What Is the Mode Dial?
The image above is the mode dial on a DSLR camera. This is sometimes referred to as the PASM wheel, which stands for Program, Aperture, Shutter, and Manual mode. Your camera does not need to be a DSLR (a big chunky camera with removable lenses) or a mirror-less (slightly smaller camera also with removable lenses) to have a mode selection as shown above. Most bridge cameras and many compacts have this wheel.
If Your Camera Does Not Have a Mode Dial
I am not a proponent of replacing hardware until one has squeezed every last bit of functionality from their current camera, but I do feel that the mode dial is necessary in order to take the next step beyond auto mode. If your camera cannot be set to at least manual or aperture priority mode, perhaps the time has come to consider a hardware change. Refer to our section on Essential Gear to see the cameras we recommend that can shoot in manual mode.
What Modes Are There?
In the image above, many icons sit on the right side of the wheel. My advice is to not concern yourself with them. In essence, they are still automatic settings that need a hint as to what you are trying to accomplish. For example, the little athlete indicates that the shutter should be opened and closed quickly as a long exposure will cause a motion blur. But the computer can still play around with other variables and produce a result you might not have wanted or expected.
By selecting an icon, the influence you have over the camera settings is still not sufficient. You want full control or so much control that the camera just has to worry about filling in one variable to get the image exposed correctly. I might sound cryptic at this stage. Bear with me; things will become clearer in the next paragraph.
The Two Settings That Matter: A and M
To understand these two settings, we must revisit the exposure triangle as explained in the second post. Let’s use a film camera again as example to see how exposure works.
- Shutter speed: The film in the camera is light sensitive and an image will form if exposed to light. This happens if the shutter that normally blocks light is flipped up. Expose the film to light for too long and you have an overexposed image. Expose for too short a period and you have a dark image.
- Aperture: Of course, the time that the light blocker is removed (shutter speed) is not the only factor. The size of the hole (aperture) that funnels in the light also plays a role. A bigger hole will allow more light to flood the film and the image will be exposed quicker. The size of the aperture is indicated by your camera with an f-stop. The number you see, for example f/1.8 or f/16, offers information that is a bit counter-intuitive since an f-stop of f/1.8 indicates a bigger aperture opening than f/16.
- ISO: The final piece of the puzzle is the sensitivity of the film. If the film is very sensitive, it will only need a little bit of light or light exposure for a very short span of time to form a properly exposed image.
These three factors, which all play a role in how quickly an image is exposed on film are referred to as the three sides of the exposure triangle.
If the aperture (the hole that funnels in light) is very small, either the film (sensor in a digital camera) needs to be exposed to light longer to get a proper image or the sensitivity of the sensor (ISO) must be increased so an image can form on it faster.
Let’s restate the paragraph above in photo jargon: For a small aperture of say f/18, the shutter speed (the time span of exposure) may need to be increased from1/1000 of a second to 1/10th of a second or maybe the ISO needs to be increased from ISO 100 to ISO 800 so an image can form faster.
If the aperture was opened up large to about f/2 (a lot of light will come flooding in), then shutter speed could be brought down to 1/500th of a second again or the ISO (sensitivity) could be decreased to ISO 200 to expose the image properly.
To use another example, if the ISO (sensitivity of the recording medium) is pushed up very high, say from 100 to 800, an image is going to form very quickly, so the aperture needs to be made smaller and the shutter speed must be brought down.
I hope this is starting to make sense to you. If not, please revisit our first four posts from “The Basics” category again.
M Mode – Manual
This mode is relatively easy to explain. You decide to give each of the three sides of the exposure triangle a value. For example, you decide to set ISO to 100, aperture to F/5, and shutter speed to 1/200. By setting all three variables, you have just sent the camera’s computer on vacation; it has absolutely nothing to do, as you have taken full control of the settings. Your photos will come out either under- or overexposed, depending on how much light you have around you at that stage. Studio photographers love to use this mode because they have ultimate control over every setting and use a light meter to predict exposure.
Av or A mode – Aperture priority
In aperture priority mode, it is your responsibility to set the aperture size (f-stop) and sensitivity (ISO). You have now set two of the three sides of the exposure triangle, so in the camera computer’s universe, only one variable remains: the shutter speed. If the light around you is lower (indoors for example), it will expose longer, as it knows how much light it needs to soak up for a proper exposure. If you are on the beach in sunny conditions, the shutter can open and close very fast, as there is a lot of light around to flood the sensor.
Why do you want control over the aperture size? If you are still unclear about depth of field, refer to the third posting. A shallow depth of field (for example f/1.8) can give you a lovely out of focus background for a portrait, but you do not want this effect for a landscape shot.
What about S – Shutter Priority?
This mode is not used widely. Since shutter speed and ISO are pre-defined for this mode, the camera only has aperture size to play with in its attempt to expose a proper image. This can cause depth-of-field issues. The one instance where shutter priority becomes necessary is when a main subject (the bride above) needs to be sharp with the background a motion blur.
And the Winner Is…
My recommendation is to use aperture priority mode 95% of the time. If you let the camera only worry about one variable, shutter speed, then it will make a safe predictable choice in its attempts to expose your photo correctly.
In the next post I will show you some everyday scenarios and how to set your camera’s ISO and f-stop for great photos in aperture priority mode.