EF vs EF-S

MasonHoy wrote:

I have always been taught to account for crop factor on a crop sensor when using a lens not designed specifically for the crop.
I've never questioned this until I tested the 50mm EF 1.8 vs the 55mm-250mm EF-S on my 700D, and the images (although with a difference of 5mm focal length) were roughly the same FOV. That would suggest that the 50mm focal length is true even on an APS-C sensor.
Can anyone provide insight here?

As others have said... all lens markings are the same.  50mm is the same if it's EF or EF-S.  So, you are right on there.  EF-S lenses are desgined for crop sensors, so they will not project light on the entire full frame sensor, but the focal lengths are all the same as EF lenses.

What you need to be aware of is that the focal lengths will mean different things for crop sensors and full frame sensors.  This becomes important as you read reviews and think about purchasing lenses and whatnot.

For example, you may read about people suggesting a 24-70mm lens as a great standard zoom.  Most of the time people suggesting this are doing it for Full frame users where 24mm is wideangle and 70mm is just past standard:  a very nice general photography range.  For crop users however, this lens would not be very wide at the wide end and would be slightly into the telephoto range on the long end.  A very different view through a crop sensor camera in other words.