Canon 60mm AFS micro v Canon 100mm USM micro lens

[alex_foong]

Have anyone tested out the 60mm AFS micro lens on the smallest

aperture ie.f:16 onwards? I am seriously considering to purchase the

60mm micro over the Canon 100mm micro due to the small lens size and

shorter focal length. I have read that the Canon 100mm sharpness

deteriorate when set at f:16 and beyond. The 60mm AFS micro is a

purpose built lens for the EOS 20D, will it suffer the same

predicament as compare to a non EFS 100mm micro when set to f:16 and

beyond?

Depth of Field is the utmost importance for micro photography as most

if not all my pictures on micro is set at f:16.

[andrew_duncan]

Alex,

 

My understanding is that all lenses suffer from a deterioration in sharpness when set below f16. When a very small aperture is used diffraction causes the image to lose some sharpness. Bob Atkins has a good explanation here:

 

http://www.bobatkins.com/photography/technical/diffraction.html

 

I hope Bob doesn't mind me posting links to his website. I am surprised he hasn't already answered this one.

 

Andrew

[topher]

Alex,

 

Deterioration of the image due to diffraction is one of those laws of physics problems. It occurs with all lens with adjustable diaphrams for restricting light. For how it differs for different lens and sensor sizes, see Bob's article. However, you will get more DOF with the 60mm over ther 100mm.

 

p.s. the are called MACRO lens rather than MICRO lens, as counter-intuitive as that may sound.

[mark u]

"You will get more DOF with the 60mm than the 100mm"

 

That is only true if you aren't using it as a macro lens. In the macro regime, DoF depends essentially on just magnification and aperture - focal length becomes irrelevant to the calculation.

 

In terms of macro useage, your primary concern should be working distance and the consequences for lighting and the difficulty of approaching subjects such as insects at the magnifications you intend to use. The increased working distance of the longer lens can make it a more practical choice in many situations.

 

On a 20D, assuming you accept a ~19 micron circle of confusion as your sharpness criterion diffraction will start to become more important at apertures above f/11, rather than f/16 (the equivalent point for full frame).