Scaning shining and metal artifacts

Hi again @nebulousflynn, thanks and sorry for the delay!

It was made under studio lighting conditions, which are very good for this matter. As I’ve seen in your twitter, you did too.

3-D Laserscanning Antiglare Spray (Helling, Germany). Or any other equivalent.

I came across a spray used in conservation inspection processes that dissipates after a while but unfortunately I forget the name of it … will ask our conservation department. It’s primary function wasn’t to reduce reflections, but it was a handy characteristic with the benefit of being temporary. i haven’t done many shiny objects, but one strategy I employ if to take many more photographs at small increments. This allows for better local detail as the reflections don’t change the appearance of the surface as much

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@port0228 what product do you use to cut down on the shine of lithics? Would it be suitable for ceramics and other more delicate objects?

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I’m actually currently working on this issue for a presentation at the upcoming CAA conference in Oslo! Specifically, we’re comparing different coatings as well as different scanning methods (i.e. structured light vs. photogrammetry) for use with obsidian artifacts, which are frustratingly both shiny and clear.

Normally, for lithics I use developer spray. This is what I used to coat my core models from Les Cottés, and what my colleagues and I published in our recent paper in Advances in Archaeologial Practice (you can download the article from my website here). I would definitely not advocate using this on ceramics, or anything that is porous. It needs to be cleaned off with water. Furthermore, it contains some acetone. Again, not a big deal for stone tools (although we commonly do have to re-label artifacts after use) but possibly a big problem for most other things.

Recently, we’ve had some good luck with dulling spray (see model below). However, this stuff only works with structured light scanning, and not photogrammetry. We also wouldn’t really recommend using any of these coatings on objects that may have residues, or that will be subject to any type of chemical analysis.

The next thing we’d like to try is cross-polarized photography. Anyone here have any experience with that?

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Depending on the material, and if geometry only is required I’ve referred a few people at work to the 7T MRI scanner at our uni. Unfortunately didn’t work for “potted” specimens in formalin.

I’ve seen a few samples using cross polarisation and it works well if you have the flash power. Used to use it on our copystand for all reprography.

@NestorMarques @lapin @uomdigitisation thanks for tips! @port0228 - what a great model, very cool :sparkles:

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@otto_bagi just shared this video of @port0228’s CAA presentation over on this thread, thought it best to share here too - very interesting and thorough research!

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I was experimenting with the team in the Institute with cross polarisation and I must say it works pretty well.

This setup, in effect, cuts off almost all surface reflections, although, it requires a bit of work with the shader on sketchfab to get back the original appearance of the object.

Also, the photographing can be time consuming but this depends on the strength of the light you use. Since the polarising sheets cut off a fair amount of the light, in this particular case we had to use 8-10 sec shutter speed to compensate, but I think the final result had made that 5 sweaty hours in the studio in 35C worthwile. :slight_smile:

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James Busby wrote a detailed tutorial on scanning reflective surfaces and shared with everyone. At the end of the tutorial there is a link to download the scene of the lesson.
A big thank you James!

3D Scanning Reflective Objects With Photogrammetry
By James Busby

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@lapin that’s a great tutorial! Thanks for passing it along. As the author notes in his intro, it’s not likely to help with expensive or historical objects that can’t be covered in matte-ing (matting?) agents, but it’s an extremely useful tutorial nonetheless. :slight_smile:

I’ve heard that some people use talc to make shiny objects less shiny. I haven’t tried though.

@uomdigitisation I guess the name is Cyclododecane.

Hello very nice scan. thank you for sharing with us. we have problems with scanning of reflective historical objects. could you pleas help us to deal it?

Hello. thank you for sharing. Could you pleas give more information?

removing the background is necessary for Photoscan to process images captured with a turntable. I used photoshop actions to batch select the background and delete (mask) it.

@otto_bagi does this same lighting set up work with a large object? My task is scanning a large animal sculpture made out of shiny stainless steal knives, forks and spoons welded together. It’s about 5 feet long. I am assuming the only light in the studio should be totally controlled/just coming from polarized lamps or flash? I have a ring light that I have fitted with a polarized sheet but I think it’s not quite doing the trick. My other question is about the fact that the metal looks almost black when the glare its taken out from cross polarization. Is this an issue?

Trying to get a tight 3-d model for 3d printing, no color/texture necessary.

Hi, the size doesn’t really matter as long as you can keep the whole object in a controlled environment. A bunch of shiny cutlery welded together? Sounds like you’re ahead of a few sleepless nights. :slightly_smiling_face: Cross-polarization will not solve your problem entirely, it might help somewhat but you will have to correct the geometry in post-processing. It would perhaps worth to ask if you can coat the object with powder spray. As of the colour, you are right, cross-polarized lights will turn silver or stainless steel black, or almost black, but you can get back the original look with shaders.

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I assume you didn’t mount the ring light on the camera but had it on a stand? You need to be able to control the angle between the cross-polarized light and the camera lens for the best result. Also, you might need to consider getting something a bit more powerful, cause as I mentioned earlier, the filter cuts of quite a big chunk of the light which can make photographing rather tedious.