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07-27-2017, 04:46 AM   #1
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K-70 Rear converter and 55-300 PLM

I am considering to purchase the new HD Pentax-DA 55-300mm F4.5-6.3 ED PLM WR RE as a fast focusing lens for bees and flies macro photography, using the K-70 body.
I wonder if the HD Pentax-DA 1.4X AW AF Rear Converter is compatible -and effective- with that combination of K-70 and 55-300 PLM lens, or which could be the main limitations for that combination of body and lens.
Anticipated thanks !

07-27-2017, 06:16 AM   #2
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It should be.... but how are you achieving macro? Tubes? Bellows? The big problem with the 55-300 is going to be light loss. You lose a stop on a slow lens. I'm not familiar with the lens, and I can't recall hearing that it had a macro function.

As per the following description
HD PENTAX-DA 55-300mmF4.5-6.3ED PLM WR RE / Telephoto Lenses / K-mount Lenses / Lenses / Products | RICOH IMAGING
maximum magnification it .3x. A macro lens like the 50 macro goes 1:1 or 1x. The 55-300 is only slightly better than the 16-85 or 18-135, and no where near lenses like the Sigma 70-300 with 1:2 (.5x) magnification. There is no TC that works with a Sigma 70-300, but you get as much magnification without the TC than the Pentax would with it, as long as you can handle the 7 foot minimum focusing distance, which is actually good for insects as you're far enough away not to disturb them.
07-27-2017, 06:54 AM   #3
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You'll want to investigate the minimum focus with the lens and with the TC attached. Then figure out what your FOV really is at that range, and whether just getting a 100mm macro would do the job better...

I used to get some good results with a Tamron 70-300 at the 300 "macro" setting. I still have the lens, I should investigate how it works compared with my current rig - which has been great. Maybe for dragonflies, toads, snakes, or other skittish critters
07-27-2017, 07:49 AM   #4
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I like the 55-300, but I do not use it as a macro. It doesn't focus all that closely. When you can, pick up a 100mm f2.8 D FA. Lovely lens (mine looks like it was inside a nuclear explosion, works great though)

07-27-2017, 07:50 AM   #5
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Focusing will be the issue. Manual focusing should be fine but if you are expecting to use for fast focusing on moving insects I suspect it might not work as well as you hope. The problem is the 55-300 is f/6.3 at 300mm add the extra stop loss for the TC and you are at f/9. Rather questionable how good the AF will be at that aperture. But I've tried it, so who knows it might work.
07-27-2017, 07:54 AM   #6
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Tricky! That combination is probably not going to autofocus well or at all when the lens is @ 300 mm (effective f-stop of f/8.8 with the 1.4X TC) and focused on something close to the lens (which may further push the effective f-stop to f/11.4).
07-27-2017, 08:07 AM - 1 Like   #7
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QuoteOriginally posted by jatrax Quote
Focusing will be the issue. Manual focusing should be fine but if you are expecting to use for fast focusing on moving insects I suspect it might not work as well as you hope. The problem is the 55-300 is f/6.3 at 300mm add the extra stop loss for the TC and you are at f/9. Rather questionable how good the AF will be at that aperture. But I've tried it, so who knows it might work.
I've used my A 400 5.6 and ƒ1.7 AF converter at ƒ9. Auto focus was terrible. All my good images were manual focus. If you didn't turn the AF off it would change your focus point and ruin your pictures.


Last edited by normhead; 07-27-2017 at 01:28 PM.
07-27-2017, 08:08 AM   #8
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With the TC AF will require plenty of light, and even then it might be slow or unreliable.

Also, the 55-300mm PLM cannot focus (even manually) without power from the lens contacts, so your macro tubes will need such contacts. Hollowed out auto TCs are often used for this purpose.

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07-27-2017, 08:18 AM   #9
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A 1.4x TC coupled with any of my long zooms and using AF, the lens hunts and never finds focus. Best if you want macro, buy a macro lens.
07-27-2017, 09:43 AM   #10
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I assume you'll be focusing close, so I'd make sure the TC still actually gives 1.4X when focused at less than infinity. Maybe it does; I don't know. But optics can be funny.
07-27-2017, 10:35 AM   #11
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QuoteOriginally posted by TER-OR Quote
You'll want to investigate the minimum focus with the lens and with the TC attached. Then figure out what your FOV really is at that range, and whether just getting a 100mm macro would do the job better...

I used to get some good results with a Tamron 70-300 at the 300 "macro" setting. I still have the lens, I should investigate how it works compared with my current rig - which has been great. Maybe for dragonflies, toads, snakes, or other skittish critters

I have an older Tamron AF 70-300mm F/4-5.6 LD Tele-Macro [1:2] (Model 772D)

https://www.pentaxforums.com/userreviews/tamron-af-70-300mm-f-4-5-6-ld-tele-...odel-772d.html

which offers near macro at 300 mm - 1:2

I also have an older SMC Pentax-D FA 100mm F2.8 Macro

SMC Pentax-D FA 100mm F2.8 Macro Reviews - D FA Prime Lenses - Pentax Lens Reviews & Lens Database

which offers true macro 1:1

you may want to investigate those if you are interested in near macro or true macro photography
07-27-2017, 10:39 AM   #12
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Thank you all...
Even more, it seems that Pentax TC1,4 is not admitted by the K-70...
KAF4 looks like a rather tricky subject.
I just wanted to improve the noise and the speed of my K-5 using Sigma 70-300 APO f4.0-5.6 or Pentax 100 WR/2,8, (this one admitting TC1,4X).
For dragonflies, beetles and few more, Sigma es fine. For flowers, spiders and few more bugs, Pentax 100WR works also fine, but trying to do it in AF is like to hear a noise symphony.
Well, I am still not convinced that the main statement for macro (1:1, 1X) oy close-up photography (0,3X, 0.5X) is that Manual Focus is a must.
07-27-2017, 10:49 AM   #13
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For my work, quick access to manual focus is a must. Autofocus works great once you are "one with" the camera. The little AF/MF switch works wonders when I need to drop to MF...
My FA100 macro has an on-lens control for manual focus - and a focus limiter. The MF swap is easier on the camera, and I don't use the limiter very often because in the field I can never predict where I'm going to be shooting.

I did evaluate a 1.4X Tamron TC which did deliver good results but wasn't as consistently good as the lens alone.
07-27-2017, 10:59 AM   #14
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I have been experimenting with the K 3 + SMC Pentax-DA L 55-300mm F4-5.8 ED + HD Pentax-DA 1.4x AW AF Rear Converter

if anyone is interested, you can see the some of the resulting photos here:

The 300mm plus lens Club discuss your long lenses. - Page 3 - PentaxForums.com

Pollinators in action - PentaxForums.com

The 300mm plus lens Club discuss your long lenses. - Page 5 - PentaxForums.com
07-27-2017, 01:30 PM   #15
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QuoteOriginally posted by MacLoz Quote
Thank you all...
Even more, it seems that Pentax TC1,4 is not admitted by the K-70...
KAF4 looks like a rather tricky subject.
I just wanted to improve the noise and the speed of my K-5 using Sigma 70-300 APO f4.0-5.6 or Pentax 100 WR/2,8, (this one admitting TC1,4X).
For dragonflies, beetles and few more, Sigma es fine. For flowers, spiders and few more bugs, Pentax 100WR works also fine, but trying to do it in AF is like to hear a noise symphony.
Well, I am still not convinced that the main statement for macro (1:1, 1X) oy close-up photography (0,3X, 0.5X) is that Manual Focus is a must.
I hardly ever use manual focus, but I will force the camera to refocus s few times by focusing on something in the distance then coming back to my macro subject.
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