Here is my guide to camera controls for Digital SLRs. For Nikon, the settings are P for Program, S for Shutter speed priority, A for Aperture priority and M for Manual. Canon uses Tv for Time Value in place of S and uses Av as Aperture Value.

Program mode

This gives little control but is fine for daylight or if you don’t want to choose a shutter speed or aperture setting. If in low light handheld, Progam is still fine is ISO is on Auto – then your shutter speed doesn’t drop too close to 1 second. Auto ISO will have little effect on daylight photos, so it is a good idea to leave it on anyway.

I’ve just checked on my camera and here the settings you will experience in P, from a bright scene to a dark scene.

  • 1/2000 f/22 looking at a bright surface (sand, metal) or at the sun
  • 1/1000 f/16
  • 1/500 f/11 sunny day
  • 1/250 f/8
  • 1/125 f/5.6 cloudy or shady
  • 1/60 f/4
  • 1/30 f/2.8 indoors
  • 1/15 f/2
  • 1/8 f/1.4 night time

You might notice that  as the scene gets darker with each step, the shutter speed is brighter by 1 stop (halfed) and the aperture is brighter by a stop (changed by 1.4 – see Aperture Scale post). Doing either would let in 2x as much light (“one stop”, both together means 4x the amount of light (“two stops”). There are a few in between steps too – between 1/125 and 1/60, you will find 1/100 f/5 and 1/80 f/4.5, with are increments of 2/3 of a stop (1/3 brighter by shutter speed and 1/3 brighter by aperture). If you increase by 2/3 for three increments, you’ve increased by 2 stops.

For each situation, I expect those settings to come up at about ISO-100. As you increase the camera’s sensitivity by increasing ISO value, the shutter speed will get shorter and the aperture will get narrower (letting in less light in an instant).

Shutter priority

By keeping Shutter speed fixed at a daylight speed like 1/320, your aperture will get wider (like f/2.8) in the shade to less in more light and will get narrower (like f/22) in bright sunlight to let in less light.

If you are in low light handheld, you’ll probably shoot around the slowest value which will get sharp pictures. On a cropped-sensor DSLR, the factor is 1.5. At 50mm, you would aim for 1/75 of a second. At 100mm, you should shoot faster than 1/150 (such as 1/160 or 1/200).

For sport you would set a short shutter speed (say 1/1000) and your aperture and ISO could be allowed to change depending on time of day and if the player is running into the shade or sun. At a fixed lowest ISO, your aperture could go from f/8 in sunlight to f/4 in the shade (2 stops of light difference) and probably f/2.8 in the evening. If you set your ISO from 100 to 200, you could shoot at f/4 in the eveing to get more in focus. Or you could shoot at 1/500 f/2.8 ISO-100 if you are willing to accept a few blurred shots.

You would also use S mode for landscapes or nighttime to capture movement of cars, people, water etc. At 1/2 second, your aperture at night might be f/2.8. In the day it could be f/22, but it could jump to f/16 or f/32 if you aimed at something darker or light respectively, or if clouds changed the sunlight.

Aperture priority

I find this setting more useful than the previous mode.

In A or Av, you can shoot portraits at a wide aperture (f/1.4 or f/2 or f/2.8) to blur the background and get a short shutter speed (especially with a long focal length).

Use this mode for landscapes too. If you are shooting in bright light or with a tripod in darker scenes, then set the aperture to get plenty of Depth of Field (to have more foreground and background in focus). I like to use f/11 at 18mm or 24mm, since that gets a lot in focus and is before the limits of diffraction* (see note and end). When I shoot a landscape at f/11 with a tripod, I would use A (instead of S), since I don’t usually care if my shutter speed is 1 second or 1/500 (unless movement of water, people, cars, etc. could be distracting).

If I shoot handheld, I might shoot at f/5.6 knowing that my shutter speed might go from 1/125 to 1/500. I watch in the viewfinder – if it drops to below 1/125, I would consider steadying my feet more, using wide a aperture (like f/4), raising ISO in the shade, or putting my camera on a make-shift tripod like my camera bag, table or rock.

Manual mode

Briefly, this mode gives you total control of shutter speed and aperture value.

Manual mode does give a metering function. The horizontal bar with a minus on one side and plus on the other will help you. If you the line goes to the minus side, you need change your shutter speed and/or your aperture to let in more light. On the plus side, your current settings will give an overexposed photo so you should shorten your shutter speed and/or use a narrower aperture until the meter is back at zero.

Of course, you might want an under- or over-exposed photo for creative purposes. Or if you think the meter is being confused by backlighting. Or if you have bright sky or sun in your photo and there is an object in the shade, a correctly exposed photo will have  the sky close to white and the shade too dark. You could choose to have darker settings to get the blue back in the sky, or use brighter settings to get shade details and the expense of a bright sky (maybe you can crop out the sky or use it creatively or in black and white).

Manual exposure means that if you walk into the shade from the sun, you need to remember to check your meter again. I like to use my intuition and experience, to increase exposure by 2 stops walking into the shade. At the same time for this move, I can choose to use a slower shutter speed, wider aperture or higher ISO or a combination of these to suit the situation. That may sound complicated, but it becomes a quick decision with experience.

The advantage of the settings not changing from scene to scene, is that the camera isn’t overly sensitive to underexposing the ground if you get a bit more sky or sun in the the top of the photo. And the photo won’t suddenly overexpose with a slower shutter speed if you crop the sky and sun out.

Reasons to choose Manual:

Firstly, an understanding of shutter speed and aperture is important for effective use of Manual mode. If you don’t feel capable yet, stick to P, then move to A or S. But also learn to use AE-L to lock the exposure so you can recompose with more or less sky. And also learn to use the Exposuse Value (EV) settings for the 3 modes, to make the scene brighter or darker (if you think the camera’s “correct” calculated exposure setting are confused by the lighting, or you want to be more creative with high key or low key looks).

Program mode gives very little control over shutter speed or aperture, so photos tend to look average. But if you pass your camera to a friend to use, P is probably the best mode (other than the green Auto button).

The downside of Shutter Priority mode:

At say 1/1000 and a fixed ISO-100, the aperture will drop to the widest (say f3.5 on a kit lens) and the viewfinder will indicate Lo (for low or insufficent lighting). The camera will take the photo but will be underexposed. Similarly, in daylight at 1 second in S mode, the aperture will set itself to  f/22 (the narrowest value on most lenses). Yet it will probably give an over-exposed photo and the camera will complain that it can’t choose a narrower aperture, by indicating Hi (higher Aperture needed). If you were in Program mode, you would probably end up with 1/500 f/11 (with lens in focus). If you were in manual, you could set shutter speed to 1 second and aperture to f/22, then decide that you’d be happy to have something like 1/30 shutter at f/22 to get a correct exposure.

The downside of Aperture Priority:

At f/22 if you walk from the sun into the shade, shutter speeds could go from 1/125 to close to 1 second. A fixed low ISO, your shots will be blurry and you might only realise later. At night, your shutter speed might be insufficient at the 30 second maximum, indicating Hi (higher shutter needed) and giving an unexderexposed photo. If you were in Program mode, your aperture would change to something usuable like f/4.

*Diffraction: If you shoot at f/13, f/16, f/22 or f/32 or in between steps, the small opening of the aperture causes diffraction. More of the scene is in focus, but overall the sharpness and picture quality drops (very noticeable if you zoom in 100% on a computer or make large prints).