Rinze - i wasnt refering to that effect. i was refering to the size of the subject / perspective relative to the framing, not the crop - to get the false 85mm crop there you are probably cropping more than the 1.6x of the sensor.

Get that same setup and take a shot with an 85mm lens, then move the camera closer and take the same shot with a wider angle lens so that on frame the subject is exactly the same size... the background thus changes.   It is that change in perspective i was referring to

Let me think about this out loud. To test my theory in 3DS Max you will have to take 2 shots.  So set up on your screen a measuring marker - side of a window to pull over the "viewfinder" so you can match the object size in the viewfinder when it comes to changing focal distances. Also a simple setup would be a sphere with a chequered background in the distance:

Shot 1 - 10mm so the sphere is a good size - say 50% of the frame.  Then take the result into photoshop and crop it by the 1.6x factor.

Shot 2 - 16mm so the sphere is the same size on screen as the previous shot *make sure you are measuring agains tthe CROPPEd version of that shot - this is where the measuring marker is useful (just resize a notepad window or something). You will obviously have to move the camera to get the same size of sphere in the frame.

Now shot 1 represents the 10mm on a 1.6 crop sensor, the 16mm the "equivalent on a full frame".  The subjects should be the same size on frame, but i am guessing that the chequered background will show a difference of perspective.

You could then try a similar thing with 200mm and 320mm to see what the difference is...

Hope that helps to explain what i was talking about - as it is a very difficult thing to explain i think :)

Thanks for the cookie... hope it is a bendable/soft one - hate the ones that just snap - they suck

Yeah - viewing angle is a good way of seeing it i suppose... I am just used to what 18mm means on a 1.6 crop anyway so i'll get to the problem when i get a FF ;)

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