Camera Exposure Modes Explained

There has always been a great deal of conflict within the digital photography community regarding which exposure mode is best. Many experienced photographers advise to only shoot in manual mode, while others say it is perfectly fine to rely on your camera’s automatic or semi-automatic exposure modes. This article aims to address this debate, explain the different modes, and provide advantages and disadvantages of each.

Your digital camera is a device which captures light, and while it may sound like a simple function it is truly a magnificent feat. It has sophisticated electronics which can automatically direct the camera on how much light to capture, or it comes equipped with alternative modes which provide varying levels of manual control to the photographer.

The four main modes that will be discussed in this article are

⦁ Automatic mode

⦁ Aperture-Priority

⦁ Shutter-Priority

⦁ Manual mode

Automatic exposure mode is a mostly fool-proof way of ensuring properly exposed photos. When you depress the shutter release the camera automatically sets the variables of the exposure triangle: shutter speed, aperture, and ISO. This can be an incredible feature as it can eliminate the common problem of missed moments caused by photographer frantically fiddling with camera settings, as well as freeing up the photographer to focus on other things such as composition. Moments pass all too quickly, and with the tremendous number of things a photographer has to be concerned with, automation can be a great thing.

However, by relying on your camera to determine all of the exposure settings, the photographer is giving up a great deal of creative expression. The creative decisions made possible through manually controlling exposure are what can turn a dull, flat image into a photograph which can truly recreate a moment in time.

Automatic exposure mode uses your camera’s built in reflective light meter and sophisticated algorithms to attempt to optimally adjust aperture, shutter speed, and ISO to set the exposure to 13% (middle) grey. This means the camera converts the image to black and white, averages all of the pixel tones, and then increases or decreases the exposure until it achieves 13% grey. This number was experimentally chosen by Kodak based on extensive studies, and often produces a “properly” exposed photograph. However, there are cases where the camera’s light meter can be fooled, resulting in an incorrect exposure, such as with images that are mostly white, or mostly black. In those cases, the camera will still attempt to make the image 13% grey, so whites are underexposed to look grey, and blacks are overexposed to also look grey.

white paper middle grey

The camera’s built in light meter will underexpose white making it look grey

black paper middle grey

Similarly the camera’s built in light meter will overexpose black, also making it look grey.

Both Shutter-priority and Aperture-priority provide a transition into the manual world. In these modes the photographer controls either the shutter speed, or the aperture respectively while the camera adjusts the other parameter to achieve 13% grey.

The benefit of these modes is that it allows the photographer to control key aspects of the photograph such as motion blur and depth of field. In Automatic mode, the camera may choose too slow of a shutter speed producing a blurry picture. Alternatively, the photographer may wish to intentionally introduce specific and targeted motion blur to imply motion, such as when capturing spinning wheels of a vehicle. Shutter-priority allows the photographer to control the amount of time the shutter is open, which directly effects how much a subject can move within that time window, and hence controls motion blur.

how to freeze action with shutter speed photography 101

DOF is another key variable a photographer often needs to control. This determines how much of a scene is in focus. DSLR cameras allow a photographer to produce bokeh effects, which is a de-focused or blurred background that serves to eliminate distractions and help accentuate a subject. This effect is highly desirable for portrait shots, but could be detrimental for shooting landscapes. In Aperture-priority mode, the photographer can choose what f-stop the camera will use, providing precise control of the DOF.

depth of field aperture bokeh blur photography 101

These semi-manual modes provide more control over image attributes that cannot be corrected in post, while still allowing the camera to automatically set exposure. In cases where the camera does incorrectly set the exposure, adjustments can be made in post, although at the expense of added noise.

This brings us to Manual mode. Here the photographer is responsible for setting aperture and shutter speed. ISO, which is the third variable effecting exposure, can still be set to auto or manual. If ISO is set to auto, the camera will continually make adjustments to maintain a 13% grey exposure. With ISO set to manual the photographer has full responsibility to capture the scene with correct exposure. This allows a photographer to create more dramatic, and moody scenes as well as allowing a photographer to correct for predominately white or black backgrounds.

There is no one “best” mode for all situations. However, if you find yourself in a fast-paced environment where missing a key moment would be catastrophic, such as a wedding, relying on manual mode without a great deal of practice can often lead to missed shots, blurred images, incorrect DOF, or incorrectly exposed images. In these situations things are often changing very fast, and a photographer typically has a multitude of factors to consider besides just camera settings, therefore some amount of automation is usually recommended.

In fast-paced environments with critical photographic moments, using Aperture-priority or Shutter-priority is often a good choice, but even full Automatic mode can be useful. In more relaxed situations where a photographer has a bit more time, and/or wishes to create a more dramatic image, Manual mode is often the appropriate choice. Here the photographer can take the time to correctly adjust his camera settings, and often take several test shots to ensure a good image. It is the recommendation of Journey Photo Academy that a photographer becomes highly proficient with Manual mode, and shoots in that mode whenever possible to hone their skill. Once a photographer has become intimately familiar and comfortable with manually setting exposure they will be equipped with the experience necessary to choose the optimal exposure mode for any situation.

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