This is actually a pretty awesome question. Many beginning photographers don’t quite understand all the power their cameras are capable of, so it’s best to explain some of it to help folks take the best photos they can.
Manual mode is one of those elusive settings that not a lot of photographers know what to do with. When I first began photographing about a decade ago, I avoided Manual mode as much as I could. Auto mode was my best friend and honestly, I think I took some pretty great photos with that setting. It wasn’t until years later that I discovered why Manual mode is so important and why photographers might want to use it.
If you look at the mode settings on your camera, you’ll likely find Auto, Aperture Priority, Shutter Priority, Manual and a few presets, such as Sports (Action), Night (Low Light), Beauty (Bokeh) and a few others. Don’t worry about these presets right now. All they do is prioritize some settings, depending on which preset you’re using.
To keep a long story short, Manual mode allows the photographer to fix the ISO, aperture and shutter speed settings. You can also set your white balance under this mode for most cameras and perhaps always change that setting on other cameras, no matter the mode you’re in. Anyway, instead of keeping your camera in Auto mode and allowing the camera to make all the decisions for you, you’ll set everything. Instead of switching your camera to Aperture Priority mode where you would choose that setting and allow the camera to set everything else, again, you would make all the decisions for your camera’s settings. When you’re in Manual mode, you’ll tell the camera which ISO setting you’d like to use, which aperture setting you’d like to use, and which shutter speed you’d like to use.
Now, I understand that to a beginner, this seems overwhelming. If you don’t know a lot about photography yet, it is overwhelming. But remember, that’s only because you don’t know a lot yet. Once you learn what each one of these aspects of your camera does, you’ll be flipping these settings around like crazy. It’s honestly not that difficult. All you need to do is wrap your head around a few concepts.
So here’s a question for you. When might a photographer want to use Manual mode? I mean, if Auto is so great, why not just use it all the time? The answer is, when you’re goal for the photograph is different than the camera’s. Here’s an example. Let’s say you’re taking pictures of your son’s soccer game. You have your camera set to Auto and you snap away. Your goal is to have the resulting photos be crisp and clear because there’s lots of action and nobody really wants to see pictures full of motion blur. Since the camera has no way of knowing that you wanted crisp results of all the fast movement, it merely composed the photo for the proper exposure (lighting). It may have chosen to adjust the aperture setting to deal with the light in the scene as opposed to quickening up the shutter speed. If you were using Manual mode, you’d know that you would need to use a fast shutter speed because that would coincide with your goal of sharp photos of lots of action. You’d likely also set the aperture yourself to obtain the desirable background blur. While taking shots like this, it’s very common to set the ISO to Auto because it’s so much easier to let the camera meter the atmosphere for the proper exposure.
Another example might be when you’re taking photos at an indoor birthday party. It’s dark and the birthday girl or boy is blowing out the her or his candles on the cake. You want to take a photo and you use Auto mode. This is fatal mistake. During situations like these, you’ll need to manually hasten the shutter speed so you don’t get motion blur again and you’ll probably want to set the aperture nice and wide as well so it’ll let lots of light in.
Finally, another example of when photographers use Manual mode is when they’re in a fixed scene and when they want consistent photos. This is generally the situation when taking studio shots. The lighting in the studio is always the same and the subject of the shot is always sitting in the same chair. Senior photos are a good example of this. Once you meter the scene with the camera and choose the proper exposure settings, there’s no reason to change them. Manual mode is great for locking in camera settings so the camera doesn’t constantly try to choose them over and over again, which could sometimes cause varied results.
I hope this helped you understand what a camera’s Manual mode is and why someone might want to take advantage of it. If you have any questions, please ask. Thanks!