Back to the Basics: What is a Stop of Light? – Episode 2 from the HDR Photography Workshop Series
The following is an excerpt from HDR Photography | A 3 DVD Comprehensive Guide to Mastering Professional HDR Photography by SLR Lounge. This workshop dubbed “the gold standard of HDR education” by FStoppers contains over 13 hours of tutorials, RAW files for you to follow along, and dozens of full prep to post examples. We cover bracketed HDR, in-camera HDR, single-shot faux HDR, single-shot bracketed HDR, panoramic HDR and more! Click here for more info.
When capturing images manually, a photographer must understand the interactions between f-stop or aperture, ISO, and shutter speed within a camera in order to get the correct exposure for the image. For this reason, we are providing a video tutorial as well as a written article to help give you a basic understanding of these interactions, particularly the concept of a “stop”, which is probably the most fundamental subject for new photographers to learn.
Watch the Video
Definition of a “Stop”
The term “stop” of light is a relative unit of light entering the camera. Since there is not a quantifiable measurement of light within each stop (it depends on what light is available), these measurements are calculated by the comparison of dispersion between two or more units. Simply put, increasing by one stop doubles the amount of light, and decreasing by one stop halves the amount of light entering the camera.
For example, here is our original image:
If we now decrease the exposure by one stop, it will look like this:
Increasing the exposure of the original image by one stop would look like this:
So what about when you increase the exposure by two or three stops? It is important to understand that each stop increment changes the exposure by a factor of two. If you increase the original exposure by two stops, you are quadrupling the amount of light entering your camera because you are doubling it on one stop, and then doubling it again on the second stop. Increasing by three stops is then increasing your exposure by 800 percent (8 times brighter than the original exposure).
You should now have a basic understanding of stops of light within photography. This rudimentary knowledge is indispensable when bracketing images, which we will explain in further detail in the next article in the HDR series.
For more HDR education, be sure to check out HDR Photography | A 3 DVD Comprehensive Guide to Mastering Professional HDR Photography by SLR Lounge. This comprehensive “gold standard” guide will give you a mastery of HDR photography, from the scene considerations to the actual shooting to the post production. Click here for more info.