Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
02-26-2010, 10:58 AM   #31
Pentaxian




Join Date: Aug 2007
Location: Madison, Wis., USA
Posts: 1,510
I'm very suspicious when the researcher tells us that he cannot really make the test conditions identical (focal length) so he jiggered some other factors (shutter speed) to "correct" for it.

If it's not identical, then it's not. If we knew, precisely, what the impact of focal length and shutter speed were, perhaps, maybe, that's OK. But I, for one, do not know what I don't know. And Rice High isn't helping by "correcting" one calibration error with another.

When we see that non-stabilization is to be preferred, I again suspect there are factors at work here we don't fully understand.

And we won't without a bit more rigor.

Anyway, I prefer the test with the laser pointer. At first glance, that seems to account very nicely for all factors - as it's done in a single shot. No comparison or calibration needed. I would, though, like to see it replicated .....

02-26-2010, 12:21 PM   #32
Pentaxian
Wheatfield's Avatar

Join Date: Apr 2008
Location: The wheatfields of Canada
Posts: 10,132
QuoteOriginally posted by glanglois Quote
I'm very suspicious when the researcher tells us that he cannot really make the test conditions identical (focal length) so he jiggered some other factors (shutter speed) to "correct" for it.
A valid test can only test for one thing at a time. Consequently, only one parameter at a time can be changed.
IE: Testing shake reduction, the only thing that can be changed during the test is shutter speed.
Anything else gets changed (even aperture) and the test is of questionable value.
People who start changing all sorts of parameters during a "test" and then drawing a conclusion are idiots.
02-26-2010, 12:32 PM   #33
Forum Member




Join Date: Feb 2010
Photos: Gallery
Posts: 56
QuoteOriginally posted by LRaven Quote
Here it is comparison optics IS with Pentax built in SR: RiceHigh's Pentax Blog: When OIS Lenses are Put onto Sensor-shift IS Bodies..
The study is subject to serious methodological shortcomings. First what is a blurry photograph? When examined closely enough all photos are blurred. So where do you draw the line? And whose line is it? Why not simply measure the motion blur? This is very simple to do, repeatable and accurate. Then I must ask if the study was not cherry picked to suit a certain point of view? It is valid to quote studies but then one must be fair and reference all available studies or at least a balanced cross section. This is common practice in the sciences and is known as a meta-study. Other observers have reached very different conclusions. Why should that be so? And why discard other conclusions?
02-26-2010, 12:49 PM   #34
Veteran Member
GoremanX's Avatar

Join Date: Dec 2009
Location: Georgia, VT
Photos: Albums
Posts: 1,653
QuoteOriginally posted by Wheatfield Quote
A valid test can only test for one thing at a time. Consequently, only one parameter at a time can be changed.
IE: Testing shake reduction, the only thing that can be changed during the test is shutter speed.
Anything else gets changed (even aperture) and the test is of questionable value.
People who start changing all sorts of parameters during a "test" and then drawing a conclusion are idiots.
But then how do you compare one shot to another if the picture's darker? If you change shutter speed, you need to change something else to keep the exposure constant. Otherwise your pictures just get progressively darker (or brighter) throughout the test, making it a pointless comparison. If you change the ISO, you're changing noise characteristics and possibly introducing noise reduction (which often appears as blur).

I don't see how changing the aperture to compensate for shutter speed affects camera shake. As far as I can tell, it would only affect focus tests, not camera shake tests. Increased depth of field does not reduce camera shake.

I'll refrain from calling you an idiot back.

02-26-2010, 01:08 PM   #35
Junior Member




Join Date: Feb 2010
Location: Kiev
Posts: 32
Anyway have anybody experienced with other than Pentax SR?
I have compared ~10 years old Canon S1 optics IS and modern Pentax k-x SR. In this case for my opinion Canon is winner!
02-26-2010, 01:26 PM   #36
Forum Member




Join Date: Feb 2010
Photos: Gallery
Posts: 56
QuoteOriginally posted by LRaven Quote
Anyway have anybody experienced with other than Pentax SR?
I have compared ~10 years old Canon S1 optics IS and modern Pentax k-x SR. In this case for my opinion Canon is winner!
Asking who is the winner is asking the wrong question. This is not a race or competition. I am glad that you are happy. We all belong to the community of photographers. This is what defines us and we should celebrate that. The equipment badge we wear is a minor consideration. We make different choices because we have different circumstances, needs and goals. That said, modern photographic equipment is wonderful technology made to high standards. It is legitimate to take pride in our equipment and to enjoy it. Just as long as we pause to respect (and not diminish) the enjoyment other people experience with other equipment.
02-26-2010, 01:29 PM   #37
Pentaxian
Wheatfield's Avatar

Join Date: Apr 2008
Location: The wheatfields of Canada
Posts: 10,132
QuoteOriginally posted by GoremanX Quote
But then how do you compare one shot to another if the picture's darker? If you change shutter speed, you need to change something else to keep the exposure constant. Otherwise your pictures just get progressively darker (or brighter) throughout the test, making it a pointless comparison. If you change the ISO, you're changing noise characteristics and possibly introducing noise reduction (which often appears as blur).

I don't see how changing the aperture to compensate for shutter speed affects camera shake. As far as I can tell, it would only affect focus tests, not camera shake tests. Increased depth of field does not reduce camera shake.

I'll refrain from calling you an idiot back.
Change the light level one stop at a time to compensate for the change in shutter speed.
It's still a compromise, but at least the machine you are testing is then having only one parameter changed at a time.
I realize that this would be too much for most people, and that more than likely the movement of the aperture assembly in the lens will have a negligible effect, but if you allow several small changes to come into play, they can often affect the result.
True scientific testing doesn't change more than one parameter at a time, so that an accurate gauge of how that parameter, and that parameter only, affects the results.
Far too many people don't practice anything even close to a scientific test method, and then post results to the internet like as if they are some sort of expert.

I'm glad you refrained from calling me an idiot, because I am right on this one.
02-26-2010, 02:20 PM   #38
Veteran Member
GoremanX's Avatar

Join Date: Dec 2009
Location: Georgia, VT
Photos: Albums
Posts: 1,653
QuoteOriginally posted by Wheatfield Quote
Change the light level one stop at a time to compensate for the change in shutter speed.
It's still a compromise, but at least the machine you are testing is then having only one parameter changed at a time.
I realize that this would be too much for most people, and that more than likely the movement of the aperture assembly in the lens will have a negligible effect, but if you allow several small changes to come into play, they can often affect the result.
True scientific testing doesn't change more than one parameter at a time, so that an accurate gauge of how that parameter, and that parameter only, affects the results.
Far too many people don't practice anything even close to a scientific test method, and then post results to the internet like as if they are some sort of expert.
But then the ambient light is a changing parameter. You're advocating changing the ambient parameters instead of the camera's parameters. Since we're dealing with an auto-focus system that's heavily dependent on ambient light, changing the ambient light affects the likelihood that the auto-focus will be responsible for a blurry shot instead of camera shake.

QuoteOriginally posted by Wheatfield Quote
I'm glad you refrained from calling me an idiot, because I am right on this one.
Wouldn't matter if you were right or wrong, calling people "idiots" on a whim is a pretty lame way to interact with the world. You may not be an idiot, but you sure suck I hate learning things from you. Luckily, I don't think I've learned anything from you in this thread yet.

02-26-2010, 04:49 PM   #39
Pentaxian
Wheatfield's Avatar

Join Date: Apr 2008
Location: The wheatfields of Canada
Posts: 10,132
QuoteOriginally posted by GoremanX Quote
But then the ambient light is a changing parameter. You're advocating changing the ambient parameters instead of the camera's parameters. Since we're dealing with an auto-focus system that's heavily dependent on ambient light, changing the ambient light affects the likelihood that the auto-focus will be responsible for a blurry shot instead of camera shake.
You still don't get it. If you are letting the AF do anything, then you have added a variable.
You need to remove all of the mechanical variables that you can, which means turning the AF off.
Changing the light level allows the tester to compensate for altered shutter speeds without making any further changes to the device being tested.
QuoteQuote:

Wouldn't matter if you were right or wrong, calling people "idiots" on a whim is a pretty lame way to interact with the world. You may not be an idiot, but you sure suck I hate learning things from you. Luckily, I don't think I've learned anything from you in this thread yet.
I don't ever call anyone an idiot on a whim, but I'm glad our mutual admiration society is still alive and well.
OTOH, if you haven't learned anything from me in this thread......
02-26-2010, 07:50 PM   #40
Veteran Member
GoremanX's Avatar

Join Date: Dec 2009
Location: Georgia, VT
Photos: Albums
Posts: 1,653
QuoteOriginally posted by Wheatfield Quote
You still don't get it. If you are letting the AF do anything, then you have added a variable.
You need to remove all of the mechanical variables that you can, which means turning the AF off.
Changing the light level allows the tester to compensate for altered shutter speeds without making any further changes to the device being tested.
That's a good point regarding auto-focus. But I maintain that changing shutter speed and aperture simultaneously has no effect on results of SR performance. When I performed my super-highly scientific and infallibly accurate test , all shots at 1/100 were taken at the same aperture. And all the 1/50 shots were taken at the same aperture, and so on. So results between SR turned on and off still correlate directly.

In any case, I was simply responding to a request someone posted on this thread. I find my results perfectly relevant for my own uses, and I feel confident in stating that I get 3-4 EV advantage thanks to my camera's shake reduction. I'm also glad to have shared my results with others so they can draw whatever conclusions they want. (edit: I don't think my intentions or my results were "idiotic" in the slightest) Hopefully the detailed description of my method will help put those results in context.

QuoteOriginally posted by Wheatfield Quote
I don't ever call anyone an idiot on a whim, but I'm glad our mutual admiration society is still alive and well.
You call people idiots all the time. You throw the word around and apply it to everyone and anyone without thought. Your observations are laced with so much contempt and disdain, it's a wonder you even consider yourself a mere mortal. You're like the anti-Canadian. It's unfortunate, because it seems like you have insight to share from experience, but I just can't take anything you say seriously. It's delivered with too much arrogance.

Last edited by GoremanX; 02-26-2010 at 08:44 PM.
02-27-2010, 01:19 AM   #41
Pentaxian
Wheatfield's Avatar

Join Date: Apr 2008
Location: The wheatfields of Canada
Posts: 10,132
QuoteOriginally posted by GoremanX Quote
That's a good point regarding auto-focus. But I maintain that changing shutter speed and aperture simultaneously has no effect on results of SR performance. When I performed my super-highly scientific and infallibly accurate test , all shots at 1/100 were taken at the same aperture. And all the 1/50 shots were taken at the same aperture, and so on. So results between SR turned on and off still correlate directly.

In any case, I was simply responding to a request someone posted on this thread. I find my results perfectly relevant for my own uses, and I feel confident in stating that I get 3-4 EV advantage thanks to my camera's shake reduction. I'm also glad to have shared my results with others so they can draw whatever conclusions they want. (edit: I don't think my intentions or my results were "idiotic" in the slightest) Hopefully the detailed description of my method will help put those results in context.
I believe earlier in the thread I indicated that with careful shooting technique, Pentax shake reduction would probably net well over a 4 stop advantage.
However, I also believe that the results that we were directed to in post #29 are probably false, and I took the time to explain why, and expanded on that somewhat with an explanation of scientific testing.
It's a a pity that you are so argumentative that you can't see when you are being agreed with.
QuoteQuote:

You call people idiots all the time. You throw the word around and apply it to everyone and anyone without thought. Your observations are laced with so much contempt and disdain, it's a wonder you even consider yourself a mere mortal. You're like the anti-Canadian. It's unfortunate, because it seems like you have insight to share from experience, but I just can't take anything you say seriously. It's delivered with too much arrogance.
Well, you do have a good handle on arrogance yourself. I suppose that for you, looking at me is like looking in a mirror.

Best regards.
02-27-2010, 02:48 AM   #42
Veteran Member




Join Date: Mar 2007
Location: U.K.
Posts: 685
QuoteOriginally posted by labnut Quote
Rob, as near as I can make out the roll they refer to is the rotation detection and horizon levelling function that Pentax pioneered with the K7. They specifically refer to the roll induced by depressing the shutter release button. I think the roll is rotation around the lens axis.
Wouldn't any rotation be around the axis of wherever the other hand is holding the non-shutter end of the camera?
02-27-2010, 04:30 AM   #43
Forum Member




Join Date: Feb 2010
Photos: Gallery
Posts: 56
QuoteOriginally posted by SteveB Quote
Wouldn't any rotation be around the axis of wherever the other hand is holding the non-shutter end of the camera?
Steve, it is a little more complicated than that. You see, camera shake is a misleading name. We commonly interpret shake to mean up and down motion or left to right motion of the camera, that is translation of the X-Y axes (the Z axis we don't count because that is in the direction of the subject and auto focus takes care of that)

But the shake reduction system doesn't measure this at all. What it measures is the forward up/down rotation around the X axis (pitch), the left/right rotation (yaw) around the Y-axis and the rotation around the lens Z-axis (roll). So all three measurements are rotations around the X, Y and Z axes, which we call pitch, yaw and roll respectively. Until the K7 only pitch and yaw were measured which made the camera vulnerable to roll induced by shutter depression.

So why do they measure rotation around the axes and not translation of the axes? In part it has to do with the way we point a camera. When we point a camera to keep the subject centered any short term deviations from the aiming point tend to be rotational in the form of pitch, yaw or roll.

In part it has to do with technology. We can readily make linear measurements of angular velocity using piezoelectric gyroscopic sensors. It is not so easy to make linear measurements of displacement at low frequencies where the axes are translated.

Sorry about the long answer. What I am trying to say is that all three measurements are about rotation and which one we call roll is a matter of definition. Pentax have defined roll as rotation around the lens axis.
02-27-2010, 05:01 AM   #44
Forum Member




Join Date: Feb 2010
Photos: Gallery
Posts: 56
QuoteOriginally posted by SteveB Quote
Wouldn't any rotation be around the axis of wherever the other hand is holding the non-shutter end of the camera?
Oops Steve, I've just realised I misread your question. What you say sounds plausible.

But see this extract from the relevant Pentax patent

DESCRIPTION OF THE RELATED ART
[0008]By delaying the commencement of the calculations of these hand-shake angles, the parallax may be reduced. However, the third hand-shake angle caused by roll due to the depression of the release button can not be calculated so that the third hand-shake angle can not be accurately calculated.

SUMMARY OF THE INVENTION
[0009]Therefore, an object of the present invention is to provide an anti-shake apparatus (an image-stabilization apparatus) that can accurately calculate the hand-shake angle caused by roll.

Below is how Pentax define the rotational axes (taken from the same patent)

02-27-2010, 05:51 AM   #45
Pentaxian




Join Date: Apr 2007
Location: Sweden
Posts: 1,927
QuoteOriginally posted by SteveB Quote
Wouldn't any rotation be around the axis of wherever the other hand is holding the non-shutter end of the camera?
It doesn't matter where the center of rotation is, as long as you can counter rotate and keep the horizon at a constant level. Translation of the sensor in x-y plane could compensate for an off-center rotation, I don't know if they actually do that, but in theory...
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, dslr, photography, sr
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Pentax SR effective when panning! falconeye Pentax DSLR Discussion 12 03-26-2008 09:32 AM
is SR effective simons-photography Photographic Technique 24 03-22-2008 03:48 AM
Quality, Effective Memory Card dales Pentax Camera and Field Accessories 10 12-12-2007 06:04 AM
When and how to use SR and how effective? Takman Pentax DSLR Discussion 11 11-02-2007 07:37 AM
NEW Pentax rebates effective TODAY! macdaddy Pentax News and Rumors 13 05-03-2007 12:45 PM



All times are GMT -7. The time now is 04:11 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top