Members of the mysterious and magical craft of photography may have mentioned that mastering manual mode may be the most meandering path to making magnificent masterpieces. There's a shortcut, though.
Mode of the Wizards
For some beginners, the "M" dial stands for "magazine," "master," or simply a mode for hipsters and elitists. Indeed, there are photographers who may tell you that you can't make good photos unless you solder your dial at the M position. While I, personally, have it set there, I'd like to discuss the advantages and disadvantages of using manual mode versus the semi-automated modes.
Back to the Basics
For those that are starting up, there are three basic settings for something called "an exposure." This is a term for capturing an image in camera with the appropriate level of brightness. If the image is brighter than it should be, it is called "overexposed." Otherwise, it's "underexposed." The correct brightness, or correct exposure, is a subjective term. Sometimes, we might want a slightly lighter or darker image.
In order to create a well-exposed image, the camera needs to have the following three settings in the right combination: aperture (measured in f-stops: f/2.8, f/8.0, f/5.6, etc.), shutter speed (measured in seconds: 1/250, 1/800, 1/50, etc.), and ISO (with values like 100, 640, 1,600, etc.).
Remember those old-fashioned cameras with bellows and a cap in front of the lens? Here's how these three parameters fit there: the size of the opening of the lens is the aperture. The bigger the size, the more light enters, and the brighter the image is.
When the photographer removes the cap, light enters through the lens to the back part of the camera where a plate with photosensitive coating resides. The longer the cap stays off, the brighter the image and vice versa; the shorter the duration, the darker the image. This is the shutter speed of the modern camera. On DSLRs, there are two thin lamellae that cover the sensor and block the light. When you photograph something, these open and close for the duration defined by the shutter speed setting.
There are different types of plates and coatings. Some react faster, while others are slower. This is how the ISO setting on the modern cameras work. The higher the setting, the faster the sensor reacts to light and the brighter the image becomes.
That's all the mystery behind these three settings: they are mostly for controlling how dark or bright an image is. There are side effects such as the depth of the focus field (the blurred background and foreground), motion freezing, noise, and others. If we photograph a static object, there are many combinations of values that will give you the same result. It is like having three numbers that when summed must equal 10. You can have 1 + 2 + 7 or 3 + 3 + 4, or 1 + 8 + 1. This is why the statement "correct settings" is the shortest joke in camera clubs.
Semi-Automated Versus Manual Mode
You know what manual mode is. That's when you freely fiddle with the aperture, the shutter speed, and the ISO. Semi-automated modes let you lock some of the settings manually, while the camera calculates the rest of them for you. How does it do it? It has an arbitrary level of exposure called "18% gray" and simply calculates values for the non-locked settings that produce that kind of exposure.
If I have to use the sum-of-numbers-analogue, that's when you say "I lock three and five" and the camera calculates the third value: two. Or you lock "four" and the camera thinks that "one and five" would be suitable for your image. In cases like the last one, the machine may not come up with the best combination of numbers. This is when you might regret using semi-automated modes.
Advantages and Disadvantages of the Semi-Automated Modes
The obvious advantage is that the camera helps you by figuring out the settings for you. One of the most used semi-automated mode is where you set the aperture. That decision is based upon the focal depth you'd like to have: a smaller value makes for a more blurred background (often used for portraits) and a greater value makes more objects in focus (used by most landscape photographers). Semi-automated modes are very convenient for photographers who have a more photojournalistic approach to their projects, where capturing important moments is the ultimate goal and dialing settings manually may ruin that opportunity.
The drawback from using these is that your exposure may vary from shot to shot, depending on the variety of subjects in frame. If you photograph a wedding and you make a group portrait of groomsmen in black suits, the camera may think that the image needs to be brighter. As a result, those photos will be overexposed. At the same time, if you take photos of white-dressed bridesmaids, the camera may think the subjects are too bright and underexpose the result. In reality, both groups of portraits have to be with the same level of exposure, because they are taken under the same lighting conditions.
Another drawback of semi-automated modes is when using external flash. When the camera guesses the settings, they may vary from shot to shot. The flash power needs to be automatically adjusted as well. This is not a function many flash guns or strobes support, and if they do, they are more expensive. The ability of the light sources to be adjusted automatically is called TTL. The flash "talks" with the camera, firing one or more pre-flashes in order to make better guesses on the power level it has to be adjusted to.
If you want to give your clients or viewers images that have a balanced exposure, but your shots vary, this will cost you more time in front of the computer, which is the price of the convenience of using a semi-automated mode.
Advantages and Disadvantages of Manual Mode
There is a misconception that for manual exposure you have to dial in settings every time. That is not the truth. If the lighting conditions are the same, you adjust your camera settings once and then simply focus on your framing and composition. This establishes exposure consistency from shot to shot and gives you the possibility to work with a flash that is not necessarily the most expensive one. Even the cheapest flashes work with manual settings. This also spares you the somewhat cumbersome operation of balancing the exposure of photos in post-production. Imagine you have to shoot a panorama that you need to stich in software, and all your photos were shot with slightly different exposures. This is where manual mode comes in handy.
The disadvantage of manual mode is that you need to dial those settings in manually. One might think it is like finding a needle in a haystack. There's something called "an internal camera meter," which helps you guess the exposure easily. Using that meter, you can nail the settings with the first click almost every time. I have already covered that topic in a previous article. You should know what the side effects of the three basic exposure settings are in order to choose the best combination.
Let's say you want to photograph a portrait with a blurred background. Your aperture has to be a smaller value. Let's say you choose f/4.0. It's a bright, sunny day, so you can keep your ISO at a low value to avoid noise, and the only step that has been left is to set the shutter speed. Point the camera to the subject and dial in the shutter speed until the white dot is around the zero. Remember, you can always check the results on the back of your camera and make further adjustments if necessary.
If you learn the basics of photographing in manual mode, you will be able to make a correctly exposed image with any film camera as well.
Every mode has its supporters, and this is why they exist. At the end of the day, it is the final result that matters, not how you achieve it. If you shoot in semi-automated modes and make your clients and viewers happy, that's what you should care about. However, if you find yourself spending a considerable amount of time in front of the computer tweaking exposure, it may be a good time to consider shooting in manual mode on the next project. Manual mode is not exclusively for professionals. It's for those who want consistency and absolute control of the exposure. I have taught several non-professional photographers how to shoot manual mode, and they admitted it made their photography easier, contrary to the popular belief. Don't be afraid; try it out as well.