With today's sophisticated metering systems and automation, Manual exposure may be seen as arcane but it still has its advantages.
Long ago, before The Beatles entered the Charts, Manual exposure was the only exposure mode avilable. Many view it as an anachronism.
Why struggle to set the camera controls yourself to get a correct exposure when powerful algorithms will do it all for you?, It's not a struggle, though it does take a fraction longer to change settings. No matter what the marketeers try and make you believe, algorithms aren't intelligent and certainly aren't creative.
Why do 'serious' and 'professional' photographers use Manual? That's another myth, as on the whole they don't.
Manual settings make you learn about exposure. There is some merit in this. It certainly focuses the mind on what settings to make and more importantly the relationship between aperture and shutter speed.I wouldn't recommend this as the default mode for someone starting out, but would suggest giving it a go in 'learning mode' when there's time to carefully consider what you're doing. With the instant feedback on screen, and real time display with mirrorless systems, the learning process is quick. You can of course set the camera to Manual and use whatever aperture and shutter speed you want, but with Auto ISO set. There are still limits you need to understand, though this is really an automatic mode – there's a bit of a clue in 'Auto ISO'.
While some will use this as their default mode, it should be regarded as just another tool in the arsenal that's available should you require it, in the same way that you may want to occasionally use a tripod. With that in mind I'll give a few examples of when I prefer to use Manual exposure.
Studio flash. The exposure depends on the intensity of the studio flash units. The camera's shuitter has no effect, as long as it's at or below the synchronisation speed. It's only the aperture that can control the brightness. So, by manually setting the shutter speed to the synchronisation speed (often 1/125) and the aperture to that suggested by a flash meter, shoot away and all will be good. There are some higher end studio flashes that work with the camera's metering but then that's akin to using your Speedlights (where you can of course set the camera to Manual aperture and shutter speed settings letting the camera control the flash output). A good result of using Manual is that you can set slower shutter speeds to record ambient light. This means you can have a frozen image of a subject together with some movement, or allow the background to become visible. Adjusting shutter speed means you have control over how much of that ambient light is recorded. You have to make that decision, algorithms can't.
On and off-camera Speedlights. For creative effects as described above for studio flash. Technically with the flash output adjusted automatically this can be regarded as Automatic Exposure but the camera's Mode setting is Manual. It's possible to go the whole hog and set the Speedlight to manual output of course, for a purist experience.
Close-up and Macro work. More specifically for insect work with flash, where I set an aperture I need which is generally below f/11, the shutter is set at the synchronisation speed, and the flash output is controlled automatically.
Tricky lighting. This can cover numerous scenarios, but I'll consider just a couple for illustration. A subject in constant light but moving about so that sometimes it's in front of a light background one moment and a dark one the next. This could be a bird with shade or sky behind. An aircraft against a sky with varying degrees of brightness and occupying varying amounts of the frame area. Automatic modes would struggle to various degrees. In these cases I take a reading from a mid-tone such as grass and use that, shooting away knowing the subject will be well exposed and not worrying about having to apply exposure compensation. Of course you need to keep an eye on the light level for changes but that soon becomes second nature. Taking a reading from such a mid-tone is something I do in the Automatic modes when necessary, and at the very least should give you an indication of what the exposure should be.
Bulb setting. Some cameras have this as a dedicated setting, some have it at the bottom end of the shutter speed range. Either way, the exposure is controlled by you. I typically use it when I want to use a shutter speed longer than that timed by the camera such as very low light level photography.
Next time I'll look at Aperture Priority Mode.
All text and images © Keith Rowley 2021