Vibration control, when and when not?
Jan 2, 2017 18:11:32 #
When I think of vibration I think of the physics of the phenomon. Take a particular feature of an image, like a sharp corner. If either the camera or the subject is vibrating or jiggling then that corner will hit several different small clusters of sensor cells. So how does vibration control work. Why should it make any difference depending on tripod or not. Would vibration be at the root of any lack of focus sharpness. Point is I do not thoroughly understand the phenom.
Jan 2, 2017 18:32:45 #
Jan 2, 2017 19:05:03 #
Jan 2, 2017 19:19:16 #
John_F wrote:
When I think of vibration I think of the physics of the phenomon. Take a particular feature of an image, like a sharp corner. If either the camera or the subject is vibrating or jiggling then that corner will hit several different small clusters of sensor cells. So how does vibration control work. Why should it make any difference depending on tripod or not. Would vibration be at the root of any lack of focus sharpness. Point is I do not thoroughly understand the phenom.
I happen to have an A6000 so IS is done entirely within the lens. But let's assume it is done by the camera body rather than by the lens. As I understand it, when IS is on, the sensor is moved around to compensate for movement of the image.
How IS can be accomplished within the lens is a mystery to me.
Jan 2, 2017 19:56:53 #
pecohen wrote:
...How IS can be accomplished within the lens is a mystery to me.
make a shift in a lens group and change the optical axis, works every time
Jan 2, 2017 22:00:38 #
oldtigger wrote:
make a shift in a lens group and change the optical axis, works every time
For this to work the lens must have some measurements of the movement. It would seem those measurements would have to come from the camera sensor in the body. It seems it would be simpler and cheaper to just put all of this in the body instead.
Jan 2, 2017 22:19:15 #
pecohen wrote:
For this to work the lens must have some measurements of the movement. It would seem those measurements would have to come from the camera sensor in the body. It seems it would be simpler and cheaper to just put all of this in the body instead.
Many cameras sense camera movement using little accelerometers in the
camera body to control the lens or sensor.
A more sensitive system combines phase detect from the sensor with the
accelerometers to provide both predictive and corrective drive signals.
This results in improved acquisition times on moving subjects and the use of even
longer shutter openings.
Jan 3, 2017 06:28:30 #
pecohen wrote:
I have a related question: br br There seems to b... (show quote)
My own experience is that IS is great at correcting for low frequency movement such as when hand-holding, but higher frequencies produced by machinery vibration will transmit through a tripod, and defeat it. On a ship, better to lean yourself against something, or rest your arm against a rail, and hand-hold. Otherwise a small bean-bag or rolled-up towel helps
Jan 4, 2017 13:46:25 #
oldtigger wrote:
don't confuse focus error with motion blur
Agreed, do not confuse the two, but how can you tell which from the picture.
Jan 4, 2017 15:10:09 #
John_F wrote:
Agreed, do not confuse the two, but how can you tell which from the picture.
Motion blur is usually in one direction, focus blur is generalised. For example, a distant light, such as a star, leaves a line with motion, but just looks 'mushy' when focus is poor. Most images have highlights which help to distinguish.
Jan 4, 2017 16:29:41 #
Jackdoor wrote:
My own experience is that IS is great at correcting for low frequency movement such as when hand-holding, but higher frequencies produced by machinery vibration will transmit through a tripod, and defeat it. On a ship, better to lean yourself against something, or rest your arm against a rail, and hand-hold. Otherwise a small bean-bag or rolled-up towel helps
That makes sense to me. There are processors that can easily keep up with analyzing and compensating for a 100 Hz vibration but probably they are not in many cameras. I'm thinking now of bringing along some material, foam rubber perhaps, to put under the tripod legs to absorb the vibration from the ship's engines.
Jan 4, 2017 17:23:26 #
pecohen wrote:
That makes sense to me. There are processors that can easily keep up with analyzing and compensating for a 100 Hz vibration but probably they are not in many cameras. I'm thinking now of bringing along some material, foam rubber perhaps, to put under the tripod legs to absorb the vibration from the ship's engines.
I will be very interested to see how well this works. A problem with rubber might be that it would allow the tripod just to resonate -it's not well damped. It might be worth trying small squares of carpet - I would try four thicknesses under each leg, with the carpet pile face-to-face. That works quite well at damping movement.
Jan 5, 2017 09:48:24 #
I leave the VR on all the time on all of my cameras. One less thing to worry about when I am shooting wildlife. I turn the VR off when I use a tripod but not when I use a monopod. Don't know if that is "camera politically correct" but it works for me.
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