11-22-2019, 02:20 AM
(This post was last modified: 11-22-2019, 02:24 AM by marco-gimp.)
Light absorption test - Is it possible using Gimp?
I have just received 150 ml of Black 3.0
... the blackest of all blacks outside of nano-tubes.
The idea is to use it for flocking a telescope, as a one stop solution.
A black paint is anyway required for blacking the lens edges
... but it might replace the need to line the scope with black material.
... also, it can cover the places where material flocking is not possible, such as inside the focus tube.
... and it can be applied to cloth.
The concept is, that stray light cannot bounce down the inside of the scope tube.
Flocking is required; so why not Black 3.0 (3.2 revision)?
YouTube Tests
The YT tests were mostly very poor.
Typically, the testers hadn't even read the instructions.
Most were artists (I guess we can forgive them), but even a photographer for business, with a highly organised setup ... no ... didn't read the instructions
... which were:
(obviously a dark undercoat would be sensible - Black 2.0 is recommended)
One chap did paint a model human head, first with Black 2.0 and then Black 3,0
The result was quite remarkable.
He rotated the head, and it wasn't possible to know which way it was turning!
In a second video, he used a mobile phone luminance app, to attempt to measure reflected light.
However, the numbers were all over the shop - the camera software was modding the ISO, and the camera was being waved (causing a shadow) by hand, over differing samples.
A light absorption figure was produced, but hey ... in truth, the results were meaningless, from a perspective of the quoted precision.
It was a 'good fun' test, with an interesting twist at the end - 11.6m views and counting, so he certainly got the concept right.
I thought of Gimp
A set of sample cards, of different blacks and prep methods.
- Create a black enclosure, with a side opening for a light source, and a top opening for a camera lens.
- Place a card in a set position.
- Photograph each card, with the camera adjustment locked.
- Compare to an image of the closed enclosure
Presumably, the images taken under lit conditions, will be lighter.
The camera can save in raw, or 100 jpg (is this raw, but in jpg format?)
What tool should I use, to analyse the difference between the different samples, and total darkness?
... something that can give me a number, to indicate total reflected light.
(currently using 2.8)
I have just received 150 ml of Black 3.0
... the blackest of all blacks outside of nano-tubes.
The idea is to use it for flocking a telescope, as a one stop solution.
A black paint is anyway required for blacking the lens edges
... but it might replace the need to line the scope with black material.
... also, it can cover the places where material flocking is not possible, such as inside the focus tube.
... and it can be applied to cloth.
The concept is, that stray light cannot bounce down the inside of the scope tube.
Flocking is required; so why not Black 3.0 (3.2 revision)?
YouTube Tests
The YT tests were mostly very poor.
Typically, the testers hadn't even read the instructions.
Most were artists (I guess we can forgive them), but even a photographer for business, with a highly organised setup ... no ... didn't read the instructions
... which were:
- Use an undercoat
- mix with water
- apply multiple thin coats
(obviously a dark undercoat would be sensible - Black 2.0 is recommended)
One chap did paint a model human head, first with Black 2.0 and then Black 3,0
The result was quite remarkable.
He rotated the head, and it wasn't possible to know which way it was turning!
In a second video, he used a mobile phone luminance app, to attempt to measure reflected light.
However, the numbers were all over the shop - the camera software was modding the ISO, and the camera was being waved (causing a shadow) by hand, over differing samples.
A light absorption figure was produced, but hey ... in truth, the results were meaningless, from a perspective of the quoted precision.
It was a 'good fun' test, with an interesting twist at the end - 11.6m views and counting, so he certainly got the concept right.
I thought of Gimp
A set of sample cards, of different blacks and prep methods.
- Create a black enclosure, with a side opening for a light source, and a top opening for a camera lens.
- Place a card in a set position.
- Photograph each card, with the camera adjustment locked.
- Compare to an image of the closed enclosure
Presumably, the images taken under lit conditions, will be lighter.
The camera can save in raw, or 100 jpg (is this raw, but in jpg format?)
What tool should I use, to analyse the difference between the different samples, and total darkness?
... something that can give me a number, to indicate total reflected light.
(currently using 2.8)