Short review: Yezl T9 "big head" aspheric zoom

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DrJones
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Short review: Yezl T9 "big head" aspheric zoom

I finally found the time for some measurements, so here's my small review (no pictures) on the Yezl T9 from the group buy (see there for pictures) for 30$ incl. shipping at CN Quality Goods.

Conclusion:

If you want a nice, even flood, this light is good (even though a big bulky head is not needed for that purpose), but if you hoped for good throw due do the big diameter (as I did), then this light is one big disappointment.

 

Flood mode: good 

Actually the performance in flood mode is quite good. I measured 3.2A on high, and it produces a nice even wide flood with lots of light. My EDI-T P4 zoomie produces a smaller and weaker flood cone.

XM-Ls typical tint shift (cold center, warmer towards the edges) is noticeable.

Modes are 100%/37%/7%/strobe/SOS, with noticeable PWM (90Hz). Funny: there's even some PWM on high... I wonder why. 

 

Throw mode: below expectations

The head is ~43mm in diameter, the lens only 33.5mm (border not included). The plastic lens has a back focal length (bfl) of about 35mm, which is quite long. Thus you must pull the head out quite a lot (compared to others), and you will almost automatically touch the lubed part of the slide mechanism.

The relatively long bfl (for an aspheric) results in a full aperture of only about 50°, which means that only ~17% of the LED flux hit the lens (stronger aspherics get >25%). Additionally the lens shows some aberrations at the edges, reducing throw. I measured intensity and NEMA-throw as 17kcd/260m when fully pulled out (with a relatively sharp image of the die) and 20kcd/280m when slightly pulled in again (ugly fuzzy image, but the lens edges can contribute better).

The long bfl also results in a smaller spot than I hoped for: My EDI-T P4 (XR-E, 21mm lens) throws as well and with the same spot size, but is much smaller and consumes less power. T9's spot looks nicer and has a nicer tint though.

Edited by: sb56637 on 12/04/2011 - 10:08
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Nice write-up. I agree with your findings.  Laughing

Your lux intensity readings mirror mine....I am getting slightly less, IIRC its 18k when slightly pulled in.  But then i get 2.3A at the tail only.  LOL!   And also my meter always under-reads somewhat, but that few % is ok.

I posted several times before in other threads, get this light for flood. Bro Vectrex even did the mathematical calculations as well as detailed drawn-up diagrams.

I got it for flood and also for the darth vader looks.  LOL!  This would be useful for very close range work where you need a bright 45-60 deg flood, even wider than a Xeno E03 XM-L can muster. Diffusers would just take away power. In such cases, the majority of the light from the LED still gets captured by the lens. If you gun the light without the head, the lux is not as high.

But i also figured that a lot would still miss the point, because throw, metres, cd/lux@1m is always much more talked about and "measurebated" in the hobby...of course i do understand coz this IS a hobby. hehe...

 But I do use the lights for my servers sometimes. My EDC is too spotty, and its a small Tank007 TK-737, spot size like a iTP A1 EOS. It is very difficult to operate under the flood boards, behind servers....when you are tracing C-forms, cables etc...... Or maybe you wanna take pictures with your handphone and you need a wide angle shot of something for documentation, say server racks and you know there are usually not enough space there to move back. (I know there are ceiling lights in the server room but if you want details and lower ISO operation/less noise then you'd want a direct fill-in light).  Try reflected ceiling bounce of your Q5 light...hey where's the light man?  LOL!

Vectrex
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The PWM has killed every interest in the light for me. 90 Hz is really low and especially for it's main purpose, close-up work, very annoying.... at least for me. We need more current regulated budget lights imo.

agenthex
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Close up you're going to have it on full flood anyway which is supposedly quite wide on this, so pwm not really as much of a problem. But 90hz is pretty lol though.

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In my opinion close-up low pwm is more annoying than pwm in a distance.

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Vectrex wrote:

The PWM has killed every interest in the light for me. 90 Hz is really low and especially for it's main purpose, close-up work, very annoying.... at least for me. We need more current regulated budget lights imo.

Yeah man, more Xeno E03 pls....but in 18650 bodies.  No need HA.  All the Solarforce, Sky Ray, Fandyfire, Tank007, Romisen, P60 drop-ins that I have are pretty low as well.   The only usable low light is my Ultrafire U80, i am guesstimating at least 400Hz.  The UF-980L is also very slow.  Actually i use the U80 quite a lot.

I guesstimate by moving my fingers and then see if i can see individual fingers or just some vibrating fingers that seems like a mess.  The U80 shows a fast mess, which is good.   The best is iTP!

Regulated lights with 1 x 18650, what is the main hurdle?

The only "4.2V" light that is regulated is the CQG 3x18650 extreme runtime light......

PS. The Yezl M7X that I have also has pretty ok PWM, I think 400Hz. ie I cannot show individual fingers no matter how fast I move my fingers. I only managed to show "finger-sticking-to-finger" if i really try to fling my hand around so fast that I'd think any hard my hands would fly off.  LOL!   Try it.

Confirmed with the camera. U80 is 450Hz and Yezl M7X is 500Hz. Most would be happy with either.

 

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Vectrex wrote:

In my opinion close-up low pwm is more annoying than pwm in a distance.



Yes, but the "spot" is large so for same frequency, angular velocity has to be far higher for same visible effect. 

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