A Comparison of David and Artec Eva

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letstry001
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Joined: 27 Jan 2020, 09:06

Re: A Comparison of David and Artec Eva

Post by letstry001 »

Ok next week will modify the mount point of the cameras, (power of prusa mk3s) and the i will come back.
Ps: in your opinion what is the better chouce: to get a more close distance cameras-projector (es: cameras angle 15 degreese ) or give a less strict camera angle (es: 25 degrees)?
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Micr0
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Location: New York City

Re: A Comparison of David and Artec Eva

Post by Micr0 »

letstry001 wrote: 30 Oct 2020, 20:32 Ok next week will modify the mount point of the cameras, (power of prusa mk3s) and the i will come back.
Ps: in your opinion what is the better chouce: to get a more close distance cameras-projector (es: cameras angle 15 degreese ) or give a less strict camera angle (es: 25 degrees)?
David doesn't like camera angles that are too shallow. It introduces error, especially around sharp edges. Too large and you lose parts of the projected image that the camera can see. This makes scanning negative space more difficult.
µ
letstry001
Posts: 12
Joined: 27 Jan 2020, 09:06

Re: A Comparison of David and Artec Eva

Post by letstry001 »

hi, Micr0

In a previous post you typed "I thought about picking up an AXXA P5..."
Why not a aaxa p7 ?

Some other questions about projector choice:
1) high Contrast in projector specs = images with better details? Es: 2000:1 vs 150000:1
2) Generally It is better "low resolution" projector (720p) and near focus distance (20cm) or "far" object (40cm) but "hi resolution" projector (full hd)
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OBNRacerMan
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Location: Obninsk, Russia

Re: A Comparison of David and Artec Eva

Post by OBNRacerMan »

150,000: 1 is the "marketing" dynamic contrast ratio. You should not be distracted by it when choosing a projector.
The closer the projector is to the subject, the shallower its depth of field, but also the higher the pixel density.
Also, when the projector and cameras approach the object, the illuminated / visible surface decreases (in the sketch - on the right).
Modern projectors tend to decrease the projection ratio, as a result of which, from the same distance, the density of the pixel grid can be almost the same as with an HD projector and throw rate 1.6 and FullHD c throw rate 1.2 (in the sketch - on the left)
throw_rate.jpg
letstry001
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Joined: 27 Jan 2020, 09:06

Re: A Comparison of David and Artec Eva

Post by letstry001 »

Ok, so, what are the parameters to consider ?

1) Throw Ratio
2) Resolution

What are other needed parameters ?

Color Processing? (es 8bit,10bit....)
Throw Distance ?
....
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OBNRacerMan
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Location: Obninsk, Russia

Re: A Comparison of David and Artec Eva

Post by OBNRacerMan »

letstry001 wrote: 04 Nov 2020, 14:51 Ok, so, what are the parameters to consider ?

1) Throw Ratio
2) Resolution

What are other needed parameters ?

Color Processing? (es 8bit,10bit....)
Throw Distance ?
....
It is highly desirable that the throw ratio be at least 1: 1.4 (however, now most modern projectors have 1: 1.2 or even 1: 1.1). Also, according to unverified information, projectors using pixelshift to obtain FullHD resolution from a 1380x768 matrix produce a rather "blurry" picture (this does not matter for watching movies, but not very good for a scanner).
The brightness of the projector (preferably) must be at least 500ANSI Lumens
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Micr0
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Location: New York City

Re: A Comparison of David and Artec Eva

Post by Micr0 »

OBNRacerMan wrote: 27 Nov 2020, 08:04
letstry001 wrote: 04 Nov 2020, 14:51 Ok, so, what are the parameters to consider ?

1) Throw Ratio
2) Resolution

What are other needed parameters ?

Color Processing? (es 8bit,10bit....)
Throw Distance ?
....
It is highly desirable that the throw ratio be at least 1: 1.4 (however, now most modern projectors have 1: 1.2 or even 1: 1.1). Also, according to unverified information, projectors using pixelshift to obtain FullHD resolution from a 1380x768 matrix produce a rather "blurry" picture (this does not matter for watching movies, but not very good for a scanner).
The brightness of the projector (preferably) must be at least 500ANSI Lumens
I'll second the concern with the projector throw. The AAXA I just got is 1: 1.2 and it is a problem with the camera lenses I have. With that short a throw, I seem need much wider focal length lenses. Wide lenses cause distortion to the image unless you buy the expensive ones. The other option is to mount the cameras further back but that make their mount more complicated as (in my cases) they may need to be almost completely behind the projector.
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