Difference between Blf Gt94 and BlfGt4

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Jimo
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Difference between Blf Gt94 and BlfGt4

I’m still fairly new to the flashlight collection family. I am wondering how the BLF Gt4 has a higher lumens than the Gt94. The Gt4 has 4 70.2 emitters with a lumens count of 32.000 and a candela of approximately 500 thousand. The Gt94 has 4 90.2 emitters with a lumens count of 20.000 and candela of approximately 1.5 million. Shouldn’t the light with the larger emitters have the most lumens. I would like to understand how this works. Please can I be advised on this topic. Jim

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Sunnysunsun
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The XHP70.2 has a larger emitting area than the sbt90.2. The 70.2’s emitting area is ~31 square mm while the she’s emitting area is ~ 9 square mm

Firelight2
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To elaborate on what Sunnysun posted:

The main criteria for throw is the intensity of the light emitted by an LED. Think of intensity as lumens emitted per square mm.

A pin-point source of light focuses better, and thus throws further. Larger LEDs tend to be more efficient and produce more lumens than smaller, more intense emitters.

The larger emitting surface of the XHP 70.2 is more efficient and overall produces more light… hence the 32,000 lumens. However, the light it produces isn’t as concentrated as the 90.2’s light and it has lower intensity. The 32,000 lumens is spread out over 31 square mm, while the 20,000 lumens from the 90.2 is split among only 9 square mm.

Each of the square mm of the 90.2 is brighter than each of the square mm of the 70.2, which means the 90.2 has higher intensity and throws further. But because the 70.2 has more square mm, the 70.2 produces more light.

The GT with 70.2 produces overall more light, but the light isn’t as concentrated. It will have a wider hotspot, but the center of the hotspot isn’t as bright as the 90.2’s hotspot.

Superstocker
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It might also be worth pointing out that the two emitters are from different manufacturers and so the fact that the one is called a 70.2 and the other a 90.2 is not relevant to determining size or power, just like the nomenclature of a Ford F150 truck is not relevant in comparison to a Suzuki CBR250. The Cree XHP families of 35’s, 50’s and 70’s do increase in size and power according to nomenclature. The GT4 uses Cree XHP70.2’s in it. The Luminus SST family increases in much the same way (though it is more complicated with SBT, SFT, CFT, etc. being “variations” of the SST models) and goes 10, 20, 40, 50, 70, 90 (those are the ones I know of). The GT94 uses Luminus SBT 90.2 (more technically SBT90 gen. 2, Luminus does not, as far as I know, use .2 to designate generation two. That’s a Cree thing. but it is a handy and convenient way to put it and many abbreviate it that way).

The error occurs in thinking there is some sort of correspondence between the names across manufacturers, even if due to not realizing there are different manufacturers. This confusion is also more likely to occur when the other parts of the name are left off. For instance, saying “70.2” and “90.2”, rather than “XHP70.2” and “SBT90.2”. That’s a little bit like saying “150” and “250” rather than “F150” and “CBR250.” Context and being in-the-know will usually clear up any possible ambiguity but it can be confusing.

Sunnysunsun
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Cree’s xhp line’s number refers to the die’s width/length. 35 is 3.5mm, 50 is 5mm, 70 is 7mm. Luminus’ number refers to the emitting surface area. Sst-20= 2 square mm, sft40= 4 square mm, sbt90= 9 square mm

Jimo
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Wow thanks I really appreciate you all.I am understanding much more. Mabey a standardized system of measuring or listing output would be helpful for the industry. I’m going to purchase a Gt94 soon and want to know more about it. Thanks anymore information or advice is welcome, Jim

Jimo

ChrisGarrett
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Jimo wrote:
Wow thanks I really appreciate you all.I am understanding much more. Mabey a standardized system of measuring or listing output would be helpful for the industry. I’m going to purchase a Gt94 soon and want to know more about it. Thanks anymore information or advice is welcome, Jim

Hi Jim,

I don’t think that a few thousand flashlight geeks over on CPF , or here on Budget Light Forums are going to sway them at all.

Best to just read stuff from the smart people here and absorb it.

Chris

Jimo
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Your probley right. But it would be good if they did standardized the way light was measured and listed.

Jimo

CNCman
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Watch Matt Smith’s video and you can see the difference. Wink
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https://budgetlightforum.com/node/74602
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zoulas
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Sunnysunsun wrote:
Cree’s xhp line’s number refers to the die’s width/length. 35 is 3.5mm, 50 is 5mm, 70 is 7mm. Luminus’ number refers to the emitting surface area. Sst-20= 2 square mm, sft40= 4 square mm, sbt90= 9 square mm

What is the 2 in XHP70.2? Second gen?

BurningPlayd0h
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Don’t put too much weight in what numbers are chosen as model names. Manufacturers change their numbering systems all the time, they certainly vary between brands, and often they mean nothing at all and are just arbitrarily chosen.

Jimo wrote:
Mabey a standardized system of measuring or listing output would be helpful for the industry.

I’m not sure I understand, they do have that already? That’s how and why you can compare the lumens (total output) and candela (intensity) of these two flashlights.

zoulas wrote:
Sunnysunsun wrote:
Cree’s xhp line’s number refers to the die’s width/length. 35 is 3.5mm, 50 is 5mm, 70 is 7mm. Luminus’ number refers to the emitting surface area. Sst-20= 2 square mm, sft40= 4 square mm, sbt90= 9 square mm

What is the 2 in XHP70.2? Second gen?

Yes, and all the “.2” emitters (with the possible exception of the XHP35.2?) and XP-L2 are “flip chip” versions of the originals.

CR888
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I’m glad I read this thread…tis got lots of details, facts & stuff.

CR888