What image is displayed for raw files

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Joined: Wed Jun 20, 2018 7:23 pm

What image is displayed for raw files

Post by ajax » Thu Nov 01, 2018 4:39 pm

It is very nice that XnViewMP displays an image for the raw files produced by my camera. Insofar as raw files have yet to be developed that causes me to be a bit curious about what is being displayed. It is my understanding that raw file formats normally contain an embedded jpg image that has been developed by the camera. I'm afraid I don't know enough to know what quality such an image might possess. However, I do know that a jpg is going to be 8 bit. Since, XnViewMP displays a message saying the file is being converted to 8 bits that implies that the embedded jpg is NOT what is being displayed. This implies, according to my understanding, that XnViewMP must do something to develop the image. Possibly this is done with some supporting software like DCraw but that would still involve the need to establish parameters to be supplied to that software which must come from somewhere.

I'd be most grateful for some elaboration about how XnViewMP creates a displayable image from a raw file.

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Re: What image is displayed for raw files

Post by cday » Thu Nov 01, 2018 5:10 pm

XnView software currently only supports 24-bit colour, so images with a higher colour depth such as 48-bit are automatically converted to 24-bit colour when they are opened, with a warning message displayed. The embedded JPEG preview in RAW files is already 24-bit colour, as you say referring to 8-bit per channel, as the JPEG format only supports 24-bit colour and grayscale.

The type of image displayed when a RAW file is opened is set in the viewer File > Format setting... -- Read tab so that setting should be checked.

I think that's about right!

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