Depth of Field with EFS 18-75 lens

[keithw]

I photograph close-ups of small insects. I used to use an EOS300 (for slide film) and a 28-90mm lens and close-up filters at around F22. Images were always sharp and Depth of Field was good.

I have just moved to a 20D, 18-75mm EFS lens and close-up filters. Image sharpness is terrible and Depth Of Field almost non-existent. I am shooting between F16 and 32.

Lighting is unchanged and I am shooting remotely so it can't be down to camera shake.

Can anyone help please?!

[GeForceFX]

digital images are always a bit soft out of the camera. (because of the anti-aliasing filter)

you have to use USM (unsharp mask) in photoshop or an other program.


here some extra info:
http://www.luminous-landscape.com/tutorials/understanding-series/understanding-usm.shtml

[slin100]

I have just moved to a 20D, 18-75mm EFS lens and close-up filters. Image sharpness is terrible and Depth Of Field almost non-existent. I am shooting between F16 and 32.

You may be running into diffraction effects. On an APS sensor, diffraction starts to take effect at apertures smaller than f/8. By f/16, and definitely f/32, diffraction will be quite noticeable. That may explain the lack of sharpness.

You might try opening up the aperture a bit. True, you need every bit of DOF you can get when taking closeups, but the smaller sensor buys you a bit of extra DOF.

[Jesper]

Like the others already said, setting the aperture very small (above f/16) will not make your images sharper - in fact, you will loose sharpness due to diffraction.

Here's a good explanation of why you shouldn't go higher than f/16 on an 1.6x crop factor DSLR: Optimum Aperture - Format size and diffraction (http://www.bobatkins.com/photography/technical/diffraction.html)