to be open and the camera decides how big the opening should be. This mode is predominantly used to deliberately set the time of exposure when you shoot flowing water such as in a waterfall. The more time the lens is opened, you will see the ‘silkiness’ of the water depicting the flowing of water. If you just take shot of a waterfall in Auto mode, you will only see sparklets of water. The increased opening will cause the sparklets to form a stream and give the appearance of ‘flow’.
M – The M mode is called the Manual mode, where you set the BOTH the time and opening of the shutter. You would think with the Shutter priority or the Aperture priority modes, you are covered, but the camera cannot make the best decision as compared to the eye. In situations where the lighting changes quickly, the eye can be the best judge. If you have to use this mode, I suggest take some shots with the P/Auto mode, read the parameters while viewing the photo and take those as the starting point.
When you take photographs, study the image and vary the setting and re-compare. You will get a good sense which direction you need to go i.e., increase or decrease exposure.