Just got my light meter. Disappointed with 7G5 V2.

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Slewflash
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Just got my light meter. Disappointed with 7G5 V2.

So recently I ordered a light meter, and it just came in today.
I tested my Skyray STL-V2 which I bought for $37, and my Crelant 7G5-V2 which I bought for $87.

Here are the results (I forgot which distance, but you can tell which one is higher, the STL-V2 if you can’t).

7G5-V2: 20120922_000258

STL-V2: 20120922_000324

After seeing this I took many readings, and let them both cool off, I think the STL-V2 stayed on for longer than the 7G5V2, and it still had a higher lux reading. The thing is though, the 7G5-V2 has a brighter ceiling bounce but less spill. The only thing that can redeem it’s throw is the collimator head, which more than doubles the lux reading. I knew I should have bought the 7G9.

Massive sadface right now. Sad

Slewflash 

Edited by: Slewflash on 09/21/2012 - 10:15
Pok
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How long distance?
.
7G5-V2’s spot is small (but more corona ) than STL-V2.
Try 4 or 5 meters to measure the spot.

Try to move lux sensor at middle spot.

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I was about 2 meters back, tomorrow I’ll do a 5 meter reading.

I think the overall lumen output goes to the 7G5V2 by just a hair, but it has a smaller spill, but probably brighter than the STL-V2.
I can’t say I’d recommend the 7G5-V2 anymore though, the STL-V2 is just insane for such a price.

Slewflash 

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Hi Slewflash and congrats on the meter. It is a wonderful thing to be able to suddenly quantify some aspects of the hobby like this. That said. on to the readings.

Do listen to Pok about the distance.

I am, as you may very well know, quite endeared by the little Jacob A60 that DX sells. But I find that if I do lux measurements on it at 2 meters I get 35 kCd. 4 meters gets me ~50 kCd but 10 meters gets me 55 kCd readings.

That little sucker needs some room to "stretch its legs" so to speak. What happens is that the beam is not focused at the shorter distances. So you need that distance.

Another thought for you.

Since the Crelant gives the brighter ceiling bounce it puts out the most lumens - right?

But if it does that and at the same time has less spill then more of that light must go into the center beam - right?

That should mean that it has more lumens converted to lux by the reflector. Only fault I can find in my ramblings above is that I do not know which light has the tightest/brightest spot.

(If someone who reads this is thinking "What IS the guy on about now?" please correct me. The above observations are my laymans perspective on this issue Smile   )

BTW: TY for posting this Slewflash. It is interesting to me to see the measurements people are getting with these lights.

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Yes the V2 was a step down from the original I believe, the collimator let’s it punch above its weight tho Smile

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Ledsmoke wrote:

Hi Slewflash and congrats on the meter. It is a wonderful thing to be able to suddenly quantify some aspects of the hobby like this. That said. on to the readings.

Do listen to Pok about the distance.

I am, as you may very well know, quite endeared by the little Jacob A60 that DX sells. But I find that if I do lux measurements on it at 2 meters I get 35 kCd. 4 meters gets me ~50 kCd but 10 meters gets me 55 kCd readings.

That little sucker needs some room to “stretch its legs” so to speak. What happens is that the beam is not focused at the shorter distances. So you need that distance.

Another thought for you.

Since the Crelant gives the brighter ceiling bounce it puts out the most lumens – right?

But if it does that and at the same time has less spill then more of that light must go into the center beam – right?

That should mean that it has more lumens converted to lux by the reflector. Only fault I can find in my ramblings above is that I do not know which light has the tightest/brightest spot.

(If someone who reads this is thinking “What IS the guy on about now?” please correct me. The above observations are my laymans perspective on this issue Smile   )

BTW: TY for posting this Slewflash. It is interesting to me to see the measurements people are getting with these lights.

I do love to be able to measure the lux on my lights which is why I bought it. I just want to know everything about the light Smile
The crelant gives a smaller and tighter hotspot see here
Later today I’ll measure the readings again at 10 meters to let them both ‘fully stretch their legs’, hopefully I’ll be pleasantly surprised.

The crelant has brighter ceiling bounce, but smaller spill and hotspot (so I suspect that either the spill or the hotspot has to be brighter).

Slewflash 

Slewflash
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An update: I took readings at 5, 10 and even 15 meters.
The Skyray STL-V2 still comes out on top. What a disappointing result. Hopefully when I can get my hands on a modded X6 I’ll be happy with the results Smile

Slewflash 

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I've found that my light meter doesn't do as well with the beam pointed directly at the sensor.  A dedicated thrower having overall lower lumens output can read higher because of the more concentrated beam.  That's the whole theory behind a sphere and why, when even using my meter comparing ceiling bounce, the relative results are not always reliable.

 

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Yeah Foy that’s exactly what i want to do. Measure lux by pointing directly at sensor.

Slewflash 

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Sorry dude, guess I saw your picture wrong.

 

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There’s no need to apologise. Smile We all make mistakes :bigsmile:

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Can I ask what your readings on the Skyray STL-V2 were?

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I’ll do it now, I actually haven’t taken readings yet but I’ll do it now.

EDIT: Measured at 1 meter.
STL-V2: 48,700
7G5-V2: 46,600
SR King: 22,200
7G5-V2 (w/ collimator head): 95,900

EDIT2: changed the collimator head readings, I did it wrong the first time.

Slewflash 

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Are you using the beam center, or panning a bit to find the brightest bit of the spot?

I wonder if there's a bit of a centering/focus issue; it can have relatively large impact on lux in a thrower design.

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I’m panning it around to find the brightest spot.
With the collimator head, it gets a bit tricky because it’s an aspheric so the readings can go from very high (125,000 lux) all the way down to 65,000 lux.

Slewflash 

amaretto
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@Slewflash

did you try 2 batteries instead of one, f.e. 2× 18350 or 2× 18650 with extender?
Max output with two!

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We're glad that you joined, amaretto!

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Slewflash
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amaretto wrote:
@Slewflash

did you try 2 batteries instead of one, f.e. 2× 18350 or 2× 18650 with extender?
Max output with two!

Welcome amaretto,

And yep, I used 2 fully charged cells for the readings. But now that I think about it, even if they were at 50% capacity it would still have the same output, since they’re not direct drive.

Slewflash 

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Once you get the LUX reading @10meters, how do you convert it to 1meter? is it a linear function or requires a special formula?

scaru
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As I understand it it goes by the inverse square law so the amount of light at 2 meters is equal to the amount at 1/2^2 or 1/4 of what it would be at 1 meter. 

Jinx
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FX-32 wrote:
Once you get the LUX reading @10meters, how do you convert it to 1meter? is it a linear function or requires a special formula?

Lux x 100

9m would be x81
8m would be x64
etc

Accurate distance measurement is important as this can throw readings well off when people guesstimate it.

Slewflash
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Yep it’s the amount of distance in meters squared.

Slewflash 

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Many thanks scaru, Jeansy and Slewflash, now it’s very clear Smile