Some tests on different diffuser materials
May 25, 2022 14:35:13 #
Sorry that this is verbose, but maybe some are interested.
I have been playing around with new diffuser designs, and along the way I’ve been testing different materials for diffusion. What is especially wanted is a material that resists giving a “hot spot” in the center of the light, since what I really want out of life right now is to have less of that. Here are results of tests of different materials that are commonly used for diffusion.
The simple rig used in these tests is shown first. Different diffuser material was hung in front of an LED light, and the illuminated area was photographed by focusing on the diffuser surface. Of course the results will be affected by the camera settings, but I used settings that matched what I commonly use in flash photography (f/14, 1/160 sec, ISO 200). Also, distances from the light to the diffuser material, and from the diffuser to the lens are in the ballpark of what I might be using. An external flash would be a much more powerful light source, even at low power settings, but what I’m doing here is making side by side comparisons to see how well one diffuser spreads the light away from the center in comparison to the others. With great diffusion you also get great loss of light (probably), but one thing at a time.
DiffusionTest Rig by Marcoli Sturtevantione, on Flickr
Anyway, here are some diffuser materials. From left to right they are:
1. Translucent milk jug plastic.
2. Vellum tracing paper. This is NOT ordinary tracing paper. It is very smooth and fairly durable even if its paper. Some of the best in the hobby use this stuff.
3. Flexible kitchen cutting board. This is another popular thing to use for diffusion. This stuff is also durable and can be cleaned. It also won’t tear. I can provide a brand name if someone wants it.
4. Photographic diffusion sheet. This particular one was “Roscolux #118 ¼ stop tough white”. It is pretty similar to the vellum paper in look and feel, but it is more tear resistant but also more expensive. There are many varieties of these diffusion sheets that photographers use. Some diffuse more, and some diffuse less, and its certainly possible that there is one that is better. Here is a bunch of them if you are curious: https://us.rosco.com/en/products/catalog/roscolux
Diffuser materials 1 2 3 4 by Marcoli Sturtevantione, on Flickr
And here are the results in the same order:
Test results by Marcoli Sturtevantione, on Flickr
There is lately interest in the ‘wunderstuff’ found inside of LCD screens such as laptops and flat screen tvs. These are a series of thin plastic layers that diffuse the lighting in these screens. Here is a detailed exploration about these layers (although its not about photography): https://www.youtube.com/watch?v=8JrqH2oOTK4. Here, a hobbyist macrophotographer learns how to make very good diffuser with this stuff: https://photography-on-the.net/forum/showthread.php?t=1525737&page=2
I had an ancient laptop computer laying around, so I cracked it open and found 3 different layers that are indeed quite interesting candidates for diffuser material.
Here are the layers that I found:
5. A thin layer. Similar to vellum but this is plastic rather than paper.
6. A much thicker layer.
7. The “Fresnel lens” layer. This was reflective, like a mirror, while also letting light thru. But what was weird is that what you see coming thru is distorted and displaced.
Diffuser materials 5 6 7 by Marcoli Sturtevantione, on Flickr
And here are their results in the same order:
DiffuserTests2 by Marcoli Sturtevantione, on Flickr
Some closing remarks:
I feel like the vellum paper was perhaps best at giving me what I wanted (no hot spot), under these conditions, while the Roscolux and thin LCD screen were close 2nds. Truth be told most of the other diffuser materials would also work, provided that one fiddles with distances and camera settings and of course flash power. Distance is a huge effector of how well a diffusing material is seen to work. I can make hot spots with vellum. I can cancel the hot spot from the cutting board.
There is another well regarded diffuser material called ¼ stop China White Silk. It might make it easier to reach the Ultimate in Diffusion (although I do think other materials can compete if you work at it). But the China White Silk is a bit expensive and I’m reluctant to buy yet another thing that I wind up not using. Here is some if you are curious: https://www.bhphotovideo.com/c/product/73423-REG/Westcott_1931_Scrim_Fabric_Only.html/?ap=y&ap=y&smp=y&smp=y&lsft=BI%3A514&gclid=Cj0KCQjw1ZeUBhDyARIsAOzAqQJJe18QIJrBrEdGWB3qUQ8kfF3FXKCKo8lOWo-Oz-ZPN6XgiMHjJSwaArQREALw_wcB
Of course one can (and likely should) use more than one diffuser layer to increase diffusion and cut back on any central hot spot. One gets the most benefit from this by separating the diffusion layers.
People who are really good at this sort of thing write often about various parameters. Having a big diffuser surface is said to be helpful. But also bringing the diffuser layer close to the subject is a big benefit, and this effectively makes the diffuser bigger to the subject (so you don’t necessarily need a big diffuser). That makes sense since any brightened center to the diffuser effectively becomes the entire diffuser front for the subject if its very close. One mainly adjusts settings to have that area not be blown out. Working closer than 1:1 makes things easier, and smaller camera sensors makes things easier too. So I've heard, anyway.
As shown in the video above, a Fresnel lens keeps light from diverging They are also a popular kind of pocket lens that can be used to focus light. You can read fine print, or start a fire with one that you keep in your wallet. But did you know that the front of your flash has a Fresnel lens? That clear plastic cover on the front, with the fine concentric grooves – that is a Fresnel lens and its working to keep light from your flash from spreading out! I wonder if removing it would be a net benefit for dispersing the light. Maybe it could be replaced with something that spreads out the light without blocking it. Whether or not that is done, I’m curious about trying this little doo-dad to spread out the light: https://www.amazon.com/dp/B002I7PWXI/?coliid=I17EOH76GORJK1&colid=1V6SX5W6Z17J6&ref_=lv_ov_lig_dp_it&th=1, or even a clear plastic dome light cover normally used for interior lights in a car.
The search continues ...
I have been playing around with new diffuser designs, and along the way I’ve been testing different materials for diffusion. What is especially wanted is a material that resists giving a “hot spot” in the center of the light, since what I really want out of life right now is to have less of that. Here are results of tests of different materials that are commonly used for diffusion.
The simple rig used in these tests is shown first. Different diffuser material was hung in front of an LED light, and the illuminated area was photographed by focusing on the diffuser surface. Of course the results will be affected by the camera settings, but I used settings that matched what I commonly use in flash photography (f/14, 1/160 sec, ISO 200). Also, distances from the light to the diffuser material, and from the diffuser to the lens are in the ballpark of what I might be using. An external flash would be a much more powerful light source, even at low power settings, but what I’m doing here is making side by side comparisons to see how well one diffuser spreads the light away from the center in comparison to the others. With great diffusion you also get great loss of light (probably), but one thing at a time.
DiffusionTest Rig by Marcoli Sturtevantione, on FlickrAnyway, here are some diffuser materials. From left to right they are:
1. Translucent milk jug plastic.
2. Vellum tracing paper. This is NOT ordinary tracing paper. It is very smooth and fairly durable even if its paper. Some of the best in the hobby use this stuff.
3. Flexible kitchen cutting board. This is another popular thing to use for diffusion. This stuff is also durable and can be cleaned. It also won’t tear. I can provide a brand name if someone wants it.
4. Photographic diffusion sheet. This particular one was “Roscolux #118 ¼ stop tough white”. It is pretty similar to the vellum paper in look and feel, but it is more tear resistant but also more expensive. There are many varieties of these diffusion sheets that photographers use. Some diffuse more, and some diffuse less, and its certainly possible that there is one that is better. Here is a bunch of them if you are curious: https://us.rosco.com/en/products/catalog/roscolux
Diffuser materials 1 2 3 4 by Marcoli Sturtevantione, on FlickrAnd here are the results in the same order:
Test results by Marcoli Sturtevantione, on FlickrThere is lately interest in the ‘wunderstuff’ found inside of LCD screens such as laptops and flat screen tvs. These are a series of thin plastic layers that diffuse the lighting in these screens. Here is a detailed exploration about these layers (although its not about photography): https://www.youtube.com/watch?v=8JrqH2oOTK4. Here, a hobbyist macrophotographer learns how to make very good diffuser with this stuff: https://photography-on-the.net/forum/showthread.php?t=1525737&page=2
I had an ancient laptop computer laying around, so I cracked it open and found 3 different layers that are indeed quite interesting candidates for diffuser material.
Here are the layers that I found:
5. A thin layer. Similar to vellum but this is plastic rather than paper.
6. A much thicker layer.
7. The “Fresnel lens” layer. This was reflective, like a mirror, while also letting light thru. But what was weird is that what you see coming thru is distorted and displaced.
Diffuser materials 5 6 7 by Marcoli Sturtevantione, on FlickrAnd here are their results in the same order:
DiffuserTests2 by Marcoli Sturtevantione, on FlickrSome closing remarks:
I feel like the vellum paper was perhaps best at giving me what I wanted (no hot spot), under these conditions, while the Roscolux and thin LCD screen were close 2nds. Truth be told most of the other diffuser materials would also work, provided that one fiddles with distances and camera settings and of course flash power. Distance is a huge effector of how well a diffusing material is seen to work. I can make hot spots with vellum. I can cancel the hot spot from the cutting board.
There is another well regarded diffuser material called ¼ stop China White Silk. It might make it easier to reach the Ultimate in Diffusion (although I do think other materials can compete if you work at it). But the China White Silk is a bit expensive and I’m reluctant to buy yet another thing that I wind up not using. Here is some if you are curious: https://www.bhphotovideo.com/c/product/73423-REG/Westcott_1931_Scrim_Fabric_Only.html/?ap=y&ap=y&smp=y&smp=y&lsft=BI%3A514&gclid=Cj0KCQjw1ZeUBhDyARIsAOzAqQJJe18QIJrBrEdGWB3qUQ8kfF3FXKCKo8lOWo-Oz-ZPN6XgiMHjJSwaArQREALw_wcB
Of course one can (and likely should) use more than one diffuser layer to increase diffusion and cut back on any central hot spot. One gets the most benefit from this by separating the diffusion layers.
People who are really good at this sort of thing write often about various parameters. Having a big diffuser surface is said to be helpful. But also bringing the diffuser layer close to the subject is a big benefit, and this effectively makes the diffuser bigger to the subject (so you don’t necessarily need a big diffuser). That makes sense since any brightened center to the diffuser effectively becomes the entire diffuser front for the subject if its very close. One mainly adjusts settings to have that area not be blown out. Working closer than 1:1 makes things easier, and smaller camera sensors makes things easier too. So I've heard, anyway.
As shown in the video above, a Fresnel lens keeps light from diverging They are also a popular kind of pocket lens that can be used to focus light. You can read fine print, or start a fire with one that you keep in your wallet. But did you know that the front of your flash has a Fresnel lens? That clear plastic cover on the front, with the fine concentric grooves – that is a Fresnel lens and its working to keep light from your flash from spreading out! I wonder if removing it would be a net benefit for dispersing the light. Maybe it could be replaced with something that spreads out the light without blocking it. Whether or not that is done, I’m curious about trying this little doo-dad to spread out the light: https://www.amazon.com/dp/B002I7PWXI/?coliid=I17EOH76GORJK1&colid=1V6SX5W6Z17J6&ref_=lv_ov_lig_dp_it&th=1, or even a clear plastic dome light cover normally used for interior lights in a car.
The search continues ...
May 25, 2022 14:52:38 #
May 25, 2022 16:11:23 #
i gave up the search a long time ago,i have been using vellum paper for several years.i hope you find something better, that would be great!
May 26, 2022 06:08:42 #
We need to know our equipment, it is beyond the camera and lens. You have given us a well-documented basis for creativity. Well documented and presented mark, said this old scientist dpullum.
May 26, 2022 11:29:51 #
Mark Sturtevant wrote:
Sorry that this is verbose, but maybe some are int... (show quote)
Diffusion of light is a big deal to me when I shoot. I have used just about everything you have minus the LCD screens but plus Fong flash type diffusers, etc. And being a board-working artist I have long used vellum. Bouncing a light off a wall instead of the ceiling is often overlooked too. Thanks for the compilation of your research.
May 26, 2022 13:27:46 #
Mark, I am an avid follower of your posts and words fail me to express the influence it has had on me. I perceive diffusion to be akin to the search for the "Holy Grail". Each time that I believe that I am getting close, I realize that I have a long way yet to go.
I will be glued to my computer waiting for postings of your explorations.
I will be glued to my computer waiting for postings of your explorations.
May 26, 2022 14:44:11 #
Mark, with reference to China White scrim fabric, I found that the White Polyester Lining Fabric at Hobby Lobby to be quite the same and it retails for $4.99 a yard. I'm not a seamstress, however, it is the white silky material used for lining clothing. If you have a Hobby Lobby in your area, it would be worth taking a look at it if you were to make a softbox style diffuser.
May 26, 2022 16:02:42 #
sippyjug104 wrote:
Mark, with reference to China White scrim fabric, I found that the White Polyester Lining Fabric at Hobby Lobby to be quite the same and it retails for $4.99 a yard. I'm not a seamstress, however, it is the white silky material used for lining clothing. If you have a Hobby Lobby in your area, it would be worth taking a look at it if you were to make a softbox style diffuser.
That is interesting! How is it that you understand this material is the same?
May 26, 2022 18:39:08 #
I put thin packing foam in front of thin LCD no hot spots
May 26, 2022 18:42:54 #
May 26, 2022 19:05:54 #
hangman45 wrote:
I put thin packing foam in front of thin LCD no hot spots
Foam can do it. I believe it has be be several mm thick. One can easily get very thin packing foam, but the thicker stuff is harder to find. Maybe multiple layers of the thin stuff?
What is even more challenging (and rare) is to not even have a brighter center in the reflection of the diffuser face on shiny subjects.
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