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Author Topic: DSLR testing sites like DXOmark and Imaging Resource use HMI and LEDs for color  (Read 56270 times)

Alexey.Danilchenko

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Alexey, what do those bulbs cost and where do they sell them? Thanks for posting the info.

Tim - this is their general site https://www.yujiintl.com/ which has some generic info (but spread across various sections somewhat illogically). They don't do bulbs, but they do LED strips or just LEDs themselves.

They have webstore with most of the LEDs data sheets. I got mine directly from them - promptly delivered. The relevant links for their LEDs:

For VTC series (CRI 98) LEDs they have big variety of chips, I just chose a largest COBs in those models to fit my application. I also designed my own driver for them since having a constant current supply for LEDs ensured the stability of the output and avoids colour shifts (but there are plenty readily available of course).
« Last Edit: March 26, 2018, 06:53:25 am by Alexey.Danilchenko »
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Tim Lookingbill

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Tim - this is their general site https://www.yujiintl.com/ which has some generic info (but spread across various sections somewhat illogically). They don't do bulbs, but they do LED strips or just LEDs themselves.

They have webstore with most of the LEDs data sheets. I got mine directly from them - promptly delivered. The relevant links for their LEDs:

For VTC series (CRI 98) LEDs they have big variety of chips, I just chose a largest COBs in those models to fit my application. I also designed my own driver for them since having a constant current supply for LEDs ensured the stability of the output and avoids colour shifts (but there are plenty readily available of course).

OK, so you have to roll your own bulb with Yuji LED chips. And quite expensive chips.

You wouldn't happen to know of any company that's manufactured a finished bulb using these Yuji chips that can be purchased in the US?

Thanks for the links and for the reply.
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DP

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You wouldn't happen to know of any company that's manufactured a finished bulb using these Yuji chips that can be purchased in the US?

https://dtdch.com/dt-photon-custom-cultural-heritage-lighting/

$6K a piece or so

PS: what you want is a "panel", not a "bulb"... if you are to illuminate a target you want less flat-fielding
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Tim Lookingbill

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https://dtdch.com/dt-photon-custom-cultural-heritage-lighting/

$6K a piece or so

PS: what you want is a "panel", not a "bulb"... if you are to illuminate a target you want less flat-fielding

$6K?! Ya' say! I guess that's the go-away-ya'-bothering-price.

Thanks for the link. Interesting info.
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Doug Gray

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One thing that is nice (or not) is that these LEDs use violet as the base emission and have a considerable amount of uV. It may well provide full D50 levels. Not spectrally, of course, but enough near and below 400nm to fluoresce OBAs. Might work reasonably well for uV compliant D50ish light booths. If so one will need to use M1 or possibly M0 profiles for papers with OBAs.
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Tim Lookingbill

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One thing that is nice (or not) is that these LEDs use violet as the base emission and have a considerable amount of uV. It may well provide full D50 levels. Not spectrally, of course, but enough near and below 400nm to fluoresce OBAs. Might work reasonably well for uV compliant D50ish light booths. If so one will need to use M1 or possibly M0 profiles for papers with OBAs.

I believe I may be seeing the uV spike in the 5000K Hyperikon LED I bought on Amazon for $9. To get good Caucasian skin tone (not reddish or jaundice) the whites of the eyes turn pinkish blue compared to the Soraa LED 5000K Vivid with Gan technology where color is more balanced and realistic. Whites of the eyes are more of an ivory off white. Not as perfect using xenon or mercury based flash though.

But what I'm describing may have nothing to do with your point about these lights exciting OBA's in paper.
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Doug Gray

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I believe I may be seeing the uV spike in the 5000K Hyperikon LED I bought on Amazon for $9. To get good Caucasian skin tone (not reddish or jaundice) the whites of the eyes turn pinkish blue compared to the Soraa LED 5000K Vivid with Gan technology where color is more balanced and realistic. Whites of the eyes are more of an ivory off white. Not as perfect using xenon or mercury based flash though.

Could be. It's not often discussed but there is a lot of variation amongst individuals, natural from small genetic differences and also age related. Even excluding the 8% of males that have color deficiencies. This is one of the main reasons the old CIE 1931 color matching functions are still used today in spite of significant technical improvements in lab equipment.

It's also in the shorter wavelengths (blues) that some of the larger individual variations occurs. LEDs generally, because they have such a large blue/violet spike, may not be as visually consistent among a group of people as flatter illuminants.

In other words, YMMV is a truism.
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Alexey.Danilchenko

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OK, so you have to roll your own bulb with Yuji LED chips. And quite expensive chips.

You wouldn't happen to know of any company that's manufactured a finished bulb using these Yuji chips that can be purchased in the US?

Thanks for the links and for the reply.

Expensive? 90$ buys 3000 lumens worth of chips (if you solder them yourself) which is not too expensive for D50 light source. Easiest route if you don't want minimal DIY is to get their D50 strips and put them on 2 panels  with off the shelf power supply. You will get ready to use lighting setup for target shooting for 150$ and minimum DIY
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Tim Lookingbill

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Expensive? 90$ buys 3000 lumens worth of chips (if you solder them yourself) which is not too expensive for D50 light source. Easiest route if you don't want minimal DIY is to get their D50 strips and put them on 2 panels  with off the shelf power supply. You will get ready to use lighting setup for target shooting for 150$ and minimum DIY

What is the cost of labor and buying the tools and acquiring the knowledge to soldier all those chips? You've got to be joking, right?

It's not worth it to me. I'm a hobbyist photographer who'ld rather make images with the lights affordable and available. I'm just looking for improvements in the industry that don't cost a fortune in time and money.

I appreciate your setting the boundaries on where and how that happens.
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Alexey.Danilchenko

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What is the cost of labor and buying the tools and acquiring the knowledge to soldier all those chips?
An evening watching Youtube tutorials

It's not worth it to me. I'm a hobbyist photographer who'ld rather make images with the lights affordable and available. I'm just looking for improvements in the industry that don't cost a fortune in time and money.

I appreciate your setting the boundaries on where and how that happens.
Have you really looked at links I sent? 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.

Their VTC series (LEDs with 98 CRI) also do come in COB (ceramic packages common in LED world) and as such they require no soldering (just mounting on heatsink and wiring a power supply).

BTW, I am a hobbyist as well not a professional and the reason I am looking at all this is that in photography most of the ready to use things do not come at cheap prices (there is of course a lot of cheap and not so good things) so I am finding and using alternatives. Printer profiling hardware and software for example cost a fortune especially if you use it occasionally - but researching a bit and getting used Spectroscan works quite well and on par with current solutions in quality.

« Last Edit: April 03, 2018, 03:45:52 pm by Alexey.Danilchenko »
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digitaldog

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An evening watching Youtube tutorials
Have you really looked at links I sent?
If you expect some to work at such understanding, it will likely fall on deaf ears. You offer solutions but like others, get more push back; the irony is seen in this comment:
http://forum.luminous-landscape.com/index.php?topic=123799.msg1033646#msg1033646
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Alexey.Danilchenko

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If you expect some to work at such understanding, it will likely fall on deaf ears. You offer solutions but like others, get more push back; the irony is seen in this comment:
http://forum.luminous-landscape.com/index.php?topic=123799.msg1033646#msg1033646

Thanks Andrew, I can only give the information in a hope that someone will find it useful.
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digitaldog

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Thanks Andrew, I can only give the information in a hope that someone will find it useful.
I did!
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Tim Lookingbill

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An evening watching Youtube tutorials
Have you really looked at links I sent? 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.

Their VTC series (LEDs with 98 CRI) also do come in COB (ceramic packages common in LED world) and as such they require no soldering (just mounting on heatsink and wiring a power supply).

Thanks for the additional info.

I'll have to pass on constructing electronic lighting with regard to heatsinks and wiring a power supply. I'm sure someone here will use this info and have enough confidence in what they're doing. I don't. Me and electricity don't get along and I now understand why there are several insignias on my Hyperikon LED's that include "UL" Underwriter's Laboratory standards and FCC with regard to frequency band regulations.
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TonyW

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Thanks Andrew, I can only give the information in a hope that someone will find it useful.
Found it very interesting thanks.  I am now wondering how they would perform as a relatively inexpensive print viewing booth light source compared to a GTI booth.

FWIW found this datasheet from another company with details on how to connect
https://led.cdiweb.com/Datasheets/citizen/Citizen-Instruction-Manual-COB-LED-Package.pdf
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Alexey.Danilchenko

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Thanks for the additional info.

I'll have to pass on constructing electronic lighting with regard to heatsinks and wiring a power supply. I'm sure someone here will use this info and have enough confidence in what they're doing

It would help if you actually read any of those links I posted (heatsinks mounting is only for COBs). The strips I referred to do not require any heatsinks - in fact they are pretty much the same as most of the led setups out there and those you frequently find in kitchens for example. The connectors are mechanical - plug and play style and come with the strips. Power supply if you want a simplest solution is also sold by Yuji and linked from the very same page (but here it is). All it requires is plugging a few wires.
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digitaldog

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It would help if you actually read any of those links I posted (heatsinks mounting is only for COBs).
 All it requires is plugging a few wires.
Too damn difficult!  :P
For some....
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Alexey.Danilchenko

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Found it very interesting thanks.  I am now wondering how they would perform as a relatively inexpensive print viewing booth light source compared to a GTI booth.

I am in the process of building something like that with D50 LEDs, placing them in two panels individually dimmable and using as a sides of the booth.

FWIW found this datasheet from another company with details on how to connect
https://led.cdiweb.com/Datasheets/citizen/Citizen-Instruction-Manual-COB-LED-Package.pdf

Thanks for those - they are very useful.

That Citizen COB on the pictures actually has mechanical holder from Molex that fits the VTC Yuji COB LEDs (13.5mm version). With that connector no soldering is required whatsover - just plugging in the wires.
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TonyW

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I am in the process of building something like that with D50 LEDs, placing them in two panels individually dimmable and using as a sides of the booth.

Thanks for those - they are very useful.

That Citizen COB on the pictures actually has mechanical holder from Molex that fits the VTC Yuji COB LEDs (13.5mm version). With that connector no soldering is required whatsover - just plugging in the wires.
It would be great to see the finished booth and your thoughts on the build when finished if you have time  :D
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Tim Lookingbill

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It would help if you actually read any of those links I posted (heatsinks mounting is only for COBs). The strips I referred to do not require any heatsinks - in fact they are pretty much the same as most of the led setups out there and those you frequently find in kitchens for example. The connectors are mechanical - plug and play style and come with the strips. Power supply if you want a simplest solution is also sold by Yuji and linked from the very same page (but here it is). All it requires is plugging a few wires.

It would help me if you had read what I wrote several times that I wasn't interested in building my own Yuji light and that I would like to know if there are any companies that have the lights already built that use the Yuji chip.

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.

I also now remember having this same conversation in this forum several years ago and still not getting an answer. My memory of these discussions starts to fritter away once I see there's no solution.

And probably several years later this conversation will come up again and will now have to commit to memory the name Yuji as an LED light that hasn't or isn't going to built at an affordable price.

And BTW I did read those links. It would've saved me some time if I'ld known I would have to build the light myself with the components bought off that site. Again, not interested.

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