Highly complex targets with cool graphics work, but so does a simple system of lines with the center line readily identifiable. I made a chart in PhotoShop comprised of a series of lines about a centimeter apart. The target line in the center is thicker than the others. With the camera at a 45 degree angle to the chart, I autofocus on the center line with center spot selected for focus. This test is the FA 50/1.4 with my final +2 adjustment. Note the varying degrees of out of focus as the lines progress. The fourth line on each side is the first to be critically out of focus. Thus, the center is identifiable. I shot this at f2.5, as I've found that results with this lens wide open can be misleading. But most other lenses are tested wide open, particularly the DA* lenses, which are engineered to be optimum at wide aps.
http://photo.net/photodb/photo?photo_id=17633001 Paul On Dec 22, 2013, at 2:32 PM, "Jan van Wijk" <pen...@dfsee.com> wrote: > Hi Alan, > > On Sun, 22 Dec 2013 15:07:24 +0200 Alan C wrote: >> >> Many thanks for the "tutorial". I'm sure it will be of use to others too. >> This is the link for Bob Atkins test chart: > > You're welcome! > >> http://bobatkins.com/photography/technical/lens_testing/reschart.zip >> >> It has plenty of "grids", etc. but no ruler. > > Ok, that is a nice chart to test how good a lens resolves detail, but totally > UNSUITABLE for focus adjust. > > This is an image about how a proper focus-adjust looks like, and how its used > (it is the one I use): > > http://regex.info//i/JEF_024924.jpg > > This is another post about a slightly different one, with images: > > http://photography-on-the.net/forum/showthread.php?t=750736 > > And yet another one, on a pentax forum, including images too: > > > http://pentaxdslrs.blogspot.nl/2012/01/front-or-back-focusing-problems-free.html > > > As you can see, a contrasty focus TARGET is needed, and a sort of ruler, > ANGLED to have its > numbering or lines at different distances. But it should be well OUTSIDE the > active focus-area > of the camera (so use center-spot). > > Unfortunately I can't find the PDF for the one I am using now, but I do have > one that is quite similar > that you can download from my own website. It includes a description on how > to use it, and you > can simply print out the one (out of 20) page that is the chart itself, to > use that. It is at: > > http://www.dfsee.com/download/focus-test-chart.PDF > > > Regards, JvW > > > ------------------------------------------------------------------ > Jan van Wijk; http://www.dfsee.com/gallery > > > -- > PDML Pentax-Discuss Mail List > PDML@pdml.net > 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 PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
