Does anybody know anything about this cheap light meter from Deal Extreme?

[Gryloc]

I know this is not the best place in CPF to post this thread, but I do not know where to go. Sorry, admin! Please move me if you have to. I am not trying to promote a single product or website. I am just trying to get some advice, comments, reviews, or just some direction.

I have noticed the one light meter sold at DealExtreme for $28, but I wondered if there is anything special about it, or if it is worth buying. It looks like it is made pretty well, and it seems to have some decent basic features. Here is the link:

http://www.dealextreme.com/details.dx/sku.5100 :thinking:

The reason I am eyeballing this thing is that I always wanted a really basic and cheap light meter just to make relative measurements of my lights so I am not left guessing. I do not need anything nice right now, and I was even considering making my own (not at all easy -no directions). If I would get this, do you think that I would get decent results, compared to other people using nicer light meters? I would never question anyone else's readings because of the readings I get, of course. I know I will get different readings because the cheaper photo sensor may be sensitive in the wavelengths that the human eyes are not. Even though I am not expecting much from this $28 light meter, I just want to make sure that I will not be getting pure junk.

This would be like a pre-starter meter to me. For my "starter" light meter, when I do plan on getting one, I will probably go with a middle or lower priced meter, but until then, I will take just about anything. It would be a far more accurate meter that is name-brand (Meterman, etc), but would still have basic functions (no data logging, etc). There are a few cheap light meters on eBay as well, but I do not know. If there is a better light meter in this price range, can someone tell me where I can get one?

I am sure there are others that are wondering whether this is a worthy meter, so any tips given may help more people than you think. There is such little information about it and I cannot find anything about this light meter using the CPF search functions. If I had missed the official discussion or any review for this light meter, can someone point me in the right direction? Thank you. I appreciate the help! :thumbsup:


-Tony

 

[LA OZ]

I would like to know also.

 

[lctorana]

Got one on order, so I'll let you know in a few days!

 

[selfbuilt]

It looks identifcal to the Chinese-made Ceto CT-303B (marketed under the Cyton name). See: Google translation

However, given that it says Ceto on the front instead of Cyton, I wonder if it isn't a knock-off? :thinking:

The good news: I bought one to test out, and it gives fairly consistent results across the range of intensities I've tested it on. Using several of my lights, I can confirm mine is log-linear over a reasonable testing range (i.e. test it with different lights at a different distances. Then take the square root of the lux reading to determine "throw" for each light at given distance, and see if that light's throw then scales linearly with distance). Note that this is only a rough test, since your light's focus point needs to be considered

The bad news: Based on my large number of lights, and comparing to the results published here and elsewhere on popular models, it seems that my DX light meter consistently underestimates lux by 15-20%, based on the average sreported. Not the end of the world, so long as the meter is consistent - which it seems to be.

 

[jsr]

I've also been eyeing that lightmeter! Glad you asked the question Gryloc, and thanks to selfbuilt for the quick review. Seems it's a decent meter. Many other people's meters also read a bit lower or higher (I think chevro's reads higher typically by about 10% relative to FR's) than others and people just compensate with a conversion factor. My main use will be for relative comparison of my lights and I can use a few lights with known numbers tested by others for reference and determining that conversion factor.

I know this is not the best place in CPF to post this thread, but I do not know where to go. Sorry, admin! Please move me if you have to. I am not trying to promote a single product or website. I am just trying to get some advice, comments, reviews, or just some direction.

I think it's sad you have to start the thread with this just to prevent it from getting closed. I've seen a lot of threads that were not product announcements, but true requests for information that were closed. I think I, and other CPFers, have missed out on some good info of products that there's questions about because of the new thread closings.

 

[Curious_character]

I've also been eyeing that lightmeter! Glad you asked the question Gryloc, and thanks to selfbuilt for the quick review. Seems it's a decent meter. Many other people's meters also read a bit lower or higher (I think chevro's reads higher typically by about 10% relative to FR's) than others and people just compensate with a conversion factor. My main use will be for relative comparison of my lights and I can use a few lights with known numbers tested by others for reference and determining that conversion factor. . .

I just got a meter along with NIST certification that it meets its manufacturer's spec of 3% + 5 count accuracy. I've just begun comparing it to the $30 eBay meter I've been using for some time. Measuring one light, I'm seeing only 3% difference. On another light (admittedly at a somewhat different light level, although the same scale), the difference is about 20%. Among the tests I'm going to make is to lower the light output from the brighter one to approximately match the other, so I can compare at the same level. I'll also check a number of other lights at various levels. My tentative hypothesis is that the spectral responses of the meters might be quite different. The new one is very close to the photopic curve, but the spectral response of the eBay meter is unknown.

I highly recommend getting the inexpensive meter. I was able to get very repeatable measurements from mine, and it allowed me to get a good quantitative comparison between the throw of various lights. In conjunction with a Quickbeam box made from a milk carton, it also gave me a reasonable approximation of the total lumen output (and some really good laughs when I read the marketing-dream lumen numbers for lights and the comments of the folks who swallow them hook, line, and sinker). Dollar for dollar, I've gotten many times more enjoyment from my meter than from any flashlight. I'm confident I'll be able to say that about the new meter, too, even though it cost a lot more.

Don't get hung up on accuracy -- remember that we can barely perceive a 20% change in light level under the most ideal circumstances. And it's often hard to tell even a doubling of light output at close range.

c_c

 

[leprechaun414]

I too would like to know how this meter rates. Good to get multiple opinions from people who just purchased these.

 

[matrixshaman]

Light meters - somewhat like Multimeters ( $3 for a digital multi-meter now at places like HF) are not rocket science. And for comparing one light to another a cheap one should work fine. This stuff used to be way expensive because it was largely used in high end photography and before the Chinese got into cranking out so much low priced electronics. You might not end up with the same exact Lux as a real piece of scientific equipment like NASA might use but for getting an idea of relative brightness of flashlights I think it would be perfect. And chances are it WILL be within a fair tolerance of high end meters.

 

[TITAN1833]

i to am going to get this.i have checked offerings on ebay which BTW are around $40 shipped to UK.so $28 shipped bargin.:twothumbs

 

[bspofford]

My lux measurements with this meter seem to be consistently less than reported. This could be the result of dealer/manufacturer exaggeration, or it could be that my meter reads lower. Precision has to do with reproducibility while accuracy is an entirely different matter. You can correct for accuracy by calibrating the light against a standard. I think this meter is precise but somewhat inaccurate, but as noted in by others, precision is all that you need when comparing lights.

 

[Nake]

deleted, wrong thread

 

[Kinnza]

I ordered it, and works fine. In the instructions (chinese :thumbsdow), comes a plot of the lux sensibility against the CIE photopic curve. It match pretty well except in the blue range. It overstimates readings in the cyan and understimate in the pure blue.

But that happens with most light meters, except if you go to a very expensive one. It works perfectly to have a good orientation of the lux level.

Compared with other cheap meters, this is the cheaper ive ever seen, but its cosine corrected, wich none of the previous light meters in that price range have. And it have a very wide lux range (up to 200Klux). The measurements i took have the expected results. Any lux measurement have about a 10% error, and higher accuracy requires far higher investment.

Resuming: excelent bang for the buck, but it isnt a precision's tool.

 

[TorchBoy]

My lux measurements with this meter seem to be consistently less than reported. This could be the result of dealer/manufacturer exaggeration, or it could be that my meter reads lower.

Many LED torches seem to have the theoretical maximum of the LED mentioned, instead of the actual number of lumens that comes out the front of it.

What's cosine correction?

 

[Kinnza]

The cosine correction gives measurement closest to reality. It correct the excesive light the sensor receives due its dome shape in a way wich inform of the actual light wich would fall in the sensor if it would be flat. As lux is lm/sq meter, this is necessary to get measurements closest to reality.

Not cosine corrected light meters overstimate lux readings.

 

[TorchBoy]

How does the meter know which way the light is coming from, and thus what sort of (or how much) correction to apply?

 

[Kinnza]

How does the meter know which way the light is coming from, and thus what sort of (or how much) correction to apply?

Sorry, i cant help on that. Ive read a description of how it works, but i dont remember it exactly. I know there is array sensors capable of detecting the angle of the light falling on in. The cosine of a angle is exactly the horizontal (flat) component of it, so i think maybe it works this way. Or just using a light sensor with lambertian sensibility (thus, it automatically derate the sensor signal proportionally to the angle). But wait somebody with better knowledge than mine confirm it.

 

[emitter]

I bought this meter and compared it to a NIST traceable Extech. The DX meter made by Ceto is always lower. There are two trim pots on the circuitboard though, which I have been tweaking because I'm not worried about exact results, just comparative. It told me my EYJ light was only making 2000 lux! My SL PP3C also measured too low. They do say it was calibrated with an incan lamp.

 

[Curious_character]

I posted a comparison between my NIST certified ExTech and $30 Chinese eBay meter on this thread, and there's a little more additional information here. The cheap meter was surprisingly good.

c_c

 

[Kinnza]

I bought this meter and compared it to a NIST traceable Extech. The DX meter made by Ceto is always lower. There are two trim pots on the circuitboard though, which I have been tweaking because I'm not worried about exact results, just comparative. It told me my EYJ light was only making 2000 lux! My SL PP3C also measured too low. They do say it was calibrated with an incan lamp.

You cant expect have coherent measurements with differents meters. Specially if one is cosine corrected, and the other not. Cosine corrected one will tend to give lower values.

Im of the opinion that its impossible have high accuracy lux reading with any lux meter, so the important is the readings you get with one meter are repeatable. As far as you take the reference readings with same meter, its OK. But not try to compare reading for different meters, because there are many factors wich can affect its accuracy.

Curious_character, congrats for that great thread! Very useful :thumbsup:

 

[Curious_character]

. . .
Curious_character, congrats for that great thread! Very useful :thumbsup:

Actually, that wasn't the thread I'd intended to link -- the one I wanted to refer to was this one. I'll modify my previous posting to mention both. My apology for the error.

c_c