Recently, the factor most limiting the quality of the pictures I take has been focus. When you shoot a few hundred pictures, a few will always constitute focus failures, but my fail ratio has been too high recently. I’ve thought about it and there are a few things wrong with my approach, but I thought I’d reassure myself that my camera and lenses were playing nice with each other.
The nice folks over at the Pentax-Discuss Mailing List recommended focustestchart.com which has Nikon in its title but the product works fine with any old camera. The idea is, you print out their PDF, you lay out the chart page really flat, you line your camera up, point it down 45º at the chart, and adjust your focus.
If the Focus Test Chart is to be believed, both the 40mm and the 30mm needed adjustment, and the 21mm didn’t. Which may only be because the 21mm is at f3.2 and thus has more depth of field. Here are the “before” and “after” shots with the Sigma, forced to f1.4 for the minimum depth-of-field.
My Pentax K20 remembers adjustments on a per-lens basis, so these ones have been programmed in.
Will this actually improve my overall sharpness? Absolutely yes it will, because it establishes that my lenses and camera are about right, so the problem is clearly with the operator. I need to bear down on this.
Oh, and then there’s the pancake wide-angle, which, even opened out wide as it goes, has more depth of field than any sane person could want in any situation.