daimo

It's not just the crop factor that matters ... a model taken by a 50mm vs a 85mm vs a 135 mm vs a 200mm, even if you use PS to crop it down to the same size, the pictures won't look the same.

daimo

The longer the focal length and the larger the aperture the more shadow the DOF, i.e. more blurred backgroud.

In other words, if you use a wide angle then it is much harder to achieve blur background then a telephoto.

daimo

原帖由 jake123 於 2008-7-28 17:47 發表


Other than deeper depth of field(about one stop more for crop?) and the characteristics of the lenses themselves, what are the differences?

what I was trying to say, simply:

If I compare a 50mm with a 1.5x camera vs a 75mm (ok, assume there is such a model) with a full frame camera,

Although they will have the SAME crop ratio, but due to the difference in the compression ratio, a portrait taken with a 75mm + FF will have a slimmer face.

daimo

What you read from those books is not true.  I suggest you take a look at the Kodak professional guide for photography.  

Jake, pardon me for being too lazy to explain, but you can do a test with a zoom lens ...