Putting a Little Light on Exposure

It is very natural to see photography as aiming a camera at an object or a landscape, pushing the button and simply capturing an image of the objects in view.  The magic in the camera makes the appropriate adjustments to make sure it isn’t too light or too dark.  If the camera didn’t get it right, the picture was either under-exposed (not enough light) or over-exposed (too much light).  Back in the day, folks really into photography would measure the ambient light with a light meter and adjust the camera settings to help control the lighting when the image was taken, many still do!

Modern technology has made it such that cameras have very sophisticated light meters onboard that take care of much of the lighting.  It would be quite normal to think that intentionally influencing or manually controlling camera lighting could be considered a thing of the past.  Frankly, today’s camera have automatic features that can produce some incredible pictures.  But, understanding the basics of lighting can really expand the envelope and make the sport of photography a whole lot more fun!

Capturing Light vs. Recording an Image

If you begin to look at a picture less as recording an image and more as capturing light, this will make much more sense.  The goal is to capture the right amount of light but using different tools to capture that light.  With this perspective, you may be better able to control and predict how the image will turn out based on how you manage your lighting controls.  The cornerstone to capturing light is understanding exposure.

As an analogy, think of capturing light in an exposure is like filling a bucket with water.

If not enough light is captured, the picture is under-exposed.  If too much light is captured, the image is over-exposed.

Variations in exposure in a picture look like:

While this is pretty basic the intent is build an analogy between capturing the desired amount of light and filling a bucket with water.  For this to have meaning, it is important to gain a little more insight on how the camera captures the light.  There are three basic lighting components to understand:

• Aperture Setting (f-stop) = determines how big the hole in the lens is that lets the light in
• Shutter Speed = how long the shutter is open allowing light to enter
• ISO = the camera sensor’s (or film) sensitivity to light  (This will be discussed in a later post)

Back to the water bucket analogy.  If you are filling the water bucket with a fire hose, it will fill very quickly.  If you are filling the bucket with a small garden hose, it will take a bit longer to fill the bucket to the same level.

From the picture above, it makes sense that using an aperture setting of f/2 will need a much shorter shutter speed to fill the bucket than an aperture setting of f/16.

Expressed as a simple math problem:

• F-stop x Shutter Speed = Exposure

The key to understanding this in photography is that all the equations below are correct.  You can change the first number (f-stop), as long as you change the second number (shutter speed) correctly, the equation works out :

• 3 x 4 = 12
• 6 x 2 = 12
• 1 x 12 = 12

Automatic cameras or cameras in automatic mode select the aperture and shutter speed to capture the amount of light the internal light meter determines for a normal exposure.  In addition to having automatic settings, most cameras have the ability for the photographer to manually control aperture or shutter speed, or both.  Using these modes, you can greatly change the outcome of the image:

• Aperture Priority = Photographer manually set the aperture, the camera determines the appropriate shutter speed
• Shutter Priority = Photographer manually sets the shutter speed, the camera determines the appropriate aperture
• Manual = Photographer manually sets both the aperture and shutter speed

Lighting controls affect far more than just the amount of light reaching the sensor.

Changing the f-stop changes the shutter speed:

If in low light conditions without a tripod or trying to freeze action, manually selecting a low f-stop number (large opening) will give a faster shutter speed.  If trying to intentionally blur water movement, a higher f-stop number (small opening) will give a slower shutter speed.

 

 

 

 

 

 

 

 

 

 

 

 

Changing the f-stop also changes the depth of focus:

Varying the f-stop affects how much of the picture is in focus from near to far (depth of focus).  A large f-stop number increases the depth of focus, a smaller f-stop number reduces the depth of focus.

While these are a couple of basic examples, there is certainly more.

Cameras do their best to capture just enough light to make a normal exposure.  When lighting is pretty even and you are not trying to optimize any special effects, the camera will do a good job.  But there are many cases when the default camera settings are not optimum for what I am trying to achieve in the photo.  So, when you start looking at taking a picture as capturing light, how you capture that light can greatly impact the outcome of the picture.  This is threshold to creativity in photography!

More to follow….

 

Disclaimer.  The goal of this site is to encourage others to get outdoors and experience what life has to offer.  Since photography is a central theme of this site, I thought it might be helpful to include a few tips and ideas for understanding the basics of photography.  Most of what I offer in the photo tips section is based off experience I have gained over many years of enjoying photography and experimenting with different camera settings.  This trial-and-error approach to learning photography has certainly been supplemented with tidbits of techniques gained from a variety of photography-based magazines and talking to other photographers.  While I would love to give credit to the sources, I didn’t keep the magazines and can’t remember what I learned from who.  Having said that, these tips are pretty basic and would be considered common knowledge by photographers.