I have bought a micro 4/3 camera recently and only getting into the basics of photography. What I heard on photo forums is that a rule of thumb is to try not to use an automatic shooting mode and prefer a manual mode. In the manual mode I can control shutter speed, aperture and ISO as well as many other settings. However, it takes quite some time to balance the aperture, shutter speed and ISO, and I am not talking about the other settings. So, I wonder why can't the automatic mode adjust these settings better? What makes it so difficult? Why should I always try to use the manual mode?
It's not so much that manual is better, but that manual is more controlled.
Shooting all the time on full manual will teach you what to do & what not to do. It will take longer & you will probably have far fewer keepers to start with, but you will learn as you go.
If you are shooting full manual, you have to balance up the depth of field you need - aperture - with the exposure time you must have to stop the action, against the ISO necessary to achieve a correct exposure allowing for the previous two settings.
Add to this manual focus, so you could choose in a wide aperture close-up to focus on the flower in front or the face peeking from behind, rather than relying on the camera to make that decision for you.
Running at full auto removes these decisions & does what the camera decides might be 'best' each time… which is rarely is what you actually wanted.
Many photographers actually use "Aperture-preferred" a lot of the time. This reduces your juggling act to fewer parameters. Think of it as 'I can choose most settings, but the camera makes sure the final exposure is reasonably consistent'.
You set your preferred aperture for the type of look you require, quickly check through the viewfinder to see if your ISO is about right to give you the exposure time you need, then you are pretty much back to 'point & shoot'.
Some cameras will override your ISO setting even in this mode, but you can usually switch that off, giving you better control.
I have my camera set up so that my single dial wheel controls aperture alone, but with one of two additional buttons, I can dial in ISO & exposure compensation. This gives me the fastest workflow. Manual/auto-focus is a hardware switch on my lenses, so if I'm sure my focus doesn't need to change for a while, I'll quickly flip across to manual focus. [I also have a focus/exposure lock button, but I don't often use it, as it disengages every time you let go.]
I don't think it's a great idea to be shooting in full manual. The same kind of people will tell you that auto focus is cheating...
The semi auto modes allow you to control what you're interested in at that point. Aperture priority mode is a fantastic middle ground that gives you control of the depth of field, and the camera makes sure you get well exposed shots. Most cameras also allow you to set an ISO in AP mode too, so the camera is simply handling the shutter speed as you shoot. If you want a slow shutter or are shooting fast action, shutter speed priority mode is useful.
Use these modes to get to know the camera and how it works. I think shooting full manual isn't a great use of time - you'll miss shots that you might have wanted to keep! Photography is surely about getting pictures at the end of the day.
It all depends on the situation and the style of photography you are into.
When I'm on holiday and I'm just taking generic landmark photos I'll keep my camera on aperture priority / automatic. Aperture priority is a nice middle ground where you can pick the idea DoF for the photo with the aperture & let the camera work out the rest.
My favourite type of photography is macro, here I exclusively use manual (Even Manual focus lens!) the camera struggles to understand the scene when I'm doing macro photography and would pick horrible setting for 99% of the shots.
Another thing I like to do is bird photography, for this I generally stick to manual or shutter priority. In both modes I would normally enable auto ISO just to ensure that every photo is fairly well exposed. Bird photography normally needs quick tracking and shutter selection depending on how fast the bird is moving (Is it in flight so 1000/1 shutter or sitting on a branch so focal length/1 shutter).
It's a good idea to use manual mode, it makes you think about why certain settings should be used. You end up understanding how to take certain styles of photos and this will make you a better photographer. This does not mean that manual mode NEEDs to be used all the time, and letting the camera automatically adjust parts of the settings is a really good idea sometimes.
If you find you are missing shots because you are in manual mode, use aperture / shutter priority for a bit that will help you get an understanding & appreciation of how to take "Good" photos :)
Cameras in auto mode will not understand the scene like we can, are you shooting fast moving objects? You know you need a higher shutter speed and the aperture / ISO is less important. Are you trying to isolate your subject from the background? then you want a nice wide aperture, the shutter speed is less important. The camera will not understand what’s going on all the time & that’s when you need to take control
The conjecture that you should use manual mode is based on the idea that your camera is not as good at doing the settings as you can be.
This idea becomes less obvious, and true in less cases, as technology progresses, and automatic modes become cleverer and cleverer. It retains its plausibility, however, when considering that the most excellent settings are sometimes informed by artistic choice, meaning, there are multiple ways of doing the picture settings well, but which one is a choice. With auto mode, the camera makes this choice; with manual, the photographer can (if he is good or fast enough), and through this, he or she is able to distinguish herself more from other photographers.
You are right, automatic mode will adjust some settings better than you can manually, for a simple reason: Your eyes are not good absolute light-meters. So, if you want to have correctly exposed pictures, you might have to take them twice (or more) to find the right settings if you start "out of the blue".
However, I talk about semi-automatic mode (A and S) here (and to some extent about M with Auto ISO). Full automatic mode (or P mode, for that matter) are generally worse than you at taking a nice picture. They will make some artistic choices for you. Do you need a nice bokeh or a wide DOF? Do you want to freeze the action or to have some motion blur?
Depending on the situation, using A mode (for a mostly static scene) or S mode (for whenever there is much movement that you need to take care of) with capped Auto ISO is what will often give you the best results. Don't forget to use exposure correction if you simply need to have a lighter or darker picture, or because some parts of the frame are really off and interferes with the light meter.
Auto ISO will allow you to go "further than the limits of your camera" (especially in S mode, where your lens' aperture can often be be a limiting factor), and most cameras use ISO boost as a last resort (with reason). But don't forget to set a cap on the max ISO, because most cameras have awful results at the high end of the ISO range they offer. You will need to experiment (or to read test) to find a value that works for you.
Learn with this, and you will find some time where you will need M mode. Those are when your camera doesn't have the right information to make a good exposure. Most of the time, you will be happy with exposure correction, but sometimes your camera just can't do a good metering: Lightning photography, astrophotography, birds in flight... In those conditions, what your camera "sees" before taking the picture is often not what will end up in the shot, so you are better off to manually control it.
If you switch to M mode for full control, don't forget to disable Auto ISO or you will have surprises.
The automatic mode is designed to give an inexperienced photographer an acceptable picture, because then they like the camera, recommend it to their friends, and more cameras are sold.
The first priority is to get the exposure right as an average over the scene. It works well most of the time, but if there is a great difference between the subject and the rest of the scene it will get fooled. Backlighting of the subject is particularly difficult. If nothing else, learning when to over or underexpose a stop or two will help a lot, perhaps coupled with spot metering.
The second priority is to keep the shutter fast enough to fight blurring due to camera movement. Modern image stabilization helps a lot with this, but it may lead to a faster shutter than you need. That will either use a larger aperture for less depth of field or higher ISO for more grain.
It works pretty well most of the time. If you are taking a shot that you only have one chance at, the auto mode has a lot to recommend it. If you are taking a shot in bright sun there is enough light that it is hard to miss. If you have a creative reason, especially if you have a tripod, it may not do what you want and the other modes become attractive.
Using the partial or full manual modes can make you think more clearly about why you are taking the shot and what settings will get you the shot you want. In theory you could think about this in auto mode, but the bias is just to fire away.
The bottom line is to use the approach (and the camera) that gets you the pictures you want to shoot. If you miss one, it is important to think about why that was and learn from it.
Personally I would try manual for fast moving object like sports.
Set on (M)anual, select the f/stop you wish, and USE AUTO ISO. This guarantees a proper depth of field, and proper shutter speed for the action you wish to capture (frozen or blur). ISO will adjust for the light condition. Set light meter to (o) avg center. Depending on the m43, the metering follows the focus. Good luck.