Category Archives: Exposure

Two interesting photos

I’m a big fan of the Day in Pictures on SFGate — the photos are generally quite interesting, they’re well-captioned, and the editor likes to play amusing games with proximity.

Today’s set had two photos that are excellent illustrations of the things you can do if you understand exposure. This one shows an elderly man praying in the middle of the road, with cars whizzing by on either side of him. The blur of the cars is worrisome– you’re sure he’s going to get hit at any moment– but it shows his conviction.

The second one shows a landscape with a closeup of poppies in the foreground. The poppies are crisp and sharp, and the background is reasonably sharp as well.

Take a moment to think about how you might shoot those two photos.

Got it? OK, here’s my take.

The first one requires a slow shutter speed in order to capture the motion of the cars. If we look closely, we can see that everything is sharp as far as the eye can see. This suggests that the photographer used a very narrow aperture and a slow shutter speed, and probably a low ISO as well. We don’t know how fast the cars are moving, but let’s guess, oh, 30MPH. We can ask Google and find out that’s 44 feet per second. I’d guess that the shutter speed was somewhere between 1/2 second and 1 second. I’d guess that the photographer also used a neutral density filter (something I haven’t talked about, but it’s basically a piece of grey glass that reduces the light coming into the camera) to get a slower shutter speed.

The poppies were clearly shot at a fairly small aperture, since the background was mostly in focus. The shutter speed is indeterminate, but was probably “whatever it takes”.

Whenever you see an interesting and unusual picture, take a minute to see if you can figure out what the photographer did to get it. This is excellent practice for figuring out your own shots when you’re trying to get a specific effect.

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Filed under Discussion, Exposure

How to take a picture of the moon

If you’re in a hurry you can ignore the discussion and skip straight to the summary


moonSince a couple of people have requested this, here’s the Stop Shooting Auto! lesson in shooting the moon.

Back in the olden days, when cameras were carved out of stone and didn’t have whizbang light meters and dozens of confusing exposure dials, photographers had to choose their settings manually. In fact, my first 35mm camera, a Kodak Pony IV, had printed inserts that went into a slot in the back of the camera to help you pick your settings. For bright sunlight you used this, for cloudy bright you used that, etc. And horror of horrors, there was no Photoshop– if you screwed up the exposure, you had to try to fix it in a (gasp) darkroom. And that was if you were lucky– most people just lived with whatever bad photos they took.

GreenCheeseBack in these dark, dark days, photographers often relied on rules of thumb to help them choose their exposures. The most common of these was called the Sunny f/16 Rule. The rule went like this: for objects that are brightly lit by the sun, set your aperture to f/16. Set your shutter speed to 1/ISO of the film. (Film? Do you remember that?) So if you were shooting with ISO 100 film, you’d set the camera to f/16 and 1/100 sec, or as close to that as you could get. At ISO 200, it was f/16 and 1/200 sec.

I know what you’re thinking. That’s great, Patti. Thanks for your little stroll down memory lane, but someone has been spiking your Geritol. I want to photograph the moon, and I want to do it at night when it’s dark out. Why would I care about sunny days?

Here’s a little secret. The moon is nothing more than a bright object lit by the sun. Sure, it’s in a dark sky and everything around you is dark, but the moon is surprisingly bright. However, it’s also pretty far away, and that makes it look pretty small in the sky and even smaller through your camera’s lens. Unless you have a very long telephoto lens, your camera’s meter just won’t know what to do with the shot. If you’ve tried to take a picture of the moon in automatic mode, you probably got a small white dot on a dark but washed-out background. We can fix that, but it will mean putting your camera in manual mode. I hope that’s not as scary to you as it would have been before you started reading this blog.

Let’s go back to that telephoto lens thing for a moment. The first thing you want is the longest telephoto lens you can get, so that the moon looks like something other than a white dot. 200mm is about the shortest, 300mm is better, and 500+ is even better than that. If you don’t have a long lens, a teleconverter is a useful accessory to have. In a nutshell, a teleconverter is kind of like a magnifying glass added to your lens. With a 1.4x teleconverter, a 200mm lens acts like a 280mm lens, and with a 2x teleconverter, a 200mm lens acts like a 400mm lens. There are some serious downsides to using teleconverters, but they can also be useful tools.

[Update: I’ve recently added an article titled What lens should I use to take a picture of the moon? It has examples of moon shots at focal lengths from 200mm to 2240mm.]

Something To Howl AtOK, so you have your longest lens out. You might want to use a tripod too, lean the camera against a wall or something to stabilize it. What settings should you use?

First off, use manual focus. Because the moon is pretty small in your viewfinder, many cameras have trouble focusing on it. If yours works in autofocus that’s great, but if not just switch to manual focus and do it the old-fashioned way.

In my experience, the Sunny 16 Rule is close but not quite right for the moon. The best settings I’ve found seem to be around ISO 100, f/11, and 1/100 sec. However, sometimes something a little slower or faster does a better job. Because of this, I recommend doing something called bracketing. Bracketing is just a fancy term for taking a bunch of shots at slightly different exposures so that you can pick out the best one.

Set your camera for manual mode, ISO 100, f/11, and 1/100 of a second. Take a picture. Now without changing any other settings, set the shutter speed to 1/200 and take another picture. Do the same thing at 1/400. When you’ve done those three, go the other way. Set the shutter speed to 1/50 and take a picture, then 1/25. If you aren’t using a tripod, don’t forget to brace the camera against something solid like a wall or a pole, so you don’t get camera shake. And voila! One of those is probably a pretty good shot of the moon.

To summarize:

  • Manual mode, at f/11 and ISO 100
  • Focus manually
  • Use a tripod or stabilize your camera against a sturdy object like a wall
  • Start at 1/100 sec and take a shot
  • Bracket a couple of shutter speeds faster and slower (e.g., 1/60, 1/30, 1/200, 1/400, or whatever speeds are closest to those on your camera)
  • Look at the images on your computer and pick out the best one

The next time you have a clear, dry night and the moon is in the sky, try it yourself.

And here are a few products that may be useful in shooting the moon:

Tamron 1.4x Pro Teleconverter for Canon cameras

Tamron 1.4x Pro Teleconverter for Nikon cameras

The Tamron pro series of teleconverters are optically quite excellent.  Their physical geometry makes them work with most telephoto lenses (at least on Canon… I’m less familiar with Nikons), and they give you a fair bit of extra focal length to bring the shot in closer.

Canon RC-1 Wireless Remote Control

This little gizmo is amazing.  It lives on the strap of your camera, completely out of your way, but just waiting until you need it.  When you do, pop it off and voila– you have a wireless infrared remote.  It works with most Canon dSLRs, it’s inexpensive, and it’s incredibly useful.

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Filed under Exposure, Lesson

Exercise: exposure modes

Are you ready for the first exercise? Great, let’s go. If you haven’t ready the last lesson on how exposure modes work, you’ll want to do that first. In this exercise, we’ll try out the various exposure modes in order to learn how the controls work.

OK, grab your camera. It doesn’t matter what lens you use, but try to find a place with a lot of light and something at least marginally interesting to point the camera at.

The first thing we’re going to do is put the camera in aperture priority mode. If this is the first time you’ve taken your camera out of its everything-automatic rut, this may be scary for you. Don’t worry, I’ll be right here to hold your hand. Now, take a deep breath and turn the dial to Av, A, or whatever your camera calls it.

See? That wasn’t so bad.

Now, pick out something nearby that you can focus on. Maybe it’s a picture or a piece of furniture or a tree, but pick something that isn’t going to move around a lot. Now, look through the viewfinder of your camera and focus on the thing that you picked out. Press the shutter button halfway, and you should see a display in your viewfinder that will tell you what the aperture and shutter speed are set to.

Turn whatever dial it takes on your camera to open the aperture as wide as it will go– remember, that’s the lowest number. It may be as low as 1.4 or 1.8, but more likely your lowest setting will be somewhere between 2.8 and 5.6. It doesn’t matter for now. Keep pointing the camera at whatever object you picked out.

If you did that quickly enough, which you probably didn’t, you’ll still have a display in your viewfinder. If not, push the shutter button down halfway to get it back. Make a mental note of what shutter speed the camera has picked out. Now, turn the aperture dial a few clicks. Do you see the shutter speed change? (If the display goes away, just keep pressing the shutter button halfway.) Keep doing this until the aperture is as small as it will go– most likely, that will be around 22, but your lens may be different.

Did you notice how the shutter speed changed automatically every time you changed the aperture? That was your camera’s meter picking out the right shutter speed to go with the aperture you chose. It’s possible that your camera had trouble with the highest and lowest settings, and couldn’t find a shutter speed fast enough or slow enough to work. If so, it probably kept the needle all the way on the left or right of the meter display, and maybe flashed it or beeped or complained in some other way. If so, remember that for the future. It’s your camera’s way of saying that something’s not right.

Now, let’s do the same thing but in shutter priority mode. Set your camera to Tv or S or whatever. Look through the viewfinder, and press the shutter button halfway. Turn the magic dial to change the shutter speed, and watch the selected aperture change. If you pick a really fast shutter speed like 1/1000, there’s a good chance you’ll get to see how your camera complains about bad exposures.

OK, there’s one more step, but before we take it you probably need a quick break from all this scariness. Get up, walk around the room, do a jumping jack, grab a beer, or do whatever it takes to get past all the scariness I’ve thrown at you.

Are you back? Excellent. Now, we’re going to do one more scary thing. Set the camera to manual mode. Ready? Deep breath. OK, go.

Still with me? Great! Now, set your aperture to f/8, using whatever control your camera uses to change the aperture in manual mode. Now look through the viewfinder and press the shutter halfway. See the indicator on the meter? It’s probably way off to one side. Keep looking through the viewfinder while you turn whatever dial changes the shutter speed. Keep doing this until the indicator is right smack dab in the center of the scale. When you get it there, take the picture.

Guess what? You just took a photo in manual mode. If you view it on the camera’s LCD, you’ll probably see that it looks pretty good. Pretty cool, huh?

If your room isn’t very bright, there’s a chance that you couldn’t make that work. If so, set the aperture as wide as it will go and try again, or go somewhere with more light.

Next lesson: Shutter speed exercise

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Filed under Aperture, Controls, Exercise, Exposure, shutter speed

Three things that go into exposure

Too Bright As we learned before, when you take a picture a few things happen quickly. First, the aperture closes to block some of the light that’s coming into the camera. Second, the shutter opens and closes. As soon as that happens, the magic gnomes on the camera’s sensor record whatever light they saw when the shutter was open.

I’m sure you’ve taken some pictures that came out way too dark, or maybe even completely black. You’ve probably also taken some that were really light and washed out. We call those dark pictures underexposed, since they didn’t get enough light. The way too light ones are called… can you guess? That’s right, overexposed! Give yourself a shiny gold star.

You’ll see three little bears next to the text in this article. The first one is too bright– he’s overexposed. The second one is too dark– she’s underexposed. Baby bear is at the bottom– he’s juuuuuuusssttt right. IF you go through all of the lessons on this site and do all of the exercises, you’ll know what it takes to get all of your pictures to be just like baby bear.

Too Dark There are three basic things that go into the equation for how a picture will be exposed. The first is how long the shutter is open– if it’s open for a long time, a lot of light gets in and lands on the sensor. If it’s only open for a very short period of time, a lot less gets in. Because photographers like fancy schmancy terms, we call this shutter speed.

The second thing that controls exposure is how big the aperture is. If it’s closed down so that there’s only a tiny hole, not much light gets in. If it’s wide open, a lot more light comes in and lands on the sensor.

If you can’t make sense of how aperture works, imagine that you’re in a plain room with no lights at all… not even the glow of a computer screen. (Stop shaking… it’s an imaginary room.) All of the light in this room comes from one window that faces out to a bright sunny day. If the room has a really big window, then the room will be bright and sunny. On the other hand, if it has a teeny tiny window, the room will be pretty dark. The aperture on your camera is like the only window the camera has. If the aperture is big, lots of light gets in. If it’s small, only a little bit of light sneaks through.

Just Right The third thing that goes into exposure is called ISO, and it’s a measure of how sensitive the sensor is. Remember our sensor gnomes? Think of them as light microphones. If the camera is set to a very high ISO (e.g. 800 or higher), the gnomes will be able to record small amounts of light. At low ISOs (100, 200) the gnomes need a lot of light.

Right about now, you’re probably thinking that you want the gnomes to be as sensitive as possible, but that’s not true. For now, just trust me on this, and I’ll explain later.

Next lesson:  Shutter speed, how it works

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Filed under Exposure, Lesson