The test having been done hand held, might one factor have been the K-7's claim of improved SR.(?)
Jack --- On Sat, 7/18/09, paul stenquist <[email protected]> wrote: > From: paul stenquist <[email protected]> > Subject: Re: More K-7 AF observations > To: "Pentax-Discuss Mail List" <[email protected]> > Date: Saturday, July 18, 2009, 5:20 AM > Good to know. It's what I suspected > based on use, but it's nice to > know that my suspicions aren't just wishful thinking. > Thanks for > taking the time to test. > Paul > On Jul 18, 2009, at 7:09 AM, AlunFoto wrote: > > > 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. > > > -- > 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. > -- 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.
