Dear DAVID Community,

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HDR

You can post your wishes for new features in future program versions here.

HDR

Postby Experimentator » Sun Jan 18, 2015 4:30 pm

Modern CCTV cameras can shoot HDR video. For example one camera on latest Sony sensor can shoot at 120 fps were each 4 sequential frames shoot with different exposures (for exampe 1st - 1/120, 2nd - 1/240, 3rd - 1/480, 4th - 1/960) and then compute it to 30 fps HDR video in real time. You can add such ability for any camera that David support.

This will allow not only simultaneously scan bright and dark areas of object, but also will give much better noise reduction than current method (just summing images at the same exposure), because stripes of patterns have dark areas that with this method will be shoot at longer exposure and much more clearer.

For most purposes probably would be enought 3 frames - 1st at 1/60, 2nd at 1/30, 3rd at 1/15. But of course the best to give user choice how many exposures take for one resulting frame and how far each exposure should be from another. Algorithm of making HDR image from series of usual images very simple so I will not describe it here.

Here you can see HDR camera in action https://www.youtube.com/watch?v=ygcm0AQXX9k
Attachments
HDR.jpg
Sentech STC-MCA5MUSB3 monochrome 5mp, Pentax H1214-M 12mm, Acer XD1270D 1024х768 (removed colour wheel).
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Re: HDR

Postby Experimentator » Tue Jan 20, 2015 10:28 pm

Also I suppose it will eliminate problem of false relief on objects with contrast textures (for example black text on white paper).
Sentech STC-MCA5MUSB3 monochrome 5mp, Pentax H1214-M 12mm, Acer XD1270D 1024х768 (removed colour wheel).
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Re: HDR

Postby mr_cg » Fri Sep 11, 2015 6:26 pm

HDR is contradicting for structured light scanning.
At the beginning i was also thinking that HDR would bring much benefit but this is clearly not the case.

I was doing tests with image grabber and created HDR images before loading into DAVID4.
3 Images .... +2EV, 0EV, -2EV ... for every pattern. Postprocessing was done with SNS-HDR.

Clear reslut was ... HDR is bad for structured light scanning.
The algorithm from HDR is to have all areas from the image bright (visible).
But this is exactly what is not good for structured light scanning.
DAVID4 Pro v4.3.6 (64bit) - david-cam-3.1-m - IDS UEYE UI-1540-M - Canon EOS 600d (Canon Lens: EF-S 18-135 IS) - Acer K135i Projector + 37mm Close-Up Lens
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