Turning auto off and making your own, deliberate, choices is indeed the way to build up some intuition on how to capture the same scene in different ways. Shoot

Turning auto off and making your own, deliberate, choices is indeed the way to build up some intuition on how to capture the same scene in different ways. Shooting digital is easier. But often reviewing what you shot is hard on tiny screens in full sunlight. Depth of field is one of the more obvious things you control with the aperture. But another thing it impacts is sharpness. Depending on your lens, it likely is a little fuzzier wide open than it is stopped down a little. Basically, you are covering part of the lens and controlling the way it distorts the light a little. Wide open it diffuses the light a bit. And it will do so differently in different parts of the photo. Knowing how your lens performs under different conditions is something you need to explore through trial and error. Another thing it impacts is color and contract. Just how, depends on the lens. Some lenses have a clear optimum, others are better across a wider range of apertures. People spend a lot of money on glass to get these effects. In the same way, the shutter speed is not just about controlling the amount of light it is also about motion and motion blur that can both mess up your photo or be something you use creatively. The best tip you can give a beginning photographer to not too slow. Your camera might be able to handle it and you might have steady hands. But stuff still moves in your scene and it will introduce blur. Some types of photography you want to have fast shutter speeds to capture really crisp moving subjects (e.g. sports photography, moving kids). Even on a bright day you might want to shoot at higher ISOs just so you can shoot a little faster. A zoom lens stopped down focused on a fast moving subject will do a lot better if you can shoot at 1/2000s of a second rather than getting a blurry thing at 1/30th. But sometimes that kind of effect is what you want when shooting e.g. a static subject against a waterfall. The ISO dial basically allows you to compensate for loss of light by pretty much multiplying the signal. This is something you can easily do in post as well if you are shooting raw. It just gives you more wiggle room with aperture and exposure. Of course the issue is that you end up boosting the noise along with that as well. More sensitive sensors can be pushed a little further for this. But mostly, lower is better in terms of noise. Basically, you pick the aperture and exposure that produce the effect you want and the iso control allows you to get away with it when that is pushing the limits a bit too far. With some cheaper cameras, you end up trading off noise against creative control. Easier to shoot at night with the lens wide open at a low shutter speed that still works hand held. But less chance of blurry photos if you shoot a bit faster at a higher iso. Then there are different focal lengths that not only "zoom" in the subject but also change the perspective. Using a very wide or zoomed in perspective and compensating with your feet can produce very different photos even if your subject ends up being roughly the same in the picture.