Exposure

1. February 2009 by Dave Mo.

This post is all about exposure. 

I suppose this should have been the first entry as far as educational material. Oh well, better late than… well, you get the idea.

Here we go, into the wonderful world of exposure (EV-exposure value). Probably one of the most misunderstood, and most important concepts in photography.

Exposure is the amount of light that hits your digital sensor (or film). In photography, it is measured by f-stops. It is controlled by three primary methods.

First is shutter speed, which was covered a bit last time. All other thing being equal, a slower shutter speed will allow more light in, and give you a higher exposure. The result of this is a brighter picture. Conversely, a faster shutter speed will give you a lower exposure, and a darker picture, all other thing being equal.

The second thing that allows you to control exposure is your aperture. This was also talked about a bit before. Aperture is the ratio of the lens opening to the size of the sensor (film), and not a specific size. Similar to the shutter speed, with all other thing being equal, a larger aperture will give you a higher exposure. Also conversely, a smaller aperture will give you a lower exposure.

Finally, the last of the primary methods for controlling exposure is the ISO, or sensor gain, or sensetivity. Imagine, every pixel (picture element) on your sensor is a small bucket collecting little bits of light as the shutter opens. Imagine further, since we are working with electrical components, you take that small amount of light collected by those little buckets (pixels), and amplify them, you get a stronger signal. This is what ISO controls. So, all other things being equal, a higher ISO will give you a higher exposure. So…you guessed it, a lower ISO will give a lower exposure, all other things equal, of course.

On a bit of a side note: be careful when raising your ISO, as it goes up, so does digital noise. Similar to film grain on high-ISO films, although most people do not find noise as appealing as grain. This phenomenon is similar to what happens when you turn a radio up too loud, eventually, the speakers can’t handle it and the sound distorts. In photography, this is noise. You will see noise as small blocks of color, especially in darker areas of a photo. However, sometimes you need that boost, and there are some noise-reducing plugins out there for your editing programs.

It is the combination of these three main tools, shutter speed, aperture, and ISO, that allow photographers to do so many wonderful things. The tricky part is experamenting with all of these things. Luckily, in the digital age, there is no fee for film and developing, except your time. So spend your time taking photos, play around with your settings, and HAVE FUN!!!

 Dave

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