A good lens to test with this TC if someone has it would be the 50-200 since it is on the slow side. At 200mm, it would be a bit over f6.3 combined? It also is a lens that tends to hunt and struggles sometimes to find the correct end to focus on. I imagine it would be really slow. The optical performance would be curious though as the 50-200 is pretty sharp.
On Wed, Mar 26, 2014 at 11:24 PM, Stanley Halpin <[email protected]> wrote: > 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. -- 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.
