HD Pentax-DA AF Rear Converter 1.4x AW


Darkmunk

Link Posted 12/01/2015 - 10:10
Yeah, that sounds like me
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LennyBloke

Link Posted 12/01/2015 - 10:13
Darkmunk wrote:
Yeah, that sounds like me

I'm pretty certain I saw it !!!
LennyBloke

johnriley

Link Posted 12/01/2015 - 10:21
Sorry LennyBloke, not in this thread. Of course it might be in some other thread, so if anyone finds it.....there isn't a prize, just the kudos.
Best regards, John

Darkmunk

Link Posted 12/01/2015 - 10:30
That's what I thought, but I just checked my history on here and I didn't write it anywhere else.
This really has gone off topic now
So to recap - I have one of these for sale - 250 inc postage, no offers.
Enjoy your converters chaps, I'm currently waiting for better weather to go wide(ish) with LennyBloke's 645 35mm
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johnriley

Link Posted 12/01/2015 - 10:54
Pictures will follow when I can get to Martin Mere to check it out.
Best regards, John

johnriley

Link Posted 18/01/2015 - 16:04
And finally today I managed to fit in a trip to Martin Mere!

If you'd like to see how it went, here's a link to my blog on ePHOTOzine:

http://www.ephotozine.com/user/johnriley1uk-22471/blog/pentax-1-4x-af-converter-...
Best regards, John

jeallen01

Link Posted 18/01/2015 - 18:37
johnriley wrote:
I've briefly tested it on the 55-300mm and that's fine as well.

John

Does "that's fine as well" mean that
- the 55-300 lens & TC combo autofocuses?
&/or
- the general image quality of the combo is acceptable/good/excellent?

The questions are asked because the 55-300 will autofocus with many TCs, but the image quality is poor with some of them (my 55-300 "does not like" my KENKO 1.4X Pz TC at all!)

Thanks in advance.

John
K-3 II, K-3 and a K-70 from SRS (having now relegated the K-30 /"K-50" to a backup body), & some Sigma and Pentax lenses (and a lot of old 35mm gear!)

johnriley

Link Posted 18/01/2015 - 20:02
It focuses fine and the quality is fine. There's no apparent difference in focusing speed between the 55-300 on its own and in combination with the converter. Quality seems excellent, and may well be even better with the DA* lenses.
Best regards, John

johnriley

Link Posted 19/01/2015 - 10:06
The EXIF is interesting. It reports the main lens without mention of the converter, not surprising perhaps as it could become a very long description. It reports the correct focal length, so the lens set on 300mm reports a focal length of 420mm.

It also reports the correct actual aperture, so the lens set on f/5.8 reports f/8, which is as close as it can be.

All in all it seems well thought out.
Best regards, John

Daronl

Link Posted 19/01/2015 - 10:11
Does the converter show up on the data table on the Pentax software when used or does that only show the lens too,

Refards

daronl




johnriley wrote:
The EXIF is interesting. It reports the main lens without mention of the converter, not surprising perhaps as it could become a very long description. It reports the correct focal length, so the lens set on 300mm reports a focal length of 420mm.

It also reports the correct actual aperture, so the lens set on f/5.8 reports f/8, which is as close as it can be.

All in all it seems well thought out.


Daronl

johnriley

Link Posted 19/01/2015 - 10:20
Unfortunately I don't use the Pentax software, so I can't help with that one.
Best regards, John

McGregNi

Link Posted 19/01/2015 - 12:19
I'm puzzled by your comment John, about the aperture exif showing the ' correct' aperture ... Does a converter have any effect on the lens aperture? I thought f5.6 remained f5.6 even with a converter? I appreciate that there is a light loss of a stop or so ... But that would only increase the shutter time value to compensate ... You seemed to be saying that with the converter f5.6 became f8 ....
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Last Edited by McGregNi on 19/01/2015 - 12:43

StephenHampshire

Link Posted 19/01/2015 - 12:45
McGregNi wrote:
I'm puzzled by your comment John, about the aperture exif showing the ' correct' aperture ... Does a converter have any effect on the lens aperture? I thought f5.6 remained f5.6 even with a converter? I appreciate that there is a light loss of a stop our so ... But that would only increase the shutter time value to compensate ... You seemed to be saying that with the converter f5.6 became f8 ....

Quick explanation:- F stop is the ratio of focal length to aperture diameter. The aperture diameter stays the same wide open, but the focal length is increased, hence the F stop (ratio) decreases. The camera doesn't try to adjust exposure, just reports the "true" f -no.
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johnriley

Link Posted 19/01/2015 - 12:58
The easy example is a 50mm lens with 25mm aperture. 50/25 = 2 or in other words it's an f/2 lens.

Now add a 2x converter so 100mm focal length and therefore 100/25 = 4 and it's now an f/4 lens.

1.4x converter = 1 stop difference
2x converter = 2 stops difference

The exposure does change accordingly, but the beauty of it all is that the focusing distance remains the same, the magnification has increased. Great for close up work.
Best regards, John
Last Edited by johnriley on 19/01/2015 - 12:59

NeilP

Link Posted 20/01/2015 - 20:18
Was going to start another thread, but I'll ask here as Its a related question:

For those with DA*300mm and a K-3, how does the image quality with DA*300mm on the HD Pentax-DA AF Rear Converter 1.4x AW on compare to just cropping to the same field of view on just the DA*300mm on its own?
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Last Edited by NeilP on 20/01/2015 - 20:18
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