Sharp corners, to soft corners, back to sharp!?

Hi all,

 

I've been shooting with an EOS 24-105mm f4 and have been extremely pleased with its performance, especially wide

open and in the edges stopped down a bit. Lately i've been shooting hung artwork (putting up sale) and other fine art

that happens to lie on flat surfaces.

 

Even when stopped down to f11, I see significant softness in corners. Why is this? In all my other images involving

3D subejcts, i see none of this softness. that's all i can deduce at this point, flat 2D images have signficantly soft

corners and 3D subjects exhibit tack sharp corners.

 

Perhaps there's a simple explanation so I apologize if I'm the only person without a clue.

 

Thanks!

I figure an image might help, but its awfully small due to posting restrictions...

Your lens has a curved field of view, like most lenses. If you want a lens to photograph flat objects, you need a copy or "process" lens, one designed to image flat objects on to the film/sensor plane.

 

How close are you to the object and what is your focal length? You might be able to get that lens to work some what better with some experimentation.

You don't have to get a "prcoess" lens for flat objects -- a Macro lens will do nicely.

The Canon 50mm compact macro lens is an excellent choice for this kind of work - or the Sigma 50mm macro. You won't want anything longer.

oh i see, thanks for the answers!