Well it probably seems pretty daunting but I'm going to explain it to you so easily, and so simply that you will regret not having used the manual setting sooner!
First of all, lets discuss what auto exposure does for you. Basically all manual exposure does is measure the amount of light coming into the camera and then determines the "correct" exposure setting. When I say exposure setting I mean the way in which the camera makes the photo lighter or darker. The reason I put correct in inverted commas is because there is no real correct exposure setting, there are many different ways of creating a correct exposure and this is the power of the manual setting, you can decide how your camera gets the right exposure setting which will give you far more creative freedom!
So how do we make the photo lighter or darker?
There are three ways to 'make the photo lighter or darker' and when taking a photo all three ways work together to produce the final photograph.
Aperture
The first way to make the photo darker or lighter is to use the aperture. The aperture is basically the hole in the lens of your camera that lets light through and into the camera. The beauty is that that hole is adjustable and the bigger the hole is, the more light it will let in (making the photo brighter), and visa versa. Pretty simple right? Yep.
Here's where it gets a bit complicated, and why people get confused. The F number measures the size of the hole in your lens. The confusing bit is that the 'smaller' the f number, the larger the hole is (and the more light let in) and the 'larger' the f number, the smaller the hole is (and the less light is let in). The reason I put smaller and larger in inverted commas (and the reason why it's actually not that confusing) is that the F number is actually a fraction. That is why a hole that is F 1/2 is bigger than a hole/aperture which is F 1/16. So if you are familiar with fractions this shouldn't be too confusing. If fractions sort of confuse you, then you will just have to come to grips with the fact that you will always be a little confused as to why an aperture of f2 is bigger (and lets in more light) than an aperture of f16.
So what other effects does the aperture have on the photo?
Well I'm glad you asked, because there is one more vital thing that the aperture does. The aperture also controls the depth of field. While not getting too technical as to how the aperture does this, the depth of field is basically how much of the photo is in focus.
You would have seen photos before where the subject, for example a person in a portrait, is perfectly sharp and then the background is very blurry. This is caused by a 'shallow' depth of field. The way you achieve a shallow depth of field is by using a large (remember, that means F/2 not F/16) aperture. The larger the aperture, the shallower the depth of field (the amount of photo that is sharp).
The opposite is also true, so say you are taking a landscape with a nice foreground filled with rocks and trees a few feet in front of the camera and nice mountains in the far distance, and you want to have both in focus then you will need to use a small aperture (remember that means F/22 not F/2).
Tip: If the area of the hole is twice as large, it will let twice as much light in, and visa versa.
Tip: The amount of depth of field you gain or lose from changing your aperture is relative to the distance to the subject. So if you're taking a photo of a subject very near to the camera (for example if you're doing a macro photograph of a bug) it will be more conducive to create a shallow depth of field effect. The opposite is also true, if you are taking a photo of a mountain that is 1km/mile away and another mountain that is 20km/miles away then you will probably only need an F2 aperture to get them both in focus and sharp.
So now that you know how the aperture works you may be wondering why all photos with a shallow depth of field and a blurry background aren't way brighter than photos with a very large depth of field. Well as I said before, there are three ways of creating a brighter or darker photo and the key to being able to use your manual setting effectively is to remember that they all work together. The second way is...
Shutter Speed
The shutter speed is basically how long you let light through the aperture for. As you may have guessed, the longer you let the light through the aperture for, the more light gets through (assuming the aperture stays the same). Of course the opposite is true where if you don't let light through for long, there wont be much light going onto the chip and assuming everything else is the same, the photo will be darker. The shutter speed is measured in seconds and fractions of a second. So for example 1/125 or 10 seconds would both be shutter speeds. The other thing you may find interesting is that if you leave the shutter open for twice as long, it will let in exactly twice as much light (and make the photo twice as bright assuming everything else stays the same).
So what other effects does the aperture have on the photo?
Well again, I'm glad you asked. While the shutter is open, everything is being recorded, so if something moves while the shutter is open it will be a blur. Now... most things move, even people standing still are moving, the key to making things not move in your photo is to lower your shutter speed so that whatever you are taking a photo of has less time to move while the picture is being taken and thus moves less over the course of the exposure (assuming of course you want the subject to be sharp and not have the motion blur effect to it). So for example if you're taking a photo of a moving car and you want it to be sharp and look like it's standing still then you will need a very fast shutter speed of say around 1/500th of a second. If however, you want the car to look blurred then you will need a longer shutter speed, for example 10 seconds.
Tip: Have you ever taken a photo which looks like the entire photo is a blurry mess? Well that's because you have moved your camera while taking the shot and it created the blur. To fix this you can do one of two things; you can buy a tripod and use that, or you can use your shutter speed to counter-act this problem. If you have a higher shutter speed then you are unlikely to have that blur. How high? Well that depends on what type of lens you are using. Lenses that have a longer focal length (or what is commonly mis-referred to as a lot of zoom) are more conducive to creating this camera blur effect. A tip to knowing what shutter speed you need for your given focal length is easy. A focal length of 25mm will usually need about a 1/25th shutter speed (or faster) to create a sharp image hand held. A focal length of 50mm will need a shutter speed of 1/50th of a second to create a sharp image hand held and a focal length of 100mm needs.. you guessed it, about 1/100 or more to hand hold the camera and and still get the photo sharp.
So you said there are three ways of making the exposure (all of which work together) so what is the third?
ISO
(pronounced I-so, its not an acronym, despite what most people will tell you)
Up until now both of the ways of creating the exposure are focused on letting more or less light through the lens in order to 'get the photo to be brighter or darker'. The third way is an exception though. ISO is essentially the sensitivity of the camera's sensor chip which reads the light. If you have a high ISO then your camera chip will basically be more sensitive to light and do 'more with less'. ISO is measured by a simple number, 100, 200, 400, 800 are all examples of ISO settings.
So what other effects does the aperture have on the photo?
ISO really only has one effect as it goes up and down, that is; how much digital noise is created on the image. Digital noise is often mistaken/called grain (which is only related to film and not digital images). Digital noise looks like small dots scattered all over your image, sort of like pixels gone crazy. It's hard to explain what they look like without showing you a picture (i'll try to upload some later) but you would have seen it before when you've taken a picture in the dark and your cameras auto setting racks up the ISO to make the most out of what light can be gotten through the lens in a reasonable amount of time. Basically, it looks ugly.
Tip: The key to a clean looking image is to always keep the ISO as low as practically possible. Now, if you're shooting in bright daylight that will usually be on your cameras lowest possible ISO setting which will create the best possible outcome. But as you will soon find out as you take more photos, that is not always possible or practical. If you have a tripod this generally isn't a problem as you can normally make a longer shutter speed and keep the ISO down, but this is not always the case. However, it is also worth noting that when you get to longer exposures (from 10-15 seconds or more depending on your camera) long shutter speeds will also create digital noise.
How do I know how much light my camera needs?
Well obviously that depends on how much available light there is in the photo. Darker scenes obviously demand you to 'try harder' to produce a correctly exposed image by making the aperture larger, shutter speed longer, and the ISO higher.
So do I have to guess? Believe it or not back in the very old days, yes you did, although it was an educated guess. Today however, almost all cameras with manual control come with a built in light meter which takes into account the light going through the sensor and hitting the chip and your current settings and tells you whether or not your photo is going to be under exposed (too dark), over exposed (too light) or just right. Where you will find the light meter in your camera, and what it will look like, depends on your cameras make and model, so as much as you don't want to hear it, READ YOUR MANUAL! Luckily, you know you want to skip to the page about your camera's light meter/exposure meter which should have its own section in the index. If you don't have a manual or lost it, you can almost certainly find it online.
So how do I change my Aperture, Shutter Speed & ISO?
Well that depends on your camera, so again, as much as you don't want to hear it, READ YOUR MANUAL!
Hopefully by now you've taken in most of what I've said and you can refer back to this page if you've forgotten anything. The main thing you need to do now is to familiarize yourself with the idea that all three of these settings work together to produce the final image and that there are many different combinations of ways to create the same level of exposure and each one depends on what scene it is and what kind of look you're going for, things that the auto setting won't ever have a clue about!
I hope you enjoyed this post, if you did please leave me a comment, it's always appreciated!
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