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12-23-2012, 11:51 AM   #1
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Just ordered a Q - A few questions

Last night I broke down & took advantage of the smokin' deal on the $246 Q zoom kit at shopNBC. I've been looking at some info on using K-mount lenses with an adapter & have a few questions from you guys who have actually used the thing:

1) From what I've gathered, (if I'm correct) using a wider aperture somewhere is preferred on the Q because of diffraction. Is there a particular sweet spot, or does it vary from lens to lens?

2) When you use an M lens on a Pentax DSLR, you can use Av mode as long as the lens is wide open. Can you do that on the Q with a K-mount lens on the Fotodiox adapter?

3) Does the firmware upgrade add SR capability only when using the genuine Pentax adapter, or does SR work with any adapter?

4) Does using a higher shutter speed negate the "jello effect" caused by the electronic shutter?

I'm hoping I have some success with the Fotodiox adapter, because there's no way I can afford the Pentax one with the leaf shutter.

I'm sure I'll have more stupid questions in the future. :-P

Bobbo :-)

12-23-2012, 01:04 PM   #2
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1) it varies from lens to lens. Lenses that have sweet spots closer to wide open have an advantage.

2) you can use any setting but with adapted lenses the camera only controls shutter speed and iso. Forcing ISO to base of 125 yields best results

3) yes with latest firmware sr works with any adapter.

4) yes higher shutter speeds help, but I have not determined at what point and how much. I use a tripod when shooting long lenses on the q. Jello may be a factor in hand held situations.

Welcome to the Q team! I had good luck with the Fotodiox, IQ wise it is no different than the Pentax.

Last edited by crewl1; 12-23-2012 at 01:09 PM.
12-23-2012, 01:24 PM   #3
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Thanks much, crewl1! I was hoping for those answers. :-) I figure a good rule of thumb for minimum handheld shutter speeds is "1/crop factor focal length". It has worked well for me in the past, anyway.

You, Barondla & Snostorm (and others) have helped me a bundle. I appreciate your expertise & I'm really looking forward to having some fun with this little gadget.

Cheers & happy holidays,
Bobbo :-)
12-23-2012, 03:04 PM   #4

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Hi GibbyTheMole,

As in just about everything, I think it's a good idea to experiment for yourself to establish workable tolerances. It's been said by many (who don't own a Q, BTW) that diffraction will start to effect a lens' performance at f2.5 or even faster, and the Photozone tests show that the 01 and 02 Q system lenses show highest resolution between at f4, then degrade at f5.6. A lot of people came to the conclusion that the cut off point was at f4. Neither of these conclusions are based on sound reasoning. The calculation of where diffraction will start to effect a lens' performance is based on the "perfect lens" and doesn't take into account how much resolution can be gained by stopping down, and how that balances against how much degradation is caused by diffraction at those apertures. The Photozone tests, like all lens tests are based on the lenses tested, and only show that those particular lenses topped out at f4.

These assumptions have not been reflected by actual user results, as those who have done tests with Qs and adapted lenses that they own have seen that peak sharpness for a given lens can come at f5.6 or, in fewer cases f8. This is really a new frontier, and we each have to test and make our own rules with our own lenses and shooting techniques.

As far as the handholding "rule of thumb" -- personally, I've found that with SR, I can usually handhold and get acceptable results for a good percentage of shots at about 2 stops slower than 1/ crop factor eq FL when I use good long lens handholding technique. Everyone is different, and some can do better than others. I have the benefit of literally tens of thousands of shots handheld with long lenses and digital cameras that give me almost instant feedback through chimping, so I can see when I need to calm down and take it to another level in technique or get some help from whatever might present itself at the time. I also practice a lot indoors so I don't have to relearn everything at the start of each spring. I probably take as many throw away practice shots of my bookcase during the winter than many people take in total for a year.

Hope you have a good holiday season -- and a happy Q Year!


12-23-2012, 05:14 PM   #5
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snostorm: You have been very helpful! I have a few K-mount lenses that I think might make good Q lenses:

Ricoh Rikenon 28mm (150mm on the Q)
Pentax-A 1.7 50mm (280mm on the Q)
Promaster 100mm macro (560mm on the Q)
Pentax-A 35-105mm (200-600mm on the Q)
Pentax DA 55-300 (300-1700mm on the Q)
Tamron 23A 60-300 (340-1700mm on the Q)
Tair 500mm mirror lens (2800mm on the Q)

These are the sharpest lenses I currently own. I'm planning on doing a series of tests to see which ones work well with the Q. I've learned that if I do some controlled & stringent tests beforehand, I can go out & shoot with more confidence later. After I do the tests, I'll post my findings.

I'm also looking forward to testing out some oddball C, D, & M39 lenses on the Q. Should be fun!

Bobbo :-)

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