"35mm equivalent"

was just wondering about the opposite of this, I know that digital lenses have

a 35mm equivalent, but was just wondering what am I effectively getting using

say a 28mm lens designed for film on a 6mp sensor

35mm equivalent refers to the angle or field of view. If the 28mm lens were placed on a Canon XT with a focal length multiplier of 1.6, the field of view would be the same as a 45mm lens on a 35mm film camera.

 

28 x 1.6 = 44.8

Focal length equivalent is determined by the size of the sensor. Canon APS-C size sensors produce a field of view equivalent to 1.6 X the 35mm full frame view. The Olympus 4/3 size sensor has a field of view equivalent to 2 X the 35mm full frame view. Point & shoot cameras with their tiny sensors have much larger "crop factors" or "focal length multipliers"

 

You need to know which sensor size to determine the "35mm equivalent"

 

<Chas>

"Digital" does not always mean your lens will behave differently. The full frame sensor Canon 5D is a digital single lens reflex camera that has no impact on the focal length, it's sensor is (roughly) 24x36mm, the same as film. Digital cameras with a sensor smaller than the normal 24x36mm simply snip away at the normal 24x36 image. How much depends on how much smaller they are, nothing complicated.

-- "...what am I effectively getting using say a 28mm lens designed for film on a 6mp sensor"

 

As already pointed out, to get the 35mm-equivalent, you need to compare the sensor size in mm (not in mp).