Gotta agree with this Clackers -- I learnt these as a 16 year old too -- I am now 60 and my learning curve hasn't been totally flat!!
EDIT: Clackers has edited post 46 after I uploaded this post. He was referring to the fact his 16 yr old students had no trouble understanding his link)
Originally posted by clackers Firstly, I love your special bokeh, GUB ... a lotta fun, like the paper valentines you can cut out and put on the front.
Secondly, it's terrible logic. Put a Velcro spot on the edge of the *outer* element of a FF lens and see what happens!
You will not see it on the APS-C sensor.
And totally agree here too clackers. Of course I wouldn't see it on an apsc sensor --- I sat it smack in the middle and I couldn't see it. The same would apply to a FF sensor. The point of the image was despite covering almost all of the centre of the lens there was an image still. It can have only come from the periphial of the rear lens which means the apsc is receiving light from the outer edge.
"You're not using any of the glass that's outside the sensor, GUB. ☺"
Where else am I supposed to be looking for this glass unused by the crop sensor?