[st_tsourkan]

Good day! I have one question about SR performance on Pentax DSLRs.
Excuse me for my english

I've noticed, that SR sometimes works better at slower shutter speeds, that at faster.
For example, I use Tamron 70-300 at 300 mm on my K20D, K10D, K-5 II. With all cameras I have the same result.
Shots are sharp at 1/125, 1/100 (about 2 stops under 1/EFL). If I set shutter to 1/80, 1/60, 1/40 s shots became blurred. I've decided, that 2-2,3 stops is a technical limit for SR. Not bad.

BUT: I set shutter to 1/30 s, 1/25 s at 300 mm and (suddenly!) shots became sharp! I've done 30 shots and at 1/30 s they were sharper, that at 1/80 s. I mean "not shaked". It isn't occasionally!
I've done 30 shots at 1/50...1/80 s and 30 shots at 1/25...1/30 s. In second series with lower shutter speed shots were sharper!

Why SR works worse at some (not slowest) shutter speeds? Is there some mechanical resonance at 1/50...1/80? Is it possible to repair it programmatically?
Maybe SR works too good at 1/50...1/80 and makes understabilization?

[dms]

Likely the shock of the mirror flipping up and hitting the stop/shutter shock. This is usually worst at shutter speeds around 1/60 sec. The specifics depend on the camera, but much longer and much shorter exposure times are fine.

[biz-engineer]

Why SR works worse at some (not slowest) shutter speeds?

It is very relative to how you hold the camera and lens. When you hold the long lens and camera (2 points), it is not the same camera+lens motion as if you hold the camera only (1 point).

Is there some mechanical resonance at 1/50...1/80?

Yes, the sensor block and actuation performs best within a range of camera shake frequency. The weight of camera and lens and how you hold them changes how the camera / lens moves. If your 300mm lens is heavier, you may experience sharper images even if the shutter speed is slower than with a light weight lens.

Is it possible to repair it programmatically?

Somehow, it's already done, the magnitude of sensor stabilization changes with the focal length (that's why if you use a manual lens, the camera invites you to enter the focal length of the manual lens you are using). But the sensor stabilization isn't a function of the lens weight because it can vary a lot from lens model to lens model.

BUT: I set shutter to 1/30 s, 1/25 s at 300 mm and (suddenly!) shots became sharp! I've done 30 shots and at 1/30 s they were sharper, that at 1/80 s. I mean "not shaked". It isn't occasionally!I've done 30 shots at 1/50...1/80 s and 30 shots at 1/25...1/30 s. In second series with lower shutter speed shots were sharper!

What was your heart rate ? How where you breathing when you made this test? How did you press the shutter button? The camera shake reduction isn't the only parameter that affects image sharpness at low shutter speeds. How the camera and lens move when you hold it also play a role to image sharpness. So, you can't really draw any conclusion when the way you hold and move the camera isn't the same between successive trials. When you change the shutter speed, did you change the lens aperture or did you change the ISO setting or did you adjust the light source on the subject so that shutter speed is changed and the ISO setting and lens aperture remain the same? Because if ISO increased when shutter speed increased, then your images are likely less sharp. Also, if when you increase your shutter speed, the lens aperture opened one stop, then the image is likely less sharp, either due to depth of field or due to the nature of lens sharpness vs aperture.

[st_tsourkan]

It is very relative to how you hold the camera and lens. When you hold the long lens and camera (2 points), it is not the same camera+lens motion as if you hold the camera only (1 point).

I've hold my camera and lens the same method in 2 cases (1/30 s and 1/160 s): left hand holds lens near bayonet, right hand holds camera.
So I think, that in my question camera hold method doesn't have a role - the role has shutter speed.

What was your heart rate ? How where you breathing when you made this test? How did you press the shutter button? The camera shake reduction isn't the only parameter that affects image sharpness at low shutter speeds. How the camera and lens move when you hold it also play a role to image sharpness. So, you can't really draw any conclusion when the way you hold and move the camera isn't the same between successive trials. When you change the shutter speed, did you change the lens aperture or did you change the ISO setting or did you adjust the light source on the subject so that shutter speed is changed and the ISO setting and lens aperture remain the same? Because if ISO increased when shutter speed increased, then your images are likely less sharp. Also, if when you increase your shutter speed, the lens aperture opened one stop, then the image is likely less sharp, either due to depth of field or due to the nature of lens sharpness vs aperture.

I didn't breath, heartbit rate was the same I've pressed shutter button by edge of my finger (I tryed not to shake the camera while pressed the button). My finger moved to the left, not down to the button.
When I use more slow shutter speed, I've used more dark objects (ISO and aperture was the same). It's about motion blur only.

I think, that mirror shake causes motion blur at 1/40...1/80 s.

Does anyone meet this problem?

[beholder3]

My cameras and lenses never showed the behaviour claimed here.
So what is described here is a failure somewhere between the user and the specific combination of equipment used.
Nothing to do with SR in general.

[biz-engineer]

heartbit rate was the same

What was your heart rate when you held the lens? Anyway, it's unlikely that your heart rate was the same if you didn't breath, because heart rate and breath are related, if you stop breathing your heart rate goes down, then goes up again after a few seconds, it's due to varying arterial pressure transmitted by the lungs when the lungs inflate, deflate or compress.

Does anyone meet this problem?

No I never considered this as a problem since I never expected 100% of my images sharp when I shoot at shutter speeds lower than the reciprocal and use SR.

Shooting bursts of 3 to 5 images strongly increases the odds of getting sharp images at sub reciprocal shutter speed and SR.
Usually, the first and last images in the burst aren't sharp due to SR engaging and camera motion during press of shutter button, and the second or third images are sharp.
My experience shooting burst of three image with SR is that I almost always get the second image tack sharp, even at incredibly low shutter speeds.

[st_tsourkan]

Shooting bursts of 3 to 5 images strongly increases the odds of getting sharp images at sub reciprocal shutter speed and SR.
Usually, the first and last images in the burst aren't sharp due to SR engaging and camera motion during press of shutter button, and the second or third images are sharp.
My experience shooting burst of three image with SR is that I almost always get the second image tack sharp, even at incredibly low shutter speeds.

I didn't breathed only when I was shooting

It's a good idea to make 3-5 images. I'll try it!

[biz-engineer]

I didn't breathed only when I was shooting

That may be the reason of your problem. The Pentax manual doesn't say that we have to stop breathing when using SR. So , just breath normally and everything will be fine.

[st_tsourkan]

That may be the reason of your problem. The Pentax manual doesn't say that we have to stop breathing when using SR. So , just breath normally and everything will be fine.

If I breathing normally while shooting, shots are more blured

[tokyoscape]

Why SR works worse at some (not slowest) shutter speeds? Is there some mechanical resonance at 1/50...1/80? Is it possible to repair it programmatically?
Maybe SR works too good at 1/50...1/80 and makes understabilization?

Similar to this?
shutter vibration and shake reduction - PentaxForums.com

As far as I know, the shutter shock/mirror shock (or whatever people call) while on SR (not on a tripod) is not a unique problem for one particular camera&lenses. It is what’s caused by the mirror or shutter and not the photographer’s ability to keep the camera still. I'm interested in learning how to minimize it too. Maybe I will have to test with all of my lenses and learn to select use / not use SR in some shutter speed. I wonder if use Live View while on some shutter speed can help?

[Lowell Goudge]

That may be the reason of your problem. The Pentax manual doesn't say that we have to stop breathing when using SR. So , just breath normally and everything will be fine.

Shake reduction rewards technique.

You should not stop breathing, but you should breath slowly and I believe be exhaling slightly when you shoot, it is the same technique when target shooting or using a rifle



The biggest challenge to overcome is the tendency to rotate or move the camera when pressing the shutter.



When holding your camera I find it best to Do the following
-You take a relaxed posture, support your camera the best you can, stand with your feet apart to make your body as stable as possible, etc.
- your arms above the elbow, should come against your body if possible, to minimize the length of your arms unsupported,
- to hold the camera, have one hand on the grip (this is the hand to press the shutter), the other hand as far away from the first as possible, (for long lenses, at the end of the lens) and the camera against your eye/cheek.


I have shot with a 500 mm lens at 1/40

just how good is the K7 shake reduction? - PentaxForums.com

[biz-engineer]

You should not stop breathing, but you should breath slowly and I believe be exhaling slightly when you shoot, it is the same technique when target shooting or using a rifle

Exactly what I learned in rifle shooting club and also with archery. What I learned is that there is a point in the breathing cycle where the body doesn't move , and I have to not to contract my lung at that point either, slowing exhale around the balance is what apparently works best. I wrote that SR isn't designed to compensate motion well when there is no motion. In fact SR is designed for optimal correction of human body motion.

The biggest challenge to overcome is the tendency to rotate or move the camera when pressing the shutter.

I think you are right, because I can imagine that SR works best to compensate by moving the sensor up / down / right / left, rotation is more tricky.

[Lowell Goudge]

snip......

I think you are right, because I can imagine that SR works best to compensate by moving the sensor up / down / right / left, rotation is more tricky.

i think later bodies are better than the first bodies in that respect, not sure the cut in of the Shake Reduction II with 5 axis that included rotation and yaw as well as x//y/z movements,

before this, using your face (literally) as a contact point with the camera was crucial to resist rotation from pressing the shutter button.

[mikesbike]

Since different camera body sizes and designs were used (actually two), with identical results, this suggests mirror slap/shutter shake not being involved. There is normally some differences in vibration frequency between cameras of various design and weight, everything else being equal. As an owner of both above styles, a K20D and K-5, K-5 IIs, I can say beyond any doubt this mechanism is extremely quiet and well-damped in the K-5 series design.

If mirror slap is involved, the same issue is likely to be there if attached in normal fashion to a light or mid-weight tripod with SR off.

Not only good holding, but also good bracing is important with the elbows in against the body.

[Lowell Goudge]

Since different camera body sizes and designs were used (actually two), with identical results, this suggests mirror slap/shutter shake not being involved. There is normally some differences in vibration frequency between cameras of various design and weight, everything else being equal. As an owner of both above styles, a K20D and K-5, K-5 IIs, I can say beyond any doubt this mechanism is extremely quiet and well-damped in the K-5 series design.

.

the K10 by comparison is the loudest camera i have ever heard