50mm x 1.6 = 80mm. The 80mm result gives the effective focal length.

Or put another way, the 50mm lens equates to an 80mm lens in focal length when used on a cropped sensor camera.




Let me jump in here.
Folks are confusing focal length with angle of view. With any given lens focal length, the angle of view comes smaller or larger following the size of the sensor. The sensor incepts a smaller or larger part of a lenses projected image depending on the size of the sensor For ease of understanding we (inaccurately) say that a 100 mm lens on a 1.5 crop sensor camera is equal to a 150 mm lesson a full frame camera. But in truth , only the angle of view is equal. The depth of field is not changed by the size of the sensor onto which a lens is focusing it's light. The dof of the center portion of a full frame camera (all the things being equal) should be the same as the DOF of a crop sensor image. (the crop sensor due to it's smaller size intercepts a smaller angle of view is all) A 50 mm lens at any equal f stop will have the same DOF regardless of the size of the sensor on which it's focusing the light.
Noted expert Tony Northup has a video in which he argues the crop factor also has an effect on f/stop. I did not follow his geometric logic on that argument though.

I thought I had a good handle on DOF as a zone of acceptable sharpness, but after reading all the posts, I am questioning what I thought I knew and think I need an adult beverage to calm my nerves.

I just keep repeating to myself: A larger aperture gives a shallow DOF and a small aperture provides a deeper DOF. The shorter the distance from lens to subject the shorter the DOF. Longer distances increase DOF. At a given distance to the subject, a longer focal length gives a more shallow DOF. The acceptable DOF usually starts 1/3 in front of the subject and 2/3 behind, but the longer the focal length the more even it is.

I hope no one posts about hyperfocal distance. I might have to take a run to a liquor store.