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Are shutterless and global shutter the same thing? Are they mutually exclusive? Or are they used together in a camera?

I have a teledyne IR Calibir 640 camera that is shutterless (based on docs) but I'm confused about what shutterless really means.

I pulled this from their white paper (https://www.teledynedalsa.com/en/products/imaging/infrared-detectors/advanced-ir-capabilities/):

How does Shutterless operation work?

The shutterless operation is a further progression of the calibration of the camera. The camera carefully monitors itself at start up and from its first images determines the correction factors that are required to obtain consistently high quality images.

Is this even related to (global) shutters?

Thanks!

  • "Global" shutters are the obverse of "rolling" shutters. If you search these terms here you'll probably find some answers. – user31502 Feb 5 at 20:36
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Are shutterless and global shutter the same thing?

No.

Are they mutually exclusive?

No.

Or are they used together in a camera?

Sometimes.

A "global shutter" requires that the entire sensor can be read out and reset simultaneously. This allows the entire image to record the same "slice of time."

A shutterless camera may have a global shutter, but most of them do not.

Instead, they have sensors, such as CMOS imaging sensors, that must be read out sequentially. This means that one side of the image records a slightly earlier "slice of time" than the other side of the image in much the same way that cameras with mechanical focal plane shutters do.

  • is this a bit like rolling shutters then? – AnkilP Feb 5 at 18:24
  • Sequential readout gives similar results to a rolling shutter. Global shutter, which is just another term for simultaneous readout, does not. – Michael C Feb 5 at 18:47
  • Iris shutters are closer to "global" than focal plane shutters are, but the light coming through the center of the lens is exposed before the light coming through the edges of the lens, and continues to be exposed after the edge light. So while there is no "rolling shutter" effect, there are other effects associated with an iris shutter that a true "global shutter" would not demonstrate. – Michael C Feb 5 at 20:55
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There are two separate concepts:

  • Electronic vs Mechanical - How exposure is controlled.

  • Rolling vs Global - How exposure happens. Rolling = A bit at a time, from edge to edge. Global = The entire surface of the film/sensor together.

There are four combinations:

  • Mechanical Rolling = Mechanical shutter using curtains. Since this is the most common, people refer to this as the mechanical shutter.

  • Electronic Rolling = Reads data from sensor sequentially. This is the most common electronic shutter, so people refer to it as the electronic shutter. Also referred to as the rolling shutter.

  • Mechanical Global = Leaf Shutter with iris design. This shutter type is less common, and people don't even think to refer to it at all.

    Even though the entire film/sensor area is exposed together, some may not consider this a true global shutter because light from different parts of the lens are exposed differentially, (see MichaelC's comment).

  • Electronic Global = Read data from entire sensor all at once. This is the type of shutter most people nowadays consider the global shutter.

  • You left out the earliest type of mechanical shutter - lens caps. – Michael C Feb 6 at 13:58

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