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-   -   Does Optical Image Stabilization Degrade Video Quality? (https://www.dvinfo.net/forum/sony-vx2100-pd170-pdx10-companion/78087-does-optical-image-stabilization-degrade-video-quality.html)

Ken McGrath October 23rd, 2006 07:34 PM

Does Optical Image Stabilization Degrade Video Quality?
 
I have a PD170, and recently used OIS when taping a competition on a tripod from the bleachers of a gymnasium (the bleachers were bouncing around quite a bit). The video quality seemed slightly degraded, even when the bleachers were still. Does OIS degrade quality (when the camera is stationary) compared to having OIS off? I aslo have a DVX100A, and have same question for that camera (but will not "double post")

Mike Rehmus October 24th, 2006 08:35 AM

An optical image stabilization system is always in the optical path. They do not change their degradation of the image quality between on and off. Which is a way of saying that the extra reflections inside the lens (at least in the Sony) are there no matter what.

Sony specifically suggests that OIS be turned off when the camera is on a tripod. What they really mean is that if you have it on and pan or tilt the camera at a medium speed, you will notice the image 'catching up' to the motion. I can be very noticable. The problem in this case is you stop the camera motion when you reach an intended framing and the image keeps moving, ruining the frame.

Stadiums are terrible camera platforms as you found. Especially the old steel and wood installations.

Ken McGrath October 24th, 2006 12:01 PM

Thanks much. I thought I noticed a somewhat diminished resolution, or blurriness in the video I shot with the OIS on, even when there was no camera/platform motion. Maybe I am just looking for something that is not really there. Next time I'll try without the OIS in a similar situation and see if I see any difference, but it sounds like any difference should not be attributable to OIS.

Alex Amira October 24th, 2006 02:25 PM

I've heard that you loose about 15 lines of res with OIS on.

Mike Rehmus October 24th, 2006 03:42 PM

Look, the OIS is permanently located in the optical path in the lens. It is always in the optical path. Power to the elements that move its parts isn't going to change the resolution of the lens.

Besides, the lens has much more resolving power than the CCD. Way more. So unless the OIS somehow moves the image off the edge of the CCD, I don't see how it can reduce resolution. Ever.

J. Stephen McDonald October 26th, 2006 01:01 AM

The idea that image stabilization systems might reduce resolution, began with some of the earlier electronic stabilizers (EIS). They allocate a margin of pixels around the outside of the CCD, to be used by the EIS, which reduces the number of active pixels that contribute to the image. If the EIS on these older models is turned off, then the full CCD is actively used and the extra pixels help produce a sharper image. However, in recent years, most (but not all) EIS systems have used the same-sized, smaller inner CCD sector for the video image, regardless of whether the stabilizer was on or off. Therefore, cameras with this type of EIS system, give the same video resolution at all times.

Cameras with optical stabilizers (OIS) always use most of the pixels on their full CCDs for the image and turning their stabilizers off gives no resolution advantage. If there was any loss of resolution due to the extra OIS lens elements being present, it would be constant whether the system was on or off. The optical image always goes through the OIS elements, even when they aren't activated.

Most of the video cameras that use EIS, automatically turn off their stabilizers for their still-picture capture mode on a memory-card and the full CCD is used. This gives more resolution to the pictures taken in that mode. Actually, there are a few of the newer HDV camcorders that do allow the EIS to be turned off in video mode and the full CCD or CMOS to be used for more resolution. This is called "full-scan" by some manufacturers. There are variations between models on this feature and you have to specifically determine how this works for each one.


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