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HermannSW
Posts: 2386
Joined: Fri Jul 22, 2016 9:09 pm
Location: Eberbach, Germany
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camera filters / welding helmet safety glass

Sat May 23, 2020 10:49 pm

I have ND2/ND4 filter that let 0.01/0.0001 light through.
I used ND4 filter successfully for 200s long exposure of bright smartphone analog clock:
viewtopic.php?f=43&t=273358#p1660315

I placed ND4 filter over 5000lm led and light is still by far too bright for human eye.

I did smartphone photos through welding helmet safety glass before:
viewtopic.php?f=37&t=267999&p=1639428&h ... t#p1639428

Today I used HQ camera and "--focus" feature to bring 5000lm led in focus.
Then I placed welding helmet safety glass between camera and 5000lm led, and turned led on.
This is screenshot of camera preview with Field Of Merit display.
I am visible since safety glass does reflect.
snapshot.png.jpg
snapshot.png.jpg
snapshot.png.jpg (48.41 KiB) Viewed 168 times

I have no idea what ND? number welding safety glass has, must be a big number.
With reduced 200µs shutter time the 50 leds can be identified through safety glass:

Code: Select all

raspistill --focus -t 0 --shutter 200
snapshot.png.2.jpg
snapshot.png.2.jpg
snapshot.png.2.jpg (35.46 KiB) Viewed 168 times
https://stamm-wilbrandt.de/en/Raspberry_camera.html
https://stamm-wilbrandt.de/en#raspcatbot
https://github.com/Hermann-SW/raspiraw
https://github.com/Hermann-SW/Raspberry_v1_camera_global_external_shutter
https://stamm-wilbrandt.de/github_repo_i420toh264

nicolap8
Posts: 490
Joined: Mon Mar 13, 2017 9:45 pm

Re: camera filters / welding helmet safety glass

Sun May 24, 2020 4:25 pm

HermannSW wrote:
Sat May 23, 2020 10:49 pm
I have ND2/ND4 filter that let 0.01/0.0001 light through.
Hi Hermann,
read the table https://en.wikipedia.org/wiki/Neutral-density_filter
you have an ND2, not an ND2.0 :)
I think that the Deutsch page has a wrong table, bringing to confusion.
N

User avatar
HermannSW
Posts: 2386
Joined: Fri Jul 22, 2016 9:09 pm
Location: Eberbach, Germany
Contact: Website Twitter YouTube

Re: camera filters / welding helmet safety glass

Sun May 24, 2020 5:15 pm

Thanks nicolap8 for correcting me.
Yes, the German page is confusing.
I do have ND2 and ND4 filters, and they only provide 0.5/0.25 fractional transmittance (not 0.01/0.0001).

I found old thread on my welding helmet:
viewtopic.php?t=215560
Currently I use shade 9.
Please note that shades greater than 7 require a face shield
filters+safety_glass.jpg
filters+safety_glass.jpg
filters+safety_glass.jpg (39.98 KiB) Viewed 80 times
https://stamm-wilbrandt.de/en/Raspberry_camera.html
https://stamm-wilbrandt.de/en#raspcatbot
https://github.com/Hermann-SW/raspiraw
https://github.com/Hermann-SW/Raspberry_v1_camera_global_external_shutter
https://stamm-wilbrandt.de/github_repo_i420toh264

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