08-05-2013, 03:56 PM
Hi Brightcolours,
hey awesome, a fellow good soul who finds interest in this matter. It's quite a "delicious" little problem isn't it. Now the reason, why I think you can't change the focal lenght is that if an object grows in three-dimensional space, it's not just larger on the screen (as if you'd simply increase it's size in Photoshop), it grows away from the center point and gets more and more distorted. But the vanishing points remain the same! All the parallel lines of a dice for example, be it big or small, meet at the same point. This is not the case when you change the focal length, because "zooming in or out" affects the vanishing points equally. Increasing the focal lenght moves the vanishing points away from the image center (or maybe it's the object center, not sure, either way, they move outwards). I'll try and do some sort of test in the following weeks to confirm this.
In the mean-time I've started a blog post about this and hope to expand it as I discover new facts.
http://obsoquasi.ch/photo-manipulation-o...d-objects/
Cheers,
John
www.obsoquasi.ch | Facebook
hey awesome, a fellow good soul who finds interest in this matter. It's quite a "delicious" little problem isn't it. Now the reason, why I think you can't change the focal lenght is that if an object grows in three-dimensional space, it's not just larger on the screen (as if you'd simply increase it's size in Photoshop), it grows away from the center point and gets more and more distorted. But the vanishing points remain the same! All the parallel lines of a dice for example, be it big or small, meet at the same point. This is not the case when you change the focal length, because "zooming in or out" affects the vanishing points equally. Increasing the focal lenght moves the vanishing points away from the image center (or maybe it's the object center, not sure, either way, they move outwards). I'll try and do some sort of test in the following weeks to confirm this.
In the mean-time I've started a blog post about this and hope to expand it as I discover new facts.
http://obsoquasi.ch/photo-manipulation-o...d-objects/
Cheers,
John
www.obsoquasi.ch | Facebook