Camera Labs

As an owner of two ASP-C cameras (Canan 60D and Nikon D7000) i remain
thorougly confused about using smaller F-Stops to control depth of
field in landscape photography. According to MTF charts on my kit
lenses (18-55mm) both of which show that @ 18mm they are sharpest
around F8. If you use a hyperfocal distance @ F8, which is 2.13 and
2.03 metres respectively, then everything from infinity to roughly 1
metre is in focus.
Why then do people use F-stops from F11 through to F22 and beyond?
Wouldn't diffraction defeat the purpose and give you a generally
unsharp image. I do understand that larger sensors like full frame etc
require a smaller F-stop to have similar DOF, but even so, should it
amount to so many stops smaller?

Hyperfocal distance is about having an acceptably sharp image in the depth of field. It does not mean it will be sharpest all the way through it. You still only have one distance where it actually is sharpest, and away from that, you will have reduced sharpness from defocus. If you stop down further, possibly the point of focus will be reduced in sharpness, but you might still increase the apparent sharpness at other distances, which might be more important.

If you want even closer parts of the scene in focus, you will have to stop down further.

Also the impact of diffraction softening is generally overstated. Actually try those smaller apertures and see how it affects sharpness. At f/11 compared to f/8, you will find it hard to see much difference even if you put them side by side. At f/16 it is more noticeable, but even then not significantly so.

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.

Thanks for your reply Popo. I guess i will have to put the camera on a tripod and try various apertures to see what works best for me