Day 8: Aperature - Expanded

Now that we have a rough idea of what the Three Biggies do, and why we would want them to do it, let's look a little deeper into each.
Let's try an experiment.  Find something far away that has lettering on it.  Now try to read it.  If it is far away enough, and small enough, what did you do?  You squinted in order to see it well.  What you are doing is forcing your iris to close enough so everything in the distance is in focus.  Same as you would if you were shooting a landscape with your camera.

The Aperture of a camera is in the lens. Imagine it as your iris on your eye. If you are in a dark room, your iris opens up to giant size, to allow more light in and lets you see better at night. Go outside on a bright day and your iris will close down to a tiny pinpoint to limit light coming in. This is the same with a camera lens. It is measured by the f-stop, where the oddly named word "stop" is replaced by a number - a fraction of the entire diameter of the lens' iris. Since it is a fraction, as we learned in Mrs. Willis's fifth grade math class, the smaller the number, the bigger it is (1/2 is larger than 1/3).

Each lens has it's own range. For instance, the kit lens that ships with most Canon Rebels have a range of f-3.5 to f-5.6. That means the widest you can open the aperture on it is 3.5, at the cameras widest angle (more on that later). Zoom out from 18mm to 55mm (more on that later), and your maximum is now limited to 5.6. On the other end of the spectrum, the smallest aperture on that lens, regardless of zoom, is f-22. So the wider the angle on that lens, the more light it can let in.

A stronger zoom lens, for the same camera, would be the 55-250mm IS (more on that later), with an aperture range of f-4 to f5.6, meaning the largest aperture that lens can allow is one stop slower (more on that later) then the kit lens. You do give up light when you zoom.

So what is to be done? What if you want to devote your life to Portrait photography? What if you want the eyes of your subject in perfect focus, and have it drop off from there? Well, that is where a faster lens would come in handy. The f-stop (more on that later) range is called the SPEED of the lens. The lower the numbers, the faster the lens. So try a 50mm. f-1.8 lens. This lens is a little more expensive, but will give you a super-shallow depth of field (see Feb 1st post). It will also allow so much more light in that it can drastically alter your shutter speed, but that is for tomorrow.

Until then, homework is: Examine your lens. Lots of numbers and such. Must mean sumptin'.

Day 7: Summery - The Story So Far

In one week, we have an OK grasp on what the three amigos do the the camera and to each other,
So, Aperture, Shutter and ISO.

We know what they do. But when and why do we use them?

Well.....

Portrait (Face is in focus, background isn't): Large Aperture (low f-number)

Landscape (Everything from foreground to background is in focus): Small Aperture (high f-number)

Running Athlete (To capture action): Fast Shutter (1/500th of a second to 1/4000th)

Starry Night (No lights, very dark): Long Shutter (1/50th of a second to 30 seconds)

For now we are leaving the ISO at 100.

The first two use the Aperture control to set your exposure. Set camera to A or AV, move the dial so the aperture value goes all the way up or down. The camera will look at available light, and where the ISO is set, and give you the Shutter speed you need for a correct exposure. The second two are controlled with the S or TV dial.

If, for instance, you want to shoot a beautiful landscape of your back yard. Set the Aperture to f-22, point the camera and hit the shutter half way. The camera will meter the light and determine what speed shutter it needs to give you that aperture. Remember, though, that the small aperture allows less light, so the camera may give you a shutter speed of 1/100th of a second. The sad news is, there is no way you can hand hold the camera that long without even a little blur. So, adjust your ISO to the next level. At 200, the shutter may move to 1/250 of a second. Better, but not great. 400? Hand-holdable*, but it now starts to get grainy.

All these factors are determined by the capabilities of your camera. VERY roughly speaking, the newer (and the more expensive) your DSLR, the better it will be at this.

There are other ways to overcome these obstacles, and but they will be covered a bit later. For now, we can live with a little graininess. That back yard will be there for future, better shots.

Homework? Hug your kids.

*My blog - my made up words!

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 2: Aperture, Part 1

This is an image I today at the Beaufort cemetery. In the foreground is a headstone in sharp focus. Beyond that, you can see the other headstones starting just a few feet away. Only the nearest headstone is in focus. This works great for portrait photos, where you would want your subject in focus, and to slightly blur the busy background, thereby drawing attention to your subject. This is called a shallow DEPTH OF FIELD.

That is where the APERTURE (Canon Av, Nikon A) comes in. It is what controls the amount of light entering the camera, as was discussed yesterday. The benefit of this is you can control the depth of field of your photo. For the above shot, I set the aperture at its largest opening (in this case, f-1.8). For the next shot, I did just the opposite: Because the entire scene is in focus, your attention is not drawn to any particular part of the scene. You get to enjoy the entire vista. For this shot, my aperture was set at f-16. As you can see, the lower the f-__, the less that is in focus. This will be explained later...