[phoebus]

Here are samples taken with Sigma - 10-20 F3.5 with Pentax HD 1.4x, all at F5.6 (wide open...):

First 4 are uncorrected.
10mm
12mm
14mm
20mm
Last one with LR Sigma lens correction + maximum vignette correction
12mm

I think it is fair to say that the teleconverter is limiting the image corners beyond recovery in LR. If there was an alternative FF TC with the KAF3 electrical contacts, you might get better results.

Note: The EXIF is not correctly showing the effective focal length

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[mee]

Excellent work and precisely the type of samples I was wanting to see (had I my druthers). THANK YOU!!!

Very odd that the HD converter didn't transmit the focal length converted.. just gave regular FL. I think a FF tele might actually be a better idea now.. you might have just saved me a few hundred dollars (and/or a lot of time and hassle).

Thanks again for going through the trouble of taking and posting those! If I could 'like' your post 10x I would.

[phoebus]

No problem - the 10-20 F3.5 is not exactly the lens you have, but close enough. Real shame about the HD TC, IQ wise it really is very good and paired with the 150-450 gives excellent results in the centre. When I need that extra focal length, the centre is the important part anyway. For wider angles, the corners become much higher up the priority list.

:-)

[klkitchens]

*bump*

Someone has this camera, lens, and converter combination and is willing to try?

Not sure if this has been answered yet or not (have not read the whole thread)... I saw this post last week before I got my K1 in and was hopeful the 10-20 would work on FF and then sadly found out it does not.

I remembered though this post and grabbed my Tamron-F 1.4x AF TC and slapped it on the 10-20. Thought, ok... this will make it a 14-28 ("Oh crap, I just bought a 14mm FF!!!).

And it works perfectly. ("Oh crap, I just bought a 14mm FF!!!). Tried it wide open and stopped down at both 10 and 20 and saw no discernible vignetting...

Did I mention: ("Oh crap, I just bought a 14mm FF!!!).

EDIT: Walking this back a little. After looking at the brick shots above, I rechecked the shots more closely that I took.

At 10mm (14mm, I just bought one of those), there is some vignetting in the corners. From 12mm and up it appears to vanish, at least on the K1 screen.

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Last edited by klkitchens; 03-10-2017 at 10:50 PM.

[klkitchens]

Shots using Sigma 10-20 + Tamron AF 1.4x TC

10, 12, 14, 17, 20

[mee]

That says a lot there. Thank you for those... it looks like the edges are rather atrocious. So your 14mm could still get a workout.

I'm thinking I might end up getting an Irix 15mm which is roughly the same as 10mm FoV on crop. With the K-1's big resolution I can crop to different "focal lengths" if I want...

[TTQ225]

I've seen a couple test shots on a Canon 5dII with a Kenko 1.4x converter and this lens (they dubbed the Wigma -- Wide Sigma. As opposed to the 50-500 Bigma haha).

It looked decent enough with no discernible vignetting. But I'm wondering, specifically, how the HD 1.4x converter with this lens on the 36MP K-1 handles?

The Wigma essentially becomes a 14-28 if it fares well. Anyone willing to post a few test shots? I'm especially interested in edge (sharpness) and vignetting performance

Guys, I am so happy I found this post here. I just tried my Sigma 10-20 F4-5.6 DC with my Tamron 1.4x Pz-AF MC4 teleconverter and it works beautifully! Not a sign of vignetting. Then I made another experiment. I placed my DA 15mm F4 Ltd. on this teleconverter and it works too. Now I don't need to but another wide angle and my K-1 is now complete. I have these two lenses for wide angle shots, then DFA 28-105 ED WR as everyday and travel lens and also HD DA 55-300 ED WR for tele shots. My other 3 primes that work very well on K-1 are HD DA 35 macro Ltd, HD DA 70 Ltd. and DA 50mm 1.8. I am all set and very happy.

[pinholecam]

The IQ from such an endeavor does not seem to be worth it.
Its only reduced/no vignette, not reasonable IQ up to the edges.

The widest one will get with such a combo is 14mm. (probably less after distortion and vignette correction ).
Might as well use the 10-20 in 1.5x apsc mode then.

Yes, the 1.4x+10-20 combi gets 36mp on FF, but the reality is that the IQ is wanting on most of it.

I would suggest a Samyang 14/2.8 (really good IQ) or even a Vivitar 17/4 (not great, but still better ).

[TTQ225]

I rented the 1.4TC last week and used it on the K1 and it vignettes a lot, it's not full frame. I'm not sure how it would turn a apsc lens to a cheap man's ff lens.

I have the Sigma lens also to bad you didn't post this question last week I would've tried it out. I never thought of putting a TC on a wide lens.

You are wrong. I took many shots with Sigma 10-20 with Tamron AF 1.4x mounted on K-1 and it produces a full FF image - 46Mb, 7360 x 4912 Pixels (36.15 MPixels) with zero vignetting. I tried the same with HD DA 15mm Limited and it works perfect, no vignetting.

Here is a link to my post on a Facebook Pentax K-1 group page:
Log into Facebook | Facebook

[madbrain]

You are wrong. I took many shots with Sigma 10-20 with Tamron AF 1.4x mounted on K-1 and it produces a full FF image - 46Mb, 7360 x 4912 Pixels (36.15 MPixels) with zero vignetting. I tried the same with HD DA 15mm Limited and it works perfect, no vignetting.

Here is a link to my post on a Facebook Pentax K-1 group page:
Log into Facebook | Facebook

I am not able to access your Facebook post.

Can you tell me which specific model of Tamron 1.4x teleconverter you are using ? There are several.

Is the auto-focus preserved ? And how is the lens speed in terms of f stop ? I have the f4 - f.5.6 version of the Sigma 10-20 . Were you using that one, or the f3.5 constant version ?

[madbrain]

I am not able to access your Facebook post.

Can you tell me which specific model of Tamron 1.4x teleconverter you are using ? There are several.

Is the auto-focus preserved ? And how is the lens speed in terms of f stop ? I have the f4 - f.5.6 version of the Sigma 10-20 . Were you using that one, or the f3.5 constant version ?

Responding to myself here :

I just bought a "Tamron-F 1.4x Pz-AF MC4 Tele-Converter for Pentax" on ebay. The teleconverter seems to work fine with my f4 - f5.6 between 11mm and 20mm . AF worked fine in broad daylight at least. At 10mm, there is vignetting in the corners visible in the viewfinder with my K-1 II, regardless of aperture . I'm not sure if it's possible to correct in post with RAW files. As a bonus, I don't need to force the camera to FF mode, since the "auto" mode seems to only switch to APS-C mode for Pentax branded lenses. I have not examined the shots closely on my monitor yet to see if I really get extra resolution vs using the lens in crop mode.