What focal length is a 35mm lens on an APS-C camera?

When you use a 35mm lens on an APS-C camera, the effective focal length is determined by the camera's crop factor. The crop factor for most APS-C cameras is typically around 1.5x (for Nikon, Sony, and others) or 1.6x (for Canon).

To calculate the effective focal length:

Effective focal length = focal length X crop factor.

For a 35mm lens on a 1.5x crop factor APS-C camera:

35mm x 1.5 = 52.5mm

For a 35mm lens on a 1.6x crop factor APS-C camera:

35mm x 1.6 = 56mm

So, the effective focal length will be approximately 52.5mm on a 1.5x crop factor camera and 56mm on a 1.6x crop factor camera.

The simple reason why I have written this short post is because I just did a quick search on the Internet for the 35mm equivalent on an APS-C camera (popular on mirrorless cameras) and the answers that I got were confusing as far as I am concerned 😊. They were back to front. It looked chaotic to me. Maybe its me! It is the way you present the information and I hope this way is good.

In short, the answer has to be that if you use a 35mm lens designed for a full frame camera the effective focal length on a cropped sensor camera has to be longer because you're taking out the middle of the frame. It's a bit like a digital zoom. You are cropping the picture digitally in effect. 

This means that you are zooming-in which means that the focal length is longer from 35mm on full-frame to to a little over 50 mm on APS-C. 

So a 35mm lens on a full frame camera which is a wide-angle lens, becomes a standard lens on a cropped sensor camera such as the APS-C format.

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P.S. please forgive the occasional typo. These articles are written at breakneck speed using Dragon Dictate. I have to prepare them in around 20 mins. Also: sources for news articles are carefully selected but the news is often not independently verified. Also, I rely on scientific studies but they are not 100% reliable.