Exposure: It’s all about reflected light

I have written about the topic of exposure before, but after a student from a local photography class complained to me and said, “I don’t really understand what the meter does,” I decided I would revisit the topic for readers.

In order for a subject to be captured by a digital camera it must be exposed to light.

This is not new information to most photographers; however, many photographers have problems understanding reflected light, and, therefore, exposure, because of the automation technology built in to digital cameras.

That student actually had the courage to put into words what I expect many of her classmates don’t understand, or even care about. Cameras are so automated that many photographers are unaware that the sensor is actually reacting to the light reflected back to the sensor, and that the photographer can have total control over the light reaching the sensor.

Readers recall that light is reflected off everything, and that the surface of every object reflects some amount of light. The camera’s light meter is calibrated to measure light in a constant value and will distinguish the difference in reflection coming off different objects.

The camera has two mechanisms to control the amount of light reaching the sensor, one – the shutter, and two – the aperture.

The shutter blocks light from the sensor until the shutter release button is pressed, then it quickly opens and closes the shutter. Setting the camera’s shutter speed controls the length of time the shutter remains open.

The aperture is an opening that lets light pass through the camera’s lens and is measured in f-stops. In actuality, it is a hole (aperture) that photographers control by opening it wider (wider aperture) for more light, and closing (smaller aperture) for less light; similar to the pupil of our eye.

What photographers are after is an optimal amount of light that will show details, in both the shadows and the highlights, and the meter is the measurement tool that allows photographers to control light.

For example, if the photographer is shooting a wedding, both the groom’s black suit and the bride’s white dress should have details, and neither should be over, or under exposed.

Photographers use the meter to determine the under exposure or over exposure of those subjects.

For example, I might want to slightly under expose the bride’s highly reflective gown on a bright sunny day, or conversely, over expose it on a heavily overcast day. In both instances I would be checking the groom’s black suit with my camera’s meter. Experience gained from practice helps and looking at the LCD after making meter tests is imperative.

Although the exposure from the shadows to the highlighted areas begins smoothly, it has a maximum value in the highlights and when it reaches that point it stops responding to any additional increase in brightness. This is called overexposure, or “clipping,” the highlights, and I warn photographers to be careful of that because the results are flat highlights without detail. It is up to the photographer to determine the correct exposure using the camera’s meter to ensure that doesn’t happen.

Fortunately, photographers have the histogram and checking it to correct a problem exposure immediately after releasing the shutter can save photographers from over exposed images. In addition, light meters on cameras have greatly improved over the years, and ignoring the camera’s meter information about the light, and relying on luck and preset auto modes, is a recipe for mediocrity.

To sum this all up, photography is all about reflected light and my recommendation to that student was to pay attention to the camera’s meter and start using the Manual mode.

Learning to use the Manual mode and the camera’s meter to manage shutter speed and/or the aperture setting gives the photographer control over how photos are viewed and interpreted.

These are my suggestions for better pictures. Please don’t hesitate to contact me. Email your comments and suggestions to me at emcam@telus.net or phone 250-371-3069

John Enman owns and operates Enman’s Camera at 423 Tranquille Road in Kamloops, selling an interesting selection of used and new photographic equipment and offers professional wedding photography and photographic instruction. Check out www.enmanscamera.com.