I feel you
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I’m gonna try to pick up some large form tracing/washi paper with fine/ultrafine texturing to project the image of an LED/ reflector to it. I’m trying to be able to quantize the phosphor pigments by high res pixelating the die and gridding it. This is just being projected to a wall, but I imagine we’d get a better “image” if we caught it “in line” with the beam.
I’m all about finding practical budget solutions to our lighting analysis tools, lol…$2,000 macro lense/$80 microscope? nah, $20 loupe and a few bucks in thin tracing paper, plus a jury rig stack of old phone books as a projection platform. And a few paper clips as anti-roll. this might also inadvertently address our beam shaping concerns, we could just directly measure the transitive light intensities on an actual flat grid rather than having to account for the inch or so off the grid because of the luxmeter being thicc.
Here’s a better shot, showing the uneven distribution of the reds in the phosphor. I used the imperfections and random scraggles on the wall to do the focus, then manually adjusted the focus of the projection until it came into view
Phones piss me off…it shows me one thing on the screen and captures a completely different thing altogether. The splotchy reds you see in the corners that looks like a bad rosacia is indeed more pronounced than it looks in the photos.
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I used to do this with lenses from small ultrafire-type zoomies–it might even be sensible to have a crappy zoomie to swap emitters into for imaging purposes. Sometimes with some emitters (like 519A), the phosphor grains are so coarse that they are easily visible when projected by a Carclo triple optic, which has a convex lens in the center.
The main difficulty, of course, is trying to pick it up with a phone camera. One just needs to play with manual controls until they find the right exposure and focus to bring out the phosphor grains.
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i even used “pro mode” to try and play with the contrast and saturation, but no dice…
here’s how it makes the paper look…like ringworm or psoriasis lol
it’s why I want a super fine textured paper, otherwise it’ll focus on the physical texturing and not the photometrics
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double paned glass?
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I see your need for fine textured paper. An alternative solution would be a convex lens that is small diameter and short focal length, which projects a large image. The image might be large enough that the size of phosphor particles is much greater than the size of paper texture, so the camera would pick up the former but not latter.
Here’s a proof of concept, without and then with saturation/CCT tweaking:
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YES! Yours looks much better than mine lol. I really see the dispersion of different pigmented phosphors in there. Another reason for the fine grained paper is to try and take a more centered shot to properly grid the phosphor distribution, no weird aberations due to angles, etc…you’d be on the opposite side of the projected image, like a negative but in full color
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I think my photos are not necessarily higher-quality than yours, the SFT40 3000K might just use rougher phosphor than your emitter (719A or dedomed 519A?).
Yes, a centered shot would be much better for gridding the phosphor distribution without distortion. I’ve tried again with a less noisy setup, and a random eyepiece lens from some crappy binoculars I took apart years ago. I also tried to stack 25 shots, but it did not help very much because the blurriness is not coming from independent noise.
Stacked and processed+sharpened:
R,G,B channels. The blue is very revealing of uneven phosphor distribution.
For those wondering why their SFT25R 5000K has a discolored hotspot center:
The center is very bright in the green channel, and dim in blue:
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This one, a dedomed 3500k, yielding around 2800-2900k.
The phosphor is more clumpy/splotchy rather than grainy. Those last two composites look like a star lol. The sft25r looks like it probably NEEDS an orange peel reflector to meld the colors better…that outer blue must wreak havoc with the blending on smooth reflectors and optics…
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Yeah the 519A tends to have single-color stripes/splotches of phosphor, and I’m not sure why. I occasionally get discolored hotspots, and mixing the phosphor a bit better would have solved this problem.
The SFT25R’s phosphor distribution problem is on too large a scale (like the whole middle 1/3 of the emitter) to be fixed by even an OP reflector. Only a TIR can fix it. It does look a bit like the sun, sunspots and all!
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Just sitting around being a couch potato and shined the light at the tv for fun and it gave some neat colors. Older tv. Could be plasma.
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The pixels and smaller structures in the TV screen are serving as a diffraction grating! You can use the shape/angle/number of the spikes to deduce the lattice structure within the screen, as in X-ray crystallography.
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Wow, that sentence has several concepts that went right over my head! 
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It’s fancy, scary words for simpler (?) things. Very small periodic patterns (“very small” as in on the scale of visible light wavelength) separate light like a triangular prism does, though by different means.
Another great example would be the colorful appearance of a CD/DVD:
This is due to diffraction by many very tightly-packed concentric ring-shaped grooves. The spacing between the grooves is the same, which makes them approximately periodic. The grooves are so good-quality that I can build spectroscopes out of them!
Here’s a CFL bulb spectrum according to my DVD:
The sun (zoom in to see the very fine Fraunhofer lines):
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“So Bob, about your daily performance, can you tell me why there are no empty glasses near the edge of the table?”
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