Canon EF-S 17-55mm VS Sigma 17-50mm VS Tamron 17-50mm?

Sovern wrote:

jitteringjr wrote:

You need to do more homework on perspective. Here read this:

http://www.josephjamesphotography.com/equivalence/#perspective

"Perspective is a function only of the distance of the camera from the subject"

So you point to some random photographers website as a reference? How come when I mount my 85mm 1.8 on my 450 and a 5D the perspective does not change? Can you explain that to me? I get the same compression just sides of the frame are chopped off on the 450D if I'm shooting at the location so I have to back up which leaves me with less bokeh or less capable bokeh.

The only thing that changes is the field of view between the different size formats which makes you either move forward or move backward if you want to get the same scene as one format.

A 50mm is going to be a 50mm on a crop body or not, the only thing that changes is field of view hence why people say 50mm on 1.6X body (or 80mm FOV).

A 50mm lens on a crop body will not magically give you the perspective (which means features such as compression) as an 80mm lens it only changes the field of view of which you see. You will have less field of view on the crop body forcing you to back up to get the same shot as you would on a FF body.

he's not random btw

this work and his work are tops

you're not getting it

to compare FF and 1.6 crop you must hold the photographer's position constant

ie, one can't be in two different places at a single instant in time when the shots are taken.

to compare equivalence, you must set the distance and same framing as a constant.

then you must use lenses that give the same framing or field of view

so let's use the 70-200 f2.8

at 70 on crop, you multiply everything by 1.6

70 mm becomes the FF equivalent of 112 F4.5

112 mm on FF is the FF equivalent of 112 F2.8

the compression's are different - because the fundamental equivalency point is that in order to fairly compare, the photographer must take the same framed shot at the same instant in time in order to simulate a fair comparison.