Aw: Re: Re: Acquiring Dental RVG on Linux
> On Wed, Jan 06, 2021 at 05:13:58PM +0530, Sonali Warunjikar wrote:
> > I think distance calibration is over. Now over to other image parameters.
>
> Some observations about depth (bits per pixel):
>
> - The proprietary software is producing images with only 8 bit depth,
> throwing away half of the data (data is 12 bit + 4 filler bits) gathered
> from the sensor.
>
> - Most monitors available commercially do not support a depth > 8 anyway.
> Special purpose monitors with higher depth aren't easy to find (might be
> costly if found). Practitioners aren't seen using them anyway.
>
> - "Even for high brightness and high contrast medical displays with
> luminance range between 0.5 and 2000 cd/m2, the human observer can
> perceive no more than around 900 shades of gray" [1]
>
> This means at the most 10 bits can be relevant for human consumption.
> It's a different matter if the images are to be analyzed by software.
>
> - "The radiologists did not attest the higher grayscale resolution a
> better image quality, they regarded the 8-bit technology to show a
> better sharpness and contrast, although this had no impact on the
> detectability of details." [2]
>
> It could be that the extra grey shades result in showing more fragmented
> view which the practitioners aren't accustomed to after years of
> practice with 8 bit depth. (My speculation.) And it's not going to be
> easy to make them adapt a higher depth.
>
> So in summary, I am just going to follow the suit and throw away the first
> byte (it's little endian) and resort to 8 bit images in pyrvg software. It
> will also open up the choices of image handling software as many of even
> widely used ones do not support depths > 8.
While I think your assessment is correct (ACM senior fellow and all)
I would strongly advise against "throwing away" information.
Maybe offer for display what the needed tools can consume, but retain
the original depth as a backup. Over here it wouldn't even be legal
to discard data due to its having been obtained by means of radiation.
(It is only allowable by law to apply the minimum needed radiation
dose. If I can throw away bits that can be construed to mean that
medically I could have gotten away with a lower dose.)
Karsten
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