Originally posted by Sean Nelson The reason there's a difference in the size of nearby vs. far objects in the photos in your link is because the pictures were taken not only with different focal lengths, but also from different distances so as to maintain the same subject size in the viewfinder. It's the CHANGE IN DISTANCES that causes the change in the relative sizes of the objects.
I thank you for your thoughts. I will point out however I
did write "And yes in retrospect, I guess I'm including one moving physically to keep the primary subject the same size, and how that affects the whole FOV... etc...". I did so because when you're using a cropped sensor, that's taken into account with the mirrorbox & eye-piece. All you're doing is trying to frame the subject the same with both cameras. But where you have to stand to do so, will factor into that! (as others have echoed too)
All right, let me write it here because I'm obviously incapable of getting my meaning across in the manner I write. I HAVE ALWAYS AGREED STANDING IN THE SAME SPOT AND CROPPING DOES NOT AFFECT PERSPECTIVE ... the link I posted to the dpreview page pages back in this thread says that. I apologize for my mis-conception in how that relates to the the sample images posted by Sean. I was definitely wrong in how I related that to what I was trying to convey, because in those photos, camera position did not change.
But my point in "is a 50mm a 75mm on digital"
is about -where- you would stand if you shot 35mm film, vs -where- you would have to stand when you use the lens on a 1.5x cropped digital camera, to fill the frame the same amount with your subject. Imagine that point WITHOUT cropping after the fact to get the final images the same size in the frame. [!] ....And then consider how that changes the background.
CF, it's m8o, not the explosive m80. Thanx for that, and I'll "LIU" ("look it up"). However LL's been very helpful to me making better pictures.
Tokina, did
-I- say anything about aperture? You mis-understood me (you said f/2 then f/3 ... is that what you thought about when I said "speed" in regards to object lines converging?). I was talking about the speed the objects lines converge to the infinity point in how they are affected by focal length when holding a primary subject at the same size. The speed the lines converge in the image you capture on either sensor or film
over the same distance decrease the longer in focal length you go. If you had a lens that had an infinite focal length, the parallel lines of an infinitely long object would not converge. ...in retrospect, maybe strike that. Is what I'm thinking the effect of cropping an infinitely small point instead?
My involvement in this subject is an exercise in masochism.