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All posts for the month April, 2010


 

Properly exposed background, dark subject

Do your photos sometimes look like this?

There must be something wrong with your camera right? You were trying to take a nice photo in front of a sunlit scene and for some reason the background looked great, but the people are just way too dark. What happened? They didn’t look this way in real life. Perhaps they’re unlucky. Perhaps they walk around with a preverbal “dark cloud” above their head which always puts them in a shadow.

NO that’s not it, but how cool would that be to have your own cloud follow you around? The reason the people in your photo are dark silhouettes is because your camera did not pick the right exposure for that scene. First a little background(no pun intended)…

Just before snapping a photo your camera employs many many sensors to create the finished photo, including an exposure sensor. This sensor measures all of the light in the scene and computes an average amount of light in the scene you are about the photograph. Oh there’s one more thing you should know about most exposure sensors it has a bit of a handicap, it can only see in black and white.

Aww the poor thing…I know it’s a sad story, but that’s ok because the exposure sensor has learned to deal with it’s disability and it excels at picking the proper exposure for your scene, most of the time. You see the exposure sensor is programmed so that everything it sees in the photo will look like a middle gray.

Now what’s a middle gray, well it’s a gray that isn’t too white, or too black, it’s sort of in the middle :) Actually in terms of numbers middle gray for digital cameras is about 18% gray. It’s different for film. So when your camera’s exposure sensor averages all of the light coming into your scene it compares it to middle gray. Middle gray is your camera’s “happy place”. Your camera would love all photos to average out to middle gray.

In fact, that’s what it tries to do. When the average light in your scene is compared to middle gray the camera will choose an exposure that comes as close as possible to making the average light in your photo register as middle gray. This works very well in most situations. Plus several newer digital cameras have pre-defined exposure templates built-in which help your camera to nail the exposure correctly more times than not.

So then how did your people in front of the sun turn out to be dark silhouettes? Well when your camera “metered” the light in your scene it detected many bright areas, this is because you were shooting towards the sun. So imagine the photo as your exposure sensor sees it, in black and white. From the cameras point-of-view it is on average a very brightly lit scene. So the camera does what it’s programmed to do and compares this very bright scene to middle gray.

As you can see from the photo above, the few people in your scene are very dark compared to the rest of the brightly lit scene. So when the average light in the scene is compared to middle gray the camera says “the average light in this scene is much much brighter than middle gray, so I need to choose an exposure value which will darken the scene.” Hence, you get a lovely exposed sky and background, but dark silhouetted people.

A great choice if you were taking a photo of the bright background. However, you wanted the camera to set it’s exposure for those people in the scene, not the big bright background. So what can we do about it? Well your camera realizing that it’s only right about 80% has a feature that will allow you to fix this problem when taking your photo. Allow me to introduce….Exposure Compensation!

Almost all digital cameras and film cameras have an exposure compensation feature, sometimes known as “backlight compensation”. Just look for the universal symbol for exposure compensation . Exposure compensation allows you to adjust the camera’s exposure to suit your scene. In our case where our people are silhouetted we would increase the exposure by +1 or so which would properly expose for the people in the scene, but the background would tend to be a bit overexposed. This is acceptable since our main subjects are the people and not the background.

I know you guys though…you’re saying “Scott, why can’t I just move my subjects so that the sun is in front of them and not behind them, wouldn’t that work too?” Of course it would, but there are many times when exposure compensation needs to be employed, not just when the sun is behind your subject. How about taking photos of your kids in the snow? All of that white snow everywhere reflecting into your camera’s lens will cause the exposure sensor to underexpose your subjects just as if it was in bright sunlight. So we can employ exposure compensation to expose those kids properly.

Exposure compensation isn’t only for bright scenes, it works the other way as well.

What if you have a friend who enjoys boating on a lake, it can get pretty dark on there, especially towards the end of the day. Say you take a picture of him or her.

Here we have your friend against a dark blue lake background. When your cameras exposure sensor meters the light it’s going to average out as a very dark scene, much darker than middle gray. So what’s going to happen?

Your camera is going to choose an exposure that makes the whole scene brighter. This is fine if you’re goal is to shoot the lake, but you’re trying to shoot your friend, who is now very overexposed and washed out.

So what do we do to fix this? Drain the water and shoot them on sand!!! No, not quite, we can employ exposure compensation to fix our exposure but this time in the negative direction. Maybe -1. Now our friend is properly exposed. However, the lake is a bit dark now, this is acceptable though because your friend is the main subject of the scene.

So the next time you find your cameras exposure sensor is not seeing things as you see them, employ some exposure compensation and make your camera expose the scene as you want it to!

Feel free to leave comments and post some of your results.

We’ve finally made it to the end of our 5-part series on exposure modes. We finish with the king of all creativity, Manual Mode. This is the mode that lets your knowledge of photography and creativity shine through. Manual Mode is the one where you basically tell the camera to “shut-up” and let you do the driving.

Are you in a dark room where the camera is telling you it’s too dark to make  a proper exposure? No problem, Manual Mode will let you take that photo. Do you want to take a photo with a very deep depth of field and also freeze the action, but don’t have enough light? Switch to Manual Mode, and give it a shot, you’re not paying for film!

Ok ok, so Manual Mode is not a magical cure for exposure problems, but it does allow you to go out of your camera’s, and possibly your, comfort zone to take some photos that the camera might not allow you to take while in one of the other exposure modes.

Let’s review a bit…we’ve already learned about the other 3 exposure modes..

Programmed Auto Mode (P-Mode) your camera does all the thinking. Aperture and shutter speed are set for you automatically.

Aperture Mode (A-Mode) you set the aperture and the camera determines the shutter speed for you.

Shutter Mode (S-Mode) does just the opposite, you set the shutter speed and the camera sets the aperture value.

By now I’m sure you have guessed that in Manual Mode (M-Mode) you’re flying solo. You’re responsible for  setting both the aperture and the shutter speed yourself. That’s a big responsibility! Are you ready for it? Can you handle it? I think you can.

Even if you don’t think you’re quite ready, I implore you to try Manual Mode. Nothing will teach you about exposure settings and the relationship between aperture value and shutter speed faster than being out there on your own making your own exposure settings.

Plus, if you make a mistake, you might it’s a part of life, because you’re shooting digital it costs you nothing to try, and it’ll be our little secret if it doesn’t turn out quite right the first time. If you’re shooting film however, you may want to borrow your friend’s digital camera to try it out. You’ll most likely be going through a lot of frames, plus the digital camera allows you to get instant feedback, instead of having to wait for the film to be developed to see what worked and what didn’t.

The toughest thing to shooting in Manual Mode is picking a starting point. When choosing your aperture and shutter speed where do you begin? It can be very overwhelming. Sometimes when shooting in Manual Mode professional photographers will use a light meter. A light meter is a hand-held device that measures the light in the scene around you and gives you values for what your aperture and shutter speed should be.

Now wait a minute…that sounds just like what your camera does when it is in P-Mode. Well you’re right, your camera has a built-in light meter which is how it determines the proper exposure values for the scene you are shooting. So what do you do when you’re new to Manual Mode and your light meter is in the shop? Put your camera in P-Mode and press the shutter down half-way.

This is going to give you an exposure reading. In P-Mode the camera will use it’s built-in light meter to “read” or “meter” the scene and tell you the aperture and shutter values that it comes up with. So now armed with this new information we can switch back to Manual Mode and plug in those values we just got from the camera’s built-in light meter. You now have an excellent starting point for setting up your shot in Manual Mode.

You know these values are going to give you a relatively decent exposure to begin with, so now you can start getting creative by varying either the aperture value or shutter speed to achieve your desired results. Want a shallower depth-of-field? Go ahead and dial in a larger aperture value, just keep in mind that you’ll need to adjust your shutter speed to keep your exposure well balanced.

A good rule-of-thumb to remember is that for every full stop of aperture value you increase or decrease you should also change your shutter speed by a full stop to maintain the same Exposure Value (EV). We learned about this a while back when we discussed reciprocity.

So for example, if our light meter (built-in or hand-held) chooses an aperture of f/8 and a shutter speed of 1/125 and we want a shallower depth-of-field. We can change our aperture value to f/4. That is a change of 2 full stops. So in order to keep the same Exposure Value (EV) we will need to raise our shutter speed by 2 full stops bringing us to a shutter speed of f/500.

This is because when we make our aperture value larger by a full stop we are letting in double the light. Since we changed our aperture from f/8 to f/4, 2 full stops, we are now letting in 4 times the light at f/4 than we did at f/8. So to compensate we use a faster shutter speed by 2 stops from 1/125 to 1/500. This causes 1/4 of the light to be let in at 1/500 than we had at 1/125 which cancels out the 4 times more light coming in from our aperture value.

How do I know that is 2 full stops you ask? Well I have included a chart at the end of this article that shows the full stop values for both aperture and shutter speed. Some high-end cameras will let you change your aperture or shutter speed in 1/2 or 1/3 stops as well, but all cameras will let you dial in full stop values.

Manual Mode also comes in very handy when shooting with flash, especially external flash. A full discussion on shooting with external flash is a topic for another blog post, but we’ll touch on it briefly. When shooting with an external flash the cameras light meter may not take this into account. Therefore it might choose a very slow shutter speed automatically for you because it is metering the available light in the scene. The light meter may not know that an external flash will be used. This is the perfect time for Manual Mode.

By shooting the scene in Manual Mode you are able to tell the camera that you would like to use a faster shutter speed. We know this still will result in a good exposure because the flash is going to provide quite a bit of light to our scene. Shooting in Manual Mode let’s you choose the shutter speed and also the aperture value that will work for your flash lit scene.

There are some people who are perfectly content taking all of their photos in P-Mode and letting the camera do all their thinking. Most of the time this yields decent photos. However, you cannot truly begin to explore the creative possibilities of photography or take your photos to the next level until you turn that dial and try shooting in one of the other 3 modes.

Maybe you feel Manual Mode is a bit too much for you to try right now, but Aperture Priority Mode or Shutter Priority Mode are just begging for you to give them a shot. They let you start taking control of the exposure in your photos without having to fly solo. And as with most things, there is no better way to fully understand your cameras exposure modes than to get out there and shoot as much as you can!

I hope you’ve enjoyed this multi-part series about exposure modes, even if the end was a long time coming. Feel free to ask questions, leave comments, and share your creative photos. Until next time.

Exposure Value Chart

Chart of full stop values and Exposure Values (EV), Courtesy of thecrosseyedbear on Flickr http://www.flickr.com/photos/thecrosseyedbear/2124175721/