• Please use real names.

    Greetings to all who have registered to OPF and those guests taking a look around. Please use real names. Registrations with fictitious names will not be processed. REAL NAMES ONLY will be processed

    Firstname Lastname

    Register

    We are a courteous and supportive community. No need to hide behind an alia. If you have a genuine need for privacy/secrecy then let me know!
  • Welcome to the new site. Here's a thread about the update where you can post your feedback, ask questions or spot those nasty bugs!

Black background for full spectrum imaging

Asher Kelman

OPF Owner/Editor-in-Chief
I have decided to go the less troublesome route and ordered the super black paint. Since ordinary black paint was black in IR too, I hope "Black 3.0" will be as good and hopefully even better than that. In the above UV shot, exposure is 10 and a 1/3rd stops higher than in the IR shot and 11 stops higher than the unfiltered full spectrum shot, so UV response is low. Shipping from the UK and getting it through the customs here in Norway means I will expect to receive it in about one or two weeks.
Great,

I loved the challenge and I personally appreciate the topic as it stimulates new creative ideas in use of very black black

Which company brand do mid you choose?

Asher
 
Great,

I loved the challenge and I personally appreciate the topic as it stimulates new creative ideas in use of very black black

Which company brand do mid you choose?

Asher
Stuart Semple's Black 3.0.
Since I need to cover between 3 and 4 square meters, something like Vantablack will be super expensive. Black 3.0 is expensive, but not silly expensive.

 

Asher Kelman

OPF Owner/Editor-in-Chief
Stuart Semple's Black 3.0.
Since I need to cover between 3 and 4 square meters, something like Vantablack will be super expensive. Black 3.0 is expensive, but not silly expensive.

Correct! That’s what I was showing you. Please check as some of the new blacks are just for visible light spectrum.

I am going to use it on a new sculpture to make things vanish!

Asher
 

Dr Klaus Schmitt

Well-known member
Thanks for the encouragement. I should perhaps add that I bought the CoastalOpt lens used locally at a reasonable price. At first, I didn't even consider it for the second hand price, but in the end I convinced myself that I could just sell the lens after the project is completed and probably not lose much (if anything).
I was looking for a used Coastal Optics 60mm for many years!! Congrats! Where did you find it? Make sure there is no rattling inside, a Norwegian colleague har that and it turned out to be a design flaw. They fixed it after long discussions for free...
 
I was looking for a used Coastal Optics 60mm for many years!! Congrats! Where did you find it? Make sure there is no rattling inside, a Norwegian colleague har that and it turned out to be a design flaw. They fixed it after long discussions for free...
Hmmm. Design flaw? Luckily there is no rattling in my sample. I think we talked about this before, but I bought it from a Norwegian photographer in Oslo; not Birna or Bjørn Rørslett. I found it on the Norwegian site foto.no where the seller had it for sale for about a year. My sample is from after Jenoptik took over the Coastal Optical brand.
 

Dr Klaus Schmitt

Well-known member
Would be interested to hear what your results have been (as I'm planning to have some black BG in my lab) - and what you are photographing with it...
 
Would be interested to hear what your results have been (as I'm planning to have some black BG in my lab) - and what you are photographing with it...
I received the paint more than a week ago, but haven't acquired the boards I am going to paint for the background. I might end up buying some less than ideal boards in order to get on with the project. I can paint the cardboard that I posted above partly with the super black paint and take similar test shots to check how Black 3.0 does in UV, visual and IR compared to the black velour. When I have done that, I will post the test images here.
 

Dr Klaus Schmitt

Well-known member
I received the paint more than a week ago, but haven't acquired the boards I am going to paint for the background. I might end up buying some less than ideal boards in order to get on with the project. I can paint the cardboard that I posted above partly with the super black paint and take similar test shots to check how Black 3.0 does in UV, visual and IR compared to the black velour. When I have done that, I will post the test images here.
Great, I would appreciate that!
 
OK. Finally I got to paint a little of the Black 3.0 on the test item I made and took some test shots. I only applied one layer and it doesn't cover 100%, but it's enough to show the differences.

As you can see in the combined photo, the expensive matte black paint is darker in both IR and UV than both the standard black wall paint (no surprise) and very much darker than the velour in IR. The black velour is quite far from black in IR, but in UV, the velour is quite black.

Apart from the IR and UV only shots, I took two shots with unfiltered lens (Coastal Optical 60mm) with the full spectrum converted camera, producing a visual + IR image: one in moderate sunlight and one in the shadow.

The tests show that the super black paint is much more matte than the standard wall paint which is called matte, but in practice is somewhat semi glossy (silk / satin). Black 3.0 is not totally matte either, but I wouldn't blame them for calling it matte, because it's quite matte.

So, if we need a background to be as black as possible in both UV, visual and IR, the Black 3.0 is a good compromise. If we shoot in UV or just visual, however, the black velour is the blackest of the three.

web_DSC2034+36+42+44.jpg
 

Asher Kelman

OPF Owner/Editor-in-Chief
Excellent demonstration.

For outdoors, does Black #3 contain a UV blocker or will it degrade fast?

Asher
 
Well-well. I have found out that if I can avoid reflections from the ordinary (but very matte) black wall paint, it is actually blacker than the Black 3.0!!! So, the artists super black color is so mostly because it is very matte, not because its pigments are extra black. Honestly, I am a bit surprised and disappointed about that.

In order to get that extra black background, I have decided on making a kind of "light trap" by painting two large, but lightweight, smooth boards and angle them sharply (about 30 degrees) so they will reflect each other exclusively. In practice, I will need to paint an area more than twice as large, but that's fine as long as I can use standard wall paint. I will use a wide soft brush, not a paint roller, since the brush will let me control the texture of the paint surface and by that, reduce any residual reflection from the paint. I will update when I have something useful to report (like photos of the finished background setup).
 

Asher Kelman

OPF Owner/Editor-in-Chief
Perhaps make a parallel array of 6” strips set 1” apart, painted with the Matt paint and the artists black behind it!

Asher
 

Asher Kelman

OPF Owner/Editor-in-Chief
Lars,

Do you have a diagram. I can’t see how “they will reflect each other exclusively”, but I don’t doubt that you have thought it out correctly.

Asher
 
Wasn't that my proposal in post #3? 😇
[/QUOTE
Well, not exactly, but kind of. The light will go right into the light trap since it's coming from behind the camera. Your (well thought) plan implied that the lighting wouldn't go into the black box. My setup implies that it will, but since I will place the two boards at an angle, there will be no reflection (in the normal sense) since they will "reflect" each other: Black paint will reflect black paint.
 

Dr Klaus Schmitt

Well-known member
I will take a picture of the setup and post it here.
Interesting findings Lars, thanks for that. That light trap is a good idea for sure, may I use a bit different words for that:
one side of the light trap will only reflect say 2-3% of incoming light and absorb the rest 97-98%, that second sharp
angled board will then receive those 2-3% reflected light and will then also absorb 97-98% of that, so only about 0.06%
will remain, making the light trap approx. 99.94% effective

Looking forward to your drawing(s), how you finally made it then...
 
Interesting findings Lars, thanks for that. That light trap is a good idea for sure, may I use a bit different words for that:
one side of the light trap will only reflect say 2-3% of incoming light and absorb the rest 97-98%, that second sharp
angled board will then receive those 2-3% reflected light and will then also absorb 97-98% of that, so only about 0.06%
will remain, making the light trap approx. 99.94% effective

Looking forward to your drawing(s), how you finally made it then...
That approach is great, but only works well when the reflection is perfect & isn't spekular (randomly distributed). With many surfaces you'll get reflections back at the camera even when mirrored reflections go off at 90 degrees.
I suspect if velvet reflect 1% of light straight back it will still reflect 0.5% when the surface is heavily tilted.
 

Asher Kelman

OPF Owner/Editor-in-Chief
That approach is great, but only works well when the reflection is perfect & isn't spekular (randomly distributed). With many surfaces you'll get reflections back at the camera even when mirrored reflections go off at 90 degrees.
I suspect if velvet reflect 1% of light straight back it will still reflect 0.5% when the surface is heavily tilted.
I am not sure how reflection increases or decreases the apparent illumination of the light trap.

Can you either use light though a grid at say 15-20 ft distance to decrease the angles.

Or the opposite, use angled bilateral tangents for either side?

Asher
 

SurrealJiggy

New member
I have no idea about a material, but you can always get a dark background by constructing an enclosure protected from light behind the subject.
 
Btw. where did you get that Triple Black Velvet from?
Just saw your post. I am not sure what you mean by "Triple Black Velvet". If you refer to "Black 3.0" which I have mentioned, then it's the third version of Stuart Semples extra black paint (mentioned several times in this thread + links also). The black velvet I have bought is the one you recommended. As seen in my tests, it's very black in visual and UV, but not very black in IR.
 
That approach is great, but only works well when the reflection is perfect & isn't spekular (randomly distributed). With many surfaces you'll get reflections back at the camera even when mirrored reflections go off at 90 degrees.
I suspect if velvet reflect 1% of light straight back it will still reflect 0.5% when the surface is heavily tilted.
If the angle between the two boards is sharp enough (30 degrees or even less) and the surface of each side is smooth, then the light will bounce deeper and deeper into the "trap". The light that will come back will largely be determined by how black the paint is and not as much determined by its glossiness.

BTW: I have painted the boards once, but will need another layer to get the paint more even.
 

Dr Klaus Schmitt

Well-known member
Yep, I mentioned that velvet, but cannot find a source to buy it here, hence my asking...

Goood idea about that light trap!!
 
Yep, I mentioned that velvet, but cannot find a source to buy it here, hence my asking...

Goood idea about that light trap!!
I think I linked to the shop in the UK where I bought it. However, if I am not mistaken, you would prefer to buy from a German seller, right? In that case, search for D-C-Fix Self-Adhesive velours film ("selbstklebende veloursfolie"). The official homepages are www.d-c-fix.com and www.d-c-home.com
 
Top