[mcgregni]

HSS flash bursts introduce some blur effect, known as 'rolling shutter', ..... I'd say it is debatable that you might well get sharper subjects with a little bit of normal flash taken at the max sync speed. This is likely to be measured in thousanths of a second, so has a good motion freezing result. You can extend the range of the flash, and therefore use less power and get even a shorter flash pulse, by using something like the 'better beamer' extender to focus and throw the light more tightly only your far away. I feel it may well be the case that this approach would result in sharper subjects for you than using HSS flash at wide apertures. The greater DOF from stopping down more might also help.

[stevebrot]

This is likely to be measured in thousanths of a second, so has a good motion freezing result.

Duration can be as long as 1/200s with some flashes at maximum output. That is the rub with my Yongnuo YN 560 III. My Sigma EF 610 DG Super is 1/700s at maximum.

In regards to the HSS performance penalty, for HSS on my Sigma, maximum guide number for 50mm with ISO 100 drops from 46 in M mode to 11.5, a four stop attenuation.* For comparison, the built in flash on the OP's K-5II offers a maximum GN of 13.


Steve

* Duration for HSS is always longer than the total curtain dwell (1st curtain start to 2nd curtain finish) and would be on the order of 1/200s and maybe somewhat shorter for the higher speeds. No motion stopping there either.

[hatsofe]

Will the built-in flash work with the same lens or with no lens mounted? If so, talk to B&H.



What are you attempting to do? The common use case for HSS is outdoor portraiture in bright light where "ghosting" is the concern and the photographer desires flash for key or fill. The other common use case is for action sports in bright light and moderate distance where supplemental light is desired using shutter speed to freeze the motion.



?????

Are you saying that you want HSS for fast moving wildlife? If so, are you aware that HSS delivers a significant performance hit that may severely limit flash range and that HSS flash will not stop motion?

As for modifying mounts...The "A" contacts communicate maximum aperture and aperture range only and that by means of a boolean (bitwise) pattern. Resistance is not part of the equation. For more information...

Features and Operation of the KA Mount | The K-Mount Page

Even if one were to successfully hack the mount (it has been tried by users on this site), the aperture actuator lever movement must be linear to the iris opening, something that is not generally present.

Translation? If one must have the functionality offered by the KA mount on a Pentax dSLR, one must mount KA and newer lenses. There is no hack.


Steve

The built in flash fires without hesitation, regardless of the objective type and even without any lens attached.
But it's short range ( 5-7 m) and that 1/180s shutter speed make the use very limited.The only time I can turn it on is just near the sunset, when there is still enough light coming from the sky, but the shaded side of the object is already too dark to reveal the details. I almost ever reduce the flash power to -0.3 or -0.7 so it's light won't prevail . So, I think the reduced power in HSS mode (because of limited recharging time) would not be a problem. I stop the movement with short exposure during the day time. Never planned to use the flash for that purpose, only as a fill light for high shatter speeds.
I read the article that you've send me the link to. So, it's all about electrical patterns rather than the resistance values. Seems hard to hack. Probably , would be easier to do it via software instead of modifying the lens mount.
As for the proper A-lens... I agree. Will try to get one in few years from now.

---------- Post added 11-05-17 at 09:15 PM ----------

HSS flash bursts introduce some blur effect, known as 'rolling shutter', ..... I'd say it is debatable that you might well get sharper subjects with a little bit of normal flash taken at the max sync speed. This is likely to be measured in thousanths of a second, so has a good motion freezing result. You can extend the range of the flash, and therefore use less power and get even a shorter flash pulse, by using something like the 'better beamer' extender to focus and throw the light more tightly only your far away. I feel it may well be the case that this approach would result in sharper subjects for you than using HSS flash at wide apertures. The greater DOF from stopping down more might also help.

During the daylight the max shutter speed of the camera ( 1/180) is useless with or without a flash ,because there is no Vibration Reduction efficient enough to stabilize 2.5 kg 500 mm (45 cm long) lens+ 1kg camera +1.5kg rig to support all that mounted on 1.8m extended tripod sitting on a gravel road.... However it has freezing effect at night, I agree and I use that sometimes. Wide apertures don't exist in old super tele photo. I normally use f8 or f11 for shooting, while focusing on f6.3 or f8. As for the DOF, it's comes to about 40cm area on a distance of 17 m away with 500 mm lens stopped to f8. Reducing the aperture will not increase DOF by a lot and actually I usually don't need it. But the resolution power of any long focus I use, increase tenfold if the object is well illuminated.