Category Archives: Exercise

Exercise: Autofocus

Let’s play with our autofocus for a bit to get a feel for how it behaves. To start with, make sure your camera is set to use all of the autofocus points. If you’ve never changed this from the default, you should already have this set up. If you need to change this, consult your camera’s manual for specifics.

First exercise: Find an object that’s maybe three or four feet away from you, has sharp edges, and is reasonably well-lit. Turn the autofocus ring on your lens all the way to one extreme, so that you’re either focused on infinity or as close as your lens will go. Point the camera at the object, look through the viewfinder, and press the shutter button halfway. You should hear the lens whir, and you’ll see the object pop into focus. Pay attention to which of the autofocus points lights up. Now turn the viewfinder all the way to the other extreme and do it again.

Try this with faraway objects and nearby ones until you get bored with it.

Second exercise: Find a well-lit, solid-colored wall. Point the camera at it so that you have nothing else in the viewfinder besides the wall. Press the shutter button halfway and see if you can focus. You might be able to, but chances are pretty good that the camera will try for a while and then give up.

Third exercise: Find a piece of paper with some text on it, and put it somewhere with a decent amount of light. Alternately, you can use your computer screen. Get up close, so that the lens is only a couple of inches away from the print, then push the shutter button to try to focus. You probably won’t be able to. Pull back a couple of inches, and try again. Keep backing up a couple of inches at a time until the lens is able to focus.

So what did we learn?

In the first exercise, you watched the camera focus. Some lenses focus so quickly that you can barely see it happening. Other lenses are much slower and will take a significant fraction of a second to find focus. You got to see which autofocus points the camera used for different situations.

In the second exercise, the camera probably couldn’t find focus. If there were no surface details, the camera wouldn’t be able to find any edges, and therefore it wouldn’t be able to focus. The period of time when the lens was searching for something to focus on is called focus hunting.

Even one small feature like a nail hole on the wall would probably be enough for the camera to focus on.

In the third exercise, you found the minimum focusing distance of your lens. Every lens has a minimum distance at which it can focus, and if you try to focus on something closer it won’t work. Some lenses, especially macro lenses, can focus very very close. Others may require you to be a couple of feet away from your subject. The minimum focusing distance is probably written on the barrel of the lens.

I did this exercise with the Canon 50mm f/1.8 “nifty fifty” lens, which has a minimum focusing distance of 1.5 feet. My most extreme lens, the Canon MP-E 65mm macro lens, has a minimum focusing distance of around one inch. Sometimes a lens will have more than one minimum distance, and a switch that will let you control it– this is called a focus limiter. The Canon 70-200mm f/4L IS lens, my usual telephoto lens, can be set to either 1.2 meters or 3 meters. A focus limiter lets you help the camera focus more accurately by limiting the range at which the camera and lens try to focus. You don’t really need a focus limiter, but in some situations it can be a useful tool.

Now, go out and play! If you have more than one lens, try them all. Try focusing in a very dark room. Try focusing on something that’s not in the center of the image. Make up your own experiments and get a feel for how your equipment works. In our next lesson we’ll use this knowledge to help you focus in challenging situations.


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Homework: a reprieve!

All of you slackers and procrastinators have lucked out.  I don’t have much free time until this weekend, so you have until the end of Friday to do your homework.  You guys have posted some really cool images… I’m impressed!  This weekend I’ll be going through the entries and finding a winner or winners.

After that I’ll post a new assignment for April.

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Hey, where’s your homework?

Hey you… yes you! Where’s your homework? Remember the homework assignment I gave you that’s due by the end of the month? Some of you have done it, and done quite a fine job, but the rest are still slacking. No, the dog dd not eat your memory card, and I won’t take a note from your mother.

If you need to review, here are some lessons that might help you:

And if you want to go through all of the lessons, walk through Exposure Lessons, in order.

Now go out there and do your homework. I don’t want to have to give you detention. Be sure to leave a comment on the homework entry with a link to your photo(s), along with exposure details and anything else you want to say about them.


Filed under Aperture, Exercise

Homework Assignment… with a prize!

flower f/4

April 4, 2008 @12 a.m:  The contest is now closed.  You’re still welcome to do the exercise and add your photos to the comments, of course, but you won’t be eligible for the March prize.

OK all you slackers… you have homework. Grab your cameras.

Go outside on a bright sunny day, or somewhere where you’ll have lots of light to work with. Find a subject. I don’t care what it is– a person, a tree, a flower, a fire hydrant– and a background. The only criterion is that the subject is clearly distinct from the background.

Take a picture of your subject in such a way that the background is intentionally blurred. You can use aperture priority, shutter priority, or manual modes at your discretion, though of course one of those is less-suited to this exercise than the others. Don’t just shoot a bunch and hope you get it right, but think about what settings you want to use before you take the shot.

Upload your photo to a photo sharing site (I recommend Flickr but any one will do). Leave a comment with the settings that you used, a link to your photo, and anything else you want to say about the image.

At the end of March 2008, I’ll pick one commenter at random and send them an 8×12 signed print from my flower porn collection.

OK, go out there and shoot!

Update! At a friend’s suggestion, I’m offering two prizes. If at least 20 people submit entries, I’ll give away two prints– one to someone chosen at random, and one to the best submission. Pass the word to your friends, enemies, photography groups, etc. You can enter more than one image but don’t get too carried away… a few is OK, but not a dozen.

Small print: void where prohibited by law. Anyone who clearly violates the spirit of the rules will be disqualified. Don’t put that in your mouth… you don’t know where it’s been. Please make sure your images are worksafe. You can post more than one photo, but you’ll only get one chance at the drawing. It must be a photo that you took specifically for this assignment, not something pulled out of the archives. Play nice. Judging is at my discretion, and is final. SSA might want to show your image in a future entry, but we don’t want any other rights to it– if we want to use it for anything else, we’ll play nice and ask for your permission first.


Filed under Aperture, Exercise

Exercise: Depth of Field

(This shall forever be known as the too-many-yellow-rulers lesson. Sorry!)

f32Up ’til now, you’ve been just reading the exercises and maybe doing them in your head, but not getting the camera out and trying them yourself. It’s OK– I’m lazy too. This one is different though. You’ll want to get the camera and do the exercise. If you don’t, I’ll hunt you down and scowl at you.

In this exercise, you’ll get firsthand experience with how aperture affects depth of field. In order to do the exercise, you’ll need a large flat surface with some sort of measurements, or sharp regular pattern. Some things that would work well:

  • a tile floor with high-contrast lines
  • a striped or checkered blanket with high-contrast lines
  • a long tape measure

You’ll need about five feet of this patterned surface, and you’ll need to be able to get fairly close to it, so that you’re looking down the length of it. See the tape measure picture at the top for an example of what I mean. You’ll also need enough light to take a steady picture at f/16.

Set your camera to aperture priority mode, f/16, and manual focus. If you’re not in a very bright area, set your ISO to 1600, or as high as your camera will go.

Stand near your patterned surface so that you’re looking down the length of it. Pick a spot in the middle, and manually focus on it. Remember that spot, because you’ll be coming back to it. Once you have the image in focus, take a picture.

Without changing your position, change the aperture to f/8. Point your camera at the exact same spot, and take another picture. Do the same thing at f/4, and as wide as your lens will go.


Pull the photos into your computer where you can examine them more closely, and you should have a set that looks something like the photos above. The photo taken at f/4 will have a narrow band in the center that’s in focus, and the rest will be blurry. The f/8 photo will have a wider focus area, and f/16 will be much wider.

For extra credit: repeat the exercise, but this time don’t take pictures. Instead, use the depth-of-field preview button on your camera to see what the shots would look like. Feel free to try out the apertures in between the ones I suggested too. You should see a much smoother transition of focus than at the widely-spaced apertures, of course.

The astute… OK, the barely-conscious reader will notice that the example photos in this exercise are also in the page header. I originally shot these as examples when I was teaching SSA! as a live class, and I wanted samples to hand out. I was happy when I saw the results. The students in the class seemed to grok depth of field as soon as they saw the images, and they had a field day duplicating them with their own cameras.

Now it’s time for you to go out and play. Put your camera in aperture priority mode, and wander around taking pictures. Create some blurry backgrounds and some crisp ones, just like you’ve always done, but this time do it on purpose. You have the power– use it.

Next lesson:  ISO: What is it?


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Quick Exercise: Focusing

This is a really simple exercise that will help you think about focusing and depth of field. It’ll only take you a minute. Grab your camera.

Find a place where there are things at various distances from you– pretty much any place will do. Put your camera into manual focus mode, and turn the focusing ring all the way either direction.

Look through the camera and see what, if anything, is in focus. We’re not trying to focus on any particular object, but rather just look to see what’s already in focus. Keep looking as you slowly turn the focusing ring all the way to the other extreme. If you want to, repeat this a few times.

As you turned the dial, you probably noticed that things close to you came into focus first and then the farther-away ones did. (Maybe it was the opposite direction. It all depends upon which direction you were turning the ring.) You can imagine that your focus point is a person who walks closer to you or farther away from you as you turn the ring. The person will always be in focus, as will some area around them.

Now look at the top of your lens. You’ll probably see a bunch of numbers with an infinity sign (a sideways figure-8) at one end. Those numbers indicate how far away the focus point is at any given time. If you turn the focusing ring so that the focus is at infinity, things far away from you will be in focus and stuff that’s close will be blurry. You’re smart– I bet you can guess what happens to far away things when you turn the focusing ring the other way.

Next up: another way to look at depth of field. (It’s important. I’m going to repeat myself.)

Next lesson:  Depth of Field: Another View

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Exercise: Shutter Speed

8In this exercise, we will take several pictures to illustrate how shutter speed affects the resulting image. We’re not going to take any great pictures here, but the ones we do shoot should help us get a better feel for the nuts and bolts with shutter speed.

You’ll need a friend with a flashlight, or some sort of light source that he can swing around. In my pictures I used a glow poi (basically an LED on a string) but you can just ask your friend to hold the light in his hand and move it around. You’ll also need a camera, of course, and a not-too-bright room. Oh, yes, one other thing. You’ll also need a beer or other Appealing Beverage to thank your friend for the help. If you know someone who wants to learn to use his dSLR better as well, the two of you can take turns being the photographer and the helper.

If you have a tripod, it will be useful for this exercise. Instead of holding the camera when I tell you to, put it on the tripod. If you don’t have a tripod that’s OK… blurry pictures won’t be a big problem. If you really want the shots to be perfect, find a table or something to brace the camera on when you take the photos.

Control PanelSet up your camera: To begin, set your camera to ISO 400 (if you now how… if not, don’t worry about it), shutter priority mode, and manual focus. Have your friend stand facing you. Pick a spot that will let you get his upper body in the frame plus a couple of feet on either side, and manually focus the camera on him. Focus doesn’t have to be perfect, but it should be good enough to get the light source pretty clearly. Set your shutter speed to one second. On my Canon that’s the number one with two tick marks after it.

Now, ask your friend to turn on the flashlight, point it at you, and start moving it in a circle in front of him. Ideally he should be doing this so that he makes one circle every second, but friends are unpredictable (especially if he’s already had that beer) so any speed that’s somewhere in that vicinity will work.

Holding the camera as steady as you can, take a picture. Yes, it’s a one-second exposure and you’re going to shake, but that’s OK. We really just care about how far the light moved. One second sure is a long time, isn’t it? When you’re done, check out the picture on the camera’s display, and you should see a circle of light.

Now, set the shutter speed to 1/2 second (indicated by 0”5 on my Canon), ask your friend to make a light circle again, and take another picture. Repeat this for 1/4, 1/8, 1/30, 1/125, 1/250, and 1/500 second.

500When you’re done with this, you’ll wind up with a set of photos of progressively smaller arcs of a circle of light. At 1 second, you should basically have a full circle. Half a second should get you approximately half a circle of light, and so on until you get to the very fast exposures. Look closely at the ones that are 1/125, 1/250, and 1/500 of a second. When I did this exercise, 1/500 pretty much froze the action, but 1/250 and slower had blurs of light.

When I did this exercise to create sample images, I put the camera on a tripod and used a remote shutter release rather than asking a friend to help. As I mentioned earlier, I also used a glowing ball on a string rather than flashlight. Still, the resulting images do a pretty good job of showing movement. I have them all in my photography class set on Flickr, and they’re tagged “light circle exercise”.

Note that some of your photos may have come out much brighter than others. That’s OK! What happened was that your camera wanted to make all of the pictures bright and shiny and happy at whatever shutter speed you chose. At the slower shutter speeds it probably closed the aperture down to block out some of the light. As you chose faster and faster shutter speeds, the camera opened up the lens to let more light in but at some point it ran out of room to do this because the lens was already as wide as it would go. When that happened, the camera just did its best but the photos started getting darker as the shutter speed got faster. For the purposes of this exercise that’s perfectly OK. In fact, it’s a good way to see how your camera’s photos turn out when the camera is starved for light.

When you’ve completed this exercise, you should have a bunch of pictures with streaks of light in them. The Guggenheim won’t be beating a path to your door over them, but you’ll have practiced setting your camera’s shutter speed to a pretty wide range of settings, and you’ll have a pretty good understanding of how much motion there is at a specific speed.

Oh, yes. Set your camera back to whatever ISO (probably 100) you usually use, and set the lens back to autofocus. That will save you from some confusion the next time you try to use the camera. In general, it’s a good idea to pick a set of “normal” settings for your camera and leave the camera in that configuratoin whenever you put it away. That way, if you want to pick it up and shoot something quickly you won’t have to worry about undoing whatever you did last week.

If you want to practice some more, find some other moving object and start taking pictures of it. If you have dogs or small children, you can probably persuade them to run around in the park while you take pictures. Cars, water, anything that moves somewhat predictably will be good practice for you.

If you want to share your photos from this exercise, I recommend uploading them to Flickr and tagging them with “stopshootingauto” and “lightcircleexercise” so that other people can see them just by looking for those tags.

Next lesson: Quick review, what we’ve learned so far


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