[OttawaPhotog]

Okay so I have another little question to add to this TC thread....

Does a AF TC - auto focus a manual lens ? I see this on DPreview somewhere and was really curious. Says if you put the lens at infinity focus, the TC will focus itself to get it right...

now to me doesn't sound right but thought I would ask anyway...

[Canada_Rockies]

Okay so I have another little question to add to this TC thread....

Does a AF TC - auto focus a manual lens ? I see this on DPreview somewhere and was really curious. Says if you put the lens at infinity focus, the TC will focus itself to get it right...

now to me doesn't sound right but thought I would ask anyway...

That's exactly what the Pentax 1.7X AF converter does - within limits. The AF range is not all that great. It is recommended only for lenses f/2.8 or faster, although I have seen some get decent results with f/4 lenses in these fora. I think you could quite easily use the converter by doing a rough focus manually and then letting the AF converter do its thing from there.

I am thinking seriously about getting the 1.7X for use with my 50-135 DA* to extend the range, and retain auto focus, but I'm not yet fully decided. I do know that I got decent results using my A 1.4X-S with the 50-135. It have me a 75 - 200+ MF zoom with better quality than my A 70-210/4 at the same f/stops.

[OttawaPhotog]

Oh okay, now is it only the Pentax 1.7x that does this or would the Sigma 2x or 1.4x do this as well...

[Canada_Rockies]

Oh okay, now is it only the Pentax 1.7x that does this or would the Sigma 2x or 1.4x do this as well...

There are two different kinds of AF converter, as near as I can tell. The first type is the Pentax 1.7X which will autofocus anything put on the front of it (well, maybe not M42 screw mount) within range limitations.

The second type of AF converter passes the AF through the converter. A manual focus lens would remain manual focus. This has to be in the fine print somewhere, but I have never been able to find it myself. I suspect that the Pentax is a rather rare treatment. Pentax brought it out early on, so that the users of good, fast MF lenses could get a form of autofocus with the SF series.

[Abbazz]

I have posted elsewhere some pictures taken with my Tamron Adaptall II 300/2.8 SP and some teleconverters (Pentax 1.7X AF Adapter, Vivitar 2X Macro focusing Teleconverter, Pentax 2X-S Rear Converter and Kenko 3X Teleplus Pro 300). For those interested, here is the link to this thread:
Manual Focus Lenses :: View topic - Tamron Adaptall II 300/2.8 SP with teleconverters

Cheers!

Abbazz

[Lowell Goudge]

Oh okay, now is it only the Pentax 1.7x that does this or would the Sigma 2x or 1.4x do this as well...

the pentax 1.7x AF TC has moving internal elements that provide auto focus to manual focus lenses, the sigma 1.4x and 2x have autofocus drive coupled through the TC so that if the lens is AF then you retain AF.

A couple of notes.

1) The Sigma TCs are specific to only a very limited number of lenses to be used on. the front element of the TC actually sticks out so far that it hits the rear element on many lenses. go to the sigma web site to see the compatibility listing.

2) the pentax 1.7x AF TC, according to the documentation only works on F2.8 and faster lenses. I think that this was due to the relitively poor low light performance of the SF-1, which it was origonally released for. I bought mine when I got my PZ-1, and tested it on both f3.5 Series 1 70-200, and my SMC-M 100mm F4 macro. It works under virtually all conditions with these lenses. When I bought my 300mmF4, I specifically tested this function also on my PZ-1 and it worked under all conditions I could try. I have since used this paring (300mm F4 and 1.7x AT TC) a lot on my dslrs

[palmor]

I have the Kenko 1.5x and the Sigma 2.0x TC and I am happy with both of them. The Kenko I have used with my Tokina AT-X 400mm f/5.6 and it does retain autofocus in good light (slower but it still works). The Sigma 2.0x TC I use with the Sigma 70-200EX and it has small amount of IQ loss but not much at all.

I've posted examples of both these TC's in other threads..

Sigma TC with Sigma 70-200EX: https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/19694-tamron-t...er-pics-6.html

Kenko TC with Tokina AT-X 400mm: https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/19694-tamron-t...rter-pics.html

Not sure if that helps answer any of the questions on this thread directly but I thought I'd throw some more examples of different TC's into the mix.

[channeler]

Does anyone know if Kenko does a TC 1.4 or 1.5 for Pentax in their Teleplus Pro 300 range? I've not been able to find one from my research. Is Pentax still producing TCs at the moment? Not been able to find them on their websites.

Paul

[John Kovarik]

Here's my (unprofessional) update: I now have the Kenko 1.5, Tamron 1.4, and PTX 1.7, all AF
version. My assessment is the Kenko is very good in consistent performance on a wide range of glass and IQ is in the upper range of acceptable. The Tamron is excellent in all respects espceially when on my Tamron 18-250. The PTX is the 'fussiest' lens-to-lens, but I have had it only a couple of days. Right now it is on a K135/2.5 (K100D) and its 'final focus' peformance is superb - fast and dead on. Though I think the Kenko is surely the best $ value, the other two will get far more camera time. And that's all I have to say 'bout TCs........(8- )

[channeler]

Kenko Teleplus 1.5 and 2.0 and Sigma 1.4 and 2.0 seem to be the only new TCs available for Pentax at the moment. Kenko also seem to do the 3.0 in their Pro300 range but not a 1.4 or 2.0 (a pity). Tamron's USA site seems to refer to a 1.4 and 2.0 for Pentax but not been able to find a dealer who sells it in UK or USA. Haven't been able to find the official Tamron site in the UK yet.

Paul

[Gumysh]

I have 6 different TCs

vivitar MC-22 2x and 3x
Takumar 2x in KA mount
Pentax 1.7x AF adaptor
Sigma EX 1.4x and EX 2x DG

I have been quite pleased with the sigma 1.4x and the pentax 1.7x (note they are expensive)

I have just gotten the sigma 2x

I have not tried enough with the TAK and vivitar reciently.

Hi, Lowell, it is good to learn a person that has so much TC experience I consider buying one, but I have some doubts and questions about Sigma's TCs, especially about 2x TC. Unfortunately I couldn't find any convincing information - you might know the answers, thanks to your practical experience. Please, could you tell me?

My first question concerns the way how the TC handles the focal length of the attached lens. I heard that it doesn't convert it appropriately. Is it the truth? And if it is, what are the practical impacts? I assume that EXIFs contain then bad focal length (annoying, but I can survive that). I'm afraid more that this also influences the shake reduction system of the body. What is your experience?

The second point is about HSM support. According to the press release on DPReview (Sigma 70-200 and 50-150 f/2.8 APO EX DG for Pentax and Sony: Digital Photography Review) it seems that the TCs already incorporate the electric contacts for powering SDM (and also power zoom and HSM etc.) and therefore even HSM lenses should operate with them without problems. Could you confirm that or do you understand it in the way that only the newly made TCs will support HSM as well? (OK, there were other threads where the support of Tamron's TCs was mentioned, but the situation with Sigma was not explicitly clarified - I'm interested in Sigma now.)

Thanks for your (or anybody's) reply in advance. Knowing the answers would help me a lot

[palmor]

My first question concerns the way how the TC handles the focal length of the attached lens. I heard that it doesn't convert it appropriately. Is it the truth? And if it is, what are the practical impacts? I assume that EXIFs contain then bad focal length (annoying, but I can survive that). I'm afraid more that this also influences the shake reduction system of the body. What is your experience?

This is correct, the Sigma TC does not pass through the updated focal length so the SR system is going by the unadjusted length making it less efficient.

I don't have any experience with SDM lenses so I can't help verify your second questions.


Hope that helps!
John

[Lowell Goudge]

Hi, Lowell, it is good to learn a person that has so much TC experience

not all of it is good experience, but that's life

I consider buying one, but I have some doubts and questions about Sigma's TCs, especially about 2x TC. Unfortunately I couldn't find any convincing information - you might know the answers, thanks to your practical experience. Please, could you tell me?

My first question concerns the way how the TC handles the focal length of the attached lens. I heard that it doesn't convert it appropriately. Is it the truth? And if it is, what are the practical impacts? I assume that EXIFs contain then bad focal length (annoying, but I can survive that). I'm afraid more that this also influences the shake reduction system of the body. What is your experience?

up until now, and that includes the current Sigma 2x TC (APO Teleconverter 2X EX DG version) for pentax, the lens data contact is a feed through contact only, no focal length change is made.

Aside for the exif data being incorrect, which I don't really care about, the focal length is wrong for the program modes where they try to follow the 1/focal length rule for hand holding, this needs to be watched because you can, in program modes get into trouble with low shutter speed. the most critical point however is on the K100, K10 and K100 super, in that the focal length used for shake reduction is incorrect.

The second point is about HSM support. According to the press release on DPReview (Sigma 70-200 and 50-150 f/2.8 APO EX DG for Pentax and Sony: Digital Photography Review) it seems that the TCs already incorporate the electric contacts for powering SDM (and also power zoom and HSM etc.) and therefore even HSM lenses should operate with them without problems. Could you confirm that or do you understand it in the way that only the newly made TCs will support HSM as well? (OK, there were other threads where the support of Tamron's TCs was mentioned, but the situation with Sigma was not explicitly clarified - I'm interested in Sigma now.)

Thanks for your (or anybody's) reply in advance. Knowing the answers would help me a lot

My copy, APO Teleconverter 2X EX DG version does not have the power contacts. I would think that they need to designate the unit different. Also you need to consider whether the new TC will be full frame or not.

[Gumysh]

Thanks to both you and palmor. You didn't make me very happy but I hope that Sigma will update the TCs in both points, so they could work seamless with the Pentax's DSLRs.

Lowell, I though that all Sigma's TCs are full-frame and the DG mark means only the better coating optimized also for DSLRs. Am I wrong? (Anyway, this is not very important to me, far not as much as the HSM support and properly working SR.)

[Lowell Goudge]

Thanks to both you and palmor. You didn't make me very happy but I hope that Sigma will update the TCs in both points, so they could work seamless with the Pentax's DSLRs.

Lowell, I though that all Sigma's TCs are full-frame and the DG mark means only the better coating optimized also for DSLRs. Am I wrong? (Anyway, this is not very important to me, far not as much as the HSM support and properly working SR.)

All present sigma TCs are full frame, but I don't know what Sigma will do for a pentax specific one to support HSM because no pentax lenses that support HSM are full frame.

Note also DG does not stand for digital, but digital full frame. DC is for Digital ASP-C sensor