I am always a bit nutty when it comes to brightness when I shoot DCG.
But in thinking about it I don't totally understand it.
I know John says it is not neccessary how high the fringes are but how low the non exposued areas are.
Fair enough
But I not sure what drives that. I would think if the object/plate doesn't move you should create good fringes. Fixing should take care of the rest.
OK so we have exposure, DCG is so broad in exposure time. I am guessing you want to exposure as little as possible, and keep it below where it starts getting noisey.
You have fixing, what ever method you use, you what to fix so you don't get milky results but not where you get too narrow band. There is a sweet spot
Water baths you are removing unexposed DCG and swelling the gel
IPAs you are shinking to remove the water
Can we talk a bit more about brightness and what drives it?
Can we explore how each variable can effect brightness?
Sometimes I get these ultra bright holograms in which I have no idea what I did. I try to replicate it on the next plate (from the same batch of film) and it is a degree or two less bright. Then I scatch my head and wonder why they were different and what should I adjust. It might be some ever tiny bit of movement that smears the image just ever so much.
Look forward to being enlighten
DCG and Brightness
-
Johnfp
DCG and Brightness
I am always a bit nutty when it comes to brightness when I shoot DCG.
Tony, you don't need to tell us your personal problems.
But in thinking about it I don't totally understand it.
I know John says it is not neccessary how high the fringes are but how low the non exposued areas are.
I am not sure what you mean by how high or how low the fringes are. Fringe size/spacing is dictated by wavelength mostly with a small amount of swelling or shrinkage. It is crosslinked gelatin areas (constructive) vs the removed gelatin and uncrosslinked ares (destructive) that gives us the different index of refraction. The further apart these two numbers (index of refraction) are, the more refraction to the object wavefront and thus the brighter the hologram.
Fair enough
But I not sure what drives that. I would think if the object/plate doesn't move you should create good fringes. Fixing should take care of the rest.
OK so we have exposure, DCG is so broad in exposure time. I am guessing you want to exposure as little as possible, and keep it below where it starts getting noisey.
You have fixing, what ever method you use, you what to fix so you don't get milky results but not where you get too narrow band. There is a sweet spot
Water baths you are removing unexposed DCG and swelling the gel
IPAs you are shinking to remove the water
Can we talk a bit more about brightness and what drives it?
Can we explore how each variable can effect brightness?
Sometimes I get these ultra bright holograms in which I have no idea what I did. I try to replicate it on the next plate (from the same batch of film) and it is a degree or two less bright. Then I scatch my head and wonder why they were different and what should I adjust. It might be some ever tiny bit of movement that smears the image just ever so much.
Ha, welcome to DCG. I have been able to repeat a great exposure one day/batch. And never get consistancy another day/batch.
Look forward to being enlighten
Things the give maximum brightness:
High difference of index of refraction of the exposed and unexposed area
---Adequate light exposure to provide enought Cr to be fully converted in the exposed area allowing maximum crosslinking
---Adequate fixing to yield maximum crosslinking mentioned above
---Water temp to provide ample swelling withough over expanding the crosslinked "spring"
---Water temp to provide adequate removal of uncrosslinked gelatin
No movement. Some movement may make a hologram dim even though it didnt move enough to see a/some black fringes on the hologram.
Alcohol drying such that the most light shown down on the final hologram gets used in reconstruction. For a white illuminated hologram a fast dry such that some water gets pushed into the emulsion and caused a differential swelling of the different layers resulting in multiple illuminating wavelengths to get reflected.
But is it alway brightness we want. I love the pastel colors. In other words a green that has a whiteness to it. Or a red that has a pinkness to it. This type of DCG has the benefit of being colored almost like a single wavelength but also the benefit of having some different fringe spacing as to use more of the white illuminating light. But that may be another story.
I was waiting to hear from others on this subject but decided to chime in since no one answered.
Tony, you don't need to tell us your personal problems.
But in thinking about it I don't totally understand it.
I know John says it is not neccessary how high the fringes are but how low the non exposued areas are.
I am not sure what you mean by how high or how low the fringes are. Fringe size/spacing is dictated by wavelength mostly with a small amount of swelling or shrinkage. It is crosslinked gelatin areas (constructive) vs the removed gelatin and uncrosslinked ares (destructive) that gives us the different index of refraction. The further apart these two numbers (index of refraction) are, the more refraction to the object wavefront and thus the brighter the hologram.
Fair enough
But I not sure what drives that. I would think if the object/plate doesn't move you should create good fringes. Fixing should take care of the rest.
OK so we have exposure, DCG is so broad in exposure time. I am guessing you want to exposure as little as possible, and keep it below where it starts getting noisey.
You have fixing, what ever method you use, you what to fix so you don't get milky results but not where you get too narrow band. There is a sweet spot
Water baths you are removing unexposed DCG and swelling the gel
IPAs you are shinking to remove the water
Can we talk a bit more about brightness and what drives it?
Can we explore how each variable can effect brightness?
Sometimes I get these ultra bright holograms in which I have no idea what I did. I try to replicate it on the next plate (from the same batch of film) and it is a degree or two less bright. Then I scatch my head and wonder why they were different and what should I adjust. It might be some ever tiny bit of movement that smears the image just ever so much.
Ha, welcome to DCG. I have been able to repeat a great exposure one day/batch. And never get consistancy another day/batch.
Look forward to being enlighten
Things the give maximum brightness:
High difference of index of refraction of the exposed and unexposed area
---Adequate light exposure to provide enought Cr to be fully converted in the exposed area allowing maximum crosslinking
---Adequate fixing to yield maximum crosslinking mentioned above
---Water temp to provide ample swelling withough over expanding the crosslinked "spring"
---Water temp to provide adequate removal of uncrosslinked gelatin
No movement. Some movement may make a hologram dim even though it didnt move enough to see a/some black fringes on the hologram.
Alcohol drying such that the most light shown down on the final hologram gets used in reconstruction. For a white illuminated hologram a fast dry such that some water gets pushed into the emulsion and caused a differential swelling of the different layers resulting in multiple illuminating wavelengths to get reflected.
But is it alway brightness we want. I love the pastel colors. In other words a green that has a whiteness to it. Or a red that has a pinkness to it. This type of DCG has the benefit of being colored almost like a single wavelength but also the benefit of having some different fringe spacing as to use more of the white illuminating light. But that may be another story.
I was waiting to hear from others on this subject but decided to chime in since no one answered.
-
Johnfp
DCG and Brightness
Things the give maximum brightness:
High difference of index of refraction of the exposed and unexposed area
---Beam ratio (added)
---Adequate light exposure to provide enought Cr to be fully converted in the exposed area allowing maximum crosslinking
---Adequate fixing to yield maximum crosslinking mentioned above
---Water temp to provide ample swelling withough over expanding the crosslinked "spring"
---Water temp to provide adequate removal of uncrosslinked gelatin
No movement. Some movement may make a hologram dim even though it didnt move enough to see a/some black fringes on the hologram.
Alcohol drying such that the most light shown down on the final hologram gets used in reconstruction. For a white illuminated hologram a fast dry such that some water gets pushed into the emulsion and caused a differential swelling of the different layers resulting in multiple illuminating wavelengths to get reflected.
High difference of index of refraction of the exposed and unexposed area
---Beam ratio (added)
---Adequate light exposure to provide enought Cr to be fully converted in the exposed area allowing maximum crosslinking
---Adequate fixing to yield maximum crosslinking mentioned above
---Water temp to provide ample swelling withough over expanding the crosslinked "spring"
---Water temp to provide adequate removal of uncrosslinked gelatin
No movement. Some movement may make a hologram dim even though it didnt move enough to see a/some black fringes on the hologram.
Alcohol drying such that the most light shown down on the final hologram gets used in reconstruction. For a white illuminated hologram a fast dry such that some water gets pushed into the emulsion and caused a differential swelling of the different layers resulting in multiple illuminating wavelengths to get reflected.