Crop Factor: Understanding Sensor Size vs. Focal Length Relationship

Every lens has a measurement in millimeters (mm), and most of us have an association with what that means. 50mm is a “standard” lens, and a 24mm is a wide angle, and a 200mm is a telephoto. This relation between a number and the terminology we use is so ingrained, so standardized, that when putting a lens like a 25mm on a camera like a micro four thirds, we feel a need to convert that number to an “equivalent” focal length that we are comfortable with. A 25mm lens on a Micro Four Thirds sensor becomes a 50mm “standard” lens. On an APSC sensor it’s a 40mm lens. 

But what do these numbers actually mean? Why is it that we think this way and feel the need to convert? And why don’t manufacturers just write the “equivalent” focal length on their lenses and make this easier for all of us, anyway? Those questions and more are answered in this week’s main video, “CROP FACTOR: Sensor Size vs Focal Length ▶︎ Why Does One Change?”

In other videos this week, we explored the ExpoDisc for achieving perfect (?) white balance:

… talked about the new professional quality ProGrade SD cards:

…and started the deep dive into ON1 Photo RAW 2018 with the Browse module:

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