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07-05-2018, 07:06 AM   #1
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Pentax DA 1.4x rear converter

Can I use the DA 1.4x converter on DFA lens mounted on K1 in full frame mode?

07-05-2018, 07:16 AM   #2
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You will get vignetting at least some of the time. Technically, it's APS-c only. That doesn't mean I haven't used it, but shoot wider than you need and be prepared to crop.

I already owned one when I got my K-1, I'm not sure you'd want to buy one specifically for use on a K-1. I use the F 1.7x AF adapter on the K-1, but, that introduces the whole manual focus element. Pentax has promised 1.4x and 2x TC will be released in the next few years.

In the meantime, the 1.4 TC in a K-3 is a like a 2x on a K-1 with the same lens.

Last edited by normhead; 07-05-2018 at 07:22 AM.
07-05-2018, 07:17 AM   #3
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...you can. There's nothing stopping that. Are you asking if it will work without vignetting? I don't know for certain, but I want to say no - I don't think the teleconverter covers the full frame image circle.

BUT! I believe Pentax is making new teleconverters that are full frame compatible! They mentioned that during a recent interview..
07-05-2018, 07:18 AM   #4
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You can but many (most) lenses will vignette to some extent. The TC was designed for APS-C cameras, not FF.

07-05-2018, 08:06 AM   #5
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The vignetting others have described is a great disappointment until you realize you can crop a little and still have a good picture.
07-05-2018, 08:32 AM - 1 Like   #6
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QuoteOriginally posted by Mikesul Quote
The vignetting others have described is a great disappointment until you realize you can crop a little and still have a good picture.
Since I do a lot of cropping to 16-9, those vignetted corners are history, long before anyone sees the image. You still get the full k-1 7300 pixels wide, much easier than doing a pano on a K-5 for a similar image. You just have to remember you are going to crop when framing.

Last edited by normhead; 07-05-2018 at 02:26 PM.
07-05-2018, 08:35 AM   #7
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QuoteOriginally posted by normhead Quote
Since I do a lot of cropping to 16-9, those vignetted corners are history, long before anyone sees the image. You still get the full k-1 7300 pixels wide, much easier than doing a pano on a K-5 for a similar image. You just have to remember you are going to crop wen framing.
Yes. I was very embarrassed after I sold my first copy because of the vignetting and then finally realized what you just pointed out. The new one stays here.
07-05-2018, 08:51 AM   #8
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The thing I haven't seen is any chart or reference material produced (even by joe average) that gives good info on what the amount of vignetting is at various focal lengths and apertures across lenses. Some do well, some poorly and it seems a big crap shoot to know which is what without finding someone who has already tested it.

Obviously not every lens need be tested - just some of the more common telephotos both prime and zoom.

07-05-2018, 09:16 AM - 1 Like   #9
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If someone will send me a DAF 150-450 , a DA*300, A DFA 70-200 I'll do all the testing you want. But the price tag for the necessary gear to do the tests would be exorbitant.
07-05-2018, 09:46 AM   #10
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QuoteOriginally posted by normhead Quote
If someone will send me a DAF 150-450 , a DA*300, A DFA 70-200 I'll do all the testing you want. But the price tag for the necessary gear to do the tests would be exorbitant.
LOL

I was thinking more along the lines of collaboration between people who may own only one of these and the 1.4x HD DA... you for example have the DA* 200 and a 300mm f/2.8 (Sigma? I can't recall and can't see signatures right now.)
07-05-2018, 10:28 AM - 1 Like   #11
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We have tested the following lenses with the TC:

DA* 300mm "red" - light vignetting wide-open, worsens as you stop down
DA* 200mm "green" - no notable vignetting
DA* 50-135mm "green" - soft corners only
DA* 60-250mm "yellow" - light vignetting throughout lower half of the zoom range (note: baffle was not removed)

TLDR, if reach is your objective, it will probably not deliver a FF image circle when you need it. But it really varies from lens to lens.

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07-05-2018, 11:05 AM   #12
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QuoteOriginally posted by Adam Quote
We have tested the following lenses with the TC:

DA* 300mm "red" - light vignetting wide-open, worsens as you stop down
DA* 200mm "green" - no notable vignetting
DA* 50-135mm "green" - soft corners only
DA* 60-250mm "yellow" - light vignetting throughout lower half of the zoom range (note: baffle was not removed)

TLDR, if reach is your objective, it will probably not deliver a FF image circle when you need it. But it really varies from lens to lens.
That 50-135 result was unexpected. I'd love to find out more about a 60-250 with the baffle modifications too. Thanks for the quick report Adam. Being able to use the 50-135 as a full frame f/4 70-189 is a really nice surprise.
07-05-2018, 03:32 PM   #13
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What about D FA 28-105mm with DA 1.4x Rear Converter?

Has anyone tested the D FA 28-105mm plus Pentax DA 1.4x Rear Converter on a K-1-series?

I'll probably do my own somewhat informal test, (I have the Converter), but it would be useful if I could draw upon anyone else's experience.

I'm especially interested where the lens is set to 105mm, and a fairly wide aperture, perhaps fully open, hence actual f/8.

I have other lenses covering the range above 105mm. But I'm interested in the "walk about" case, primarily with just the lens, but with the Converter in a pocket "just in case".

(I use Lightroom, so simple vignetting won't be a problem. Edge and corner sharpness of the lens drops off a bit at 105mm, but the Converter will presumably push those areas outside the sensor).
07-05-2018, 06:55 PM   #14
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Thank you all for the info.. Let's hope Pentax will come up with a TC for FF soon..
07-06-2018, 02:49 AM   #15
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QuoteOriginally posted by Barry Pearson Quote
Has anyone tested the D FA 28-105mm plus Pentax DA 1.4x Rear Converter on a K-1-series?

I'll probably do my own somewhat informal test, (I have the Converter), but it would be useful if I could draw upon anyone else's experience.

I'm especially interested where the lens is set to 105mm, and a fairly wide aperture, perhaps fully open, hence actual f/8.

I have other lenses covering the range above 105mm. But I'm interested in the "walk about" case, primarily with just the lens, but with the Converter in a pocket "just in case".

(I use Lightroom, so simple vignetting won't be a problem. Edge and corner sharpness of the lens drops off a bit at 105mm, but the Converter will presumably push those areas outside the sensor).
makes not much sense, because the lens is to slow. Better get an other zoom. There are a lot better options out there.

It is a little bit like to put the converter together with the FA 31 Ltd to get a bigger and slower 43 ... makes no sense either. But it works
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