"sweet spot"

i have heard people refer to a "sweet spot" aperture setting for lenses. what does this refer to? is it a particular aperture setting on a given lens that captures the best image? if this is the case, how to you determine what the "sweet spot" is? i use a 17-40mm 4 L lens a lot and i would like to know what the "sweet spot" is for this lens.

Hi Matt,

Here is one approach. I was trying to understand where the sweet spot is for different lens and port combinations.

http://wetpixel.com/forums/index.php?showt...hl=Canon+17-40L

The short answer for my copy is f/11.

Cheers,

Steve

To supplement the quick answer mid-aperture range of the lens is usually your sharpest point. Being a rank amateur, I just figured this out the hard way. I was trying a new TC which allowed me to dial down to f32. The normal range on the lens is f22. While this new setting at f32 gave me a wonderful DOF it came at the cost of some sharpness which disappointed me. Anyway, just my 2-cents worth

As people have said, its a slight trial and error, but I've heard around 2 stops stoped down. Then again, would the sweetspot for a 85 1.2 be 1/3 step under 2.8? I'd think not.

/Björn

On most lenses you will see this between f/8 and f/11. You can check lens reviews e.g. at http://www.photozone.de and look at the sharpness as a function of aperture. Usually lenses are not at their sharpest wide open (just due to optical limitations); and then diffraction starts affecting sharpness at small apertures. Usually there is a "sweet spot" somewhere in between. Note that this is rarely a "spot" -- more like a "sweet range".

Regards,

Dan