Better quantified this time. Yesterday I took stance on a bridge above a highway, and photographed large trucks coming towards me. The speed limit at this place is 100 km/h, and on top of a gentle slope. I shot series of each truck, and have tallied the percentage of out-of-focus shots from each series. The cameras were set to:
- SR on for shots with DA*300, shot freehand - SR off for shots with FA*600, shot from tripod - AF-C, multipoint - ISO 800 - Av-mode (aperture set to f/8) - DNG file format. Focus was judged by 100% view in Adobe Bridge CS4 without rawfile conversion. I took a conservative attitude, judging anything that wasn't perfectly sharp on the car front as mis-focused. I typically looked at details in the grille (hope it's the right word?) or the number plate. Between each series I allowed the camera to save all files before commencing a new series, to make sure camera speed was not held back by a full buffer. K20D + DA*300/4: 13% mis-focused, averaged over 9 series K-7 + DA*300/4: 7% mis-focused, averaged over 7 series K20D + FA*600/4: 43% mis-focused, averaged over 7 series K-7 + FA*600/4: 25% mis-focused, averaged over 11 series Each series held between 10 and 19 shots. Both lenses are focus-calibrated with the K20D, but not with the K-7. I therefore suspect that the K-7 results could be somewhat improved. There are bound to be many unchecked sources of random variation here. One is whether the trucks had cargo or not. If empty, they bounce a lot more and could introduce motion blur. I suspect the 600mm shots to be affected by this. With the small number of series, I can't rule out that the two cameras have got an uneven share of empty trucks. However I did the same experiment, at the same place, five days ago with the K20D only, and the results from yesterday seems consistent with my previous results. So all in all, the real-life numbers pretty much mirrors the nominal doubling of the frame rate. Not the subjective feeling that the K-7 is _more_ than twice as fast. Not in this situation anyway. However this test, tracking approaching objects, is very different from panning a bird flying from one side to the other. Jostein -- http://www.alunfoto.no/galleri/ http://alunfoto.blogspot.com -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
