Time for part II of this tutorial! Manual exposure. This is perhaps even more daunting than manual focus, but if you know the theory behind it and use it accordingly, it will make things that little bit easier.
So, when you switch your camera to M Mode, you have complete control over the three aspects of your exposure. These are as follows:
1) ISO - This equates to the old film speeds you used to get in your 35mm film camera, e.g. 200 speed, 400 speed etc. But on a digital camera the range is much bigger. My entry-level Pentax can go up to 3200 ISO. So what does ISO actually mean in real life terms? It basically means how sensitive your camera sensor is to light that's entering through the lens. The higher the number, the higher the sensitivity, and that means your camera makes the most of the light that's available to it. Great, fantastic, so why not keep your camera up at 3200 all the time so you get awesome shots even when it's pitch-dark out? The answer is that there's a bit of a tradeoff between your ISO and your picture quality: noise. Noise manifests as a grainy appearance to your shot, like this one. See how the white of the snow has these little purple grainy dots? That's noise - I took that shot at 2600 ISO by mistake.
So, what ISO setting should you use on your camera? That depends on how much light is available to you. As a rough guide:
Bright sunny day - ISO 100-200. There's lots of light - using higher ISOs will totally white out your shot and you'd need to ramp up your exposure and aperture to compensate.
Cloudy day - ISO 200-400. Try not to go any higher than 340 if possible - that's when the noise starts to get more noticeable (according to a more pro photographer friend - I haven't really noticed but I'm guessing if you're enlarging or cropping it would show up more.)
Evening/night and you've no tripod (well sucks to be you XD) - ISO 400+ in combo with wide open aperture and low shutter speed; more like 640 really, unless you've a really steady hand. And you're gonna get some noise - really, if you're wanting to take a photo that badly and you've got no tripod, that's the price you pay ;)
That's a bit restrictive, really, when you've got 3200 ISO to play with, but think about film cameras - most of the film you can get for that is 100, 200 and 400 speed, it's only specialist places where you can get anything higher, and people using higher film speeds are prepared for noise, and sometimes use noise as an artistic device in their photography, e.g. B&W shots. So yeah, if you're an amateur 365er you should be able to get perfectly decent shots at those speeds without needing to ramp up your ISO value, by utilising the other two aspects of your exposure.
2) Shutter speed - Shutter is what makes the click noise when you take a picture - it's a wee thing that lifts up/moves sideways to expose your sensor to light. There's one click for the shutter opening, and one for the shutter closing. If you've tried to take a pic somewhere dark with your camera on auto/P/Av or whatever mode you may have noticed there being a click... long wait... click. That's a long exposure - your camera's left the shutter open for a long time to expose the sensor to light for longer, to try and make your picture actually come out instead of being black. So, there's a relationship between your shutter speed, namely how long the shutter is opened up for, and certain aspects of your picture. You can experiment to learn these effects for yourself!
Longer shutter speeds = lighter colours, motion blur, more exposed picture (e.g. things that were dark are more visible)
Shorter shutter speeds = darker/more intense colours, frozen motion, less exposed picture (details that were visible on normal viewing might not be visible in the shot)
Having the right shutter speed is the hardest aspect of manual photography - it's the thing you usually have to tweak the most, to cope with changing lighting conditions and subject movement, etc etc. I did a shoot at Colchester Priory and the weather was so variable, with the sun coming out one minute and it being dark and cloudy the next - it drove me bonkers trying to get the shots exposed right and shutter speed was the quickest way to tweak it while preserving all the other aspects of the picture. It is something that is really learnt with practice, and I'll go into this a bit more after
3) Aperture - The aperture is something that's actually inside the lens you mount to your camera. It's a wee diaphragm that works like the iris of your eye - it expands and contracts according to the settings you give it, and blocks a certain amount of the light that enters your camera each time you press the shutter button. It works like this:
Wide open (f1)-------------------------------Nearly shut (f22 or whatever)
See the lower to higher f numbers? Obviously they depend on what lens you have - my Pentax kit lens only goes down to f4.6 whereas my Asahi 40-80mm can go down to f2.8. So that's how wide open the aperture can be, and that lets in the maximum amount of light. If you close your aperture down by putting it to a higher f number, your camera will let in the least amount of light it can. See how this tandems up with shutter speed? I'll give a few practical examples.
Say you wanted to do a long exposure of a city street in the daytime. Stick your shutter speed onto 1 second and your aperture to the smallest number possible, and hold your camera steady. Did you get a completely whited out shot? Now put your aperture up to a higher f number. Aha, it's darker now, isn't it? More things visible? Got that motion blur you wanted? If it's still a little whited out, try reducing how sensitive your camera is to light - put the ISO down to 100. Better? If you're still not 100% happy, just keep tweaking these settings till you've got a shot you like.
Now say you wanted to do the same shot at night-time. Same camera shutter speed, but if you want the details other than the lights, you're gonna need your aperture wide open at the lowest f number. Still too dark? Try increasing your camera's sensitivity to light - put the ISO up. Same things apply above with high ISOs and noise if you're shooting without a tripod.
But aperture isn't just good for modulating light input for long exposures. Knocking down your aperture (higher f number) will also intensify colours. You could take a piccy of a sunset on 1/1000 shutter speed with f2.8 and have it come out just fine. But try putting the f number up. How are those colours looking now? Any issues with underexposure, just put the shutter down a little to compensate. Same applies to just about everything else, too. I took a picture of the building across the road from my bus stop this morning - it had all the detail I wanted and was just a little bit faded in terms of colours. I could've put the shutter speed up but then some of the details wouldn't have come out so well. So I just put my f number up a few stops to narrow the aperture, and the colours came out great!
The last thing with aperture is depth of field. If you followed my previous tutorial on manual focus, you'll be starting to realise that when you've got something sharp, things in front of and behind your target will be not as in focus. To alter that, you can abuse the aperture of your lens. Basically, the aperture of your lens works like a pinhole - it cuts out the extra light that causes blur by passing through the outer circumference of your lens, where the sharpness isn't as good. This makes for a sharper foreground and background compared to if you had your aperture open wider. A similar principle occurs when you visit your local optician and they make you look through a pinhole to see if your vision improves. So to sharpen up elements of your image, increase your f number. If you want to blur the foreground/background even more and just have your target sharp, reduce your f-number.
So the three aspects of your exposure, in summary, work as follows:
1) ISO - How sensitive your camera sensor is to light. Increase if your shot's too dark, decrease if your shot's too light.
2) Shutter speed - How long your camera sensor is exposed to light for. Decrease if your shot's too dark, increase if your shot's too light. If you want it at a particular number for an arty shot, adjust aperture and ISO instead. For longer speeds a tripod is a good idea.
3) Aperture/f-number - How much light reaches your camera sensor. Decrease f-number (open aperture) if your shot's too dark, increase f-number (close aperture) if your shot's too light. If you're at max aperture and still struggling, tweak your ISO or your shutter speed.
When first starting to learn how to tweak your shutter speed, your best bet is to just have the aperture set to wide open at all times. This'll guarantee you max light and ensure you use the full range of shutter speeds available to you initially, and for those really over/under exposed shots you can modulate a bit using your ISO settings. Once you get the hang of exposing things correctly, then have a shot at changing the aperture and then you'll start to learn about altering your shutter speed to suit that. Be prepared for a lot of dud shots, but it's worth it in the end! Also bear in mind that sometimes the lighting can be just plain rubbish and you can't always get that shot that you wanted.
The last little tip I can give is about
White Balance - this is how your camera treats the different light wavelengths entering the camera and translates them into actual colours. You may have to hunt a bit to find the white balance setting on your camera and how to change it. You'll find there's a bunch of different ones but the most important out of ALL of them is the tungsten setting. This should be a little picture of a light-bulb, and using this instead of auto white balance (AWB) will make a HUGE difference to the quality of your indoor pictures. Trust me! And, er, yeah, don't forget to change it back to something else when you go back outdoors again, otherwise your pics will all be blue!! Lastly, if you're still not happy with the colours on tungsten setting in your shots, change to fluorescent light instead - that should be a little rectangle.
I've probably forgotten some stuff so if you have any questions ask away. Bear in mind I'm not using the most technical terms to describe things and they may be called a little differently in other places!
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