SR stabilisation

not just liquids, salt, sand, beads etc...
but that cornstarch will start to look like a living creature....

Absolutely Check out the little video of the cornstarch
More references: http://en.wikipedia.org/wiki/Cymatics
Matt

cool, the sceen from jurasic park, where the people see the waves in the glass of water, simulating the footsteps of the t-rex, was done with vibrations from a guitar string run through a hole in the jeep anchored to the stage, and plucked by person on cue.....
same idea!

Thanks for this link - its great
i wanted to know what happens if you then reduce the frequency back down again - do the patterns simply work their back down again to end up with the simpler ones?

Andy

Ok, back on thread...

Actually the test for this is NOT to use a vibrating plate, but to use a solid platform. I held the K20D+grip firmly down onto a table. I used 90mm and a slowish shutter speed.

1. SR enabled, hold button for a while and then fully press.
2. SR enabled, let the camera idle for a while then carefully push the button all the way.
3. SR disabled, release the shutter.

I've not done extensive tests, but on my initial test it appears that (2) was less clear - evidence that the SR was trying to kick in even though it had insufficient information. There was no discernible difference between (1) and (3) in this test - which is what you'd expect.

However, in another test (2) wasn't any different from (1). So, although the evidence seems to suggest that SR is trying to work, there may be other factors involved. Perhaps how long the camera is idling, what the camera's doing at the time (like showing a preview), what the shutter speed is, etc.

I'll try some more tests when I get a chance... but for now, at least, I have SR disabled unless I specifically need it. And when I use SR I'm making absolutely sure that the "hand" icon is visible in the viewfinder before releasing the shutter

Matt

Matt,
When my K20D focuses the hand sign and the beep come together, i,e, as soon as the beep sounds then the hand appears in the view finder.

Tel,
It's because I have "disconnected" the focus from the shutter button. I only focus with the rear AF button. This is probably why I can push the button down so quickly and catch the SR out
(Sorry I forgot to mention that!! It's an option in the custom menu.)
Matt

Sorry, Matt, I have to challenge your experimental design.

I've already shown that there's no discernible difference between the amount of (finger-induced) shake evident in SR-on-stabilised and SR-off pictures [Edit: on a sturdy tripod].

Therefore if you do an experiment that fixes the camera, you won't get enough shake for the SR to act in any meaningful manner. So by implication, neither will you get pre-SR-lock behaviour that's meaningful.

I still think this experiment needs to be done with a repeatable amount of shake, where it can be shown that stabilised SR is effective.

Only then will results from pre-SR-lock be meaningful.

Chris - disagree
I'm not trying to discern the difference between SR and no SR on a solid foundation

The problem I had was with shutter speed and conditions that I would not have expected any blur-induced shake without SR. Yet there was clearly shake demonstrated - and I was suspecting it was down to the SR trying to compensate for shake that wasn't there (because it wasn't "locked"). You see, SR was enabled, but hadn't stabilised.

My experiment is trying to reproduce this in a controlled way.

If I use a controlled level of shake - how can I discern what SR is trying to do when it hasn't had time to stabilise? I'm trying to work out which of the following applies (both with SR turned on):
1) The camera attempts to do SR even if it has insufficient data.
2) The camera behaves as if SR is disabled if it has insufficient data.

From what I've seen it appears to be (1) - which is why I'm leaving SR off - and especially so because I focus only with the rear AF button. Using the shutter release button for focus side-steps the issue because by the time the camera has focused it's already got enough data to perform SR.

Does that explain it better?
Matt

I understand this - I've been reading the thread with care.

Yes, I absolutely understand the difference you're describing. I've been using the term "pre-SR-lock" to refer, specifically, to the picture you get if you release the shutter before SR has stabilised and given you the hand icon.

And I maintain that the experiment you described will not achieve this, because on a fixed platform, as I've said, there is not enough shake for SR (even stabilised) to show meaningful behaviour.

If SR(stabilised) does nothing measurable on a fixed platform, you cannot make any assumptions about what SR(unstabilised) may or may not do. You can see if it does anything, but from your description, the results are unclear.

Well, just take the picture before SR can stabilise - ie quickly.

As I said, you need conditions where SR(stabilised) can be shown to be effective, and then compare the SR(unstabilised) pictures.

You also need to be careful that in taking the picture quickly, in order to avoid SR-lock, you do not whack the button differently, else you could end up causing more shake than in the slower release of the SR(stabilised) case.

[quote="I"]As I said, you need conditions where SR(stabilised) can be shown to be effective, and then compare the SR(unstabilised) pictures.[/quote]Hopefully it was obvious what comparison to make, but I'll be specific just in case it wasn't...

- If the SR(unstabilised) pictures are more blurred than the SR(stabilised) ones, you can conclude that the SR is trying to act, and is doing too much.

- If the SR(unstabilised) pictures are equally as blurred as the SR(stabilised) ones, you cannot conclude anything, except that it makes no difference whether SR is stabilised or not.


Of course, the SR(unstabilised) pictures might still be less blurred than the SR-off ones, in which case it is still worth leaving SR on. This is why I suggested comparing the pre-SR-lock results with BOTH SR-off and SR-stabilised.

If you got this last result, you could conclude that the blurred pictures you got, even though the shutter speeds were fast enough not to expect blur, were just those annoying one-offs that we all get from time to time.

It's only if the SR(unstabilised) pictures are more blurred than the SR-off ones, that you should turn SR off.

Points taken Chris, but the shots I mention were definitely not down to annoying one-offs. I've been taking shots for long enough to recognise and know what the limits are.

Ok then, I have proof (enough for me anyhoo)

Setup:
* Camera solidly on the desk on a grip.
* Use custom function to disable AF on half press
* "M" mode, ISO1000, 1/125s, f/8, 90mm focused about 20m away.
* Gently and repeatedly tap the hotshoe with thumb (about 2Hz if you're being picky). Not too hard to move the camera - more to trick the SR.

1) SR off - take a shot.
2) SR on - half press, keep tapping, and then take shot
3) SR on - keep tapping and press shutter down

Results - every time:
1) Sharp.
2) Sharp.
3) Blurred.

It definitely didn't want a vibrating platform Just needs a little percussive noise to upset the SR sensors.

I rest my case
Matt

PS. The suggestions, apparently, have gotten to Pentax. Hopefully they'll see some sense

Matt, that's absolutely fine to satisfy yourself, and I know enough about you to be inclined to trust your judgement.

But if you want to avoid the sort of anecdotal cobblers that abounds, and satisfy a critical community (which may not be only me, though I grant that it may ) with some actual science, you can't be saying things like that without a repeatable, verifiable, controlled experiment. You don't need me to tell you that.

If by this, you mean 2) is SR stabilised, and 3) is SR unstabilised, then I completely accept the results, and your conclusion. I'll repeat the experiment when I get a chance, and I fully expect to get the same result.

Well, with respect, this is just semantics.

You've created an easily repeatable source of shake in a very simple way. I'm delighted that it didn't need heavy engineering to achieve, but it is exactly what I was suggesting the whole time, and it's only with that source of shake that the experiment gained meaning.

But I am slightly disappointed that you didn't read my earlier posts on the subject a little more carefully - then it wouldn't have been necessary to suggest I was misunderstanding the whole issue.

I don't have your knowledge of camera technology, but I am not untrained when it comes to experimental design.

I never doubted your case - all it needed was an experiment to prove it, so well done.
And I rest mine

Absolutely. Bit rushed as I'm trying to multitask.. something I'm not too hot at

I did read it carefully I wasn't trying to imply anything about your methods, ideas, or experience - sorry if it came across like that!
My issue was with the vibrating platform and the possible verifiable result that only SR on and stabilised was sharp

It'll be interesting to see if you can repeat the results of the experiment... as I'm sure you will

...back to work now...
Matt

Hi, fellow Pentaxians!
Have been dropping by to Your friendly forum from time to time- and now discovered that I somewhen even registered here
So my 2 humble cents about Pentax SR:
1. SR start-up time is 0.63 sec.- anything shorter results in NOT READY;
2. Pity that rear AF button does not start SR at ALL- hence the confusion when taking pics such way (it could be selectable in Custom Settings, I guess).
And one more thing: sometimes it is really usable to set camera to AF-C and set AF button to cancel AF- so SR is working all the time- personally found it useful when taking handheld macros with DFA100.
Best and happy anti-shaking, JR