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Earth rotation limits in-body image stabilization to 6.3 stops (2020)

166 points by pwnna 2y ago

kqr 2y ago
6.3 stops is a lot, though. That's basically the fully usable aperture range of a kit zoom lens.
- nimbleal 2y ago
  Yes, or considered another way 1/25th shutter vs almost 1/2000th, ie a lot of motion blur vs. virtually nothing will be able to provoke blurring
  - siriaan 2y ago
    Except a moving subject, of course.
    - SassyBird 2y ago
      At 1/2000th both a running cheetah and a running squirrel are completely frozen. I haven’t yet found anything that isn’t frozen with that setting. I suspect at that point you’re in the domain of bullets, very outstretched springs and the like. Edit: yeah, a speeding bullet caught at 1/5000th: <https://flickr.com/photos/hoohaaphotos/5587502201/ https://flickr.com/photos/hoohaaphotos/5587502201/>
      - dale_glass 2y ago
        Stabilization doesn't help with subject movement, it only helps with the camera's shake. So with this level of stabilization, you'll take a picture of a running cheetah at 1/25 as if it were 1/2000 only as far as the stability of the camera is concerned. So if you're not tracking the cheetah you'll get a sharp background because the shaking of your hands has been nullified, but the cheetah is still moving within the frame and still blurry.
- noselasd 2y ago
  What are these "stops" in this context, for the non-photo nerds ?
  - poulpy123 2y ago
    it's an abstraction of the aperture size and exposition time. If you expose twice as long it gives the same light than an aperture twice the surface. Those 2 are discrete in camera, so it is abstracted as stops. Exposure time is limited by movement, and aperture size is limited by the optics itself. Sensor stabilization allows to gain "stops" by extending the exposition time before the image becoming blurry from the photographer movement, thus allowing as much more light to come
  - formerly_proven 2y ago
    A stop generally is a doubling/halving of light intensity at the sensor. For apertures this means a factor of sqrt(2) on the diameter (because the area is what matters), for exposure times a doubling/halving of the time. "Stops of stabilization" in this specific context refers to a standardized CIPA test which determines a shutter speed where the image remains acceptably sharp. They then calculate the number of stops to 1/focal-length, which is a rule of thumb for getting sharp images from the 1950s. So if a 200mm lens produced a sharp image at 1/10s in the CIPA test, then that would be 1/10 -> 1/20 -> 1/40 -> 1/80 -> 1/160 -> 1/200 about 4.3 "stops of stabilization". The results from the CIPA test don't really hold up to the real world though once you move beyond ~4 stops.
- vouaobrasil 2y ago
  However, it's not the aperture range that matters. Theoretically, if earth were not rotating, then 10 stops would still be useful for long-exposure photography. In other words, the stop differences in stabilization are more useful when you think of then in terms of shutter speed, NOT aperture.
tetris11 2y ago
I still don't quite follow the explanation. The duck and I are on the surface of the same body and are rotating together, maintaining a constant distance... why does Earth rotation need to be corrected for?
- aljgz 2y ago
  Let's do a small though experiment: Assume you have fixed your camera and the duck on a surface. Then while taking the photo, you rotate the surface. The motion sensor in the camera tries to cancel out this motion, which is suitable for taking a photo of something that's not fixed on the surface, which means it does not work well for the duck that's moving with the camera.
- seszett 2y ago
  It's explained here: > Your camera, which is using its IBIS system to attempt to keep everything as still as possible, may not realize that you are rotating with your subject and will instead try to zero out any rotation of the camera, including that of the Earth The problem is that the stabilization system tries to compensate for the rotation of Earth (because it can't make the difference between the rotation of Earth, which shouldn't be compensated for, and the movement of the holder which should be). So it would work if you were taking a photo of a subject not rotating together with the Earth. Like the stars.
  - tetris11 2y ago
    I guess I couldn't quite grok how IBIS would measure the Earth's rotation whilst being on Earth, but as I've now just learned (through various slaps of the forehead) a perfectly vertical spinning gyroscope will definitely tilt with time due to the Earth's rotation and this is measurable to high degrees of precision.
    - anilakar 2y ago
      Not just randomly tilt - it will align itself with the poles of a spinning celestial body. It's used in applications that can't rely on correct magnetic variation, like surveying and aircraft inertial navigation systems.
quonn 2y ago
Would it be possible to correct for the rotation by counter rotating if the orientation of the camera is known (or determined by GPS + compass)?
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isoprophlex 2y ago
> The second solution is much more plausible, but still very difficult. The user would have to be pointing the camera at the subject for long enough such that the drift in their aim at the subject is smaller than the drift from the rotation of the earth. This is also implausible. What is concerning though, is that this second method is one that could work very well to cancel out Earth’s rotation on the CIPA specified stabilization test apparatus. So, basically dieselgate but for image stabilization
- nick7376182 2y ago
  It seems the camera could use optical flow to get a baseline reading and calibrate the inertial frame offsets. They don't need to point accurately for a long time? Or maybe that is the method they assume for the second solution and they calculated that it's infeasible.
DoctorOetker 2y ago
This can be fixed in software: you can back calculate orientations with high pass filterd gyro data, to rotate the unfiltered gyro date into the current reference frame, then low pass the unfiltered but rotation corrected gyro data to get the earth rotation axis in the current reference frame, then one can estimate the expected rotation that should be ignored.
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t0mas88 2y ago
You don't need GPS to figure out the correction for this. Inertial navigation systems in aircraft (which use very stabilised platforms with a lot of math involved) worked before GPS was available. It helps to have a rough indication of the current latitude on startup, but you can also figure it out from the gyro outputs. Just takes longer. With modern sensors (solid state laser gyroscopes) it has all become a lot smaller so if you really want to you can do this in a camera. It's just probably going to be too expensive for what it brings, because 6+ stops of stabilisation is a lot already.
- crubier 2y ago
  Aerospace grade laser gyroscopes are incredibly expensive (and bulky), and even then, they still have massive drift after several hours. If you don't have GPS to relocalize precisely at least every day, there is no way you can know the location of the camera on earth for more than a day, even with state of the art aerospace stuff
  - TaylorAlexander 2y ago
    Realistically GPS is the answer, but it’s notable that you could also use a simple light sensor combined with accurate clocks to get your position on earth: https://en.m.wikipedia.org/wiki/Light_level_geolocator https://en.m.wikipedia.org/wiki/Light_level_geolocator
    - vmfunction 2y ago
      > Recording light levels over time Wonder how much time is needed to determine location.
      - TaylorAlexander 2y ago
        You just need to determine the time of sunrise and sunset relative to a known location and you get a rough idea of latitude and longitude.
  - labcomputer 2y ago
Asraelite 2y ago
> The first isn’t a good solution for many reasons. Don’t have GPS signal? Shooting next to a magnet? Your system won’t work. These seem trivial to work around. Just store the last known position and use that. It's rare that you'll be without a GPS signal or beside a magnet, and you certainly won't be traveling long distances in those conditions. And since when do magnets block GPS signals?
- sokoloff 2y ago
  It’s not that a magnet blocks GPS signals, but it does affect the compass in the context of using 6 of the 9 degrees of freedom in the first proposed solution: “Use the camera’s GPS, accelerometer, and compass to calculate exactly where it is pointed and its latitude. ” (This solution should also do sensor fusion with the gyroscope, not just accelerometer and compass for orientation from a 9DoF system.)
GuB-42 2y ago
On the other hand, that should be awesome for astrophotography.
- bongodongobob 2y ago
  It has no bearing. Tracking is how you keep stars from smearing, not stabilization.
- SamBam 2y ago
  I believe that fancy astrophotography tripods already do that rotation for you, right? I think that for astrophotography, the shutter times are so long that you have to build it into the tripod, instead of relying on the tiny amount of stabilization that can be done in-camera. Although maybe it would be helpful to cancel out some motor noise of vibrations from the tripod. But probably the existing image stabilization already does this.
  - matthew-wegner 2y ago
    Pentax cameras take a different approach with stabilization--rather than stabilize inside lens, which means every lens is shipping its own stabilization solution, they stabilize the sensor itself. It limits stabilization to two axes, but now any lens is essentially stabilized. And it also lets them do some tricks, since it's so integrated. One is to do sub-pixel sensor shifts for higher res photos, and another is to do astrophotography tracking when GPS data is available. Much more limited in scope than a full tracking gimbal, but not bad considering it's built into the camera (earlier bodies had a GPS attachment that slotted into the hot shoe connector): https://www.lonelyspeck.com/pentax-k-1-mark-ii-astrophotography-review/ https://www.lonelyspeck.com/pentax-k-1-mark-ii-astrophotogra...
    - Espressosaurus 2y ago
      Most cameras these days--other than the low end and the very high end--have IBIS (In-Body Image Stabilization) built in, and then stabilization built into the longer lenses (typically > 100mm). In higher-end/more recent cameras that both IBIS and lens stabilization can work together to improve how effectively the system works. I don't know if it's true of universally, but the recent cameras in Nikon's ecosystem which I'm familiar with use a 5-axis IBIS unit. A quick search suggests the K-1ii and some other Pentax cameras also moved to 5-axis IBIS--probably one of the reasons most brands are claiming 5+ stops in-body these days. OM-1, formerly Olympus, does has some very cool tricks using the tiny micro 4/3s sensor combined with a sick IBIS unit allowing hand-held astrophotography that the larger companies haven't bothered with.
moi2388 2y ago
Can somebody ELI5 this to me? The image with the 2 earths.. that only works if the camera is not also on the ground, but it is? How is the rotation of the object and the camera not identical? Why would it rotate ‘upwards’? Also, if the issue is relative motion or rotation between camera and object, wouldn’t two sensors, one on the camera and one on the subject be able to solve this, since we can see if their rotations/movement match up or not?
- SamBam 2y ago
  Imagine the camera were floating just above the surface of the Earth, and also that it had perfect image stabilization. This image stabilization would keep the camera always oriented in the same direction. Same direction relative to what? To the rest of the universe. So if it was pointing right at a star, it would continue pointing directly at that star as it went around and around the Earth. From our perspective on the surface, the camera would appear to be flipping over itself as it kept pointing at that star. Unfortunately, this would be pretty bad for taking a picture of something that was right in front of the camera (relative to the surface of the Earth). You'd be in front of the camera, ready for your picture, and the camera would appear start rotating as it kept that distant star in view. So with a perfect image stabilizer, this is what the camera is actually trying to do, even when standing on the Earth with a tripod. It actually senses the rotation of the Earth, and tries to cancel it out, just like it would cancel out your hands shaking. But while it's good to cancel out your hands shaking (because that's a motion that's independent of the subject of the photo), it's not good to cancel out the rotation of the Earth (because the subject of the photo is actually moving with you).
  - thrdbndndn 2y ago
    > Same direction relative to what? To the rest of the universe By this logic, the Earth's revolution would also cause similar issue, and even worse. But in reality only the rotation does. I think at least some part of your explanation does not calculate.
    - Filligree 2y ago
imglorp 2y ago
Is a plain phone gyroscope enough to detect Earth rotation? Is there an app for that?
Delmololo 2y ago
You should be able to calculate it out by telling the user to press a button and after this, not rotating the camera away. Right? Might just not be practical at all. On the other hand, shouldn't the earth rotate fast enough to figure this out in a short timeframe while the photographer starts looking through the finder?
- mikhailfranco 2y ago
  Yes, basically Method (2) with stable measurement window. Just put the camera down on a stable surface, click button. Let system wait some ms to allow click disturbance to pass, then integrate signal over some fixed time to establish the rotation, then pick up and continue...
gwill 2y ago
i'm curious how the OM-1 MK2 gets around this to achieve 8.5 stops. https://explore.omsystem.com/us/en/om-1-mark-ii https://explore.omsystem.com/us/en/om-1-mark-ii
eggy 2y ago
Well, if we're nitpicking here, it is not 86,000s/day (24 hours * 3600s/hour) and 7.27x10^-5 radians/s, but 86,164.091s and 7.29x10^-5 radians/s. 24 hours is the time it takes the sun to return to the same spot in the sky due to earth having to rotate for another 3m56s to make up for angle gained by revolving around the sun in the same direction as the rotation of the Earth. This applies for the other planets that also rotate and revolve in the same direction - Mercury, Earth, Mars, Jupiter, Saturn, and Neptune. A sidereal day is 23h 56m 4.091s for distant stars to return to the same spot in the sky. Damn, I knew that is why I botched my 6-stop exposure at my daughter's graduation! She can't blame me now! Thank you HN!
- trhway 2y ago
  >Damn, I knew that is why I botched my 6-stop exposure at my daughter's graduation! how about driving for 6-stop before taking the shot a tank with stabilized gun trained to the target. Now the tank gunner has the excuse too.
  - eggy 2y ago
    I shot competitively in JROTC and after, but never out to 1000 yards (914 m), only 500 yards. The Earth's rotation affects your trajectory significantly particularly if you are shooting longitudinally at a target at a higher or lower latitude. The Coriolis effect. I had more issues with varying winds or being consistent across shots.
_ph_ 2y ago
Version 2 sounds to me as the probably reason for the ability of Cameras like the OM1-2 to go over 8 stops. Yes, it is probably not a simple task to measure the earths drift with the gyroscopes, but there is one thing that might help: the frequency of that drift is exactly known - it is the speed of the earths rotation. So it should be possible to tune a very narrow filter to that frequency and only analyze the gyroscope signal for that frequency. With that one could at least partially compensate for the drift.
pixelpoet 2y ago
Yet another example of b0rked / unescaped TeX, specifically log vs \log in this case. Blows my mind that nobody sees it...
cesaref 2y ago
This is analogous to astro-photography problems with keeping stars as points rather than as blurred lines in long exposures. If you think about it, if a long exposure at night has a static landscape but moving stars, the IBIS equivalent would have static stars and a moving landscape :)
- wiml 2y ago
  There are some fairly enjoyable time lapse videos taken in a non rotating frame: https://youtu.be/DmwaUBY53YQ https://youtu.be/zRTJ5ISmVXE
sib 2y ago
Nikon claims 8.0 stops of "VR image stabilization" for their Zf camera (released late in 2023). https://www.nikonusa.com/p/z-f/1761/overview https://www.nikonusa.com/p/z-f/1761/overview ("Based on CIPA standards; when using the telephoto end of the NIKKOR Z 24-120mm f/4 S" - for clarity, that lens does not have optical VR in the lens itself, so this is all based on in-body stabilization.)
aidenn0 2y ago
You should be able to exceed 6.3 stops if you are pointing north/south rather than east/west, right? Maybe they are just measuring it pointing north/south.
chris_va 2y ago
Solution (2) as written seems to imply that the camera can only use the gyroscope signal while the camera is pointed at the subject, but I cannot see why that is a strong limitation. In theory, you can take the last N seconds of data from the gyroscope (I assume it is running while the camera is active) to get the overall drift, even if it is tumbling around for a while before being pointed at the subject... Assuming the tumbling has enough periods of time that are correlated with the earth's rotation (e.g. someone carrying it, not pointing it an an aircraft or something moving EW for the window duration that is anticorrelated with the rotation).
- felixhandte 2y ago
  That would only work in the case that the camera is fixed on a tripod and has a long period of stable / rigid pointing before the exposure during which to collect this data. This is sometimes the situation in which image stabilization is used. (But if you can be that stable for that long on a tripod, you may not actually need image stabilization.) By far the more common case for image stabilization is one in which the photographer is hand-holding the camera and may not frame the subject until the moment before the exposure begins. The camera movement will likely be several orders of magnitude (~4 to 7) larger than the drift that you want to measure. A low pass filter will tell you nothing at all. At a certain point we can just start using guide stars [0]. [0] https://en.wikipedia.org/wiki/Guide_star https://en.wikipedia.org/wiki/Guide_star
mrandish 2y ago
Perhaps in some camera firmware bug database there's a closed bug marked: "Won't fix. Tested working in orbit."
mikewarot 2y ago
Bullshit. It's ITAR, they don't want parts floating around in the world that can make a dead nuts accurate INS - inertial navigation system, as this enables weapons we don't want in the wild. You can stabilize out everything and account for the rotation by simply watching the vector of gravity over time.
somat 2y ago
Why not stabilize optically? I am probably missing something huge. But if the goal is a stable image why use gyros. use the image itself to apply the correction factor to the final integration. sort of the same way videos are stabilized.
- kybernetyk 2y ago
  This would make the resulting image frame smaller. A Nono in the current full frame meta. Photo hobbyists are snobs :)
- thrtythreeforty 2y ago
  You can do this two ways: you can take a bunch of images, and align and stack them. Or you can take one motion-blurred image and infer the convolution kernel somehow. The former is undesirable because each frame you take has a fixed amount of "read noise" from the sensor. So you'd change your sensor noise for the worse. The second way is undesirable because it's really hard. There is a lot of research into this and some of the results are good but some are not.
kybernetyk 2y ago
Nikon has 8 stops so they somehow beat physics

166 points by pwnna 2y ago

kqr 2y ago

6.3 stops is a lot, though. That's basically the fully usable aperture range of a kit zoom lens.

nimbleal 2y ago
Yes, or considered another way 1/25th shutter vs almost 1/2000th, ie a lot of motion blur vs. virtually nothing will be able to provoke blurring
- siriaan 2y ago
  Except a moving subject, of course.
  - SassyBird 2y ago
    At 1/2000th both a running cheetah and a running squirrel are completely frozen. I haven’t yet found anything that isn’t frozen with that setting. I suspect at that point you’re in the domain of bullets, very outstretched springs and the like. Edit: yeah, a speeding bullet caught at 1/5000th: <https://flickr.com/photos/hoohaaphotos/5587502201/ https://flickr.com/photos/hoohaaphotos/5587502201/>
    - dale_glass 2y ago
      Stabilization doesn't help with subject movement, it only helps with the camera's shake. So with this level of stabilization, you'll take a picture of a running cheetah at 1/25 as if it were 1/2000 only as far as the stability of the camera is concerned. So if you're not tracking the cheetah you'll get a sharp background because the shaking of your hands has been nullified, but the cheetah is still moving within the frame and still blurry.
noselasd 2y ago
What are these "stops" in this context, for the non-photo nerds ?
- poulpy123 2y ago
  it's an abstraction of the aperture size and exposition time. If you expose twice as long it gives the same light than an aperture twice the surface. Those 2 are discrete in camera, so it is abstracted as stops. Exposure time is limited by movement, and aperture size is limited by the optics itself. Sensor stabilization allows to gain "stops" by extending the exposition time before the image becoming blurry from the photographer movement, thus allowing as much more light to come
- formerly_proven 2y ago
  A stop generally is a doubling/halving of light intensity at the sensor. For apertures this means a factor of sqrt(2) on the diameter (because the area is what matters), for exposure times a doubling/halving of the time. "Stops of stabilization" in this specific context refers to a standardized CIPA test which determines a shutter speed where the image remains acceptably sharp. They then calculate the number of stops to 1/focal-length, which is a rule of thumb for getting sharp images from the 1950s. So if a 200mm lens produced a sharp image at 1/10s in the CIPA test, then that would be 1/10 -> 1/20 -> 1/40 -> 1/80 -> 1/160 -> 1/200 about 4.3 "stops of stabilization". The results from the CIPA test don't really hold up to the real world though once you move beyond ~4 stops.
vouaobrasil 2y ago
However, it's not the aperture range that matters. Theoretically, if earth were not rotating, then 10 stops would still be useful for long-exposure photography. In other words, the stop differences in stabilization are more useful when you think of then in terms of shutter speed, NOT aperture.

tetris11 2y ago

I still don't quite follow the explanation. The duck and I are on the surface of the same body and are rotating together, maintaining a constant distance... why does Earth rotation need to be corrected for?

aljgz 2y ago
Let's do a small though experiment: Assume you have fixed your camera and the duck on a surface. Then while taking the photo, you rotate the surface. The motion sensor in the camera tries to cancel out this motion, which is suitable for taking a photo of something that's not fixed on the surface, which means it does not work well for the duck that's moving with the camera.
seszett 2y ago
It's explained here: > Your camera, which is using its IBIS system to attempt to keep everything as still as possible, may not realize that you are rotating with your subject and will instead try to zero out any rotation of the camera, including that of the Earth The problem is that the stabilization system tries to compensate for the rotation of Earth (because it can't make the difference between the rotation of Earth, which shouldn't be compensated for, and the movement of the holder which should be). So it would work if you were taking a photo of a subject not rotating together with the Earth. Like the stars.
- tetris11 2y ago
  I guess I couldn't quite grok how IBIS would measure the Earth's rotation whilst being on Earth, but as I've now just learned (through various slaps of the forehead) a perfectly vertical spinning gyroscope will definitely tilt with time due to the Earth's rotation and this is measurable to high degrees of precision.
  - anilakar 2y ago
    Not just randomly tilt - it will align itself with the poles of a spinning celestial body. It's used in applications that can't rely on correct magnetic variation, like surveying and aircraft inertial navigation systems.

quonn 2y ago

Would it be possible to correct for the rotation by counter rotating if the orientation of the camera is known (or determined by GPS + compass)?

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isoprophlex 2y ago

> The second solution is much more plausible, but still very difficult. The user would have to be pointing the camera at the subject for long enough such that the drift in their aim at the subject is smaller than the drift from the rotation of the earth. This is also implausible. What is concerning though, is that this second method is one that could work very well to cancel out Earth’s rotation on the CIPA specified stabilization test apparatus. So, basically dieselgate but for image stabilization

nick7376182 2y ago
It seems the camera could use optical flow to get a baseline reading and calibrate the inertial frame offsets. They don't need to point accurately for a long time? Or maybe that is the method they assume for the second solution and they calculated that it's infeasible.

DoctorOetker 2y ago

This can be fixed in software: you can back calculate orientations with high pass filterd gyro data, to rotate the unfiltered gyro date into the current reference frame, then low pass the unfiltered but rotation corrected gyro data to get the earth rotation axis in the current reference frame, then one can estimate the expected rotation that should be ignored.

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t0mas88 2y ago

You don't need GPS to figure out the correction for this. Inertial navigation systems in aircraft (which use very stabilised platforms with a lot of math involved) worked before GPS was available. It helps to have a rough indication of the current latitude on startup, but you can also figure it out from the gyro outputs. Just takes longer. With modern sensors (solid state laser gyroscopes) it has all become a lot smaller so if you really want to you can do this in a camera. It's just probably going to be too expensive for what it brings, because 6+ stops of stabilisation is a lot already.

crubier 2y ago
Aerospace grade laser gyroscopes are incredibly expensive (and bulky), and even then, they still have massive drift after several hours. If you don't have GPS to relocalize precisely at least every day, there is no way you can know the location of the camera on earth for more than a day, even with state of the art aerospace stuff
- TaylorAlexander 2y ago
  Realistically GPS is the answer, but it’s notable that you could also use a simple light sensor combined with accurate clocks to get your position on earth: https://en.m.wikipedia.org/wiki/Light_level_geolocator https://en.m.wikipedia.org/wiki/Light_level_geolocator
  - vmfunction 2y ago
    > Recording light levels over time Wonder how much time is needed to determine location.
    - TaylorAlexander 2y ago
      You just need to determine the time of sunrise and sunset relative to a known location and you get a rough idea of latitude and longitude.
- labcomputer 2y ago

Asraelite 2y ago

> The first isn’t a good solution for many reasons. Don’t have GPS signal? Shooting next to a magnet? Your system won’t work. These seem trivial to work around. Just store the last known position and use that. It's rare that you'll be without a GPS signal or beside a magnet, and you certainly won't be traveling long distances in those conditions. And since when do magnets block GPS signals?

sokoloff 2y ago
It’s not that a magnet blocks GPS signals, but it does affect the compass in the context of using 6 of the 9 degrees of freedom in the first proposed solution: “Use the camera’s GPS, accelerometer, and compass to calculate exactly where it is pointed and its latitude. ” (This solution should also do sensor fusion with the gyroscope, not just accelerometer and compass for orientation from a 9DoF system.)

GuB-42 2y ago

On the other hand, that should be awesome for astrophotography.

bongodongobob 2y ago
It has no bearing. Tracking is how you keep stars from smearing, not stabilization.
SamBam 2y ago
I believe that fancy astrophotography tripods already do that rotation for you, right? I think that for astrophotography, the shutter times are so long that you have to build it into the tripod, instead of relying on the tiny amount of stabilization that can be done in-camera. Although maybe it would be helpful to cancel out some motor noise of vibrations from the tripod. But probably the existing image stabilization already does this.
- matthew-wegner 2y ago
  Pentax cameras take a different approach with stabilization--rather than stabilize inside lens, which means every lens is shipping its own stabilization solution, they stabilize the sensor itself. It limits stabilization to two axes, but now any lens is essentially stabilized. And it also lets them do some tricks, since it's so integrated. One is to do sub-pixel sensor shifts for higher res photos, and another is to do astrophotography tracking when GPS data is available. Much more limited in scope than a full tracking gimbal, but not bad considering it's built into the camera (earlier bodies had a GPS attachment that slotted into the hot shoe connector): https://www.lonelyspeck.com/pentax-k-1-mark-ii-astrophotography-review/ https://www.lonelyspeck.com/pentax-k-1-mark-ii-astrophotogra...
  - Espressosaurus 2y ago
    Most cameras these days--other than the low end and the very high end--have IBIS (In-Body Image Stabilization) built in, and then stabilization built into the longer lenses (typically > 100mm). In higher-end/more recent cameras that both IBIS and lens stabilization can work together to improve how effectively the system works. I don't know if it's true of universally, but the recent cameras in Nikon's ecosystem which I'm familiar with use a 5-axis IBIS unit. A quick search suggests the K-1ii and some other Pentax cameras also moved to 5-axis IBIS--probably one of the reasons most brands are claiming 5+ stops in-body these days. OM-1, formerly Olympus, does has some very cool tricks using the tiny micro 4/3s sensor combined with a sick IBIS unit allowing hand-held astrophotography that the larger companies haven't bothered with.

moi2388 2y ago

Can somebody ELI5 this to me? The image with the 2 earths.. that only works if the camera is not also on the ground, but it is? How is the rotation of the object and the camera not identical? Why would it rotate ‘upwards’? Also, if the issue is relative motion or rotation between camera and object, wouldn’t two sensors, one on the camera and one on the subject be able to solve this, since we can see if their rotations/movement match up or not?

SamBam 2y ago
Imagine the camera were floating just above the surface of the Earth, and also that it had perfect image stabilization. This image stabilization would keep the camera always oriented in the same direction. Same direction relative to what? To the rest of the universe. So if it was pointing right at a star, it would continue pointing directly at that star as it went around and around the Earth. From our perspective on the surface, the camera would appear to be flipping over itself as it kept pointing at that star. Unfortunately, this would be pretty bad for taking a picture of something that was right in front of the camera (relative to the surface of the Earth). You'd be in front of the camera, ready for your picture, and the camera would appear start rotating as it kept that distant star in view. So with a perfect image stabilizer, this is what the camera is actually trying to do, even when standing on the Earth with a tripod. It actually senses the rotation of the Earth, and tries to cancel it out, just like it would cancel out your hands shaking. But while it's good to cancel out your hands shaking (because that's a motion that's independent of the subject of the photo), it's not good to cancel out the rotation of the Earth (because the subject of the photo is actually moving with you).
- thrdbndndn 2y ago
  > Same direction relative to what? To the rest of the universe By this logic, the Earth's revolution would also cause similar issue, and even worse. But in reality only the rotation does. I think at least some part of your explanation does not calculate.
  - Filligree 2y ago

imglorp 2y ago

Is a plain phone gyroscope enough to detect Earth rotation? Is there an app for that?

Delmololo 2y ago

You should be able to calculate it out by telling the user to press a button and after this, not rotating the camera away. Right? Might just not be practical at all. On the other hand, shouldn't the earth rotate fast enough to figure this out in a short timeframe while the photographer starts looking through the finder?

mikhailfranco 2y ago
Yes, basically Method (2) with stable measurement window. Just put the camera down on a stable surface, click button. Let system wait some ms to allow click disturbance to pass, then integrate signal over some fixed time to establish the rotation, then pick up and continue...

gwill 2y ago

i'm curious how the OM-1 MK2 gets around this to achieve 8.5 stops. https://explore.omsystem.com/us/en/om-1-mark-ii https://explore.omsystem.com/us/en/om-1-mark-ii

eggy 2y ago

Well, if we're nitpicking here, it is not 86,000s/day (24 hours * 3600s/hour) and 7.27x10^-5 radians/s, but 86,164.091s and 7.29x10^-5 radians/s. 24 hours is the time it takes the sun to return to the same spot in the sky due to earth having to rotate for another 3m56s to make up for angle gained by revolving around the sun in the same direction as the rotation of the Earth. This applies for the other planets that also rotate and revolve in the same direction - Mercury, Earth, Mars, Jupiter, Saturn, and Neptune. A sidereal day is 23h 56m 4.091s for distant stars to return to the same spot in the sky. Damn, I knew that is why I botched my 6-stop exposure at my daughter's graduation! She can't blame me now! Thank you HN!

trhway 2y ago
>Damn, I knew that is why I botched my 6-stop exposure at my daughter's graduation! how about driving for 6-stop before taking the shot a tank with stabilized gun trained to the target. Now the tank gunner has the excuse too.
- eggy 2y ago
  I shot competitively in JROTC and after, but never out to 1000 yards (914 m), only 500 yards. The Earth's rotation affects your trajectory significantly particularly if you are shooting longitudinally at a target at a higher or lower latitude. The Coriolis effect. I had more issues with varying winds or being consistent across shots.

_ph_ 2y ago

Version 2 sounds to me as the probably reason for the ability of Cameras like the OM1-2 to go over 8 stops. Yes, it is probably not a simple task to measure the earths drift with the gyroscopes, but there is one thing that might help: the frequency of that drift is exactly known - it is the speed of the earths rotation. So it should be possible to tune a very narrow filter to that frequency and only analyze the gyroscope signal for that frequency. With that one could at least partially compensate for the drift.

pixelpoet 2y ago

Yet another example of b0rked / unescaped TeX, specifically log vs \log in this case. Blows my mind that nobody sees it...

cesaref 2y ago

This is analogous to astro-photography problems with keeping stars as points rather than as blurred lines in long exposures. If you think about it, if a long exposure at night has a static landscape but moving stars, the IBIS equivalent would have static stars and a moving landscape :)

wiml 2y ago
There are some fairly enjoyable time lapse videos taken in a non rotating frame: https://youtu.be/DmwaUBY53YQ https://youtu.be/zRTJ5ISmVXE

sib 2y ago

Nikon claims 8.0 stops of "VR image stabilization" for their Zf camera (released late in 2023). https://www.nikonusa.com/p/z-f/1761/overview https://www.nikonusa.com/p/z-f/1761/overview ("Based on CIPA standards; when using the telephoto end of the NIKKOR Z 24-120mm f/4 S" - for clarity, that lens does not have optical VR in the lens itself, so this is all based on in-body stabilization.)

aidenn0 2y ago

You should be able to exceed 6.3 stops if you are pointing north/south rather than east/west, right? Maybe they are just measuring it pointing north/south.

chris_va 2y ago

Solution (2) as written seems to imply that the camera can only use the gyroscope signal while the camera is pointed at the subject, but I cannot see why that is a strong limitation. In theory, you can take the last N seconds of data from the gyroscope (I assume it is running while the camera is active) to get the overall drift, even if it is tumbling around for a while before being pointed at the subject... Assuming the tumbling has enough periods of time that are correlated with the earth's rotation (e.g. someone carrying it, not pointing it an an aircraft or something moving EW for the window duration that is anticorrelated with the rotation).

felixhandte 2y ago
That would only work in the case that the camera is fixed on a tripod and has a long period of stable / rigid pointing before the exposure during which to collect this data. This is sometimes the situation in which image stabilization is used. (But if you can be that stable for that long on a tripod, you may not actually need image stabilization.) By far the more common case for image stabilization is one in which the photographer is hand-holding the camera and may not frame the subject until the moment before the exposure begins. The camera movement will likely be several orders of magnitude (~4 to 7) larger than the drift that you want to measure. A low pass filter will tell you nothing at all. At a certain point we can just start using guide stars [0]. [0] https://en.wikipedia.org/wiki/Guide_star https://en.wikipedia.org/wiki/Guide_star

mrandish 2y ago

Perhaps in some camera firmware bug database there's a closed bug marked: "Won't fix. Tested working in orbit."

mikewarot 2y ago

Bullshit. It's ITAR, they don't want parts floating around in the world that can make a dead nuts accurate INS - inertial navigation system, as this enables weapons we don't want in the wild. You can stabilize out everything and account for the rotation by simply watching the vector of gravity over time.

somat 2y ago

Why not stabilize optically? I am probably missing something huge. But if the goal is a stable image why use gyros. use the image itself to apply the correction factor to the final integration. sort of the same way videos are stabilized.

kybernetyk 2y ago
This would make the resulting image frame smaller. A Nono in the current full frame meta. Photo hobbyists are snobs :)
thrtythreeforty 2y ago
You can do this two ways: you can take a bunch of images, and align and stack them. Or you can take one motion-blurred image and infer the convolution kernel somehow. The former is undesirable because each frame you take has a fixed amount of "read noise" from the sensor. So you'd change your sensor noise for the worse. The second way is undesirable because it's really hard. There is a lot of research into this and some of the results are good but some are not.

kybernetyk 2y ago

Nikon has 8 stops so they somehow beat physics