Aperature Questions

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Tru3DScans
Posts: 12
Joined: 19 Nov 2017, 19:14

Aperature Questions

Post by Tru3DScans »

OK, so I've got a problematic object with a glossy black surface on the outside and brush metal surface on the inside.

I know that one major improvement is to coat the object to reduce reflections and matte the surface. But talcum powder is all I have at the moment until I get other supplies.


I'm wondering about aperture. Let's say that I have my object on the turntable and will be doing 8 scans. I set my aperture prior to scanning. The scan starts and scan1 completes. Then the turntable rotates to a different angle for scan2 and now there are different shiny areas showing different brightness than in the scan1 position. The aperture is no longer set correctly as the curves are now cropped in several areas. Likewise on scan3, etc.

Since there are 8 distinct scans to be done, seems like you would either set 8 distinct aperture settings or you would pre-rotate through the 8 scan rotations and find the 'worst shiny' orientation and set the aperture for the worst case scan and all other scans would use that aperture.

I realize that if this object was a matte surface with no offending shiny areas... one aperture would fit all scans easily. I've seen video tutorials that say it is OK to adjust ONLY aperture prior to each scan. Is this not correct?

If it is OK to adjust aperture prior to each scan, then the automatic turntable scanning won't work as there is not enough time to adjust aperture prior to scanning automatically starting. I guess I would have to use manual scanning (to give myself enough time to adjust aperture prior to scan start) and use the turntable control to rotate the turntable. (One problem with this is that the HP turntable control doesn't seem to allow input of certain rotation values. I had an automatic scan setup to do 10 scans - 36 degrees each rotation - and the turntable control wouldn't take the 36 degree value... maybe I was doing something wrong).

How do you handle aperture?

Thanks for any ideas!
Mike

HP 3D Scan Pro, Dual-Camera, turntable, arm, pitch-black room
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Micr0
Posts: 586
Joined: 15 Nov 2016, 15:20
Location: New York City

Re: Aperature Questions

Post by Micr0 »

Don't change the aperture. It will throw off your calibration. If you need to change the exposure, do it via the projector brightness slider.
µ
Tru3DScans
Posts: 12
Joined: 19 Nov 2017, 19:14

Re: Aperature Questions

Post by Tru3DScans »

Thanks very much for this info!

The video tutorial must have been incorrect as it said the aperture was the only setting that could be changed after calibration.

So in the case of using the Projector Brightness to adjust exposure... I wish the automatic turntable scanning had the ability to pause between scans so that the user could adjust projector brightness before the next scan starts. (When the automatic turntable scanning is in progress, I wouldn't know when it would be safe to adjust the projector brightness).

Thanks again.
Mike

HP 3D Scan Pro, Dual-Camera, turntable, arm, pitch-black room
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