You can get a good approximation using Liveview and by previewing your shots enlarged on the LCD, then double check the “final” result using the regular AF system and viewing the result on your monitor. And using Liveview at 6-10x makes it easier to do the set up, verifying that the focal spot is on the center of the target.
I have a target much like Paul’s. I have a tripod mounted stand designed to hold a slide projector. Remember those? I put the target on the stand at a 45° angle. Camera on tripod with camera level front-to-back side-to-side. Lens axis at same height as the center of the target. (All of this fiddling in the setup means that the sensor plane is perpendicular to the target, makes interpretation of the results much easier!) The distance from target is going to vary according to your lens. For a macro, you could work from 2-3 feet away. For a 300mm you’ll probably want to be 15-20 feet away. I’ve read commentary on choosing the “right” distance, don’t recall the details and don’t believe it matters that much. For a zoom lens, I calibrate at the most used end, then check the other end. Others start always at the wide end, then verify the long end. The K-3 manual has a brief discussion on the process. stan On Sep 6, 2014, at 6:40 PM, Darren Addy <[email protected]> wrote: > Very helpful, Paul. Thanks for the (excellent/detailed) reply! > > Other approaches are welcome as well. > > On Sat, Sep 6, 2014 at 5:36 PM, Paul Stenquist <[email protected]> > wrote: >> Hi Dareen, >> >> Answers interspersed. >> On Sep 6, 2014, at 5:05 PM, Darren Addy <[email protected]> wrote: >> >>> I've never messed with the AF Fine Adjustment before, but I think I >>> need to on the K-3. So those of you that have experience in this >>> area... >>> >>> First, I'm wondering if the procedure is the same on K-3 as it has >>> been for other Pentax models? If so, I don't need to limit my Googling >>> to the K-3. >> >> It’s basically the same. There may be some slight differences in the menu >> access, but the nuts and bolts of it are the same. >>> >>> Secondly, this works with third party lenses also, right? I've got 3 >>> Sigma EX to 2 Pentax in the AF department. >> >> I don’t know. I don’t own any third party autofocus lenses. But if the >> camera recognizes them for shake reduction, I would think autofocus >> adjustment would work as ewll. >> >>> >>> Thirdly, am I correct in thinking that this is of no use on manual focus >>> glass? >> >> You are correct. It merely fine tunes autofocus to eliminate backfocus or >> frontfocus conditions. >> >>> >>> Fourth, what is your procedure? I'm thinking camera should be locked >>> down on a tripod and I'm wondering what you use for a target. I've >>> seen scales (like a tape measure or yardstick) angled at a 45 degree >>> angle, with a vertical target that is perpendicular to the sensor >>> plane at the focal point. At what distance do you do the measurement? >>> Minimum focus distance? Medium focus distance? I'm also guessing you >>> do this with the lens wide open so as to be able to most accurately >>> define the in-focus point. What is your procedure on zooms? >> >> I use a 13 x 19 sheet of good paper, printed with a scale of lines >> approximately 3/8-inch apart. The lines cover the middle 2/3 of the sheet, >> but right in the center there is a blank area of about three inches square. >> In the center of the blank square is a single red dot of abotut 3/16 inch >> diameter. This is the focal point. I set the paper on the floor of my deck >> in bright shade. Then I mount the camera on the tripod. I place the camera >> about three feet away for a wide lens like the 16-50 and about 7 feet away >> for a long lens like the 60-250. I use single-point focus with the center >> dot active. I elevate the tripod head so the camera is looking at the focus >> dot at an angle of about 45 degrees. I test most lenses in the middle of the >> focal length range, but check at the wide and long ends as well. Generally, >> they’re very close. If there’s a discrepancy I’ll favor the focal length I >> use most. I look at the results on a large monitor and try to judge how many >> lines on each side of the dot are in focus. The forward lines won’t look the >> same as the rearward lines even when the focus is about the same. So you’re >> looking for sharpness. I try to count out which line is definitely out of >> focus. For example, for the 60-250 at 150mm, it might be line three or four. >> For the 16-50 at 35mm, it might be line six. Hope this helps. >> >> BTW, it’s worth the effort. >>> >>> I'll stop with the questions now. Any light that you can shed... >>> thanks in advance! >>> >>> -- >>> Photographers must learn not to be ashamed to have their photographs >>> look like photographs. >>> ~ Alfred Stieglitz >>> >>> -- >>> 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. > > > > -- > Photographers must learn not to be ashamed to have their photographs > look like photographs. > ~ Alfred Stieglitz > > -- > 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.
