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04-14-2021, 01:33 PM   #16
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I use the converter and 55-300 PLM version on the KP. Without enough light you may not get it to autofocus. I've seen it happen maybe once. But I usually only take the combo out when it is sunny, and not for a walk in the woods where it is darker. Aperture works fine, you'll be fine.

04-14-2021, 01:44 PM   #17
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Using my SMC DA 55-300 f4-5.8 with my KP and my HD DA 1.4x at 300mm in mediocre light I saw several instances of failure to get a steady green hexagon on focusing. It did however focus MOST of the time. The less challenging the focus conditions (more light, cleaner subject edges, etc gave much more confident results. I didnít take shots and examine the files for critical focus. I didnít compare the results to simply cropping the image. I did not try at moderate focal lengths where the lens may be sharper (and optically faster) than at 300.
04-14-2021, 02:40 PM   #18
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I have tested the combo in extremely low light on a tripod. Af worked great. In much better light hand held or stable against an unstationary target, real world use, low light and contrast will have trouble. Low light reliability is related to steadiness. I have tested often. When it wont focus I find a tree to stabalize against and get solid af.
04-14-2021, 03:12 PM   #19
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Nobody really seemed to answer your question so i will give it a shot. Phase detect auto focus is what the camera uses when you are looking through the viewfinder, in live view the phase detect sensor is blocked and the camera uses the contrast detect autofocus.

04-14-2021, 03:38 PM   #20
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Phase Detection vs Contrast Detection Autofocus

Small apertures lead to focus sensor blackout in phase detect sensors, just like a split focus screen blacks out at f8...

Canon can design really cheap 600 & 800mm f11 AF lenses for R mount because they use Contrast Detection as well as Phase Detection.
04-14-2021, 06:40 PM - 1 Like   #21
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Apologies for being a little late to this party, Jim, but time-zones can't be escaped........
The newish HD 1.4 X rear converter was designed for lenses F4, and faster. It will certainly work with slower lenses, but each camera-converter-lens combo will have different performance limits. The converter not only magnifies the image size, but it also magnifies any flaws the attached lens may have. As an example, great lenses like the 100mm f2.8 macro WR give virtually no image degradation with it. As the lens gets slower and cheaper, so does the image quality and low-light performance. Below is a screenshot from the In-Depth review here on the forums, a link to that review, and also a link to the Ricoh review, which has a comprehensive list of which lenses can, and shouldn't be used.

Happy shooting........

Pentax-DA 1.4x AW AF Rear Converter Review - Introduction | PentaxForums.com Reviews

HD PENTAX-DA AF REAR CONVERTER 1.4X AW / Converter / AF Lens Adapter / K-mount Lenses / Lenses / Products | RICOH IMAGING
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04-15-2021, 11:35 AM   #22
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After reading this discussion, I tested the combination 1.4 converter and DA 55-300 PLM on my K-S2
It is already starting to get dark, just photographed something, no focus hiccups or refusal and fast as always with this lens, in viewfinder mode
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04-15-2021, 02:29 PM   #23
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QuoteOriginally posted by Crooski Quote
After reading this discussion, I tested the combination 1.4 converter and DA 55-300 PLM on my K-S2
It is already starting to get dark, just photographed something, no focus hiccups or refusal and fast as always with this lens, in viewfinder mode
Now try on one of the branches behind in a slight breeze vs daylight. That is where i see a difference. About to process tiny flity birds taken under a canopy on a cloudy day. I think I got focus on 2 missed on 5 and never came close enough to press the shutter many times.
here are the photos I did get today.
Golden-crowned Kinglet from Golden Valley, MN, USA on April 15, 2021 at 03:07 PM by swanlefitte ∑ iNaturalist
Black-capped Chickadee from Golden Valley, MN, USA on April 15, 2021 at 02:41 PM by swanlefitte ∑ iNaturalist

I highly recommend this combo for documenting species.


Last edited by swanlefitte; 04-15-2021 at 03:39 PM.
04-15-2021, 07:48 PM   #24
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QuoteOriginally posted by bschriver11 Quote
Nobody really seemed to answer your question so i will give it a shot. Phase detect auto focus is what the camera uses when you are looking through the viewfinder, in live view the phase detect sensor is blocked and the camera uses the contrast detect autofocus.
thx for the explanation!
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