My slowest are the 4-5.6 zoom and the 5-6.3 zoom that I tried earlier. Anything I’ve thought of to simulate a slower smaller widest aperture would only affect the taking aperture, not the focusing aperture. Except filters. I’ll play with a polarizer a bit tomorrow, that will give some (unknown degree of) reduction in light available. I don’t have any ND filters. Ken, I think you may need to bring your 600 by and try out the 1.4x yourself.
stan On Mar 26, 2014, at 9:50 PM, Paul Stenquist <[email protected]> wrote: > 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" <[email protected]> >> 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 <[email protected]> >>>> wrote: >>>> >>>> I’ll further explore that question tomorrow. >>>> >>>> stan >>>> >>>>> On Mar 26, 2014, at 2:59 PM, Ken Waller <[email protected]> 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" >>>>> <[email protected]> >>>>> 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 <[email protected]> >>>>>>> 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 > [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.
