TK's Emisar D4 review

The white “grainy” one got really smooth within a week in my pocket. I could experience this again when I started using the short tube. But after 6 or 8 weeks of use, the D4 is just as smooth as my other lights. Just use and carry them.

For speedier results, pass the light back and forth rapidly on somewhat abrasive cloth covering a cushioned surface.

The edge of a felt covered sofa worked for me when needing to smooth the sharp edges of a Jetbeam TCE-1 purchased new at a third the price. Going Gear sold fifty of the titanium lights at 80 bucks each, purchased cheap from Jetbeam due to complaints about the grabby diamond pattered knurling on the tubes.

This has been bugging me since my last post, finally got back to look at this. I realized that you posted the part number and quoted the data sheet, while I quoted a different random data sheet. The part number listed is actually much better than the one I found.

I did not find the data you quoted (on voltage versus drain current), but diagram 6 (on page 8 of the linked data sheet) does plot the resistance of the part versus current from 0 to 50A (part is rated to 100A constant, 400A peak!!) The resistance is very flat for a given gate bias voltage, but does vary for different gate bias voltages. Since the D4 does not have a power converter in it, the gate bias voltage can be no higher than the battery voltage. So the on resistance is like best case about 0.001 ohm (1 milli ohm) but does not vary with the drain current.

I am not posting this to say “I told you so”, but more just to clear um my own thinking on this, and share those thoughts with others who might be interested. :beer:

why to choose sst 20 version? what is really better with this led?

CRI

I played around with my SST20 4000K 95 CRI D4 last night and compared it to my XPL HI D4. My impressions of the SST 20:

  • It is possibly very slightly throwier on a full cell at full power. I didn’t verify with my luxmeter though.
  • It puts out a lot less light than XPL HI. The hotspot might be marginally brighter, but is a lot narrower than the D4.
  • I suspect SST20 draws more current than XPL HI. With the SST20, the head got hotter noticeably faster.
  • Output also dipped a lot faster than with XPL HI. The thermal sensor kicked in to reduce output within 10 seconds. With Anduril installed, and XPL HI I could set my Titanium D4 with bare polished aluminum head (pretty much the worst possible heatsinking combo for a D4) at a max ramp setting of 46 clicks. The light would take quite awhile to ramp down. When I swapped in SST20, I had to set the max ramp at 51 clicks and even then the head still got hot and ramped down within 20-30 seconds or so.
  • My battery voltage depleted noticeably faster with SST20, also suggesting that it draws more current. Run the SST20 D4 for 30-60 seconds at turbo with rampdown, then let it cool and turn it on next to an XPL HI version and even the hotspot of the SST20 is noticeably dimmer than XPL Hi.
  • At all lower and intermediate power settings the SST20 displayed an unpleasant greenish tint. The tint is definitely above the black-body line. I found lower power on my XPL HI D4 to be much more pleasant and didn’t look greenish. This is a shame, because at turn-on on max-turbo the green isn’t evident and the beam looks great.

Having tried the SST20 4000K 95 CRI side-by-side with 4000K 5D XPL Hi, I have now concluded that XPL Hi is much superior. The benefits of higher CRI and lower cost from the SST20 are massively outweighed by the XPL Hi’s benefits of better color temp, higher peak output, higher sustained output and longer battery life.

I agree ,that’s what I thought, it’s still very nice though ,I probly would of kept the sst if I didn’t compare it to the XPLHI.

Thanks Firelight2! That helped me a lot on deciding between the two. :slight_smile: :+1:

Yes for mé the same

Nah, use the light outside and you’ll see why higher CRI is always better.

Also, don’t forget the SST-20s high CRI have a lower forward voltage than the XP-L HIs, so more current is consumed.

And it’s also going to last longer on regulated modes because of this too.

it is nice outside but I prefer the XPLHI.

I disagree. Vf has nothing to do with battery power consumption on regulated modes. The battery voltage appears across both the current regulator and the diode. If the regulator is working, the current through the regulator is fixed. Battery power is simply battery voltage times regulator current. If the diode Vf is higher, more dissipation in the diode, less in the regulator. If the Vf is lower, less dissipation in the diode, more in the regulator. I would argue the diode can handle the dissipation better then the regulator. If Vf went to zero or very low, one would burn up those little regulator chips pretty quick, as they have no real heat sink.

Here are some factors in how useful and pleasant I find an LED’s output to be, in order of importance (in my opinion):

  • Output - measured in lumens. The purpose of a flashlight is to illuminate something. Shear output matters a lot. A light with 100 lumens just doesn’t have as much punch as one with 500. What’s the point of having a light with fantastic color temp, tint and CRI if it’s not bright enough to illuminate what you want it to?
  • Intensity - measured in lux. or lumens per fixed unit of surface area. An LED with higher intensity has better throw. Important for some applications.
  • Color Temperature - warm, neutral or cool white. Different people have different preferences. I find 4200-4300K to be ideal, but will accept anything 4000K-5200K.
  • Tint - above or below the black body line. Tints above the black body line tend to look greenish, those below look rosy. Most people, myself included, find rosy tints to be better.
  • CRI - how well the light represents color at the given color temperature and tint. Most neutral tint LEDs are 70-80 CRI. High CRI LEDS tend to be 90+. I can immediately tell the difference between a 65 CRI and 90 CRI, but when it comes to neutral tints I find that I can only tell the difference between 80 CRI and 95 CRI if I hold the two lights side-by-side and compare beams. Because, CRI is so subtle I find it to be by far the least important of the 5 factors when it comes to picking a light. I’d much rather have 80 CRI with beautiful tint, than 95 CRI with horrible green tint. I find CRI without good tint to be pointless.

Thanks for the feedback, I was considering trying out the SST20 in my D4. Might still some time, but not in nearly the hurry now.

High CRI always comes at the cost of efficiency. So your findings are true and they were predictable.

If cri is not important for you the lower cri SST20 LEDs would have been a much better candidate as they are way more efficient while rivaling the XP-L HI in output and beating them in throw.

I personally prefer High CRI but dislike the green in the SST20 4000k variety.

Running some very rough numbers with lots of assumptions gets me this:

  • D4 SST-20 6500K, spec’ed at intl-outdoor at 4200lm. That is 1050lm/led, so about 1280lm for the bare led, which is at 86% of max and they run at about 4.5A per led.
  • D4 XP-L Hi, spec’ed at intl-outdoor at 4300 lumen, that is 1075lm/led, so about 1310 bare led lumen, which is at 62% of max, and they run at about 4A per led.

So the XP-L Hi version runs 2A less in my calculation while putting out a bit more light. The experiences above suggest a larger current difference though, so something is off, perhaps int-outdoor’s specs or my numbers :stuck_out_tongue:

Regardless of CRI I find the SST20 to be much worse. In my D4, the SST20 is noticeably inferior for my needs in the most basic test: output.

  • The SST20 D4 ramps down much faster than my D4. I like burst modes, but in the D4, the SST20 starts out with a slightly brighter hotspot, but within 10 seconds of turn-on it is already much dimmer than a D4 with XPL HI.
  • SST20 might be more efficient, but what’s the point if I’m not able to take advantage of that efficiency and see results in-use because of the higher heat generated.
  • I hate greenish tinted lights. I find tint of the SST20 at anything less than max turbo to be unacceptable.

My modded D4 looks pretty, but has the worst possible configuration for heat management. It is more susceptible to rampdown from overheating than probably any other D4:

  • Polished Bare aluminum head (not as good as copper at transmitting heat and can’t hold as much as copper. Shiny bare aluminum has lower emissivity than dark anodized aluminum).
  • Titanium body tube and bezel (not as good at transferring heat from the head as aluminum.

It is possible that a stock aluminum D4 wouldn’t see such an extreme difference in results.

yes, of course. Sans the tint these are direct results of the High CRI variant being considerably less efficient.

Your reasoning that these are not a good choice for your needs is sound.

I was merely saying that this outcome could be expected and people should only choose high cri if they appreciate the better cri so much, that they are willing to accept the impact in virtually any other area of LED performance.

Agreed.

For those who absolutely must have high-CRI in their flashlight and who don’t care about other factors, the SST-20 is a good choice. It offers considerably higher output at high-CRI than most other LEDs on the market.

It might also be a great choice of emitter for small single-cell throwers like the D1 or D1s. With only one emitter, plus more thermal mass, those lights are much more likely to be run at max power. And max power before rampdown is where the SST-20 truly shines.