[blucoala]

The Pentax HD converter is too expensive so I am thinking about getting either a Kenko or Tamron converter with SDM contacts for the PLM lens. Has anybody tried this configuration?

[boriscleto]

Even if AF works it won't pass focal lenght data to the SR. AF would be marginal because of the F6.3 aperture...

[stevebrot]

Kenko or Tamron converter with SDM contacts for the PLM lens

You had me a little puzzled at first with the "SDM" piece. SDM is a lens motor type. But then I realized you meant the two power contacts within the mount throat. The power contacts on the KAF2 and higher mounts were originally intended for power zoom on certain FA series lenses and were leveraged to supply power for in-lens focus and and aperture motors on later generation lenses. I am not sure what the proper name is, though I have seen them called both "power-zoom" and "power" contacts.

A pass-through type TC will pass through both power and data/control communication, but will not translate focal length or aperture. I don't believe that will be "fatal" though the following should be considered:

• SR may not be as effective as with a proper Pentax TC
• Recorded aperture in the EXIF metadata will not be correct
• Ditto the above for focal length
• Lens ID and other metadata should essentially be correct
• Viewfinder and LCD aperture and focal length displays will not be accurate

As far as the body is concerned, it has the PLM lens mounted directly. Likewise the lens is not aware that it is not talking to the body directly. The AF systems will drive the AF motor until focus is detected. Likewise the exposure system will detect attenuated light and expose properly in the same sense as if an ND filter were mounted. The actual f-number is not important for exposure purposes and is probably not even part of the conversation between lens and body.

Now the bad news...

As boriscleto noted above, PDAF performance will be compromised at the narrower relative aperture at full zoom and will likely fail completely as zoom approaches 420mm due to unavoidable prism 'black-out" at the f/9 maximum aperture for that focal length.

Translation: You can try it, but unless you are willing to use manual focus and/or live view, it is not going to work that well.


Steve

[blucoala]

You had me a little puzzled at first with the "SDM" piece. SDM is a lens motor type. But then I realized you meant the two power contacts within the mount throat. The power contacts on the KAF2 and higher mounts were originally intended for power zoom on certain FA series lenses and were leveraged to supply power for in-lens focus and and aperture motors on later generation lenses. I am not sure what the proper name is, though I have seen them called both "power-zoom" and "power" contacts.

A pass-through type TC will pass through both power and data/control communication, but will not translate focal length or aperture. I don't believe that will be "fatal" though the following should be considered:

• SR may not be as effective as with a proper Pentax TC
• Recorded aperture in the EXIF metadata will not be correct
• Ditto the above for focal length
• Lens ID and other metadata should essentially be correct
• Viewfinder and LCD aperture and focal length displays will not be accurate

As far as the body is concerned, it has the PLM lens mounted directly. Likewise the lens is not aware that it is not talking to the body directly. The AF systems will drive the AF motor until focus is detected. Likewise the exposure system will detect attenuated light and expose properly in the same sense as if an ND filter were mounted. The actual f-number is not important for exposure purposes and is probably not even part of the conversation between lens and body.

Now the bad news...

As boriscleto noted above, PDAF performance will be compromised at the narrower relative aperture at full zoom and will likely fail completely as zoom approaches 420mm due to unavoidable prism 'black-out" at the f/9 maximum aperture for that focal length.

Translation: You can try it, but unless you are willing to use manual focus and/or live view, it is not going to work that well.


Steve

Thanks for detailed answer. I found reading the Pentax HD converter review that, the AF works with the PLM lens. Since I am planning to use it with K-1 the I may be able to get some reasonable level of AF performance at F9. But it seems I have take into account the SR issue. Well if I do try the combination I will put the results in this thread.

[stevebrot]

Thanks for detailed answer. I found reading the Pentax HD converter review that, the AF works with the PLM lens. Since I am planning to use it with K-1 the I may be able to get some reasonable level of AF performance at F9. But it seems I have take into account the SR issue. Well if I do try the combination I will put the results in this thread.

Well, if it works, it works. I checked on the Ricoh/Pentax Japan Web site and the PLM lens is on the verified list for the HD DA AF Rear-Converter 1.4x AW, though with a caution that PDAF may experience problems. The review and example photos from dark64 are pretty compelling, however.

That the PDAF on the verified APS-C bodies can still function at f/9.5 is pretty incredible. Conventional wisdom draws a hard line at f/8, but Ricoh/Pentax apparently built additional narrow aperture range into their AF detectors.

Whether the PLM lens will work with the Tamron or Kenko TC on the K-1 is hard to tell, though with any luck it will work for you.


Steve

[pentageek]

I am planning to use it with K-1

Out of curiosity I tested my 55-300 non-PLM on K-1: without TC there is clearly visible vignette, but it's gone when I mount Tamron 1.4 TC! Let us know, please, once you test your TC combo.

[Des]

The Pentax HD converter is too expensive so I am thinking about getting either a Kenko or Tamron converter with SDM contacts for the PLM lens. Has anybody tried this configuration?

I have the Kenko 1.5x pz. I tried it with the 55-300 PLM on my K-3 in very good light and yes it focused - a bit slower than usual but still quick. Of course all the caveats mentioned above apply. In particular I haven't compared using the TC with cropping.

[cyberjunkie]

I have the Kenko 1.5x pz. I tried it with the 55-300 PLM on my K-3 in very good light and yes it focused - a bit slower than usual but still quick.

How is it called?
Mine is "Kenko Pz-AF 1,5x Teleplus SHQ" but i have never tried it with a non-screwdrive AF lens

cheers

P

[Des]

How is it called?
Mine is "Kenko Pz-AF 1,5x Teleplus SHQ" but i have never tried it with a non-screwdrive AF lens

cheers

P

Yes mine has the same designation.

But in the strange world of teleconverters, it seems that there are even two versions with the exact same name:
Teleconverter magnification comparison. (5 imgs): Pentax SLR Talk Forum: Digital Photography Review
Mine is the one that magnifies about 1.4x and is probably the same as the Tamron-F 1.4x Pz-AF.

See also this thread: How many variants of Kenko Pz-AF 1.5X TELEPLUS SHQ? - PentaxForums.com

[cyberjunkie]

Yes mine has the same designation.

But in the strange world of teleconverters, it seems that there are even two versions with the exact same name:
Teleconverter magnification comparison. (5 imgs): Pentax SLR Talk Forum: Digital Photography Review
Mine is the one that magnifies about 1.4x and is probably the same as the Tamron-F 1.4x Pz-AF.

See also this thread: How many variants of Kenko Pz-AF 1.5X TELEPLUS SHQ? - PentaxForums.com

I was aware of the two variants, but I never found the thread on dpreview.
Thanks

Btw, I started the second thread, just after I bought the Kenko 1.5x

Cheers

Paolo

[Des]

Btw, I started the second thread, just after I bought the Kenko 1.5x

Oops! Well at least you know it's become a reference point. :-)

[blucoala]

I have the Kenko 1.5x pz. I tried it with the 55-300 PLM on my K-3 in very good light and yes it focused - a bit slower than usual but still quick. Of course all the caveats mentioned above apply. In particular I haven't compared using the TC with cropping.

I finally decided against it. I was testing the new Preserve Detail 2.0 scaling method in PS and found I am able to good results with 1.5x digital zoom. The fact the PLM lens was designed for a smaller pixel pitch makes it quite sharp on the K-1 sensor. Also, vignetting is fixable at the following focal lengths : 55, 260~300 even at open aperture.

[Des]

I finally decided against it. I was testing the new Preserve Detail 2.0 scaling method in PS and found I am able to good results with 1.5x digital zoom. The fact the PLM lens was designed for a smaller pixel pitch makes it quite sharp on the K-1 sensor. Also, vignetting is fixable at the following focal lengths : 55, 260~300 even at open aperture.

Sensible decion IMO. I think it is doubtful whether it is worth getting a TC just to use on an f5.6 or f6.3 lens.

Interesting to hear your comments on the 55-300 PLM mounted on the K-1 in crop made. It vignettes on the K-3 and K-S2 as well, but should be correctable in PP. (I say should be because I use DxO and I'm still waiting for their modules for the PLM rather than trying to tinker with manual corrections.)

[blucoala]

Sensible decion IMO. I think it is doubtful whether it is worth getting a TC just to use on an f5.6 or f6.3 lens.

Interesting to hear your comments on the 55-300 PLM mounted on the K-1 in crop made. It vignettes on the K-3 and K-S2 as well, but should be correctable in PP. (I say should be because I use DxO and I'm still waiting for their modules for the PLM rather than trying to tinker with manual corrections.)

Well, as good as the PLM is, I will ditch it as soon Pentax release the D FA version.