K10D and Teleconvertors

Hi all

I received my Pentax 1.7x AF Adaptor today, got for a very very nice price and it's in as new condition too. As I already have a Sigma 2x APO I wondered how the K10D SR and EXIF hadles them, well here are a few quick conclussions.

Penatx SMC-F 1.7X Adaptor
When you mount an SMC-A lens to a Pentax-F 1.7x adaptor you are promted at switch on for the focal length, with the SMC-A50 f1.4 mounted the adjusted aperture of f2.8-40 is selectable/displayed in VF and EXIF, the EXIF also displays the focal length selected in the SR menu. MF is lit in the VF even though AF is selected, the lens does AF though.

When you mount an F/FA/DA lens to a Pentax-F 1.7x after switch on you can set the desired focal length by going into the Shake Reduction menu and select whatever focal length you wish, with the DA16-45 f4 mounted the adjusted aperture of f6.7-40 is selectable/displayed in VF and EXIF, the EXIF also displays the focal length selected in the SR menu. MF is lit in the VF even though AF is selected, the lens does AF though.

Sigma 2x APO
When you mount an SMC-A lens to a Sigma 2x APO TC you are promted at switch on for the focal length, with the SMC-A50 f1.4 mounted an aperture of f1.4-22 is selectable/displayed in VF and EXIF. No corrections to Aperture but the focal length selected is displayed in the the EXIF. MF is lit in the VF even though AF is selected.

When you mount an F/FA/DA lens to a Sigma 2x APO TC after switch on you cannot set the desired focal length, the Shake Reduction menu is greyed out, with an FA24-90 mounted the aperture range as stated on the lens is selectable/displayed in VF and EXIF, No corrections to Aperture or focal length in VF or EXIF
If you switch on with only the Sigma 2x attached you are promted for a focal length but this is over ridden as soon as you attach an AF lens.

The same is true of Kenko/teleplus Pz-AF 2x MC7, Sigma EX 2x, Sigma APO 1.4x, and also I suspect any TC with all 7 electrical contacts. The first six pins encode max/min aperture info for A series and later lenses: it is the seventh pin which communicates the lens focal length info from F onwards.

The upshot of this is that SR doesn't work properly when using these TCs. Which is a real pain for me, as I often use the F* 300mm f4.5 with one or other of the above teleconverters. I haven't done a scientific comparison, but I certainly get the feeling that SR makes a lot less (relative) difference when using the TCs.

I really think there should be an option in custom function to over-ride the greyed-out SR focal length for precisely this reason. As has been pointed out in other threads, the SR menu has apparently already changed since the original publicity material was printed, so I was hoping the firmware update might fix this. I know they're 3rd-party TCs, but there must be a lot of users out there with them.

Steve

http://www.siblingmedia.com/

[quote="stevo"]Especially as Pentax branded TC's are as rare as hens teeth, rocking horse manure, etc.

I got lucky, snapped it up for £69.01 the 2x APO will be heading out the door soon, can't see me using it any time soon since I managed to aquire an SMC-A 400.

just a thought, would a piece of insulating tape over the 7th contact on the TC solve the problem?

Has anybody tested this, or could do it?

Insulating tape is a bit of a no-no, as it tends to get gunged-up when attaching and removing lenses. I have tried taking my Kenko PzAF 2x apart and physically removing the data pin (not too tricky) but it didn't work: the camera still managed to read the focal length from the lens. No idea how: perhaps there's more going on in the K-mount than Bojidar would have us believe.

Interestingly enough, there are electronics inside the TC: a small circuit board with an IC and a few components between the two sets of pins. I had assumed the pins just went straight through as the TC seems to be invisible to the camera; quite what the electronics are there for I don't know.

My short-term solution for this problem was to purchase a Pentax A 2x-S TC. Loses you AF, but I nearly always focus manually anyway. Haven't been able to test it out on the K10D yet as it's back with Pentax being repaired.

In the longer term, I really hope Pentax include the ability to over-ride the SR focal length, or add a multiplier, in the next firmware upgrade.

Steve

PS It may just be a coincidence, but ebay prices for the 1.7x AF converter seem to have gone through the roof just lately (McBrian excepted).

http://www.siblingmedia.com/

Off topic

Whats wrong with it Stevo? Doesn't sound good that it's already in for repair!

The little lever that controls the aperture suddenly stopped working, so all lenses were permanently stopped down. Which was a bit annoying, particularly as I'd only had it for a month.

Fortunately I haven't got round to off-loading the *istD yet, so I have a back-up. Enforced use of the *istD really makes you appreciate the K10D, though...

Steve

http://www.siblingmedia.com/