Magnification factor on D50 - can somebody explain it?

[bpeck]

The D50 has a multiplier of 1.5, right? So a 50mm lens actually takes photos at a 75mm focal length? 300mm lens at 450mm? Why does this happen?

[coldrain]

It does not take pictures at a different focal length. The focal length is a function of the lens, and what image is produced is a function of the size of the film or sensor.

35mm film has by historical accident become a standard for consumer photography. That is why when we talk about focal lengths with digital cameras, digital SLRs and film SLRs, we think on what focal length means for the picture in terms of what it means in 35mm film format.

So.. we know that a 50mm lens is a "standard" lens, and its distortion seems very natural to our perception. We know that 35mm and below shows an exaggeration of distances we know from wide angle lenses, and that lenses with focal lengths of 100mm or so and over show a shortening of distances (tele effect) and seem to bring subjects closer.

Why and how is a D50 different from a 35mm film SLR?

Its sensor is smaller than 35mm film format. So it is like you cut all edges from the photo, and end up with a cropped photo. The photo shows less than you would see with the same lens on a 35mm full frame camera.

And to understand that changed field of view, we use the sensor crop factor to translate it to the field of view of a 35mm film camera.
So... while a 50mm lens keeps its 50mm focal length, the field of view of the D50 is less wide, as wide as it would be as a 75mm lens in a 35mm full frame. Due to the 1.5x crop factor.

To get an idea of what field of view focal lengths have on 35mm full frame and on APS-C digital (like your D50), play around a bit here:
http://www.tamroneurope.com/flc.htm

[wh0128]

hey, coldrain, you explained that really well. I really never fully understood what the 1.5x factor was, probably until now. I knew that shooting at 50mm on a digital camera with a 1.5 crop factor, was like shooting at the 75mm end. To me, I really can't see a difference with my photos, or a crop factor. But I know if I had a 35mm slr camera with a 50mm, the photo would have a wider viewing angle. Thanks for the explanation.

[K1W1]

For thos who want to know a bit more on this subject our old friend Mr Rockwell has a longer explanation that says much the same thing as Coldrain.

http://www.kenrockwell.com/tech/dx.htm