Photography 101: Exposure

June 24, 2009

One of the hardest things to figure out when you first switch to manual mode on your camera is getting the right exposure. On a side note, I recommend using one of your manual modes – you won’t take better pictures at first, but you’ll ultimately get better pictures. Even if you don’t, there’s something rather satisfying about changing settings yourself than letting the camera do it for you. I guess maybe I just like to think I’m smarter than a piece of electronics.

There are three things that make up the exposure of your photo (or, how light or dark it is): ISO, Aperture, and Shutter Speed. A lot of people say these three things make up the “exposure triangle”, but for some reason, I never really think of a triangle when I’m shooting, I just think of what effect I’m going for in a picture and adjust the settings appropriately. For Exposure 101, I’ll just talk about each of the three things individually.

(btw, for those of you with point-and-shoot cameras, you may or may not have control over the aperture and shutter speed, but you should have control over the ISO)

One way I drove home the difference that changing the ISO, aperture and shutter speed did when I first got my DSLR was to take a shot in Auto mode and then change the settings. I’ll demonstrate what I’m talking about in today’s article with this photo taken in Auto mode, of one of my favorite drinks – a Kiwi-Strawberry Propel (on a side note, I don’t know if you figured this out yet, but you can click on any of the photos I post to make them bigger):

Auto settings

(wow, it’s been a while since I shot in Auto – I can’t even change the white balance! I apologize for it being so off)

Anyway, after taking that picture, I looked at the settings my camera chose:

ISO: 400
Aperture: f/2.2
Shutter Speed: 1/60

Now let’s play with each of those!

ISO:

I don’t know why it’s called ISO. I tried looking it up so I could tell you, and found out it had something to do with the International Organization of Standardization, and that’s when I fell asleep from boredom, so I decided that even if I figured it out, you’d probably forget, so I’m just skipping it. What you really need to know is what it means, and how changing it affects your photos.

ISO is how sensitive the sensor in the camera is going to be to light. The higher the number, the more sensitive the sensor will be to the light. Have you ever closed your eyes outside while trying to get a tan, and then when you finally open your eyes they’re SO sensitive to the sun and everything is REALLY bright? Or how when you wake up in the morning you can see fine in your fairly dark bedroom? That’s like a really high ISO.

So, switching a higher numbered ISO will give you lighter pictures – sounds great, right? We can really use when shooting indoors and don’t want to use a flash! Well, there’s a downside to high ISO – grain. When the sensor gets really sensitive to the light, it produces grainy photos.

Let’s take a look at what changing the ISO does to our propel bottle. Remember, the camera chose 400 as the ISO setting. Let’s see what it looks like at ISO 100, but keeping all the other settings the same:

ISO 100

wow. a LOT darker.

Now let’s see what happens when we bump it all the way up to ISO 1600:

ISO 1600

REALLY bright! (I actually kinda like it this bright. As side note, I like my photos exposed a bit higher than what my camera thinks they should be). Because it’s so bright, it’s going to be hard to see the difference in grain (it’s a lot more noticable in dark pictures), but let’s compare the bottle cap of the original photo (ISO 400) to the ISO 1600 photo:

Comparison between ISO400 and ISO1600

Yes, the one on the right is brighter, but you can also see how much grainier it is. So just keep that in mind when you bump up your ISO. Different cameras will add more grain at different ISOs. My camera starts to give me noticable grain at 800. I know other cameras (more expensive than mine, obviously) that show hardly any grain at 3200. I like to shoot at 200 if I can, by adjusting my aperture and shutter speed. Why not 100? Well, I don’t notice that much more grain between 100 and 200, and the 200 lets me be a bit more flexible with my aperture and shutter speed, since most of my shoots are outdoors on photowalks, I move in and out of shadows and cloudy areas so I’d like to have that extra little bit of ISO to help me out if I need it.

Aperture:

Aperture is my favorite of the three. I know that sounds weird to say, but I’m going to write an entry later about the magic of aperture, and why I love it so much, but before I get there, you just need to know some basics. Remember, we’re talking about exposure, or the light that’s getting to the sensor. One way of controlling how much light gets into the room you’re sitting in right now is by opening and closing the shades on the window – that’s what your aperture is! It’s the “shade” that you can open or close in your lens. Technically, it’s a bunch of blades that overlap to make a circle so that it can easily open and close in your lens (since, ya know, it’s a circle and all).

Here’s where it gets just a bit confusing, though: the higher the aperture number (also known as the f-stop), the wider open the lens is, and therefore the more light you’re letting in. Typically, when someone writes about what aperature they used, they’ll say it was f/1.8 or f/22. Hey, that looks like a fraction! And in fractions, the larger number on the bottom means it’s smaller! So, if you remember that, you should be able to remember that f/22 is a smaller opening than f/1.8. And oh, what an exciting difference it can make when you really start to play with it, but now I’m just teasing you, since I’m still not going to write about it today. I love it so much, it deserves its own entry! For now, let’s just see the difference if we go back to all the same settings that the camera took in Auto mode, but this time adjust the aperture.

Here it is at f/1.8:

Aperture: f/1.8

I know, not all that different. You’ll see the camera chose f/2.2 which really isn’t that far off from f/1.8, but it should look a bit brighter to you.

Now let’s see if we go to f/8:

Aperture: f/8

Wow, really dark! and that’s only at f/8! This lens goes up to f/22! Can you imagine how black it would be if I closed the lens that much!

So, as you see, you can control the exposure a lot with the aperture. Remember with the ISO, you got grainy photos if you picked a high ISO, so you might be wondering what the difference (other than exposure) is between a high and low f-stop. Well, when you have your lens wide open (a low f-stop, like f/1.8) you have a shallow depth of field. It’s hard to see in the picture I took, but what that means only things on the same plane as what you focused on will be in focus. This is part of the “magic” I’ll talk about in a later entry about exposure, but this photo is a good example of what I’m talking about:

Landscape Lighting

See how only the second landscaping light is in focus? That’s a shallow depth of field. If I had taken that photo using a smaller opening (f/8-f/22) more (or all) of the lights would have been in focus. Neither is a good or a bad thing, it’s just what you want for that particular photo.

Shutter Speed

Shutter speed is probably the easiest of the three to understand. The shutter is what opens and closes in order to expose your sensor to the light that the lens is letting in. The longer your shutter is open, the more light you’ll get in your photo. Of course, the longer the shutter is open, the more likely it is that you’ll want a tripod so you don’t get some camera shake in your photo.

One of the best subjects to play with when it comes to shutter speed is water – using a fast shutter speed, you can freeze water coming out of a fountain so you can see the individual water droplets, but using a slow shutter speed you can make a rushing waterfall look silky smooth. I’ll talk more about this in a shutter speed article I’ll write later – for now I’ll just mention a rule of thumb when it comes to shutter speed: you probably can’t hand-hold a shutter speed of longer than 1/focal-lenght-of-your-lens. For instance, I was shooting all these pictures of the propel bottle with my 50mm lens, so I was always using a focal lenght of 50mm. The rule of thumb would state that I shouldn’t hand-hold my camera with a shutter speed any longer than 1/50 (shutter speeds are in seconds, so that’s 1/50th of a second).

So, what did the propel bottle look like at different shutter speeds? Remember, our auto settings had us at 1/60. Here it is at 1/10:

Shutter: 1/10

Remember the rule of thumb says I shouldn’t be able to hand-hold that, and you can see the camera shake and how the image isn’t really clear. You can also see how BRIGHT it is! This is even brighter than the ISO 1600 picture!

And here’s a nice dark picture at 1/250:

Shutter: 1/250

So. Now that we know how to take pictures with bad exposure by adjusting the ISO, aperture and shutter speed, in the next few Photography 101 post, we’ll go over how to take good pictures by adjusting them :)

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