Not impressed with the new TK 75 4000 Lumens

I own both. But for some reason, no matter where I compare them both, I just see very little difference in the 4000 and the 2600. No matter as hard as I try to make myself justify my new purchase I just can't find a reason for it.

I do absolutely adore the lockout function, as the original one kept coming on my by mistake inside the holster and I love the lanyard and shoulder strap. Short of that, I probably should've done It. I don't see much difference in overlap, brightness or anything honestly. I am no expert but from what I have learned on this website, I'm guessing 2600 versus 4000 is about a 30% increase in brightness???

So I can't find it. Now granted, maybe if I wasnt in my neighborhood and I was on an open football field shining from goal to goal I'd see it, but from anything that I can see around here, the exact same

Well, its mostly that humans suck at judging brightness. (I didn't check your profile, but, I'm guess you are in that group....)


I have light measurement equipment, and, really, by eye, its hard to tell brightness unless you know how to benchmark.


For example, if you pick a target both can reach, and illuminate well enough...one can be twice as bright, and you might not be able to tell.

Where you CAN tell is when you find a target that one can illuminate, and the other can't...and in a foot ball field sized area, with that light, you won't have that scenario to see a difference.


Also, remember that the beam angles are not 100% identical...so, while 4,000 LUMENS is closer to 60% "brighter" than 2,600 LUMENS, you can't SEE lumens.


To illustrate - Lets assume, for now, that the beam angles stay the same...so, 60% more lumens should give us more lux...but, with a wide beam angle, the added lumens are spread out over many hundreds of meters.

A LUX is one lumen per square meter.

You CAN see lux though...its what reflected back to your eyes.


Simplified example -

If I shine a beam so it makes a square meter have 1 lux of brightness, I'd need one lumen to do it.

If I make the area 10 meters by 10 meters (100 square meters)...to get that same 1 lux, I'd need 100 lumens to do it.

To raise the lux to TWO, I'd need 200 lumens on that 100 square meters.


Now - Imagine I don't add 100 lumens to my original 100 lumens...I only add 60 (60% more lumens), so it goes from 1 lux to 1.6 lux.

If you are looking at the area being illuminated, your eye may not register a difference of 0.6 lux...and so forth.


Where you CAN see more, and tell the difference, is if you go to a place with a LOT of targets...a cemetery for example, with rows and rows of head stones...and simply count the headstones you can see with each light.

Generally, even if you can't tell BRIGHTNESS, you CAN tell if you simply SEE a stone....and, the brighter light will show you more stones....even if you didn't KNOW it was the brighter light.

Ya gotta love this place. I read the thread title and smiled... Not at the OP's dilema, but with the thought of 4000 hand held lumens not being impressive.

Yeah Scout I got to say, I have been getting spoiled lately. LED technology has come such a long ways I'm just expecting sooooo much more.

Teej I really am confused even by listening to your explanation. I'll just leave it that humans suck in determining brightness that was the clearest answer only part I fully understood was the lumens was being distributed over a broader area and that made sense to me.

But I had the same conversation year back when I had the PD 32 versus the PD 35. 350 versus 850. I was thinking it should be more than twice as bright. And somebody told me I forget who, that even though the lumens was more than twice as many that only equated to about about 30% brighter having a 500 difference in lumens.

Now here we only have a 1500 lumens jump up or nowhere near to twice as many but you're saying it's jumped up to 60% brighter? That confuses me!

Scout I'm having the same problem with the headlights on my truck. I bought some LED off-road lights that light up the whole world and now my regular headlights just seems so horrible I almost can't see at night with them. I tell you, I guess I was just so impressed with the keep TK 75 2600 and then hearing they had a 4000 I just imagined a day and night difference. I didn't get it.

100 divided by 4,000 times 2,600 equals 65. You have an increase in brightness of about 1/3, which is about 2/3 short of what you need for it to be noticeably brighter (according to the theory that you need a light to be twice as bright to have any noticeable difference in output).

Basically you'd have needed 5,200 lumens to get that wow factor going again.

Same as I can sometimes hardly tell whether I've a light set to 100 or 200 lumens until I cycle through the modes, or compare it to another light with a known output.

An option would be send to vinh for some PDT(premium de-dome tint) magic and current bump. This with extra heat sinking will turn your not too impressive tk75 into a tk75vnQ with very good throw !!

Only a thought and it will have around 340kcd compared to around 90/100kcd of the 2600lm version.

http://www.candlepowerforums.com/vb/showthread.php?406724-TK75vnQ-Best-Searchlight

cheaperrooter said:

But I had the same conversation year back when I had the PD 32 versus the PD 35. 350 versus 850. I was thinking it should be more than twice as bright. And somebody told me I forget who, that even though the lumens was more than twice as many that only equated to about about 30% brighter having a 500 difference in lumens.

Click to expand...

Ok, now I KNOW you are bad at judging lumens; I have both the PD32 and the PD35 (850 lumen version), and I see a HUGE difference between the two. However, I can imagine it being harder to judge the difference between your two TK75s. It's already a super bright light with an enormous amount of throw, and if you don't take those two bad boys somewhere they can really stretch their legs then it may be difficult to objectively judge the difference. And like TEEJ already said, even a football sized field wouldn't be big enough.

I own the 2900 lumen version of the TK75, and I think the next light of this size I buy has to be at least 6000 lumens for me to justify upgrading.

Best way to judge brightness that I been able to find, is the ceiling bounce test. (cavemen style)

As output increases, does it take an increasingly larger multiple increase in output to produce a noticeable difference, or is the 2x increase rule of thumb constant?

Be careful, lumens and throw can be like drugs...

I would be more curious if you could take some beam shots. Make sure the camera settings are the same for each shot. What would the camera show? Can you do that?

Are you doing a side by side comparison? Or putting batteries in one, then playing, then removing batteries and putting in other, then playing?

Also, if you are running both at the same time, curious to know what kind of batteries are being used in each light?

I would also say, I have found that judging lumen output, and led tint colors can vary wildly between just two people.

scs said:

Be careful, lumens and throw can be like drugs...

Click to expand...

Ain't it the truth? I bought a TM16 because I wanted lumens. Then I bought an XP-L HI Barracuda because I wanted throw. The Barracuda is ridiculous, but now I'm back to wanting lumens. I have my eye on that new 7k flooder that Thrunite has. Does it ever stop?

JimTokle said:

Ain't it the truth? I bought a TM16 because I wanted lumens. Then I bought an XP-L HI Barracuda because I wanted throw. The Barracuda is ridiculous, but now I'm back to wanting lumens. I have my eye on that new 7k flooder that Thrunite has. Does it ever stop?

Click to expand...

:devil: It never stops!! Flood, throw, ahhhhh!!!! And being "spoiled" is definitely a real thing. Get beyond the ~1500lm mark and nothing really seems to change. OK it does, but just not the WOW FACTOR you used to get between something like 300lm and 1000lm.

For me, I really think the brick wall is something like them TM16. I love that light, but sold mine since I just don't have enough use for a ton of throw. It does a great job of throwing but without using a laser beam pattern. Lots of lumens, lots of throw, nice spill. It will be hard to beat this IMO. Currently my light to end all lights. Now, back into the flood game for me :shakehead

I use a lightbox.... it is very difficult to gauge output differences with the naked eye, particularly if there's tint or beam profile differences. I'm big believer in the square/square root laws of light perception - eg, it takes ~4x the lumens to appear 2x as bright, or ~9x lumens to appear 3x as bright...it just feels right to my eyes knowing the real lumen differences.. YMMV.

In your case, the math would be 4000/2600=1.54 or 1.54x more lumens, so 1.54^0.5 (or sq rt of 1.54) = 1.24x perceived, or a 24% increase in perceive brightness. IMHO, that difference is tough to see.

This is just like the comments when the TM06 Tiny Monster came out. People saw no difference between high and turbo. If you turned the light off in turbo, waited a couple of minutes then turned the light back on in turbo then stepped down to high you could see a difference in brightness.

I've got little use for flood type lights as most of the lights I have more than enough spill to appear to be flood. Any of my smaller lights can be used to supplied fill/flood light since they lack the throw of my search lights.

Stream said:

Ok, now I KNOW you are bad at judging lumens; I have both the PD32 and the PD35 (850 lumen version), and I see a HUGE difference between the two. However, I can imagine it being harder to judge the difference between your two TK75s. It's already a super bright light with an enormous amount of throw, and if you don't take those two bad boys somewhere they can really stretch their legs then it may be difficult to objectively judge the difference. And like TEEJ already said, even a football sized field wouldn't be big enough.

I own the 2900 lumen version of the TK75, and I think the next light of this size I buy has to be at least 6000 lumens for me to justify upgrading.

Click to expand...

I think you misunderstood. I never said I didn't notice a difference between the 32 and the 35. I simply said that percentages for percentages the 35 was 2 1/2 times more lumens than 32 I was expecting it to be 2 1/2 times more brighter and it wasn't. But I definitely noticed a big difference. Another words I assumed that the percentage of lumens increase equaled the percentage of brightness increase as well

But according to the math calculations that I just learned evidently I got wrong information from someone when they said the 35 was only going to be about 30% brighter than the 32.

cheaperrooter said:

I think you misunderstood. I never said I didn't notice a difference between the 32 and the 35. I simply said that percentages for percentages the 35 was 2 1/2 times more lumens than 32 I was expecting it to be 2 1/2 times more brighter and it wasn't.

Click to expand...

No, I read you right the first time; you were basically saying the same that you said now. I have both of these lights, and to me the PD35 (850 lumen version) seems at least twice as bright as the PD32. Someone already mentioned the ceiling bounce test. This is what I use if I have trouble telling the difference between two lights, and it works very well. It's worth noting that you need to have both lights side by side, and toggle by switching one off and the other on.