I have a disclaimer before I even begin this article. I shoot much more often in Shutter or Aperture Priority than I do in Manual mode. I save Manual mode specifically for studio shooting, for some tripod work where I have a lot of time to get the settings perfect, or for situations where the lighting is very consistent.
Learn Manual Mode to better understand exposure
However, I think it is immensely important for you to try to periodically shoot in Manual early on, especially if you’re just learning. Take a look at your camera. How many buttons does it have on it? New cameras these days can have 20 or more buttons on them all doing different things, but in reality, there are only three settings that make the photograph: the ISO, the Shutter speed, and the Aperture.
Before you even go out, turn your camera to Manual mode and figure out the fastest and most comfortable way to change each of these settings. You’re going to do a lot of that in Manual.
Understanding shutter speed
The next step is to understand a couple of important points. The shutter speed always needs to be at least one over your focal length to offset handheld camera shake. So if you are at 50mm (on a full-frame camera), then your shutter speed needs to be 1/50th of a second. To freeze the motion of moving subjects such as people, I like a shutter speed of around 1/250th or 1/320th of a second, but you can get away with a little slower than that. You will need a faster shutter speed to freeze faster moving subjects like cars, etc.
For your aperture, the lower the number (such as f/2.8), the less depth of field and more bokeh there will be. This is counterintuitively called a large aperture because the size of the aperture hole in the lens is actually larger. This will also let in a lot of light due to the size of the hole. A small aperture (such as f/11 or f/16) will create a much larger depth of field, but the tradeoff is that it will let in less light.
The ISO is the sensitivity of your camera’s sensor to light. The higher the number, the more noise that an image will have, but the more sensitive to light it will be. Newer cameras can make beautiful photos up to ISO 3200 or even 6400, but older or entry level cameras can have a lower limit of around ISO 1600 (test your camera to find your comfort zone with its upper ISO limits).
If you want a lot of bokeh in your image, and you set your lens to f/2.8, that means the camera will be letting in so much light that you will usually want a low ISO. However, if you are shooting street photography, fast moving subjects, you want a shutter speed of 1/250th or faster, and/or a smaller aperture such as f/11 – unless you are in bright sunlight, you will often have to raise your ISO to be able to let in enough light to use those settings. In general, if it’s darker out, then your ISO will often have to go up unless you are on a tripod.
Now play with them
Those are the main considerations that you need to learn; now just walk out the door and mess around with your settings. Screwing around with the settings in Manual is the fastest way to start to learn them well. Start off with your aperture. How much depth of field do you want in the image? Once you pick that, then take a guess at the shutter speed and ISO and see how it looks. View the back of the screen, look at the histogram, and zoom in on the details.
If an image is too dark, then slow the shutter speed, raise the ISO, or use a larger aperture. If the main subject is too blurry, then speed up the shutter speed.
Try different lighting scenarios
Explore different lighting situations. Paying attention to lighting is the first thing that you should do before you take a photograph. How strong is the light? Where is the sun or artificial light in relation to what you are shooting? The strength of the light will be the number one factor in helping you figure out your settings. From there, you can figure out the depth of field that you want and if you need to freeze the motion of your subjects or not.
Get comfortable walking from one lighting situation to another. If you walk from the sun into the shade, what will you need to change to expose the scene correctly? Pay attention to scenes with both bright highlights and darker shadows. With these scenes you need to figure out which is most important to expose correctly. If the shady area is more important, then let in more light. If the highlights are the most important, then darken the scene so they are correctly exposed and the shadows are closer to black. If you are in sunlight, learn how your settings will change if you are shooting into the sun versus shooting away from it.
Go out in the morning, in the middle of a sunny day, at dusk, or in light rain. Learn how your settings change in each of these lighting situations.
Most digital cameras will show you the light meter reading for what they believe will correctly expose your image. For instance, if you choose the three settings, the light meter might show you that it thinks you are underexposed by one stop (look in your viewfinder for a + 0 – scale, press the shutter button part-way down to activate it). Keep an eye on this because it can help you, but also try to not pay too much attention to it. The point of Manual shooting is to learn the numbers yourself without relying on the camera. You can rely more on the camera later.
Conclusion and practice
The only way to learn these things is to experiment and do them. Shooting in Manual at first will make you screw up much more than in Shutter or Aperture Priority, but a handful of dedicated days of doing this will have you understanding the settings in a much more intuitive way. Then if you decide to shoot in Shutter or Aperture Priority, you will have a strong understanding of how to use those modes to the best of their ability.