I need to add more to this section and figured this would work as a start. First off, I don't consider myself anything special when it comes to photography. My knowledge may be very small compared to most that are at all serious about it. So excuse me here for stating some truly basic things. That said, what I know about photography seems to show me how little there is to it. When I started and wanted to learn, I thought there was going to be so much more to it(and in some ways I'm sure there is). Some of the questions I get asked now make me wonder. So here is a place with some hopefully useful info for those knowing very little about it.
I'll keep this short as it wasn't my intention to do a whole thing up on how to for photography. But, then again knowing me, I always have to start at the very beginning and go from there, often rambling on in the process.
Basically all you need to worry about is exposure, composition(how you frame it), and focus. Focus is pretty straight forward. When I'm chasing and only care about being focused at infinity(most of the time) I am sure to use autofocus and get it locked on something on the horizon, then flick the lens to manual and leave it alone. If it is a big zoom(not used much for chasing) then I'll be more inclined to get the focus myself in manual to begin with. With a wide angle though it can be tough to see how well you are focusing. Composition....eh, I'm sure it can be tought, but not so sure it should be. It is usually rather obvious what works and what doesn't, even if it is figured out after the fact. Exposure is pretty darn simple as well. Think of it like using hot and cold water to wash your hands(I'm making this up as I go, bare with me). When you do that you kind of like it at a certain temperture and volume right? If it is way too hot you have more than one choice to get it where you want it. You can increase the flow of the cold water(if there is room to do so!) or you can decrease the flow of hot water. You also like it at a certain volume of flow right? Washing your hands under fire hydrant pressure wouldn't be much fun, nor would a trickle. Think of exposure like this(or google as I'm sure there is a much better way to look at it lol). You have THREE ways to get to the "happy spot". Too much exposure and the image will be too bright. Too little exposure and it will be too dark. The three tools that control this are:
1. Aperture size - This is the size of the opening on your lens. The wider open it is the more light it will let in. The smaller it is the less light. Pretty simple! It is given in F/numbers like 2.0 or 5.6 or 16, etc.....pretty much from F1.4 to F32. Keep in mind this contol has another function besides exposure and that is depth of field...but ignore that for now.
2. Shutter speed - This is the duration the shutter opens and allows light to hit the sensor or film. Pretty simple too! These are the two main controls to get you the exposure you desire.
3. ISO speed - This is simply the sensitivity setting, like a gain control. Most common numbers are ISO 100 to ISO 1600. With ISO 1600 you need less of an opening or not as long of an open shutter to get the exposure right, than you would with ISO 100(higher the number the noisier it is though....I stick with 100 for as much as I can...even if the slower sensitivity means I have to get a tripod for a longer shutter).
If you haven't done much photography and want to understand it well, I'd start by never using the various "special modes" on the camera. I can't remember the last time I used the portrait thingy or the sports thingy...or any of them. If you want to be "in the dark" about things, just keep on using those modes. Stick with Av, Tv, or M. If you don't know where they are, find them. Av is aperture priority, Tv is shutter priority, and M is manual. Why not use those special modes? Because they aren't doing a thing you can't do with the other, more manual settings. With Av or aperture priority, you set the aperture size and it picks the shutter speed appropriate for the amount of light. It's pretty simple. It's the setting I use the most. With Tv or shutter priority, you set the shutter speed and it picks the aperture. Thanks to depth of field concerns and/or just wanting the aperture wide open so you can get as much light in to keep your shutter speed up, this Tv mode is rather useless. Most times you want to be able to set that aperture yourself and just deal with whatever shutter you are left with. Then there is full M or manual where you set both.
So all you really need to worry about are the size of the opening(aperture) and the shutter speed for exposure. But there is sometimes one problem and that is what you want for a depth of field. It's really simple too though.
Here is what you'd call a shallow or small depth of field. It is the depth of things in focus from near to far. It is how "thick" that area is. See the closer cat on the left here is pretty blurry. I'm also blurry. The cat in the middle though is in focus. Just look at the carpet from the front of the shot outward to the middle cat. It's blurry then in focus, then where I'm at is back out of focus. The area the camera is focused is right in front of the middle cat, obviously. Now this was taken with a wide open aperture of F/1.8. The more open you have it like that the smaller the area in focus is. (This was a tough shot btw! I used the self timer and guessed when to throw the dog food that the cats are chasing....hoping a cat would be in the area it was focused on). Now why did I use such a wide open aperture? I needed the shutter speed to stay high since the cats were running and the indoor lighting wasn't very bright. I needed all the light I could get to have a fast enough shutter. If I used a smaller aperture/opening the lighting conditions would have forced a much longer shutter speed. It's pretty simple.
Now guess what kind of aperture the above shot needed. It needed a small aperture (opening). It was outside in bright daylight this time though, so the shutter speed still was able to be fairly fast. I think it was down at around F14 for an aperture setting. The depth of field is now MUCH larger(deeper) since the grass in the foreground is sharper(it was windy as hell out though so they were really moving) and the focus goes clear out to infinity, or the far horizon, basically. Now if all I cared about was things far away(like most storm photography) I wouldn't have cared if the aperture was much wider open. If you do a landscape or similar shot and want things close and far in focus you HAVE to user a smaller aperture like F14 or smaller. You can run into lens issues if you go much smaller than F14 though. I see small round circles all over the place if I go past F16(tiny spots of dust in this case....hell if there is no detal, like snow or fog, I can see them at F9 or less).
Now when shooting storms, if you aren't able to tripod things and don't care about the foreground sharpness, you'll often want to just focus out to infinity and use a wide open aperture. Lenses will have their limits. Like my canon 17-40L is an F4 lens, so I can only open up to F4....no more. My canon 50mm is a F1.8 lens so it can go clear to F1.8. They make an F1.4 and even an F1.2 now(fastest I think there is...canon used to make an F1.0.....that new 50mm F1.2 is like $1700 though, I think). So my 50mm F1.8 would be considered a fast lens while the 17-40L F4, not so much so.
So if you are a storm chaser and you are running around shooting storms in lower light and hand holding things, do you want to be on F16? No. That will usually give you a shutter that is too slow to be hand holding. I'm almost always on F4 on my 17-40L, just so I can have the quickest shutter possible. If I can mount it then that is much less of a concern. I have some images I wish I had been stopped down past F4 because the foreground wound up too soft(thanks to the shallow depth of field).
Now what if you HAVE to hand hold something, or you simply need a faster shutter for something moving, but the lighting is too low? Then you have to adjust the ISO up to a higher amount. This will make the sensor more sensitive and allow you to move your shutter up. By using a faster shutter, you are letting light in for a shorter period of time....but the increased ISO setting counters that by making the sensor more sensitive. The drawback to moving the ISO up is that it increases the noise. With a digital camera this should all be very simple to understand after just playing around with it.
So when it comes to exposure think of it as volume and time of volume. Each scene will require a specific combination of the two, while being able to tweak one to allow you to tweak the other.
None of this tells you how to expose things right. With digital it is pretty darn simple. There is a thing called a histogram that will display your shot info and exposure for you.
This is a histogram for an image. The left side of this represents BLACK or shadows. The right side represents WHITE or highlights. With digital the brightness is given from 0 to 255. Black is 0(left).....white is 255(right). The peaks of black stuff on this is the info in your photo, where it lands on the brightness scale of black to white. You can see most of it fit in the middle, so there isn't much too dark and not much too bright. If the photo was taken and it was overexposed all that info(black spikes) would be rammed up against the right side of the histogram. If this photo had a bright sky and it was blown out, you'd have a peak of black info on the right side. The same goes for under exposing things. If you didn't give it enough exposure(too slow of shutter or just not a wide enough aperture) then most of it would be on the left side or off the left side if it was left totally black. So right after you take a shot you can view this thing on your digital camera(most all have it). You can tell right then exactly how well it was exposed. If it was all a bit to the left and you wanted to get a better exposure then you'd just decrease the shutter speed, increase the aperture opening, or up the ISO speed if you wanted. That is what exposure is and how you control it. Aperture, shutter, and ISO. That's it.
It is too bad many scenes(outside of some controlled indoor lighting setup) won't fit within that range. A lot of landscape scenes will leave you with blown out highlights AND clipped to black shadows. In that case you shoot to save whichever you want. You can use a split filter that will have a dark half to it so you can dim down the sky(this doesn't work with a storm and sunlight below it). That can help you get a dynamic shot to fit within the camera's range. What I do is just shoot and try to not blow out the sky. With a lot of storms though, it's just really unavoidable. One thing to consider in this is to "shoot to the right" of the histogram. That is getting that info/shot as far right on the histogram without going over the edge as possible. I guess there is a lot more info over there than in the midtones and shadows. Here is a great link to read more on that: http://www.luminous-landscape.com/tutorials/expose-right.shtml Hell if you really want to learn a lot about photography, just read everything on that site that you can. (I have no idea why I type any of this on here instead of just saying "here" and putting up a link to sites like that)
I guess here is something pretty darn important to understand when trying to get a good exposure. Know where your metering points are! With a DSLR you should be able to see them while looking through the lens. There should also be a button for you to select which one you want to work, if not all of them. My rebel has 5 going left to right and then 3 going from top to bottom in the middle. Those are the metering points and are also used for focusing. On the rebel you can push the top right button on the back of the camera then spin the wheel to move them around. Whichever one you have it set on will be lit up red. That spot will be where it tries to focus on as well as where it meters your shot, trying to figure out the exposure needed.
So what does it do to figure out your exposure? Not a lot. On that histogram at the top, the right side is highlights/white, the left side is shadows/blacks....what is the middle? The middle is midtones....grey. It is the middle between bright white and dark black. Well, wherever that metering point is setting(wherever you point it at in your shot) it will try to make that spot middle grey(as far as lightness). It will keep moving things around so that whatever you have it resting on is middle road as far as brightness. So what if you have the metering point on....say a black cow? Your shot will be over exposed. If it exposes the scene so that your black cow is now a lightness of middle grey, what does that do to the brighter areas of the shot? It makes them even brighter. Now what if your metering point lands on a bright white puffy cloud in direct sunlight? Instead of setting the exposure so that cloud is closer to a bright white highlight, it will want to make the scene so that it is middle grey. Your shot will be horribly underexposed. If you want to get things close at all, it is of major importance to understand how your metering points are setup and which ones are working. Then when you take the shot you'll obviously want to know what the hell it is on out there in your shot.
If you want you can set that so that they all work and it just averages them all out. That might work pretty darn well for metering. For whatever reason I've always liked to have it set to one, that way I know exactly what it is metering on. Doing it this way can allow you a bit more control over where your exposure winds up.
One way I like to shoot storms is using the AE lock. The majority of the time the metering point won't be where you want it while at the same time framing your shot. What you can do is point the metering point at the location you want the shot metered and push the AE lock button. On my canon it is the symbol of a * on the back. You push it and let go and it will hold that meter setting, so you can now move it and frame it like you want. If you have a changing scene(like off and on clouds real quickly) and are short on time, that might be the best way to go about things. Here is how I usually use it for shooting storms. Lets say I have the camera set so that the center dot is the one metering. Now lets say it is nearing sunset and there is some brighter sky below the storm or to the side. If I want to try and get some shots with the sky not blowing out I'll point that center dot at the brightest point and push the AE lock. But there is another step here. If I just do that and nothing else, then it will make that spot that middle grey lightness and everything else will be less(in other words the whole shot will be left of middle on the histogram). You don't want that. You still want that bright point to be bright, but stop short of going over the right side of the histogram into the area it blows out and is all white. You'll want to use the exposure compensation button on the camera and shift the auto exopsure(via the camera's metering) to an offset of +1 to +2 stops. There should be a scale on the back of your camera(if it is somewhat decent) showing a bar from -2 to -1 to 0 to +1 to +2. Then there will be an indicator below it showing where you are set(unless you are on full manual, then it'll just move around to show you where you are with the shot). If you set it up to +1 then it will increase the exposure one full stop from wherever you have the metering point on. So if you do this and AE lock the shot on the brightest point, instead of that brightest point being middle grey lightness it will now be +1 stop brighter than middle grey. If you want it even brighter then set it to +2 or something. But if you are doing this you'll obviously have to be AE locking on the brightest point out there. This is also useful in other settings where there isn't much of anything much brighter than everything else. If the scene is all pretty evenly lit and the dynamic range isn't too great for the camera, you can offset this +1 or more so it gets the shot onto the right side of the histogram. By the way, to change that compensation/offset you push the Av button on the back and roll the wheel.
I guess I should say something real quick about stops. A stop is a measurement of exposure. I think our eyes are capable of seeing 10 stops of light in a scene. Something like a sunset might be close to 10 stops. A camera on the other hand is really only capable of capturing 5-6 stops. So on a lot of shots you'll either have areas of the sky blowing out to white or shadow areas being completely black. If you bump the ISO up from 100 to 200, that is a one stop increase. Now if you change the shutter 3 clicks from say 1/100 to 1/80 to 1/60 to 1/50 that is one stop more exposure. Just think of 3 clicks as a stop worth of change(if your camera is set to 1/3 incriments and not 1/2). Same goes for the aperture. Say you go from 5.6 to 6.3 to 7.1 to 8.0 in aperture change. Those 3 clicks are also equal to one stop worth of change. So if you are 1/50 for a shutter speed and would really like to be able to use 1/100 instead(faster so less shake) you could just up the ISO to the next setting or you'd have to open the aperture 3 clicks from say 8.0 to 5.6. The correct way to explain that is doubling an exposure amount is increasing one stop...halving an exposure amount is decreasing one stop. Because 100 ISO to 200 ISO is doubling. 200 ISO to 400 ISO is also doubling. 400 to 800......and then 800 to 1600....each step in those is a double.....so a 1 stop increase for each double/step. Same goes for the shutter. What shutter speed is a doubled increase of exposure from 1/100? 1/50 is. An increase is something open longer, so 1/50th of a second is twice as long as 1/100th.....or a 1 stop increase in exposure. If you wanted a 1 stop decrease of exposure from 1/100th of a second, you'd need 1/200th. The easier way may be to think of full seconds. Using 2 seconds instead of 1 second is a 1 stop increase. The exact same thing works with aperture size. An opening half the size of another is a 1 stop decrease of exposure. F8 happens to be half as big as F5.6. I only know that because I know my carema is setup in 1/3 stop incriments, and I can move the wheel three times from F5.6 and be on F8...lol.
Cameras really are not that confusing. They'll make sense much quicker if you never bother with those other modes on them, like sports, night, portrait, landscape, etc.