Seoul P4 initial Evaluation- Production LEDs

[McGizmo]

Newbie,
I have not had a means of calibrating my IS for color so beyond relative comparisons, I wouldn't put any credability to the numbers. I didn't look at them. The drivers used in the data point I offered were DBx2's and I would expect that there is some variation in them as well. No telling which was higher in current or if so, by how much.

Lumileds is the winner on even tint in beam and I put Cree next up. Seoul has done better, IMHO,with the P4 than previous samples I have seen. It is what it is and whether it can be quantified in any reasonable fashion is an issue and concern for others. :shrug:

In terms of flux, the core of the Seoul P4 is the EZ1000 and I have viewed enough of these in flashlights now and taken lux measurements and by and large, they do what one would expect them to do. I have an Aleph 3 DB917 and a HD45 917 both with P4's and both lights break the 10k lux barrier. I don't believe they could do that without some flux in the volume one would expect from the EZ1000.

As you have stated, the P4 is no star on a white wall.

I have lights using P4's that couldn't be improved upon, with current technology, by replacing the LED by another. I have lights using the XR-E that also couldn't be improved upon by replacing the LED by another. This is subjective opinion and not objective fact.

 

[NewBie]

Here is another point of reference.

FYI, I rinsed off the Seoul P4 again, it keeps reaching out and grabbing dust out of the air... : (

If I decide to use many of these, I might think about making my own mini laminar flow bench, along with a +/- ion generator for equalizing charges to help keep the static down. Besides rinsing with water or isopropyl alcohol/water mix, anyone come across any great ideas on removing/preventing the dust collection on the Seoul P4?

My batteries started getting low on the flashlight on the right for the shot below, so the Luxeon III here has a bit less light, otherwise the extreme clarity of the Lux III in comparision to the Seoul P4 would have been quite obvious, but here it is anyhow:

 

[SuperTorch]

Are there no type of clear coating/sprays that would stand the heat(not crack/yellow) once the led is on and at the same time offer a smoother and maybe different/protective cover as far as repelling dust/foreign matter, surely the great DuPont has something up their sleaves.

 

[kogatana581]

Here is another point of reference.

FYI, I rinsed off the Seoul P4 again, it keeps reaching out and grabbing dust out of the air... : (

If I decide to use many of these, I might think about making my own mini laminar flow bench, along with a +/- ion generator for equalizing charges to help keep the static down. Besides rinsing with water or isopropyl alcohol/water mix, anyone come across any great ideas on removing/preventing the dust collection on the Seoul P4?

My batteries started getting low on the flashlight on the right, so the Luxeon III here has a bit less light, otherwise the extreme clarity of the Lux III in comparision to the Seoul P4 would have been quite obvious, but here it is anyhow:

My staff engineer provides the rest of us each an aerosol spray-paint cannister-sized aluminum can of compressed air to clean some of our tools such as flashlight lenses, googles, etc.

The Seoul LED looks like an unfinished project.

 

[NewBie]

Unfortunately, with this sticky gummy dome, blasts of air don't help much, except stir the dust around the area, and the part yanks more dust out of the air.


Okay, this next section will be of concern to white wall hunters and Ring Wraiths.

Anyhow, I finally got one of the Seoul P4 emitters mounted on a post, so I could put it in a nice perfect and smooth MagLite reflector. I let the camera AWB, since due to the tints that come out at different exposure levels, I was getting some really wierd looking photos which made one look decent, but the rest looked like the set white balance was kaddywhompus.


First a series of photos at different exposures:

Above, in the smooth "perfect" MagLite reflector, some of the issues of the P4 start to really stand out, like bond wires getting in the way, tints (which the camera barely picks up), and a very, very distinct ring.


I fiddled a bit with emitter placement and adjusted the focus spot a few mils, and instead of dark lines from the bond wires, you get the shiny distinct reflection of the gold bond wires shown below at 2 o'clock and 4 o'clock:

I wish my digital camera had the latitude to show the tints like the human eye sees them.


Like I said before, I'd *really* recommend rough surface reflectors with the Seoul P4, they should do a decent job smoothing out the tint variation in the LED, and hide the shadows/reflections of the bond wires. They should also fix the ring wraith problems, as evidenced by the same problem with the CREE XR-E, that McGizmo managed to smooth out with his rough reflectors for his products. I can't emphasize how much better these Seoul P4 look in the McGizmo reflector, and I'd very highly recommend McGizmo's outstanding reflectors for fixing these issues.

There are more than plenty enough extra lumens in the Seoul P4 to spread things out, blend them, cover/hide shadows/reflections, send the Ring Wraiths back to Mordor, and create a nice smooth hotspot transistion, and still walk all over a Luxeon III.

 

[ICUDoc]

Hi Newbie- thanks for another great thread! Good photos, cogent comments- it's all good, as we say.
The translucent stroma of the Seoul is very surprising and a bit concerning- I am sure lumens are lost due to inefficient diffraction through the gel.
Also it will interfere with the ability of the LED to be focused, as the phosphor will no longer be the sole emitter, but will be joined by a hazy surrounding band of gel i.e. act as less of a point source.
That said, the high efficiency and output of the Cree die would seem to shine through (as it were!) in your beamshots, so perhaps the primary optic (being closer to acting Lambertian) makes up for this.
The thing I like about it above the Cree XR-E is that it doesn't have a ruddy great metal ring blocking some of the light!
Thaks again- I look forward to playing with these....

 

[NewBie]

I hauled out one of Don's (McGizmo) outstanding reflectors (a prized possession), the rough surface HD45 and got MUCH better results. All the artifacts disappeared (rings, lines, etc), and the tint and rings really blended better. All that is really left is a cold white hotspot which blends to a warm (yellowish) corona that gets warmer for a ways into the flood, then a cold white flood.

It reminds me of why this McGizmo reflector is such a prized possession!

While fiddling around with the various McGizmo reflectors I have, I noticed that different parabolic shapes cause different tint effect blend patterns, and some of them cause a "double image" flood.

Anyhow, I got to looking at the side emitted light color profile a little closer, pay attention to the banding and tints, and then look from one side of the photo to the other and notice how the tint changes (close-up):

 

[chimo]

Okay, this next section will be of concern to white wall hunters and Ring Wraiths.

Thanks for the continued flow of info on this.

Why do you suppose they went to the gummy domes - more suitable index of refraction or easier to manufacture?

 

[jtr1962]

Besides rinsing with water or isopropyl alcohol/water mix, anyone come across any great ideas on removing/preventing the dust collection on the Seoul P4?

There are several types of antistatic sprays for plastics available which might work although I haven't tried one yet. I found the problem very annoying when I was working with Seoul LEDs. I don't know why they can't use a polycarbonate lens like the Luxeon or a glass one like the Cree. That and the fact the slug is not isolated are both negatives to me.

 

[Erasmus]

Good job NewBie!

 

[EngrPaul]

NewBie, Thanks for your many pictures, including side profiles. They are very useful!

 

[photorob]

I you were take the gummy bear off the top of the led would it be possible to just lay down some clear high temp epoxy instead. If there is such a thing as clear high temp epoxy.

 

[NewBie]

I went back and manually tweaked on the LED flood profile photo to get it looking closer to what I see with my eyes, using my monitor and my wife's.

 

[NewBie]

Well, I wasn't that satsified with the P4 tint photos, so I decided to re-take a braketed series of them. I found if I turned it down to 250mA (instead of 700mA), it wasn't as tinty looking in the photos for some reason. Maybe the sheer brightness range in the photos was messing up the camera or something. Anyhow, these are closer in some ways to what I see:

 

[McGizmo]

Newbie,

If you pair up your big aspherical lens with the Seoul and compare it to the Cree XR-E, Seoul P4 and a Luxeon, I think you can see the differences in the light images we are working with. Although the EZ1000 die is smaller than the Luxeon, in both the case of the XR-E and P4, there is diffusion and probably refraction and even some diffraction occuring as the light travels through the silicone and on out. More so I think than in the case of the Luxeon and as a result you are also projecting the "ghost" of the domes themselves. The effective spot diameter of the P4 is larger than that of the XR-E due in part I think to this and larger than that of the Luxeon as well. Even with a specular reflector, the edge of the spot is softer with the P4 compared to the XR-E or Luxeon. I would guess that this is also due in part to the phosphor in the P4 that extends past the die itself.

With some lenses and a specular reflector, I have seen the bond wire cat whiskers but it doesn't take much of an orange peel to remove these.

Had the K2 amounted to much more than a curiousity, I think the gummy bear's affinity to be surrounded by dust bunnies would have been a well addressed topic of discussion here.

I see your Luxeon sample has some of the separation of its goo. I had a X bin that had a large "bubble" in it and kept from using it in any builds because it was clearly obvious to the naked eye. 6 months later, it had gone away?!? :shrug:

These macro shots are not flatering to some of these LED's but down range where it matters, the peach fuz, cat whiskers and "laminar stratification" of goo doesn't matter; or so it would seem. :shrug:

 

[PlayboyJoeShmoe]

Thanks for all you do Newbie!

I don't have the means to acquire and mess with all these new fancy LEDs. But somewhere down the road, some of my lights that don't quite "have it" will get MUCH better!

 

[kogatana581]

I'm seeing some green at the top of the hotspot in the 3rd and 4th photos. Is it just my monitor?

 

[NewBie]

Good Morning Don!

If you look carefully at around a 45 degree angle, you will notice the Seoul P4 has an extra milky layer of silicone above the phosphor layer that is down at the die level.

Also, if you watch the die at various angles and rotate the Seoul P4 LED, the lens on it causes different magnifications at different angles, it is somewhat more aspherical shaped than a half circle of the Luxeon, if you look back earlier.


I second your suggestion on the rough reflector surfaces helping with the various defects/reflections/shadows/rings/etc, as I'd mentioned before, and the rough reflector surfaces also help with smoothing out the tint, so you just end up with smooth tint donuts/bands- where the more heavy ruddy/bumpy reflectors help out with the tint rings/donuts/bands more than just a slight orange peel. IMHO, the more agressive finish also blends out the hotspot better, but it is a personal preference for me (the intensity blending).


I took another photo, with things focused on the paper surface, up close:

Side note- from different emitters off the same strip, I am seeing different items for tint variation in the profile and such, in some ways some are better, others are worse. But it is more a trade-off this for that.

.

 

[DFiorentino]

I applaud your attention to detail Newbie. This post has been shockingly interesting to read through. :goodjob:

-DF

 

[AlexGT]

Very nice review, thank you for all your effort in documenting this.

I wonder if these leds come on a star?

AlexGT