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MAF3 with Cross Polarization Filter and external ligth

  • TT

    You built this with the THREE API? If so, that is impressive indeed! 

  • CG

    Here some new results from texture image capturing in comparison to ...

    • Out of box (using projector as light source, no CP filter) with 3x images and HDR creation.
    • With external light, without Cross Polarization. 3x images and HDR creation.
    • With external light (polarized) and Cross Polarizing filter in front of left camera. 3x images and HDR creation.

    It proves again that even with additional light the dynamic range from the MAF3 camera is not enough to propperly capture light and dark areas with one single shot. HDR with 3x images completely changes the situation which is improving the image quality a lot!

    HDR with "out-of-box" situation (only projector used as light source, no external lights, no filter) is a real game changer. And this require just simple software implementation, without the need for any additional HW or modification.

    With the use of external light and HDR the image quality is further improving. But as said, also here HDR is needed because of low dynamic range of cameras. If reflections on glossy surface is not a problem than this aproach provides excellent (maybe best!) results. Using light box with only small holes for cameras could also help to eliminate reflections.

    When using external light with cross polarization lot of light is getting lost and also here HDR is absolutely mandatory. But the final HDR image is almost completely without reflections. For glossy and shiny surface this is the best soluton from my pov.

    In the tests i have used only one external light source place on the left side of the MAF3. To optimize the shaddows it's better to use two external lights, one right another left.

    Here the results:

    HDR with out-of-box image capturing:

    HDR with external light, no filter:

    HDR with polarized external light and CP filter in front of left MAF3 camera (cross polarization!):

    Which image you like most? Feedback very much appreciated.

  • JP

    @Christian Gassner 
    This idea and execution is superb. I can see clearly different between settings.

    Basic HDR setup has overcome tiny Sony sensor's DR limit some amount,

    then HDR + External light : probabaly due to MAF Three's projecting light's CRI quality is limited, hence external light (usually CRI 90 to 95) shows alot better color rendering which is closer to real life color.

    Last, HDR + External light + linear polarizing filter : previous two setup still shows direct reflection, especailly Basic HDR (from single spot light source). But magic of linear polarizing, this setup is definately the best. But HDR + external setup is very nice in general. ofc Basic HDR setup is alot better than stock color rendering. 

    Big thanks for your idea and example, also thanks for your 3d stl file of polarizing filter for the Three.

  • CG

    @JP

    Many thanks for positive reply! Such feedback is good motivation to proceed sharing the results here.

    Meanwhile i switched to more powerfull LED light (2x Godox LDP18bi).

    Thanks to cross polarization, even with such powerfull LED lights, there is almost zero reflection on the object. Texture quality with cross polarization is just amazing! I mean when you see this texture later rendered with reflection and shadows in Blender you will be blown away! 

  • CG

    Hardware setup and API control SW is almost finalized.

    For the comparison i used an apple which can be quite reflective what can be seen from the images with out-of-box setup.

    MAF3 out-of-box texture (texture not bad, but color look quite pale without dynamic. White spot reflections clarly visible, especially at the back side.)

    MAF3 with Cross Polarization and HDR (texture with dynamic colors, much more realistic to the real apple)

    And finally comparison with Photogrammetry using DSLR with cross polarization ring flash.

    The DSLR texture is extremely close to the real apple because setup is color calibrated.

    LEFT = MAF3 out-of-box texture

    MIDDLE = MAF3 with CP + HDR

    RIGHT = Photogrammetry with DSLR and CP Ring Flash

    Do you think it's worth to use HDR + CP on MAF3 ???

    What's your opinion?

  • JP

    @Christian Gassner it's huge different, especially if someone just use MAF3 to capture texture. Glad to see bigger sensor camera's similar condition (cross filtered and well lighted)! Obviously bigger sensor has anyway better color depth, and DR, but MAF's improved texture is nice enough to use it!
    If you happen to share your valuable API, I would glad to try it. Great job throughout months. 

  • CG

    @J P I am open to share but all the code is also depending on specific HW setup. I have made custom PCB to trigger movement of liniear actuator in front / away of left camera. This is getting controlled by http get commands via API and the use of shelly product. Also LED light off/on controlled by shelly power plug. The HDR image download to my server and processing on Windows PC is somehow specific to my HW.

    If you want to try only HDR without cross polarization you can simply make 3x scans with different aperture settings. Download the project on Windows PC and process the 3x images into one HDR image. This one you use and replace with image from the first scan, update the zip archive and import into MAF3 again.

     

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