Blog

MEASURING LIGHT.  CONTROLLING THE OUTCOME.

If there is one thing that has scared more people away from photography than anything else, it’s the topic of camera settings.  To some, the mere sight of terms like shutter speed, aperture or f-stop can cause developing photographers to throw their hands up out of frustration.  While it’s really, really tough to explain each concept in the text of a book, they are simply too critical for successful bald eagle photography.  Boiling these concepts down to their core is the first step toward gaining an understanding of how light is not only measured, but controlled within the camera.  Using nothing but automatic settings with a DSLR is like a chef that cooks with nothing but a microwave.  Without the knowledge to harness the light and use it to your advantage, your camera is little more than a point-and-shoot with a big lens.

Allowing it to make the decisions is like blindly throwing a dart at a dart board.  You might get lucky every now and then and increasing the number of darts certainly improves your chances.  But growing as a photographer starts with understanding the “why” behind the “how”.  Whether you are trying to control depth of field or deliberately add motion blur, it starts with gaining control over your camera’s settings.  The camera doesn’t understand the result you are trying to achieve, nor can it determine the most critical part of your image.  Gaining the ability to control the light entering your camera is to gain the ability to control the result.

If you’ve looked at your camera you’ve likely noticed several numbers that pop up.  There might be some fractions.  There are some decimals.  When set on any of the automatic modes, the numbers change and fluctuate on a seemingly constant basis.  Let’s take a look at each component of exposure to gain a better understanding. 

YOUR CAMERA’S METER – THE FORGOTTEN TECHNOLOGY

To squeeze the most out of your time and talent, we need to squeeze the most out of your camera.  That starts with taking your camera’s suggestions, then second guessing the technology by making an informed decision.  The difference between a person with a nice camera and a professional photographer is often how much faith they put in their camera’s suggestions.  An amateur believes in it almost entirely.  The professional instinctively distrusts it.

The first number we need to look at is zero.  Often overlooked when using automatic exposure modes, your camera’s light meter is constantly working to measure the light in a given scene.  Any attempt at outthinking the camera starts with recognizing what the camera has already determined, then overriding its assumptions based on your own observations.  You are going to look at this merely as a suggestion rather than the rule.  For example, when photographing the dark colors of a juvenile bald eagle surrounded by snow, the only way to achieve a good exposure is to compensate for the camera’s limitations.  In this scenario, the camera will tell you what it thinks is the “correct” exposure for the entire scene, often underexposing the subject due to the amount of brightness in the frame.  We have to take control of the because the camera can’t record an accurate exposure of both.  So here’s the question.  Again, the scenario is a juvenile bald eagle (dark in color) against a background of snow (bright in color).  If you had to choose either the snow or the eagle to be exposed perfectly, which would you choose, the snow or the eagle?

If you chose the eagle, you are correct.  We only care about the bird.  Again, the best camera settings start with allowing the camera’s meter to establish a starting point, then making adjustments accordingly.

During the early days of built-in light meters, the display was unapologetically analog.  The fact that you had to manually advance the film to the next frame meant that there was no need for a large power source to make the camera operate.  In fact, all the camera needed to function was a battery that resembled one that you would find in a mechanical watch.  You simply made sure that the arrow was in the sweet spot based on the camera’s recommendations and the overall scene was well exposed.  Compensating for the meter’s shortcomings was simple.  If you wanted to overexpose the shot, you purposely adjusted your settings toward the “+”.  Conversely, if you wanted to underexpose, you adjusted your settings toward the “-” side of the meter.

Thankfully, today’s built-in light meters work the same way.  While the methods that the camera uses to measure the available light of a scene are far, far more advanced than what was found in early light meters, assessing the information has never been easier.  Most companies simply illuminate the reading that corresponds to your current settings.  By default, each line represents 1/3 f-stop with the larger markers representing a full f-stop.  When compensating for a scene that includes drastically different light values, you follow the same pattern as if you were using an analog meter.

F-STOPS. UNDERSTANDING THE THREE LEVERS

Shutter speed, aperture and ISO are directly related and the term “f-stop” (or “stop” for short) has been used as a consistent unit of measure for all three.  Before we dive into defining each one, it’s critical to understand this relationship.  When you gain an f-stop in one, you lose an f-stop in another.  Read that last sentence again.  Then read it again.  Then tattoo it to your forehead.  We will review a few examples in a bit (f-stops, not tattoos).

If photography is defined as “drawing with light”, then the ability to control that light is essential to understanding the craft.  In other words, light is important, and there are three ways to control it with your camera:  shutter speed, aperture, and iso.  Let’s examine each of these terms.

SHUTTER SPEED DEFINED

Shutter speed simply refers to the amount time that the film or sensor is exposed to light.  If it’s exposed for a long time, it will record motion blur.  If it’s exposed for a short time, it will freeze the action.  The faster the action, the higher shutter speed needed to stop it.

Camera companies have unfortunately muddied the waters as of late, making the learning curve a bit more difficult for budding photographers.  By removing the “1” in front of the number, beginners have often missed out on one key concept.  For the vast majority of photos taken throughout history, the shutter speed has been a fraction of a second.  In other words, when your LCD screen lists “500”, your shutter speed is actually 1/500^th of one second.  When it lists “2000”, your shutter speed is 1/2000^th of one second.  While some camera companies continue to provide this information in the form of a fraction, some have ditched this practice to make room on the LCD screen for other information. Again, this can delay a photographers growth by muddying the waters.

To look at this another way, let’s use landscape photography as an example.  I am a sucker for seascapes and like to blur the crashing waves to create my images.  In order to accomplish this, the sensor needs to be exposed for a significant amount of time to record the motion involved.  Throw out the action-stopping speeds of 1/500^th and 1/2000^th of a second and replace them with exposures that run anywhere from 2 to 30 seconds. 

APERTURE DEFINED

There is a series of numbers that have been in place for many, many decades that mean almost nothing to the vast majority of photographers, myself included.  It wasn’t until I began to conduct research for this book that I actually tried to gain a deeper understanding what each number of the aperture scale represented. Most photographers are certainly aware of the relationship that each particular number has on the result of their images.  We understand that f2.8 will deliver shallow depth of field and blur out the background and f16 will have the opposite effect.  This understanding is, by far, the most important thing to understand when it comes to aperture.

If you haven’t done so already, your homework assignment is to memorize the following bold numbers.  Write them down.  Shut this book.  Spend the next few minutes reviewing until you can recite each one.  Again, only memorize the bold numbers.  We will review the entire list in a bit.

2.8 4.0 5.6 8.0 11.0 16.0 22.0 32.0

As mentioned previously, there are three ways to control the light that enters the camera.  Shutter speed controls the amount of time that the sensor is exposed to light.  Aperture controls the amount of light that actually passes through the lens.  This time vs amount relationship is tough to describe in text, so let’s start by looking at a visual related to aperture.

Each circle represents a camera lens as if you were looking through it.  As your aperture increases, the amount of light that is allowed to pass through a lens decreases.  In other words, an aperture of f2.8 will allow more light to pass through than an aperture of f4.0.  Stop down to f8.0 and you reduce the light even more.  In other words, lower numbers (f2.8, f4.0) mean more light.  Larger numbers (f11, f16) allow less light to pass through the lens.  Again, the larger the number, the less light that passes through to your sensor.

How does this impact the image?  If f2.8 allows more light to pass through the lens, why not just shoot at f2.8 all of the time?  Shooting “wide open” gives you very little room for error.  If your focus isn’t spot on, your subject will not be in focus.  This concept is exacerbated when using larger and larger focal lengths.  As your subject gets closer, the need for depth of field can be intensified. 

ISO DEFINED

To review, shutter speed controls the amount of time that the sensor is exposed to light and aperture controls the amount of light that is allowed to hit the sensor.  To discuss the third method (or lever) of controlling the light within your camera, we need to take a look at the sensor.  ISO refers to the numerical value assigned and the value depends on your settings.  In order to understand this, it’s good to start with a bit of a history lesson.

For decades, the letters ASA were used to define a given film’s ability to absorb light.  The acronym “ASA” is short for American Standards Association and ensured that each film manufacturer used the same scale.  Just like driving a car, the higher the number, the faster the film was able to absorb light.  ASA 100 was generally used for daylight photography and ASA 400 was considered a good multi-purpose film speed (ASA).  When shooting action, photographers had the option to jump up to ASA800 or ASA1600, depending on the manufacturer.  There was a trade-off, however, with faster ASA speeds producing more “grain” (old school noise) throughout the image. 

Fast forward to today, when we use the acronym “ISO” which stands for International Organization of Standardization (yes, they aren’t in order).  Just as ASA ensured that film manufacturers like Kodak and Fuji were using the same standard, ISO ensures that camera manufacturers are consistent regarding the light sensitivity of the sensor in your camera.  An ISO setting of 400 in one camera will absorb light at relatively the same speed as an ISO 400 setting from another manufacturer’s camera.  Unlike traveling to a foreign country and having to calculate the exchange rate for our currency or kilometers to miles per hour, camera manufacturers have done us a huge favor in abiding by the same standard.

Whether it’s the ASA standard during the glory days of film or the ISO standard of today, increasing the ISO setting will increase the sensor’s ability to absorb light.  A setting of 400 ISO will absorb light twice as fast as a setting of 200 ISO.  Just like the trade off with faster ASA films, higher ISO settings will generally lead to more noise.

So there you have it.  Shutter speed controls the amount of time that the sensor is exposed to light.  Aperture controls the amount of light that is allowed to pass through the lens.  ISO controls the sensor’s sensitivity to light.  Now let’s take a look at the relationship between each setting.

FULL, HALF OR THIRD.

Why are there so many numbers?  If camera manufacturers limited us to changes of one full f-stop, photographers would lose the ability to make small adjustments.  Bald eagle photography is a perfect example of this due to the high contrast nature of the subject.  Rather than limit our options, most of today’s cameras allow photographers to set their cameras to change in full f-stop, 1/2 f-stop, or 1/3 f-stop increments.  The default for most cameras is 1/3 f-stops, hence the extra numbers in the aperture visual.  Again, this is critical when trying to properly expose the white of a bald eagle’s head, when 1/3 f-stop can mean the difference between good detail and great detail.

When looking at how each of these elements is intertwined, it’s important to start with a few rules:

• When a shutter speed is doubled, the amount of time that the shutter is exposed to light is cut in half.  In other words, when you increase your shutter speed from 1/1000^th to 1/2000^th of a second, the time is cut in half.  When you cut shutter speed by half, that equals one f-stop.  Conversely, if you change your shutter speed from 1/2000^th of a second to 1/1000^th, you’ve essentially doubled the amount of time.
• ISO operates on the same set of rules.  For example, reducing your ISO speed from 1600 to 800 cuts the amount of sensitivity in half.  When you reduce ISO by half, that is a reduction of one f-stop.  On the other hand, doubling the ISO (i.e. 200 to 400) and you’ve doubled the sensor’s ability to absorb light.
• I really, really wish I could tell you that aperture works by the same standard but it doesn’t.  Remember those seemingly arbitrary numbers that I asked you to memorize?  This is when the start to make sense.  When you change your aperture setting from f5.6 to f8.0, you are cutting the amount of light hitting your sensor by half.  Cutting the amount of light in half is the equivalent of one f-stop.

In the next lesson of this series, we will examine the fundamentals of camera settings by taking a deep dive into each lever to gain a better understanding of how to put each one into practice. Be sure to keep up to date on upcoming blog posts by subscribing.

This excerpt was taken from my latest project, a book titled Bald Eagle Photography – A Photographer’s Guide, which is scheduled to be published in 2020. To add your name to the mailing list for updates on its release, let us know who you are: https://ajharrisonphotography.com/book-release-update-request/