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06-01-2015, 12:20 AM   #16
kwb
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If you do the astrophotography, the ability to go slow up to 30 sec shutter speed could be another big reason.
I have cheapo adapters for C mount, Canon FD, and Canon EF, and these share the same limitations as cheapo Q-K adapter, one of which is that the long exposure is limited to 2sec.
Whenever I feel an irrational urge to buy a Pentax Q-k adapter just to go slower than 2 sec, I have to go through some mental process like "I don't wanna buy that one, do I? Because I have no K mount lens! Haha, see? And even if I do have a K mount lens, it goes up to only 30 sec, is that really long enough for astro? Of course no! Seeee?", get a bit jealous ("though 30 is 30, it's much better than 2 at the end of the day"), maybe sigh and inhale, and get back to stacking 2 sec frames.

06-01-2015, 04:15 PM   #17
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Pentax Q with 240 sec. Bulb = The Astro Killer ! ;)

QuoteOriginally posted by kwb Quote
If you do the Astrophotography, the ability to go slow up to 30 sec shutter speed could be another big reason.
I have cheapo adapters for C mount, Canon FD, and Canon EF, and these share the same limitations as cheapo Q-K adapter, one of which is that the long exposure is limited to 2sec.
Whenever I feel an irrational urge to buy a Pentax Q-k adapter just to go slower than 2 sec, I have to go through some mental process like "I don't wanna buy that one, do I? Because I have no K mount lens! Haha, see? And even if I do have a K mount lens, it goes up to only 30 sec, is that really long enough for astro? Of course no! Seeee?", get a bit jealous (" though 30 is 30, it's much better than 2 at the end of the day "), maybe sigh and inhale, and get back to stacking 2 sec frames.
Of course it is...

but Pentax could have managed the Bulb mode to keep the IR-Remote trigger working !
... and knowing the huge Pentax skills about Astro (SDUF refractors)
they should have given us 240 sec. Exposure !

Cameras with small sensor up to 1" that hold 60 or 250 sec. Bulb exposure :

Nikon Coolpix P330-340 P7000-7800, Olympus XZ1-XZ2 Stylus1 = Sony 1/1.7 = 60 sec
Pana LUMIX DMC-LX3-LX5-LX7-FZ28-FX150-FZ200 FZ1000 = Sony 1/1.7 & 1" = 60 sec
Casio Ex-10-100, Leica C, PanaLUMIX DMC-LF1, SamsungNX Mini = Sony 1/1.7-1" =250 s

Sensitivity = ISO per mm² of sensors area... because your Telescope can't zoom :

CanonAPSc=5,33 - Eos 60d, 60d-Astro & 600d = ISO ~800 for ~15 x 22,5 mm ~ 2,37 iso / mm²
Sony=APSc=4,40 - Sony Exmor APSc 16 MPix = ISO ~1200 / 15,6 x 23,5 mm - 3,27 iso / mm²
Sony=APSc=6,55 - Sony Exmor APSc 24 MP = ISO ~1365 / 15,6 x 23,5 mm - 3,72 iso / mm²
Sony=1"FSi=17,2 - Sony Rx100 1st FSI 1" = ISO ~390 / 8,8 x 13,2 mm - 3,36 iso per mm²
Sony=1"BSi=17,2 - Rx100², NXmini BSI 1"= ISO ~505 / 8,8 x 13,2 mm = 4,35 ISO / mm²
Sony=1/2.3=44,0 - Pentax Q and Q10 = ISO ~186 / 4,6 x 6,2 mm = 6,52 ISO / MM2
Sony=1/1.7=29,0 - Nikon P340 (Q7)= ISO ~273 / 5,6 x 7,5 mm = 6,50 ISO / MM2
PanSon4:3=7,10 - PanaSony 4:3 = ISO ~765 / 13 x 17,3 mm - 3,40 iso / mm²

1st data = MPix/cm² -- ISO ~ = Low-Light ISO rating from DxOmark

and you discover that the BSI CMos in the PentaxQ-Q7 are the most sensitive !
... they could have extended Bulb exposure up to 240 sec. at least
so at low ISO 100-400, the Raws would be way cleaner...
instead of ISO 1600 which is mandatory !
( ISO 800 is feasible if you mount the Q on a F2.8 lens, a F4 Newton ?? )



Last edited by geo444; 06-02-2015 at 02:05 PM.
06-17-2015, 09:58 AM   #18
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Coming from the other side of the fence, I was given the 'official' Pentax K/Q adapter and it is capable of excellent results. I've had no issues with it whatsoever: the aperture adjustment is smooth and useful, and I've been using it predominantly for macro so haven't missed the AF component. Partnered with the 35mm Limited macro it's a close-up beast. Whether it's worth the cost to buy for yourself...not so sure. I also have the tripod foot for it but have yet to use it for anything other than a stand when it's not on-camera might get hold of some older cheaper long glass and give that a go.

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