Has anyone tried this TC? $89.95

Russell-Evans · 09-09-2009, 04:44 PM

Does it work with SDM lenses? I looked through google's search results and didn't really find any information or a solid review.

Pro-Optic Multi-Coated 1.4x Tele-Converter for Pentax Autofocus SLR Cameras.

Thank you
Russell

danielchtong · 09-09-2009, 05:17 PM

No. See my reply in dpreview

Spock · 10-19-2009, 03:54 AM

Originally Posted by danielchtong

No. See my reply in dpreview

Link please?

In additions to opinions on its IQ, I'd also like to know if when used with A lenses does it
1. auto focus?
2. transmit and convert f-stop info?

Thanks!

Ben_Edict · 10-19-2009, 04:15 AM

Originally Posted by Spock

Link please?

In additions to opinions on its IQ, I'd also like to know if when used with A lenses does it
1. auto focus?
2. transmit and convert f-stop info?

Thanks!

Why would it transform A-lenses into AF lenses? There is only the Pentax 1.7x AF-adapter, that was build to do that. The product in your image is a simple, low-end tc and will not convert MF löenses to AF.
Whether it can calculate the total fl I don't know. But that that this ability is not indicated anywhere seems to be an indicator, that it is just a "dumb" tc and does not provide these additional information.

Ben

Ahab · 10-19-2009, 09:38 AM

No, and I wrote a review about this at Adorama but they never posted it. It is well built, but is as another posted, a dumb TC.

*aerodave* · 10-19-2009, 09:53 AM

Based on the pics on the Adorama site, I'd say it tranmits the info from the "A" contacts, so it should let the camera know what kind of lens is attached. I don't know whether it can let the camera know the focal length is now 1.4x longer and the lens is now 1 stop slower. I bet it doesn't do anything that smart.

There is also a screw drive connection, so it obviously will allow autofocusing on lenses that accept screw drive (F, FA, D FA, and DA lenses, except the DA 17-70mm).

As for SDM compatibility, it looks like no. On the body side of that TC, it looks like there is a pair of contacts for the SDM connection. But that same connector on the lens side looks blank. That's curious.

*clawhammer* · 10-19-2009, 01:41 PM

It looks similar to my quantaray 2x converter, which does pass power for powerzoom so I imagine the SDM lenses would work as well.

*SOldBear* · 10-19-2009, 02:36 PM

Originally Posted by clawhammer

It looks similar to my quantaray 2x converter, which does pass power for powerzoom so I imagine the SDM lenses would work as well.

In my experience, "passing power" doesn't necessarily means "AF working with SDM" lenses.

I have a Tamron 1.4X TC with the power contacts. It doesn't work with Pentax DA* 50-135mm F/2.8 ("ultimately" achieving focus but I don't call that "working").

The Tamron 2X TC, also with the power contacts, doesn't even attempt to auto-focus.

*SOldBear* · 10-19-2009, 02:42 PM

Originally Posted by aerodave

...I don't know whether it can let the camera know the focal length is now 1.4x longer and the lens is now 1 stop slower. I bet it doesn't do anything that smart.

You're right. None of the TCs currently on the market modifies the focal length and the aperture information. The only TC that modifies the aperture information is the Pentax AFA 1.7X. But this adapter treats the lens as manual focus. In other words, it blocks the focal length info and thus the body will ask for it (for SR purpose).

Spock · 10-19-2009, 08:54 PM

Thanks for the replies.

So I guess the 'AF' in the name of this and other converters such as the Tamron refers to the fact that they have screw drive connectors that pass through to allow the camera to autofocus AF lenses attached to the converter? (As opposed to the Pentax 1.7AF which autofocuses the converter - not the lens).

Spock · 10-19-2009, 08:56 PM

Originally Posted by SOldBear

The only TC that modifies the aperture information is the Pentax AFA 1.7X.

What about the Pentax-A 1.4x and 2x converters (S & L versions)? Surely they do also?

Ben_Edict · 10-20-2009, 03:49 AM

Originally Posted by Spock

What about the Pentax-A 1.4x and 2x converters (S & L versions)? Surely they do also?

No, they don't - just simple (though very high quality) tele converters. (I have all of them, so I know there strengthes and limitations.)

Ben

Spock · 10-20-2009, 08:07 AM

Originally Posted by Ben_Edict

No, they don't - just simple (though very high quality) tele converters. (I have all of them, so I know there strengthes and limitations.)

Ben

That's strange - so what's the purpose of the electrical connectors on the A- teleconverters then?

Ben_Edict · 10-21-2009, 06:25 AM

Originally Posted by Spock

That's strange - so what's the purpose of the electrical connectors on the A- teleconverters then?

That's not strange. The A-contacts where already in use long before AF was adopted in SLRs. They transfer for example the max. aperture, the chosen aperture etc. to the camera. Later power contacts where added in some lenses (Power Zoom function), but these are absent in most tcs.

You will find a detailed description of the A-contact's function here:

Features and Operation of the Ka Mount

Ben

Spock · 10-21-2009, 08:53 AM

Originally Posted by Ben_Edict

That's not strange. The A-contacts where already in use long before AF was adopted in SLRs. They transfer for example the max. aperture, the chosen aperture etc. to the camera.

You misunderstood me - I wasn't referring to AF - I thought it was strange that apparently the only TC that modifies the aperture information is the Pentax AFA 1.7X. If that is the case, I asked, what purpose do the electrical contacts have on the A-series converters?