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11-27-2011, 08:05 PM   #16
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QuoteOriginally posted by creampuff Quote
I think it would help if you can come up with a photo taken with a Pentax (preferably the K-5 to answer the OP's post) to prove this instead of just stating Wikipedia or making assertions without actual proof.
Don't see how 1 photo would have answered the original question. I have the K20 and my experience at airshows with long and short lenses is that the the shot is gone before SR locks. Is it your 'opinion' that SR is equally effective at long focal lengths as it is for shorter focal lengths? The vast majority of the reading I have done on the subject says you are wrong. I quoted wikipedia as it seemed to state in a concise manner other articles and blogs I have read on the subject. In the future, you may wish to confine your posts to answering the original question and not belittling the efforts of others.

11-27-2011, 08:38 PM   #17
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QuoteOriginally posted by mdave13 Quote
I have the K20 and my experience at airshows with long and short lenses is that the the shot is gone before SR locks.
What do you mean by SR locks? How do you know? You would be panning to follow the flying aircraft, presumably taking multiple shots as it goes by. Are you getting degradation when SR is on?
11-27-2011, 08:50 PM   #18
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The SR is locked when the little hand lights up in the viewfinder. No, I don't get degradation with SR on when locked. Just think you should only use SR when necessary, as when you are shooting at a shutter speed slower than the inverse of the focal length. My longest lens is a 300mm and I rarely shoot in the daylight at less than 1/300, especially at airshows. I do use SR when necessary and find it helpful.
11-28-2011, 10:27 AM   #19
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QuoteOriginally posted by mdave13 Quote
Don't see how 1 photo would have answered the original question. I have the K20 and my experience at airshows with long and short lenses is that the the shot is gone before SR locks. Is it your 'opinion' that SR is equally effective at long focal lengths as it is for shorter focal lengths? The vast majority of the reading I have done on the subject says you are wrong. I quoted wikipedia as it seemed to state in a concise manner other articles and blogs I have read on the subject. In the future, you may wish to confine your posts to answering the original question and not belittling the efforts of others.
Apparently all the sharp tele images posted on this thread have not made the point to you that perfectly sharp images with SR are possible. If you didn't know, all Pentax cameras with SR get focal length info from the lens (A, F, FA, DA, DFA series) and factors this info to determine the extent of SR needed. There are lots of Pentax users who have successfully shot at airshows with SR on, perhaps your technique needs work.

11-28-2011, 01:43 PM   #20
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Since I never stated that good telephoto images are not possible with SR, I have to assume you are a flaming troll, one who argues and demeans for the sake of getting a rise out of someone. I merely opined that SR is not necessary or desirable at all times and situations. As for my technique, you couldn't possibly have a valid opinion on my skills. I noticed that the photo you posted has been heavily processed and is missing the exif data necessary to prove that the shot was taken in a situation where SR was used and necessary.
11-28-2011, 07:36 PM - 1 Like   #21
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QuoteOriginally posted by mdave13 Quote
... I noticed that the photo you posted has been heavily processed and is missing the exif data necessary to prove that the shot was taken in a situation where SR was used and necessary.
FYI I don't heavily process my images and the photo I posted definitely has the exif intact... which leads me to the conclusion that you don't actually know what you're talking about.
Instead of calling others a troll, perhaps you should back up your own assertions with actual photographic proof.

Last edited by creampuff; 11-28-2011 at 07:48 PM.
11-28-2011, 08:50 PM   #22
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When did PF morph into DPR?
11-29-2011, 06:30 AM   #23
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Of course the system in hind sight can't "really" (I don't think?) compensate at high shutter speed; but in no official place does it say to shut it off because your shooting over 1/1000 or panning (only panning at too low of a speed and motion blur occurs). I have been researching this including reading the owners manual and looking at pics. Seems some reviewers misstated how you can use Pentax SR system. In no place does it say you can not pan, as long as you have enough speed. Here is an info ad that in fact says to use it panning.


Airshow challenge with the Pentax K20D

There has been a group of Pentax users who have always said its ok to leave SR on while panning. Seems they may be right.

11-30-2011, 04:15 AM   #24
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Hand held, 1/500th, f5.6, ISO 200, using Sigma 500 f4.5 APO DG EX. SR on.

I think SR works above 300mm!
Attached Images
 
11-30-2011, 06:03 AM   #25
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As dosdan was so kind to refer to in his post #3 ( https://www.pentaxforums.com/forums/1724938-post3.html ), SR with 300mm+ lenses on Pentax is effective.

As is confirmed by user experience here too.

Maybe, let me make a number of additional remarks:

- Pentax SR efficiency with long FL is about 2 stops, much in line with most long lenses optical stabilization efficiency. So, replacing SR by a Sigma OIS will most likely not improve things.

- Pentax SR with short FL and long exposures such as 1/15s can be better, like 3+ stops. And at around 1/80s, the K-7 has the problem that SR cannot compensate for shutter-induced shake and seems to be less efficient. At some point in the past, this confused discussion of the topic.

- Contrary to common belief, the sensor shift technology is not limited by FL: This is easily seen: If you want to improve by 4 stops, you need to shift 2^4 x the circle of confusion which is only .16mm and independent of the FL. The higher FL is compensated by a shorter exposure time and both effects cancel out. However, longer FL requires higher acceleration (read stronger motor) and any particular implementation has its limit. Pentax' is at 800mm.

- SR works by electronic coriolis force sensors which measure angular velocities, not acceleration. This is why panning can be a problem.

- The Pentax SR mechanism needs a time to initialize (called "lock" earlier up in the thread), indicated by a hand-symbol in the viewfinder. During this time, it measures angular velocities and brings the sensor into a starting position. However, it only starts shifting as soon as you press the trigger. The initialization happens during half press. The K-5 then seems to stay initialized as long as the viewfinder remains illuminated.

- It is possible to fully press the trigger before SR is initialized. The result normally then is a blurry image. I've already lost a panorama because I turned and shot to quickly in succession with SR on. So, if you need to shoot extremely fast, better switch SR off. That's particularly true with super wide angle which can be shot at hyperfocal distance.
11-30-2011, 06:31 AM   #26
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QuoteOriginally posted by falconeye Quote
- The Pentax SR mechanism needs a time to initialize (called "lock" earlier up in the thread), indicated by a hand-symbol in the viewfinder. During this time, it measures angular velocities and brings the sensor into a starting position.
Are you sure about the "brings the sensor into a starting position"? Because my understanding is that it does not move at all until you fully depress the shutter. (Not using live view, that is.)




QuoteOriginally posted by falconeye Quote
- It is possible to fully press the trigger before SR is initialized. The result normally then is a blurry image.
Maybe the result is a blurry image, but not because SR messes up. Again my understanding is that if SR hasn't "locked" then you will effectively shoot as if SR was off. Sensor held still in center.
11-30-2011, 08:49 AM   #27
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QuoteOriginally posted by Gimbal Quote
Are you sure about the "brings the sensor into a starting position"? Because my understanding is that it does not move at all until you fully depress the shutter. (Not using live view, that is.)






Maybe the result is a blurry image, but not because SR messes up. Again my understanding is that if SR hasn't "locked" then you will effectively shoot as if SR was off. Sensor held still in center.
I'm not sure about the starting position thing. Just would be a good idea to do because the sensor isn't in its middle (neutral) position when camera is off. But it isn't a necessity, so I don't know and catually, it doesn't matter.

I'm pretty sure though that pulling the trigger while SR is initializing can blur images. I've seen this happen too often with SR on and to rare with SR off for me to believe it is unrelated. But I didn't systematically study it.
11-30-2011, 08:52 AM   #28
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Thanks falconeye.
11-30-2011, 08:56 AM   #29
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QuoteOriginally posted by falconeye Quote
I
I'm pretty sure though that pulling the trigger while SR is initializing can blur images. I've seen this happen too often with SR on and to rare with SR off for me to believe it is unrelated. But I didn't systematically study it.
I remember checking this when the K10 was new. Shooting in manual with a long exposure time, say 3 seconds and no lens attached. Waiting for the SR icon and then shoot would show a moving sensor when the shutter opened, not waiting long enough would show a sensor locked in the middle. But maybe things have changed since then.
11-30-2011, 09:16 AM   #30
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QuoteOriginally posted by Gimbal Quote
Waiting for the SR icon and then shoot would show a moving sensor when the shutter opened, not waiting long enough would show a sensor locked in the middle.
That's a nice test. Except that everything happens far too fast for the naked eye to see. It would suffice if the sensor is just a bit delayed to reach its starting position and it would still appear to sit locked in the middle to the naked eye. So, the only test would be doing test shots on a vibrating bench, waiting for variable length amounts of time. AFAIK, nobody did this test.
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