Photography Group – Exposure Nuts & Bolts

I’m hosting a sorta monthly photography group for some local women interested in improving our skillz. I make no claims to being a great photographer, but I do have a few great cameras (hand-me-downs from my dad) and I’ve been exposed (heh, couldn’t resist) to photography all my life.

I’m posting the notes here mainly because it’s the easiest format for people who missed the meeting to see the photos in context. If I am off-base somewhere, or you’re reading this and have additional tips to share… please comment and set me straight! 🙂

Exposure Nuts & Bolts

Exposure is how light or dark the final image is. Learning about how it works will help you correct problems, and it will allow you to be more flexible with the kinds of shots you can take (backlit, black background, indoor, etc.)

Here is a photo that is under-exposed:

Properly exposed:

And here it’s over-exposed:

To get a good exposure straight out of the camera, you can often just leave things on “auto” and let the camera do the work. But if “auto” isn’t doing the trick, or you want to achieve a certain goal (freezing action, or creating a creamy background for portraits), it helps to keep some things in mind:

Consider your circumstances

  • How much light is around? Remember from our first meeting, that photography is all about light. Harsh sunshine or dimly lit scenes are trickier to capture properly.
  • Reposition you and/or your subject to get flattering light.
  • Do a gut check on what is essential in the final image. If you don’t want to lose detail in a white wedding dress, for example, you may want to underexpose a bit.
  • ISO is how sensitive your camera is to light. Choose your ISO based on your circumstance. Generally you’ll want to go low if you’re dealing with very bright lighting (100). In all other circumstances, I leave mine as high as it goes without introducing graininess (800 for me). I’ll go higher if the lighting is really dim but I am determined to get the shot.
    TRY IT: Take some test shots with your camera in a situation where there is plenty of light. Change the ISO with each shot. Look at the images on your computer afterward and note at which point the image becomes noticeably “grainy”. You’ll want to keep the camera set below that number, unless low light makes it absolutely necessary to exceed it.

This picture was taken in a dimly lit delivery room and the ISO was up at 2000 (with a really nice camera, so it’s not actually very grainy). But even if it was, the important thing in this case was definitely to “get the shot”:

This photo was in the open shade on a sunny day, ISO 100 (thanks, Lonica!):

How a camera lets in light

Aperture = How wide your camera opens up.
Measured in “f-stops”. The range available depends on your lens. The lower the F-stop, the wider the aperture and the more light being let in. The lower the F-stop, the shallower your depth of field, and the more out of focus the background will be. Here is an example of an f/2 shot:

Here is an example of an f/13 shot (it keeps plenty of detail in the background):

TRY IT: Set your camera on Aperture Priority mode to play with this. Turn the main dial to “A” or “Av” and click the wheel to change the aperture more open or closed. Take a picture with the smallest aperture (largest number) and then take another shot with the largest aperture (smallest number). Check the difference later on your computer.

A low f-stop is great for portraiture because it makes the background creamy so it doesn’t distract from the subject. However because of the shallow depth of field, it also makes focus crucial. If you focus on a hand instead of on the eyes, you’re in trouble!

Shutter speed – How long the shutter stays open to let in light.
Often displayed as a number like 30 or 300, but that actually means 1/30 or 1/300 of a second, so the higher the number the faster the shutter speed and the less light is allowed in.

Faster shutter speed is essential for freezing action. A lower shutterspeed shows blurred motion, like for a beautiful shot of a river.

Here is a shot at 1/800:

Notice how the boy is frozen but you see a little blur on the water droplets?

Here is 1/8000:

The water is at a complete stand-still.

TRY IT: Set your camera on Shutter priority (S or Tv) to play with this. Have your child clap their hands and take a shot at 1/60 or 1/100 and another one at the fastest shutter speed your camera allows. Compare the shots on your computer later.

Typically if you get below 60, you will need a tripod or something to stabilize your camera so your images don’t show hand shake. Rest your camera on something stationary OR widen your stance, squeeze your elbows to your body, and exhale before clicking the shutter.

How much light your camera will decide to let in

Metering – How the camera views the scene
Unless you are in fully manual mode, your camera is auto-metering your shots. That means it’s deciding how much light to let in and setting either the shutter speed or the aperture accordingly (or both, just depending on what mode you’re in). In aperture priority mode, for example, you pick the aperture and your camera picks the shutter speed that will team up with your chosen aperture to let in the proper amount of light.

When it auto-meters, your camera gathers information about what’s in the frame and tries to expose the mid-tones properly. That means a predominately black frame or white frame could skew the results in one direction or another.

Unless you’re on fully automatic mode (in which case you automatically get evaluative metering), you can help your camera gather the RIGHT information by changing to spot metering, partial metering, or center-weighted average metering.

Read your manual, but generally “spot” metering takes a very small spot in the very center of the photo (generally you’d want to spot meter on your subject, perhaps on a person’s cheek). “Partial” metering takes a bigger slice of the center of the photo, and “center-weighted” uses predominately the center of the photo but also takes into account the rest of the photo as well.

In this photo, I had the camera on “partial metering”, which means it takes the center ~9% of the photo and uses that to decide on exposure:

See how the very center is supposed to be black?

The camera tried to make some “mid-tones” by letting in a lot of light and the whole photo ended up over-exposed.

This shot was taken next, still with partial metering on:

But in that shot, the center of the photo had black, white, and some in-between and the camera used that to properly expose the photo.

The good news is that although spot, partial, and center-weighted metering all look at the middle of the frame for exposure, your final shot does not have to have the subject right in the middle!

Press the shutter half-way while the face (or your subject) is centered on the frame, then re-frame the photo and press the shutter all the way down.

For this shot, for example, you could position the baby at the center of the frame, then hold the shutter half-way down and move the camera to include the father before taking the picture. It will be properly exposed with partial metering, even though there is a lot of black, including at the center of the frame:

Notice that we lose the detail in the shadows and that’s ok!

A quick fix

Exposure Compensation

  • Many cameras have a great little adjustment you can make to override the camera’s decision. If the camera is taking consistently dark photos of a certain situation, just dial up your compensation (EV). If your camera is blowing out the highlights, dial down your compensation. Try a full stop and see how you like it.

It typically displays something resembling a numberline. Here’s what it looks like on my camera, straight from the manual:

The difference between these two shots is me just brightening things up one stop:

(Thanks to my dad for many of the shots in this post. The good ones. Any bad ones are courtesy of me. 🙂 )

Advertisements

About beanland

Scott is a family practice doctor and Anne is a full-time mother and teacher to three beautiful girls and one boy.
This entry was posted in Nothing but random. Bookmark the permalink.

One Response to Photography Group – Exposure Nuts & Bolts

  1. Leslee says:

    This is great Anne! Thanks for your tips… I’m looking forward to the next meeting!

    Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s