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Author Topic: DSLR testing sites like DXOmark and Imaging Resource use HMI and LEDs for color  (Read 55661 times)

digitaldog

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It would help me if you had read what I wrote several times that I wasn't interested in building my own Yuji light....
Naturally he never said that. Let alone several times....
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DP

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we are going in circles now...
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Alexey.Danilchenko

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Since you didn't answer the last part I'll take it that you and anyone else here don't know of any companies that's made this light at an affordable price like say under $50.


The solution if exists out there is not going to cost $50. You do need to research LEDs because the panels, strips and COBs is by far the most popular packages they come in -  not as a prepackaged panels. They are also the only cost effective solution if you want high CRI and full spectrum coverage.

Btw, Yuji does sell ready made lights (not with D50 to my understanding) here but their prices of course are nowhere near $50.

As with anything - all those manufacturers are happy to answer questions, so why not to write to them and ask instead of complaining here that no one answers what you want to know? As with any quest: where there's a will - there's a way
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Alexey.Danilchenko

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It would be great to see the finished booth and your thoughts on the build when finished if you have time  :D

Sure, as for most of my projects full details will go on github so they can be reproduced.

The panels now taking a slight backseat though as I am in a process of replacing Xenon light source in my Spectron device (camera sensors spectral responsivity measurements) with the Yuji LEDs (4x VTC COBs in a single compact and controllable package).

I will try to make panels ready though before summer and will post the details if interested. My primary goal with them is a well lit booth for target shooting but of course that can be used for more than this. If I were to construct viewing booth from scratch, I would probably go for the prebuilt panels and Yuji power supply. This will require just mounting the panels at the top with a few screws and connecting power supply with a few wires and mechanical clips. The panels they sell will be enough for 2 booth so it could be joint purchase to spread the cost (well just a thought anyway).
« Last Edit: April 05, 2018, 05:30:11 am by Alexey.Danilchenko »
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Tim Lookingbill

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So now asking questions on the availability of a bulb is considered complaining? WTF?! :o
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Alexey.Danilchenko

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So now asking questions on the availability of a bulb is considered complaining? WTF?! :o
Complaining for not getting an answer of course. An with that tone I doubt anyone will be willing to answer.
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digitaldog

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Complaining for not getting an answer of course. An with that tone I doubt anyone will be willing to answer.
+1; plus, no reason to feed the trolls!
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DP

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Tim, don't give up... go trolls, go !!!
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digitaldog

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Tim, don't give up... go trolls, go !!!
It's in their nature; a lack of experience too. As seen in this series of posts:
http://forum.luminous-landscape.com/index.php?topic=124034.msg1037298#msg1037298
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WayneLarmon

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Quote
The CRI replacement that is gaining the most interest lately is IES TM-30-15.

There are now LED light sources that have high CRI, TLCI and R9 values.  I'm wondering if the manufacturers are gaming the system and that the bulbs/panels don't really render color as well as the CRI (et. al) specs indicate.

Will ColorMeter support this?

[Edit.  It has been a while since I posted on Luminous Landscape.  This was a response to a post by GWGill.]

[2nd Edit.  Sorry again.  I just realized that GWGill addressed this in another thread.
« Last Edit: May 29, 2018, 09:23:17 pm by WayneLarmon »
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WayneLarmon

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Soldering is only required is you buy naked chips - the panels as I said require no special skills - only connecting things together. At $180 + power supply this is still a lot cheaper than any other D50 light sources I have seen.

Alexey, I'm jumping in here because I'm interested.  Just to make sure I understand, I'd need to order one

VTC Series D50 5000K High CRI MCPCB LED Module - Pack: 10 pcs $209

This page says

One pack (10pcs MCPCB) needs 2pcs power supply.
When choosing a power supply, please be sure to select 24V to ensure compatibility with this product.


So I'd need to order two

Yuji Flicker Free Dimmable Power Supply, 48W - Pack: 1 pcs $45 and choose the 24V versions.

OK, but the modules come like this



This shows five strips bonded together.  "Pack: 10 pcs" means two of these modules, correct?   

The connectors look like



which means a lot of pins sticking out of each module (of five strips)  Don't we need some kind of jumper wire harness to connect to the power supply?  (I can handle soldering, but it would be easier to start out with jumper wires that I can cut apart in the middle to solder to.)

They don't give the voltage requirements.  Are the strips connected in serial or in parallel?

I'm trying to get it down to knowing what to order so I can plug everything together to mount in enclosures that I'd fabricate.

Quote
An evening watching Youtube tutorials

Suggestions on Youtube search terms?

« Last Edit: May 31, 2018, 03:03:29 pm by WayneLarmon »
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Alexey.Danilchenko

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I ordered bare naked LEDs not the board and do all soldering myself. The boards with presoldered LEDs you looking at seems to be an easy option in term of connecting them all. I would suggest you email them with all the questions - they so far have been answering mine promptly. I can only base my replies on what I can read on their site regarding the strips.

So I'd need to order two

Yuji Flicker Free Dimmable Power Supply, 48W - Pack: 1 pcs $45 and choose the 24V versions.

Yes - one for each panel of 5 strips it seems.

OK, but the modules come like this



This shows five strips bonded together.  "Pack: 10 pcs" means two of these modules, correct?   

No idea - but I would guess the picture may be for illustration and it may come as a single block or two blocks. They can be broken down to individual strips and connected into one long strip with supplied Wago straight connectors.

The connectors look like



which means a lot of pins sticking out of each module (of five strips)  Don't we need some kind of jumper wire harness to connect to the power supply?  (I can handle soldering, but it would be easier to start out with jumper wires that I can cut apart in the middle to solder to.)

The connectors on those boards are Wago 2060 series and from description the package you looking at comes with 10 straight Wago 2060-902 connectors. Those will allow to build one long strip of lights mechanically. If you want to connect them as they are in the panel, I think all you would need is a 1mm thick wire (pair) since connector is locking and wire them at the sides like you would if you connect those strips into one long one. You will notice that the panel are already done like that so connecting part of each strip are adjacent to each other.


They don't give the voltage requirements.  Are the strips connected in serial or in parallel?

I'm trying to get it down to knowing what to order so I can plug everything together to mount in enclosures that I'd fabricate.

No idea but judging by power supply specification they all connected in parallel (power supply does produce voltage enough for one LED with current for 30-40 of them).

For my board/panel I am targeting 4 strips of LEDs in parallel, 12 LEDs in each strip in series.

Suggestions on Youtube search terms?

"Soldering SMD", "wiring LED COB" etc
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WayneLarmon

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"Soldering SMD", "wiring LED COB" etc

Thanks for your informative response!  But I see that I phrased my question backwards.  I should have limited it to asking about this.  I Googled for both these phrases and the results show that the subject isn't trivial. 

Starting with "wiring LED COB"  It would take a lot more than an evening to be comfortable with powering up the LED modules described above.  There are a lot of questions that need to be answered about connecting in parallel (namely about avoiding thermal runaway.)  Parsing component data sheets into finished project schematics (let alone pictorial diagrams) isn't something that can be learned in an evening.  I have a sort of head start because I was a reasonably hard core electronics experimenter in the 1970s and 80s (metric: I have an electronics workbench and test equipment.  But dating from the 1980s.) 

"Soldering SMD" is an even longer detour.  It looks like it may be cheap, but only when you know what you are doing.  I also have a sort of head start because I know people that can do this.  But not well enough to get personal lessons.  I looked through some of the written tutorials.  I get the impression that the people who write the tutorials are very optimistic about what is "easy."

I've done enough electronics project assembly that I'm not afraid of wiring from AC to finished project.  I know the safe guards.  But I wouldn't recommend that a non technical person do this without guidance.  In person.

I'm not afraid of being electrocuted with the LED modules.  I'm afraid of hearing a loud pop and then seeing a cloud of magic smoke.

For those of us that are queasy about wiring up LED panels and power supplies, what about the finished bulbs?
 
BC Series A60 High CRI Remote Phosphor LED Bulb - Pack: 4 pcs  $80

I note that they don't give any spectral plots for these.  They only give a bland

CRI Value (Ra typ.)  Above 95

which leaves a lot of wiggle room.  These are pricey but the cost would be livable.  If they gave good light.

I recently found some Cree bulbs locally that cost less than $10 ea.  for 100w (equiv.) and measure a lot better than older hardware store bulbs. 



The CRI, TLCI, and R9 are nice.  (Duv is iffy, though.) They are real easy to use.  But the spectral plot is telling me that I need better.  $160 worth of the above Yuji bulbs would give me enough light to do what I'm doing now with the Cree bulbs.  But I don't know if the Yuji bulbs' spectrum is closer to my Cree bulbs, or is closer to the COB LEDs that you are using.

« Last Edit: June 01, 2018, 06:17:13 pm by WayneLarmon »
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Alexey.Danilchenko

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Thanks for your informative response!  But I see that I phrased my question backwards.  I should have limited it to asking about this.  I Googled for both these phrases and the results show that the subject isn't trivial. 

Starting with "wiring LED COB"  It would take a lot more than an evening to be comfortable with powering up the LED modules described above.
I gave those as an example (since those were what I referred to in my original post) - the modules you have been looking at are not COBs and already come presoldered on boards so require only wiring to their power supply.

Regarding COBs, in reality - there is nothing complicated about LEDs and COBs specifically if all you want to do is to have a lighting system. Plenty of COB mechanical fixing packages exists that allow them to be fastened to a radiator with a few screws and won't require any soldering (just connecting wires). For COBs all you generally need to do is pick radiator(s), drill some holes, fasten the COBs to radiators and attach the wires to power supplies.

Reference to soldering SMD was given in for the "going all the way" case - soldering LED chips yourself. True, it is a bit of a learning curve but this will give the ultimate control over LED configuration package you can create.

I'm not afraid of being electrocuted with the LED modules.  I'm afraid of hearing a loud pop and then seeing a cloud of magic smoke.

As with anything else - it is a matter of reading specifications for the chosen LED module and matching it to power supply connected.

But I don't know if the Yuji bulbs' spectrum is closer to my Cree bulbs, or is closer to the COB LEDs that you are using.

The page you referenced has a spec with the spectral plot. Their BTC series have lowest CRI from all their offerings and pretty much match those CREE ones with lack in blue part of the spectrum (400-420nm) and typical for these LEDs hump just after that. All that is on Yuji site - if you look at "SHOP BY CRI LEVEL" you can see all those categories in decreasing CRI order.
« Last Edit: June 02, 2018, 04:51:36 pm by Alexey.Danilchenko »
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WayneLarmon

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Regarding COBs, in reality - there is nothing complicated about LEDs and COBs specifically if all you want to do is to have a lighting system. Plenty of COB mechanical fixing packages exists that allow them to be fastened to a radiator with a few screws and won't require any soldering (just connecting wires). For COBs all you generally need to do is pick radiator(s), drill some holes, fasten the COBs to radiators and attach the wires to power supplies.

COBs + mechanical fixing packages may be more attractive.  Drilling holes and plugging in wires is reasonable. (If I can get past that thermal runaway issue.)  SMD soldering is a long detour.   If fabrication is truly the only option to get usable lights.

Quote
The page you referenced has a spec with the spectral plot. Their BTC series have lowest CRI from all their offerings and pretty much match those CREE ones with lack in blue part of the spectrum (400-420nm) and typical for these LEDs hump just after that. All that is on Yuji site - if you look at "SHOP BY CRI LEVEL" you can see all those categories in decreasing CRI order.

Hmm, the spec sheet I found for the BTC series doesn't have a spectral plot.  It just shows luminosity distribution.

"SHOP BY CRI LEVEL" not informative.  For instance, here is the spectral plot of an Aputure Amaran AL-H198 I have that has a CRI of almost 97.



We can see that judging by CRI, TLCI, R9, and Duv alone is problematic.  The only way to get a spectral plot was for me to buy the AL-H198 and measure it myself.  The cost of these panels was low enough that I don't mind having a pair.  But I'm trying to avoid getting into a "buying, measuring, and then returning" cycle, which is what I'd need to do if I wanted to find out if more expensive LED panels were really worth the additional expense. (I've gravitated back to prefabricated panels here.)

There is a gap in the luminaire industry.  Photographers really shouldn't have to be reading spec sheets and moonlighting in DIY electrical engineering in order to have usable lighting.   Or be independently wealthy (to afford museum quality lighting.)

However, right now photographers should be more conversant with products like ColorMeter.   Getting going with ColorMeter isn't such a long detour.  So we can hold big luminaire's feet to the fire.
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Doug Gray

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It's less of a problem than it "appears"  :)

The spikey characteristic of any illuminant isn't what matters directly. It's the degree of matching after the illuminant's spectral curves are combined with the print's spectral reflectance curves then the color matching functions.

The various measures of color rendering are based on a much larger variety of reflective surfaces than what exists with an inkjet print.

Printers, fortunately for us, have a much more limited spectral distribution. So the important measure of an illuminant used for prints is how closely they match D50, D55, D65, or whatever your preferred illuminant. The spectral distribution of an illuminant, especially LED types, will not correlate well with actual sensed color rendition from a print.

You can get a better sense of how different illuminants impact a print by making two custom profiles. The first made with D50 illuminant and the second with the illuminant you wish to compare the print to. Then convert to printer RGB space using the standard D50 profile. Next, select "assign profile" but don't hit OK,  and toggle the "view" box to see the difference in how the print will look under one illuminant compared to D50.

There are ways to do this quantitatively as well but the point here is that it's really hard to tell how well an illuminant will work for a print looking at the illuminant spectrum.
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WayneLarmon

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It's less of a problem than it "appears"  :)

The spikey characteristic of any illuminant isn't what matters directly. It's the degree of matching after the illuminant's spectral curves are combined with the print's spectral reflectance curves then the color matching functions.

The various measures of color rendering are based on a much larger variety of reflective surfaces than what exists with an inkjet print.

I'm not illuminating prints.  I'm shooting paintings.  (And eBay pictures.)  I don't think that painting pigments are as predictable as broad spectrum inkjet print colors, are they?

This is my second go round shooting family paintings.  For my first attempt I used "full spectrum" daylight balanced CFLs.  I never could get accurate color, no matter how many Adobe DNG Profile Editor camera profiles I made.  So I'm a bit leery of illuminant spikes.
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Doug Gray

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I'm not illuminating prints.  I'm shooting paintings.  (And eBay pictures.)  I don't think that painting pigments are as predictable as broad spectrum inkjet print colors, are they?

This is my second go round shooting family paintings.  For my first attempt I used "full spectrum" daylight balanced CFLs.  I never could get accurate color, no matter how many Adobe DNG Profile Editor camera profiles I made.  So I'm a bit leery of illuminant spikes.

Yep, colorimetric rendering of paintings is harder. Much harder. Paint pigments are much more diverse spectrally than inkjet prints. So they are impacted by both the illuminant and the camera. And so-called "full spectrum" CFLs are pretty bad to start with. And so is the camera. You can always take pictures of the paintings in daylight but that won't fix the camera's divergence from Luther/Ives.

As for the spike at 450nm and dip at 480, these both affect mostly the Z in XYZ colorspace and only where there are significant reflectance differences in 450-500nm transitioning in the painting pigments over the range of 440nm to 520nm. One way to quantify it would be spectrally sampling colors in the painting and comparing calculated  Lab values for the led v D50. It's a major hassle to do.
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Tim Lookingbill

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I'm not illuminating prints.  I'm shooting paintings.  (And eBay pictures.)  I don't think that painting pigments are as predictable as broad spectrum inkjet print colors, are they?

This is my second go round shooting family paintings.  For my first attempt I used "full spectrum" daylight balanced CFLs.  I never could get accurate color, no matter how many Adobe DNG Profile Editor camera profiles I made.  So I'm a bit leery of illuminant spikes.

Thanks for the info and links on the Yuji and Cree bulbs, Wayne. That was very helpful.

My local Home Depot indicates they have 15 of the Crees. I'm going to check them out and see if they render Cadmium Yellow as Lemon Yellow (bad CRI) shooting and AWB'ing a WhiBaL card and whether the Xrite CCchart cyan renders as just another sky blue. I'm also going to test how they render the whites of my eyes shooting a selfy. The Soraa Vivid LED I have is the best at this but finding it hard to buy a second one online of the exact model. The Hyperikons make the whites of my eyes overly blue. Most of the other colors look pretty close but they employ a trick manipulating the color of white by making it slightly greenish desaturated yellow which of course will add magenta to other cooler colors AWB a neutral target.

It's never a perfect rendering. I always have to manipulate WB against HSL panel in ACR. It's never a one off and I'm done.

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Alexey.Danilchenko

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COBs + mechanical fixing packages may be more attractive.  Drilling holes and plugging in wires is reasonable. (If I can get past that thermal runaway issue.)  SMD soldering is a long detour.   If fabrication is truly the only option to get usable lights.

Soldering is only if you want to go down that road. The packages you were looking for (panels) require no soldering. I am struggling to understand the logic really.  Yuji site has comprehensive selection of various packages for pretty much different installation requirements - bare LED chips (the ones you need to solder), COBs (where available), prearranged panels with LED chips already soldered on PCB and flexible strips (I am not considering various lamps at this moment). The latter two are by far the easiest to connect - a few wires, connectors  to be connected to power supply and you are done.

Hmm, the spec sheet I found for the BTC series doesn't have a spectral plot.  It just shows luminosity distribution.
They do but not for that lamp. Yuji have 3 categories of LEDs - BTC, VTC and D50 (in order of increasing CRI). Select any chip in that category (COB for example) and spec there will contain technical details including spectral curves.  Here for example https://cdn.shopify.com/s/files/1/0344/6401/files/YJWJ007-1.2_YJ-BC-135L-G02.pdf?1044822003027063112

Same for VTC and D50 series.
 
"SHOP BY CRI LEVEL" not informative.  For instance, here is the spectral plot of an Aputure Amaran AL-H198 I have that has a CRI of almost 97.

I was referring to Yuji site not anybody elses and how informative it will be in all other cases. Yuji tend to structure their LEDs in categories by CRI and within those by CCT. I had a look through pretty much all of those in search of the spectral response that I need vs light output and its a good starting point.

As I also said before - do ask them. In my view it is a waste of time to hypothesize what may or may not be the case - much simpler just to ask Yuji or any other manufacturer for spectral plots if that is what you need.
« Last Edit: June 04, 2018, 07:01:24 am by Alexey.Danilchenko »
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