K5 focussing issues spoiled the day.


malcolmk

Link Posted 27/05/2013 - 19:24
I was taken to the flying display at Duxford yesterday and whilst I didn't really need any pictures it would have been silly to leave the camera behind. The only lens I own which was likely to be useful was a DA* 200mm which to be honest has not seen a lot of use, most of my photogrpahy is street scenes and people. My K5 has proved perfectly acceptable for that, any focussing shortcomings have been very rarely seen.

All that changed yesterday. The conditions were mainly blue sky and some high thin cloud. The 200 hunted back and forth noticeably. If I locked on to an aeroplane and someone walked in front of me the lens instantly focussed down to six feet or whatever, and absolutely refused to auto focus back to a longer distance when the obstruction was removed from view. I have several shots of blurry blobs in the sky, which is a bit odd bearing in mind the camera is set to fire only when in focus.

It wasn't all bad, as I began to overcome the foibles, I was swinging the manual focus barrel and some shots were good enough to see if the pilot was wearing goggles or not, but overall, if I was an aircraft photographer, I think I may have been in despair.

If I was in that position, would a K5ii fix the problem, or is the DA* 200 known for that sort iof thing?

I tried to fine calibrate the lens this morning. At long distances wide open the AF was OK but at around 15 feet it seems to be focussing a little bit close.

Probably I should have stopped the lens down a bit for the planes, every propellor is absolutely static, which looks a bit odd. Exposures were typically F5 at faster than 1/2000. Obviously I have a lot to learn about aircraft photography.

Mike-P

Link Posted 27/05/2013 - 19:41
malcolmk wrote:

Probably I should have stopped the lens down a bit for the planes, every propellor is absolutely static, which looks a bit odd. Exposures were typically F5 at faster than 1/2000. Obviously I have a lot to learn about aircraft photography.

Should be the other way around for prop planes ... shutter speed of approx 1/180th (slower for helicopters) and as fast as you can get for jets.

K-5 is fine for airshows and you shouldn't have had any problems with the 200mm .. the first and last were taken with the 50-500mm and the middle one was the 60-250mm f4 although I do seem to remember the DA* 200mm I had was quite slow focusing (seems to be a theme with the * lenses)









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Last Edited by Mike-P on 27/05/2013 - 19:42

malcolmk

Link Posted 28/05/2013 - 09:09
Not all shots were failures, far from it, but I was disappointed by the failure of the lens to recover from a 'totally out' position without manual intervention.

Thanks for the shutter speed tip, much lower than I would have anticipated.

I have generally steered clear of zooms but I can appreciate the advantage for finding a small plane in a big sky.




K5 DA*200mm 400ISO
Last Edited by malcolmk on 28/05/2013 - 09:11

dangie

Link Posted 28/05/2013 - 10:12
Assuming the aircraft were all a similar distance from you perhaps it may have been worthwhile to prefocus and then put the lens to manual. I don't photograph aircraft but that is what I usually do when photographing birds in flight.
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fatspider

Link Posted 28/05/2013 - 13:02
I've only tried it with a zoom (50-500) locating a fast moving plane is relatively easy, then it's a (fairly) simple matter of keeping it in the frame while zooming in and keeping the focus locked on, I used centre point focus and AF-C.

My biggest problem was not having enough experience at panning which resulted in a lot of half planes
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malcolmk

Link Posted 28/05/2013 - 13:33
If anyone looked at my collection of Duxford photos, they might ask what I am complaining about. I last photographed aircraft as a teenager living in Farnborough in the 1950s (see camera to the left) so was effectively a total beginner on Sunday, but I obtained a high proportion of nice sharp shots. Spoilt only by the knowledge of the large number missed because the camera was not ready in time.

I too used centre point and AF-C but the lens needed manual help to keep it at the infinity end of its travel.

Mike-P has my admiration for being able to hold a 600mm lens at 1/180th second!

If this was something I planned on doing often I think I'd be trialling a K5ii but as it is I am hoping to remain patient until it is superceded by something better.

padmk3

Link Posted 29/05/2013 - 16:24
In most side by side tests I have seen there is very little if no difference between the K5 and K5ii focusing speed and accuracy in good lighting conditions.

I would say that the problem here is the lens as Pentax's SDM drive is known to be on the slow side compared to other manufacturers 'silent' drives. It also lacks a focus limiter which seems to be a large part of your problem.

I use my old Sigma 300 APO f4 for airshows, sometimes with a x1.4 tele-convertor. The AF for this is driven by the camera and is pretty responsive plus this lens has a focus limiter which prevents it close focusing. I still am probably only happy with 20-30% of my shots though as these are fast moving objects which are pretty testing for an AF module and photographer alike!
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Pentax Silver DA70 2.4 Ltd : Sigma 300 APO AF 4.0 + Sigma x1.4 TC EX : Metz AF 50

malcolmk

Link Posted 30/05/2013 - 09:26
My theory is that when a foreground obstruction took focus away from infinity, I lost track of the aircraft leaving nothing but cloud or sky to focus on. The 200* simply gave up.

The good news is that having compared prints with my Canon toting companion, my shots are clearly better than his. He was using a 200mm zoom, all I know about it is that it was only half the weight of my DA*.

jeffstclair

Link Posted 30/05/2013 - 10:37
I think I agree with dangie on this , I don't do airplane or birds in flight photos very often, but when I do I manual focus and just keep clicking, I find it works ... Maybe if I could afford to upgrade to faster kit ..jeff..

merryhampton

Link Posted 06/06/2013 - 22:18
I too have found that if the lens I amusing (usually Pentax 50-300 or Sigma 150-500) loses focus it's impossible to regain it quickly. What I usually do is quickly refocus on a terrestrial object such as maybe a very distant tree or some other high-contrast distant object. I can then regain the aircraft, focus and continue.

It's not a brilliant solution but does work although there have been several times when I've thought about buying a different marque specifically for aircraft photography.

sbrads

Link Posted 07/06/2013 - 10:29
The K-30's Expanded Area AF definitely works in AF-C but I haven't yet had the chance to try it for real at an airshow. It should help to not lose focus when the target briefly moves off the AF point. The K5II has this also.

If it isn't up to the task then the best method I reckon would be to use the AF button for focus instead of the shutter button, then once an AF lock is accomplished you just don't touch it again and snap away.
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