Part 1b - Exposure Is Everything. What is the camera's meter saying to me? (continued)

Well, how did the "mind" photography go?

Before I show you the answers to this exercise, I'll spend a few sentences laying some important ground work. We are talking about exposure. Exposure is the total amount of light that strikes the film in traditional photography or the light sensor in modern digital cameras.

Three exposure possibilities exist.

1. Too little light strikes the film or sensor -- producing an underexposed (dark) final picture.
2. Too much light strikes the film or sensor -- producing an overexposed (light) final picture.
3. Just the right amount of light strikes the film or sensor -- producing a final picture that's very close (in all aspects of color, density, contrast, etc.) to the original scene.

When a camera is in any of its "auto modes" (full auto, aperture preferred or shutter preferred), it's the built-in light meter that takes over to determine how much exposure (light entering the camera) is just enough to create the perfect picture. Unfortunately, most photography newcomers (and far too many "oldcomers") fail to recognize the assumptions the light meter is making, and how to interpret the information that the light meter ultimately returns to the photographer.

Now, let's look at the results of our experiment.

The answer to each of the three questions in my last post (What does each final picture look like?) is the same. Each final picture is gray. In fact, each picture is the same middle shade of gray:







So, what does this mean? For one thing, it means your camera's light meter and "auto" exposure processor are working perfectly and doing just what they are designed to do.

When I teach in a Photo 101 setting and conduct this same exercise, I invariably receive these answers:

1. The picture of the white card is white.
2. The picture of the gray card is gray.
3. The picture of the black card is black.

Think about those student answers. If the resulting pictures were actually white, gray and black, that would mean the camera's light meter (and internal processor) were able to distinguish objects in the real world, understand which picture element was your subject, and translate that information into a perfect exposure. Well, that's not the real photographic world (yet). If it were possible, photographers would be lugging around more computing power than they would be willing or capable of carrying. The light meter in your camera does not understand your shooting conditions or have the ability to read your mind.

It does, however, have one solitary mission in life: It accurately measures the light entering the camera's lens and relays this measurement to the camera's exposure processor. The processor then uses this information to adjust the settings of the shutter and aperture (in auto modes) to allow just enough light to strike the film or sensor to produce a "middle gray" image. Every time.

There's an important note to add about this "middle gray" thing. Your camera's meter "sees" in terms of black and white densities. So the results of this exercise would have been exactly the same if we had used three different shades of a color for our original cards -- for example, a very light green, a middle shade of green and a very dark green. The final prints would have all rendered the various green cards as the same middle green shade (see example below):






Let's equate this exposure process to a more real world situation that you have probably encountered. I'll use a picture from my New Jersey home where winter snow storms are common. (Sun worshipers please substitute a brightly lit beach scene. The results are similar.)



The scene of your home and landscape covered in fresh snow is straight from a fairy tale and worthy of capturing for posterity. Photographers who don't understand the light meter's capabilities and resulting measurements will invariably be disappointed when their final picture looks similar to the image below:



This typical result is UNDEREXPOSED -- not enough light was allowed to strike the camera's sensor. Is the camera broken? What was the camera thinking? If we could listen in on the digital conversation in the camera it would go something like this.

• "WOW! Where did all that light come from?
• But "no problem".
• I'll measure the amount of incoming light.
• Then I'll set a shutter speed and aperture setting that will produce an exposure that renders the scene as middle gray."

And it did just that. The snow in this scene was exposed to render that factory-set, middle gray shade of color. Unfortunately, this middle gray is not true to reality (unless, of course, you were trying to simulate a moonlit snow scene. But that's another can of worms for later discussions). As you know, snow is an extremely light shade of gray (almost pure white).

Please don't think of this situation as hopeless. The opposite is the truth. Knowing what the meter is trying to accomplish is the starting point for all of your photographic heroes. It also places you well on the path of becoming the best photographer you can be.

So, now that we understand what the camera's meter is built to do, the post titled Part 4 will help you use this knowledge to learn exactly what's so special about your camera's specific "middle gray". Then you can begin taking control of your exposures and gain the confidence to know that "what you see is what you get". Photographic WYSIWYG.

Hope this series is helpful to you. As always feel free to send along your comments and suggestions.

Part 1a - Exposure Is Everything. What is the camera's meter saying to me?

Having spent most of my career on the technical side of photography, I've learned that the real mechanical challenge is to take a picture that renders a final image closely matching the reality we saw through the viewfinder. I also know that "auto mode" is not synonymous with "auto success".

We can manipulate images, add special effects and tweak the color/density/saturation/contrast characteristics of a photograph in programs like Adobe's Photoshop®. But the trick is composing a picture and "knowing" that when the shutter goes "click", we've captured the moment inside a digital file that will need little or no digital enhancement.

This kind of photographic certainty begins and ends with EXPOSURE. For the beginning DSLR photographer, mastering exposure will put you on the path to taking great pictures and loving every minute you spend behind the camera. It was his insights and understanding of the importance of exposure that enabled Ansel Adams to capture unforgettable images and inspire the generations of photographers that followed.


So critically fundamental is exposure to photographers of all skill levels, that I'm posting a series of entries on the topic. Each post will be bite size and include a practical assignment aimed at helping you form a life-long creative partnership with your camera.

The three images above are indicative of the exposure problem every photographer faces. The left image is UNDEREXPOSED. While the picture on the right is OVEREXPOSED. Finally the center photo is correctly exposed. What's interesting is that with your camera set in "auto mode" the odds that this picture would have been exposed as shown in the center picture are only about 50/50.

As you may or may not know, it's ultimately your camera's shutter and aperture controls that will determine just how much light strikes your camera's sensor to record the picture. These light controls will be discussed at length in later posts.

But, for this discussion, we must start with the device directing the actions of the shutter and aperture -- the camera's built-in light meter. This is where we'll start our understanding of exposure. Keeping the three pictures above in mind, the question is: "What is the camera's light meter trying to tell me?". Followed closely with: "Why doesn't the meter 'automatically' give me good pictures every time?".

The answers to these questions lie in our own misconceptions about the functioning and capabilities of the light meters built into every modern film or digital camera. Understanding what the light meter is attempting to accomplish, leads to a simple experiment. In this assignment, only use the camera in your mind. Your real camera isn't needed at this time. I ask you to take three mental pictures, develop them in your mind and report on the results. Here are the subjects for your three pictures:

Picture 1: A white card approximately 16" x 20" in size. Instructions:

• Go outdoors and find a nice shady spot to take the picture.
• Place your camera in full "automatic mode"
• Compose the picture by moving close enough to the white card so it fills the entire viewfinder image. (All you see through your viewfinder is "white")
• Take the picture.

Picture 2: A BLACK card approximately 16" x 20" in size.

Instructions: Follow the same instructions as described for Picture 1 above.









Picture 3: A middle GRAY card approximately
16" x 20" in size.

Instructions: Follow the same instructions as described for Picture 1 above.





Now it's time to finish the assignment. Process these three pictures in the same way you normally process all your photos. Only this time do it in your mind. Again in your mind, take a look at the final three prints from the pictures you took.

Describe what you see.

Picture 1: What does it look like?
Picture 2: What does it look like?
Picture 3: What does it look like?

That's it for this entry. The answers and explanation are available in my next post.

As always, feel free to comment as to the usefulness of this discussion in your understanding of photography.