Day 9: Aperature - More

Long post the last few days, so we'll have a short one today. Large aperture shots are not only for portraits. A shallow depth of field can give you very striking images, like this one from the bridge over the Beaufort River I took last week. If I had used a smaller aperture, this railing would have been lost, making a rather dull shot. Thus:

Food for thought.

Homework for today: Have some food. And think.
Tomorrow - Shutter Speed.

Day 6: Tying It All Together

Okay - APERTURE controls two things: The amount of light that comes in and the amount of focus it gives us.

SHUTTER SPEED controls the time that amount of light comes in.

and

ISO controls the amount of light that is needed for a correct exposure.

So you have a decision to make.  What do you want to emphasize in your picture:

IF you are shooting a portrait, and you only want your subject to be in focus, pick a large aperture (f1.8).  This will give you a very fast shutter speed. (A/AV MODE)
If you are shooting a landscape and wish th show off the entire scene, use a smaller aperture (f22). This will give you a long shutter speed - so use a tripod. (A/AV MODE)
IF you are shooting a hummingbird and wish to capture it's wings, shoot with a fast shutter speed (1/1000 sec). This will open your aperture to let enough light in. (S/TV MODE)
IF you are shooting fireworks and want to capture the trails of light, use a long shutter speed (5 secs). This will close down your aperture to a tiny dot. Again, use a tripod. (S/TV MODE)

However......

IF you wish to shoot a landscape you would close your aperture to allow a tiny bit of light in and give you that large depth of field, so everything will be in focus, the camera will say, "Well, he's letting a tiny bit of light in here, so I better give him a long shutter so the shot is not underexposed!".  But here's the problem: .  You might set your A/AV to f22, and the camera will set the shutter at 1 full second to compensate.  But what if you didn't bring your tripod?  You need a faster shutter in order to keep the shot sharp and not blurry.
This is when you will need to adjust the ISO. The higher that number the less light the sensor needs to get the exact same exposure,  So in this case, raise the ISO from 100 to 800.  Now the camera does not need as much light and will speed up the shutter to be hand-holdable.

As an example -  say, a dog on his leash wagging his tail. What do you want out of this? Well, maybe a fast shutter so the wagging tail is not a blur. A large aperture so the dog is in focus and not Old Man Johnsons' barn in the background. So set the aperture at f-1.8 (remember, the lower that number, the less in focus there is), but that will allow a ton of light to come in, allowing you to use a very fast shutter speed for the tail. Because it is daylight you don't need a ton of light so your ISO should be ok at 100 or 200.

But suppose there were a bunch of deer in the field. You still want a fast shutter to get their wagging tails, but you want everyone of them in focus. So you adjust your aperture to maybe a f-22, but that would severely limit the light coming in, forcing you to use a much longer shutter to get a correct exposure. But you still want a fast shutter because of that whole tail issue. That's when you raise the ISO to 400 or 800, so the camera does not need as much light, allowing you to use the settings you wish.

Mind wrenching, isn't it? I promise you this will all make sense after thirty or forty years of practice.

Tomorrow, a better recap.....

Day 5 - ISO

Okay. APERTURE controls the amount of light coming in, and the amount of focus. SHUTTER SPEED controls the amount of time that light is let in. The third and final piece of the exposure puzzle (for our purposes, anyway) is the ISO*. ISO, or FILM SPEED, controls the amount of light the sensor needs to give you the proper exposure.

Here is a shot of my wives relatives. Keep in mind that all three photos in this post were shot with the same aperture and shutter. I wanted my aperture set at f-1.8, and my shutter set at 1/10th of a second. My ISO was then set at 100, meaning the camera needed a ton of light to get a good exposure. With only one lamp, at night, that just wasn't enough light, and here is the result:

So. Increase the ISO to 1600, make the sensor more....um.... sensitive... and voila':

Now, with this you can decide to make a more moody image, like the first one, or what is considered a correct exposure, like the second. Or, if you want to get crazy, set your ISO to 3200, and take a look:

Now, a word of warning. You may be asking why you wouldn't just keep your ISO at 800, 1600 or 3200 all the time, so you don't need as much light, meaning a faster shutter to catch that hummingbirds wings. And well, you may ask. Just keep in mind, there is a drawback to higher ISOs. DIGITAL NOISE, or graininess. Anything above 400 could easily make an exposure so full of noise that it would be unacceptable.

So tomorrow, we will learn how to make all three of the puzzle pieces work together to get exactly what you want in your image. Until then, today's homework: Try a shrimp egg roll.

*ISO = International Standards Organization. You will never need to know this until well beyond your dying day.

Day 4: Shutter Speed - Part 1

The Fireplace. At night. Here we have two shots that give a pretty good idea of what the SHUTTER does. Yesterday, we shot in A or AV. Today, it is S or TV (Time Value, NOT television). As the name implies, this is the TIME in which light is allowed into the camera. In the first shot, I wanted to see the flames of the fire, so I set the shutter for a quick shutter speed. (1/250th of a second). As you can see, at this relatively fast speed it does not allow a ton of light in, so it is a bit dark. But that didn't matter much to me - yet. I wanted to see the flames. If I were to give it a longer shutter speed, say - one full second, you would be able to see more of the fire place, but the fast moving flames would blur, as shown:

Once again, as I chose my shutter speed, my camera chose the APERTURE and the ISO (tomorrows topic). So, yes I now control the speed of my shutter, but the camera now controls the amount of the scene which is in focus. Soon, we will take control of everything. Baby steps...

Today's homework: Have some Southern Brew Iced Tea.

Day 3: Aperture, Part 2

Yesterday, we took two shots of the same subject. The first was shot with a huge APERTURE, f-1.8 to be exact (Yeah, I'll explain later) and the second at f-16. The second showed the entire scene in focus, while the first showed only the subject in focus.

We did this by shooting in the A or AV setting on the camera. (Yeah, I'll explain later). Using that setting, you control exactly what you want the aperture to be - within the limits of the lens - (Yeah, I'll explain later). Earlier, we learned that the aperture is just one of three forces that affect the exposure of the camera. When you shoot in A or AV, and set your own aperture, the camera measures available light and adjusts the SHUTTER and ISO to maintain a good exposure.

The reason this is important is the OTHER function of the aperture. We learned that the aperture also controls HOW MUCH light comes in. So, using the above apertures, with the shutter set at 1/6th of a second, and the ISO at 100, (Yeah, I'll explain later), I took two shots of a candle. The first, shot at f-1.8 is shown here.

Not a lot of light if the shutter is only open at 1/6th of a second, and the sensitivity is set at 100. But what happens if I let a lot less light in? For one thing, both candles would be in focus, but...

Sure it's in focus, but we can't see it. The moral of the story is that as we control the amount of focus, the light let in changes dramatically. If we want just our subject in focus, we let a lot of light in, forcing us to have a very fast shutter speed. And if we want the entire scene to be in focus, we need a ton of light, and a much longer shutter speed. The danger of that is that you can not hand hold a camera for that long, causing a blurry shot.

But that is for tomorrow.