Your right of course. I don't own a slower autofocus lens. Paul via phone
> On Mar 26, 2014, at 9:22 PM, "P.J. Alling" <webstertwenty...@gmail.com> wrote: > > Since the lens was wide open it wasn't really focusing at f22, it was > focusing at ~f5.6. Now the relatively slow Pentax FA 28-105 with an > effective aperture wide open of 8.0 with a 1.4x TC is getting to be a test. > There ate two things that effect auto focus, absolute aperture, and absolute > light level. I expect that in bright light that even f8 lenses of a long > enough focal length will have no great issue auto focusing. > >> On 3/26/2014 8:09 PM, Paul Stenquist wrote: >> I shot a frame at f22 last week with the 1.4x and 60-250. It focused quickly. >> >> Paul via phone >> >>> On Mar 26, 2014, at 7:01 PM, Stanley Halpin <s...@stans-photography.info> >>> wrote: >>> >>> I’ll further explore that question tomorrow. >>> >>> stan >>> >>>> On Mar 26, 2014, at 2:59 PM, Ken Waller <kwal...@peoplepc.com> wrote: >>>> >>>> I'm more interested in the smaller aperatures at which it fails to focus. >>>> It would be nice to be able to use it on my 600. I have both the A-1.4X-L >>>> & A2.0X-L but of course I lose AF with those. >>>> >>>> Kenneth Waller >>>> http://www.pentaxphotogallery.com/kennethwaller >>>> >>>> ----- Original Message ----- From: "Rob Studdert" <distudio.p...@gmail.com> >>>> Subject: Re: Because inquiring minds want to know (more on the 1.4x) >>>> >>>> >>>>> Thanks for the report Stan, it does look useful, but I will have to >>>>> sell a K5 body to afford it :( >>>>> >>>>> >>>>>> On 21 March 2014 02:38, Stanley Halpin <s...@stans-photography.info> >>>>>> wrote: >>>>>> I just did a couple of focus "tests" with my two slowest lenses. I won't >>>>>> post any results - I was just handholding on random twigs, turkeys, lawn >>>>>> sculptures, trees, etc. The images would tell you nothing about >>>>>> sharpness. All of the following using center-point focus, K-3. >>>>>> >>>>>> 1. Sigma DG 150-500mm f5-6.3 APO HSM + Pentax 1.4x TC >>>>>> With the Sigma at 150mm zoom (presumably f/5.0) >>>>>> - Sigma AF OFF: nothing happens - no AF. >>>>>> - Sigma AF ON: snappy AF, no searching or other bad >>>>>> behaviors >>>>>> >>>>>> With the Sigma at 500mm zoom (presumably f/6.3) >>>>>> - Sigma AF ON: Quite a bit of searching on low contrast >>>>>> targets (e.g., tree trunks.) Fairly quick "snap" to focus on a weed seed >>>>>> head 20 feet away against a backdrop of the river ice 150 feet aw -- 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.
