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09-13-2010, 10:39 PM   #1
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Odd Shake Reduction Failure

All,

I just recently got back from a shoot where the majority of my pictures had noticeable motion blur. About 75% of the pictures taken were at 18mm at 1/25 with SR on. Out of those shots, I'd say 2/3rds were significantly blurry (motion blur not focus blur). I'm fairly confident I waited for the SR icon in the viewfinder before shooting each shot. I'm also confident I wasn't THAT shaky!

Odd thing is I hadn't noticed the issue before on other shoots, and I can't reproduce it anymore. I'm thinking it may have been a software glitch (I have the latest 1.10 firmware) and I just needed to turn it off then on.

Has anyone else had this problem? I'd post a sample but it's covered under a confidentiality agreement.

I had to send my K-7 in for repair for other reasons (front scroll wheel stopped working), and I asked the repair personnel to take a look at the SR mechanism, but since I can't reproduce it I doubt they'll find anything wrong.


Last edited by jeffshaddix; 09-13-2010 at 10:45 PM.
09-13-2010, 11:15 PM   #2
Raylon
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1/25th is pretty slow. Even with SR, I find that about half of my pictures will be blurry at that speed. I can get lucky with as low as 1/15th or even 1/10th sometimes, but I generally try to stay 1/30th and above. Sounds like maybe conditions were just bad that day.
09-13-2010, 11:24 PM   #3
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QuoteOriginally posted by Raylon Quote
1/25th is pretty slow. Even with SR, I find that about half of my pictures will be blurry at that speed. I can get lucky with as low as 1/15th or even 1/10th sometimes, but I generally try to stay 1/30th and above. Sounds like maybe conditions were just bad that day.
I agree that 1/25 is slow, but at 18mm it shouldn't be a problem even handheld without SR I would think (if we follow the ~1/f rule).
09-14-2010, 01:02 AM   #4
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You can see in the exif of a Jpeg out of the camera in PhotoMe if the stabilisation was completed at the time of the picture was taken.

09-14-2010, 11:11 AM   #5
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Keep in mind it is an APS-C crop camera, so the rule should actually be 1/(f*1.5)
09-14-2010, 07:35 PM   #6
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And it's not a "rule", just a sort of rough guideline that sort of works for many people much of the time. It's no guarantee. BTW, I don't suppose your *subjects* were moving?

Last edited by Marc Sabatella; 09-16-2010 at 06:12 PM.
09-14-2010, 07:47 PM   #7
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QuoteOriginally posted by RonHendriks1966 Quote
You can see in the exif of a Jpeg out of the camera in PhotoMe if the stabilisation was completed at the time of the picture was taken.
Didn't know that! I assume that should be written into the RAW file as well. I'll have to check that out when I get back to home base tomorrow, I don't have the images on me.
09-14-2010, 07:54 PM   #8
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QuoteOriginally posted by kxr4trids Quote
Keep in mind it is an APS-C crop camera, so the rule should actually be 1/(f*1.5)
But of course!
I guess 1/25 @ 18mm would be cutting it close without SR, but with SR it should certainly handle it.

QuoteOriginally posted by Marc Sabatella Quote
And it's not a "rule", just a sort of rough guideline that sort of work for many people much of the time. It's no guarantee. BTW, I don't suppose your *subjects* were moving?
Nope, the shots were of architecture/landscape. The blur was noticeable at all depths and had distinct motion blur characteristics (double image at a fixed offset of a few pixels). I guess I could do a 2D FFT transform of the image and check out spectral information; that would confirm it as motion blur.

09-14-2010, 07:56 PM   #9
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For architecture/landscape, a tripod is a good idea.
09-14-2010, 08:13 PM   #10
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QuoteOriginally posted by brofkand Quote
For architecture/landscape, a tripod is a good idea.
True, but these shots were taken around noon on an overcast day. There was plenty of light. Am I crazy to expect more than 1/3 of my shots be sharp at 18mm 1/25s with SR at f/8?

Going by the f/1.5 rule of thumb, 1/30s should be sufficient to obtain sharp pictures on the majority of shots. SR offers up to 2.5 stops of shake reduction, which works best at lower focal lengths, so even if we round down to 2 stops improvement, I should be able to shoot at 1/8 without blur in the majority of my shots.

Falk Lumo did some analysis and provided a handy chart at the bottom of this page to determine shutter speed at focal length for varying levels of typical sharpness:
Falk Lumo: Pentax shake reduction revisited

Based on this I should be OK. I definitely don't think I had mega wrist twitch that day either. :P

Like I said earlier, this really only affected one shoot, so I bet it was a software glitch, I just wanted to see if anyone else noticed any problems.
09-15-2010, 12:37 AM   #11
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I had my SR fail in the k20d, it would ruin any photo using it pretty much. So it cant break. They replaced entire mechanism.
09-15-2010, 12:57 AM   #12
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QuoteOriginally posted by jeffshaddix Quote
All,

About 75% of the pictures taken were at 18mm at 1/25 with SR on.
I'm also confident I wasn't THAT shaky!

Odd thing is I hadn't noticed the issue before on other shoots, and I can't reproduce it anymore.
Since the problem has not persisted equipment failure seems to be ruled out.
Did you take a lot of photos in a sequence without much rest in between?

When I measured motion blur in my photos I found that after 10 photos or more in a row I was becoming more shaky. Subjectively I was not aware of it but the measurements clearly showed it. Fatigue definitely increases physiological tremor.
Peter
09-15-2010, 01:10 AM   #13
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OP, one thing you should not rule out is to check your camera holding technique. I have seen so many shooters jab at the shutter release button without they even realizing that they are doing it, and later complain that the camera can't give sharp pictures.
09-15-2010, 07:13 AM   #14
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At those specs, you should be getting "decently" sharp shots.

Make sure you're not stabbing the shutter release with your finger, kind of roll your finger across the button, as creampuff said. It really helps.

I have also noticed that sometimes SR or VR or IS can introduce shake; the systems look for camera shake and where none exists, it creates it by moving the sensor or lens elements to compensate for shake, even though none is there. This is especially prevalent on a tripod, but I have experienced it during handholding as well...

Next time, I'd turn off SR, prop yourself onto a lamp post, car, or some other sturdy object, and try the rolling finger technique.
09-15-2010, 06:12 PM   #15
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Thanks for the comments guys! I'd be na´ve to think my holding method doesn't contain flaws. I haven't heard the finger roll method, so I'll try that.

Does anyone have more info on the SR introducing shake when there isn't any? I could see it introducing an imperceivable amount of blur, only noticeable compared to a non-sr shot. am I accurate or could it be worse than im thinking?
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