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02-18-2016, 02:30 PM   #1
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Is the Pentax HD DA 1.4 Converter truly Full Frame compatible?

I ask this question because there seems to be some conflicting information about this. The DPReview, for example, says that the Pentax HD DA 1.4 Converter is NOT Full-Frame compatible. On the other hand, in the Pentax Forums database it appears as full-frame. Can we get a definitive answer?

I am particularly interested in using the converter with some prime DA lenses (35mm and 70mm limiteds, and the FDA 100mm macros, for example). Using the converter would give extra length, and resolve any slight vignetting problems with the limited lenses.

Regards, johnmb

02-18-2016, 03:10 PM   #2
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No, it is not fully FF compatible, at least not with all lenses. You can check the DPR forum somebody posted a sample.
However, the 35mm ltd in particular seemed to be fine when I had a chance to test the combination on sony ff a while ago.
02-18-2016, 03:48 PM - 1 Like   #3
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QuoteOriginally posted by npc Quote
No, it is not fully FF compatible, at least not with all lenses. You can check the DPR forum somebody posted a sample.
However, the 35mm ltd in particular seemed to be fine when I had a chance to test the combination on sony ff a while ago.
I believe the 1.4 TC is FF compatible when used with a FF compatible lens, but it does not correct DA lenses that aren't FF compatible.
02-18-2016, 04:17 PM   #4
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This article below mentions FF in the specs for the teleconverter. It may be used with a lens such as the Pentax 150-450, which has a full frame compatibility spec.

Ricoh announces HD Pentax DA AF 1.4X AW rear converter: Digital Photography Review


Last edited by C_Jones; 02-18-2016 at 04:37 PM.
02-18-2016, 06:49 PM   #5
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If this TC can work w/ full frame lenses (on a 35mm film camera) which I gather is true (so the potential image size is FF), and since 1.4 x magnification is almost equal to the 1.5 reduction in image size for older Pentax dslr, it would seem most of the DA lenses would be okay, or at worst almost FF--after all the TC is magnifying the lens (output) image by 1.4.

Last edited by dms; 02-18-2016 at 07:19 PM. Reason: Clarify/add "on a 35 mm film camera"
02-18-2016, 10:07 PM - 1 Like   #6
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A lot rose-tinted glasses here.

The elements are substantially smaller than even the cheap Tamron 1.4x PZ. Perhaps someone will argue that Tamron put in extra glass for the fun of it. Pentax flatly indicates "no." This means most lenses are a no go, but I am sure there will be some FF lenses that pass muster, but not the faster ones most likely.
02-19-2016, 04:26 AM - 3 Likes   #7
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QuoteOriginally posted by ScooterMaxi Jim Quote
A lot rose-tinted glasses here.

The elements are substantially smaller than even the cheap Tamron 1.4x PZ. Perhaps someone will argue that Tamron put in extra glass for the fun of it. Pentax flatly indicates "no." This means most lenses are a no go, but I am sure there will be some FF lenses that pass muster, but not the faster ones most likely.
A few hours ago I put my Pentax HD 1.4x Converter on my Pentax Z-1p camera, then added various lenses and examined the image in the viewfinder. The lenses I tried were: DA* 300mm, DA* 60-250mm, D FA 150-450mm, D FA 100mm Macro, DA 16-85mm.

In all cases I was able to see right into the corners of the viewfinder, typically even reading text there. I realise that this is not the same as taking a photo! And also that the viewfinder of the Z-1p is not 100%.

But - I certainly don't believe the Converter can't be useful in FF mode. Perhaps it won't be good with all DA lenses. Perhaps it will mostly only be useful at some sensor size intermediate between APS-C and FF, needing cropping in post-processing.

Arguments based on theory or what some people in Ricoh say are not sufficient to decide this matter! When I get the K-1 I will test all my lenses both with and without the Converter, at various focal lengths and apertures. I expect to publish results on my website, and post a link to PentaxForums and DPReview.
02-19-2016, 04:47 AM   #8
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Thanks Barry. Thanks for spending the time to do that text. And thanks also for your thoughtful reply. I look forward to seeing the results you get when your Pentax K'1 arrives. Warm regards, John

02-19-2016, 05:04 AM   #9
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QuoteOriginally posted by johnmb Quote
Thanks Barry. Thanks for spending the time to do that text. And thanks also for your thoughtful reply. I look forward to seeing the results you get when your Pentax K'1 arrives. Warm regards, John
You may be interested in tests I have already done, (in mid-2013), but some these were with a Kenko 1.4x Converter, not the Pentax Converter. These results all used my Pentax Z-1p, and I had the film developed and uploaded the images.

Pentax Full Frame tests

That is probably where I will publish any tests I do with the K-1.
02-19-2016, 06:57 AM   #10
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I did a quick "backyard" test just now with the 1.4 tc on my A7RII. There was full frame coverage without vignetting using the M50 1.7 and M135 3.5 at f1.7/3.5 and f8. Both lenses gave clean full coverage. I then tried it with te 150-450. this was a very difficult test for a number of reasons but mainly because I am doing the tests from my living room chair Oddly there is slight four corner vignetting with the 150-450 and the tc at both 150 and 450mm. I suspect there may be some other factor than the tc causing vignetting here. Anyway there is cause for optimism about using the HD DA 1.4 TC with the new K-1. I hate waiting!
02-19-2016, 10:37 AM   #11
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The x1,4 TC itself certainly is FF compatible, there is no shadow of doubt on this.

The question is if some people have the specs to understand how photography works.

The TC will not make every lens FF compatible, simply because the crop factor is x1,5 and the TC is only x1,4. So used with any lens which has an ultratight APSC image circle the end result will still vignette due to the x0,1 gap.

Also the TC is not engineered for each and every lens to provide good results. For example you can try 8mm (Sigma 8-16) with the TC on FF. I did already. Nigh vignetting, but only a very small part in the center is (very) sharp, the rest is utter crap. I assume this is due to the extreme angles at which light is going through the combination.
02-19-2016, 10:51 AM   #12
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Agreed - we will just have to wait and see about the results, and even then what "works" as opposed to what is "acceptable IQ" will be open to debate endlessly.

As for things like taking wide angle lenses (retrofocus) and putting a TC on them - well that will always result in a crappy look no matter how good the TC glass.

Crop factor and TC magnification are not directly related to image circle coverage. It just isn't that simple.
02-19-2016, 11:53 AM - 1 Like   #13
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Well Barry has done some more testing (with some limitations of course), that can be found in the other forum. So his initial conclusions, for me at least, are most encouraging. For the DFA 100mm macro and the DA 60-250 f4 zoom, it seems that they both may wiell be quite usable on full-frame when combined with the converter. As they are two lenses I am very keen to use with a converter on the K-1, that cheers me up considerably. Thanks Barry for your work in doing this testing! Much appreciated.

Regards, John
02-19-2016, 01:58 PM   #14
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I thought I read that the converter would not work properly with wide aperture lenses fully open. Eg the 50 1.4 became something like 70 2.5?? I can't recall the exact figure, but the elements are not anything like as wide as the back element of the 1.4 and I suspect they act like another iris on cropped sensor, and worse for FF.
02-19-2016, 03:30 PM   #15
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QuoteOriginally posted by phoebus Quote
I thought I read that the converter would not work properly with wide aperture lenses fully open. Eg the 50 1.4 became something like 70 2.5?? I can't recall the exact figure, but the elements are not anything like as wide as the back element of the 1.4 and I suspect they act like another iris on cropped sensor, and worse for FF.
I've just found the leaflet that comes with the Converter. It says the DA* 55mm f/1.4 ends up with a maximum aperture of f/2.4. (Whereas it should have been f/2).

But I've just put my D FA 24-70mm f/2.8 onto the HD 1.4x Converter onto an Me Super, and it looks OK through the viewfinder; for example no obvious vignetting. Without taking photos I can't give reliable conclusions, such as corner sharpness. And the viewfinder won't be 100%.

Ditto for the DA* 55mm f/1.4. And I've just noticed with this combination (55mm + Converter) that I can see these words on the computer screen while looking at them in the edges of the viewfinder!
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