Perhaps in some camera firmware bug database there's a closed bug marked: "Won't fix. Tested working in orbit."
Earth rotation limits in-body image stabilization to 6.3 stops (2020)
91–100 of 112 posts
Re: Earth rotation limits in-body image stabilization to 6.3 stops (2020)
#92Earlier quoted context omitted.
Except a moving subject, of course.
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/ >
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.
Re: Earth rotation limits in-body image stabilization to 6.3 stops (2020)
#93Bullshit. 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.
Re: Earth rotation limits in-body image stabilization to 6.3 stops (2020)
#94Can 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 rotation…
We all want to keep missiles out of the hands of bad people.
Parts to make really good cameras could be taken out and used in missiles, to tell them where to go.
So we now have laws to keep those really good parts out of cameras, for safety. Cameras still work fine, but you need a tripod to get good pictures when it's dark out.
Re: Earth rotation limits in-body image stabilization to 6.3 stops (2020)
#95Earlier quoted context omitted.
> Inertial navigation systems in aircraft (which use very stabilised platforms with a lot of math involved) worked before GPS was available. Inertial measurement units for aircrafts and submarines cost as much as a house in California. Good luck putting those in a phone.
The IMUs that existed on aircraft before the invention of GPS have been superseded by the ones which actually are in your phone, in much the same way and for much the same reason that a $20 Casio F-91w keeps better time than a fancy Rolex that costs more than a house in California: electronics are cheaper and better than mechanical systems. We have, naturally, also made better IMUs for places where it matters, ones w…
Actually that F91W does not keep very good time.
There pretty excellent if you keep them on a shelf bit if you run around outside in the hot and cold (you know, like people use a watch) they'll deviate quickly. Because they don't have a temperature controlled (or even compensated) oscillator. A real TXCO (basically putting the crystal inside a temp calibrated oven) is not feasible on a watch battery but compensation sure would be.
Re: Earth rotation limits in-body image stabilization to 6.3 stops (2020)
#96You 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 sma…
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
But the location of the camera doesn't matter. You only need to figure out very roughly at which latitude you are to know by how much to compensate for earth rotation. And you can do that with the sensors that you're already using to do the stabilisation. That was my point... no need for GPS.
Re: Earth rotation limits in-body image stabilization to 6.3 stops (2020)
#97On the other hand, that should be awesome for astrophotography.
It has no bearing. Tracking is how you keep stars from smearing, not stabilization.
Re: Earth rotation limits in-body image stabilization to 6.3 stops (2020)
#98Solution (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…
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].
Re: Earth rotation limits in-body image stabilization to 6.3 stops (2020)
#99Well, 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 al…
>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.
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.
Re: Earth rotation limits in-body image stabilization to 6.3 stops (2020)
#100Earlier quoted context omitted.
The IMUs that existed on aircraft before the invention of GPS have been superseded by the ones which actually are in your phone, in much the same way and for much the same reason that a $20 Casio F-91w keeps better time than a fancy Rolex that costs more than a house in California: electronics are cheaper and better than mechanical systems. We have, naturally, also made better IMUs for places where it matters, ones w…
Actually that F91W does not keep very good time. There pretty excellent if you keep them on a shelf bit if you run around outside in the hot and cold (you know, like people use a watch) they'll deviate quickly. Because they don't have a temperature controlled (or even compensated) oscillator. A real TXCO (basically putting the crystal inside a temp calibrated oven) is not feasible on a watch battery but compensation…
I picked it not because it's good, but to illustrate the cheapest digital is still better than any analog mechanism that money can buy.