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Lux - hows good is your image?

By Oz_Media ·
bein gin a market where I provide security and surveillance cameras (as one of many related product lines)I was comparing stats and came up with a daunting question, one which i will aso ask manufacturers and post any info of interest to anyone here.

LUX is a statistic used to illustrate the light sensitivity of a given lens. A commomn LUX reference is as follows: 0.00005 lux = Starlight, 0.25 lux = Full moon on a clear night, 50-Lux = family living room etc. Each to show teh low light capabilities of a particular lens.

Okay so LUX is defined but then I thought, who decides what a clear image is at certain light levels? A 0.25 lux camera could be barely showing outlines of an image, where another manufacyturer's image may state 0.25 LUX but offer a crystal clear image where you can determine facial features.


according to Wikipedia, it is very loosely defined as the level at where an 'acceptable image" can be seen. Acceptable by whom?

Seeign a figure at all, may be acceptable to some people. Havign clear facial definition would probably be preferred.

So here again we have another scenario of an inconsistent, or undefined stats used ot sell product, just like Frequency range is used ot sell speakers.

With speakers, everyone claims they handle 20Hz to 20kHz. the perfect human ears hearing range, however most high end manufacturer;s offer very definitive frequency ranges and graphs, whereas a cheapo speaker will ALWAYS state 20-20. Take for example MaCIntosh, a very high end speaker manufacturer. Thier stats may state, 55Hz to 20 kHz +/-3db. Meaning that the soundwave only varies in volume by + or - 3db across that frequency range. A competitors speaker, of much lower quality, may say 20hZ to 20kHz but it is +/- 12db. Meaning that sounds near the edge of that frequency range may be so quiet as to not be hear or so loud as to distort, a VERY big difference but according to useless specs, the cheap speaker appears better.


So what's with Lux? Is it a relevant stat or just another number used competitively due to poor definition?

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How do they use the measurement?

by seanferd In reply to Lux - hows good is your i ...

Lux is actually well-defined, but image definition as captured by the camera's CCD, stored in a format on some media, and displayed on whatever quality monitor is a whole other ball game.

The candela, which is a base unit, is defined in terms of the wavelengths of green light that is most easily detected by the human eye. If I remember correctly, full-spectrum calculations take into account the perceived brightness of the other wavelengths in relation to the standard green.

To get the luminous flux, it's the candela projected across a radian in three dimensions. A radian is roughly 60 degrees, so that is like a 60 degree cone of light with an intensity of a candela.

The lux is that flux per square meter.

Still gibberish, probably. Have you ever had to read the data sheets for Armstrong ceiling tile?

OK, so following you Wikipedia example:
http://en.wikipedia.org/wiki/Luminous_flux
http://en.wikipedia.org/wiki/Lumen_(unit)
http://en.wikipedia.org/wiki/Candela

Geez, they've got 'em all.

It is mind bending, but it is standard. The question is, how are camera dudes using lux to market cameras? Is it in the reputed sensitivity? So many other factors come into play, lux could be meaningless. The camera could report single photons, but with a 10 pixel CCD and a 2 pixel display, what good would it do for security?

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Exactly

by Oz_Media In reply to How do they use the measu ...

Yet another irrelevant spec that consumers rely on for purchasing decisions. As with my previous post, just like frequency range and speakers.

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Right

by seanferd In reply to Exactly

That spec would make more sense for a light source, not a light detector. Which, incidentally, is not the human eye for which the lux has meaning.

Perhaps this article
http://en.wikipedia.org/wiki/Photometry_(optics)
would bear some reading by the folks using lux as the spec. They could look up exposure value as well, which would be more applicable. They'd also need to consider the light source. While incandescent lamps are fairly full-spectrum white, most other sources are not.

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Thanks for all the links

by Oz_Media In reply to Right

A very helpful reply indeed. I was curios as to measurement standards and this really 'sheds some light' on the subject for me.

Something to do and a reason to hang out in the office tomorrow.

Many thanks for the links!

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You're welcome

by seanferd In reply to Thanks for all the links

I thought these might be interesting as well.

http://hyperphysics.phy-astr.gsu.edu/hbase/vision/radiant.html

http://hyperphysics.phy-astr.gsu.edu/hbase/vision/photomcon.html#c1

http://www.optics.arizona.edu/Palmer/rpfaq/rpfaq.htm

http://en.wikipedia.org/wiki/Radiant_flux

Again, I can see it as sensible if they say that some type of recognition (e,g., movement, or an identifiable face) is visible under so many lux at such a distance with respect to all equipment factors. If they are saying that a camera is sensitive to so many lux, that is pretty much a pointless spec, I think. The camera can pick up all the light it wants, but if you don't get any useful visual output, what's the point?

Have fun.

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Yeah that's what I'm getting at

by Oz_Media In reply to You're welcome

Without a common standard, the spec is irrelevant. However products ar esol don irrelevant specs all the time.

One company will make a high end product, and offer it at a premium price, with specifications that clearly illustrate its superiority.

Another company will release a low end product, cheap price and can match the same specs as the more expensive product.

This winds up misleading people into purchasing low end products. Mind you, I was always taight you get what you pay for, but it seems that these days people compare such specs and just think it is the same thing for less money.

Take computers for example, you can buy a Dell or an IBM, IBM costing twice if not three times what the Dell costs.

The specs are all the same, the Dell may even have a 2.0 GHz processor to the IBM's 1.8. The Dell may have 3GB RAM to the IBM's 2GB RAM.

The specs may appear superior on the Dell, but the IBM will have a faster FSB and a 7200RPM drive compared to the Dell's 5200 RPM drive.

Ultimately th IBM is a far superior product, yet on paper and especially the checkbook, the Dell seems like such a better deal, while it is actually dwarfed in performance by the IBM.

The info you have provided has helped me see through manufacturer's specs and find out who really is building the better lens, in this case Computar (nice product!).

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I see

by seanferd In reply to Yeah that's what I'm gett ...

Yeah, you could stick some cheaper PC RAM in a server as well, but you'll get what you pay for.

Hope your business goes well with your client.
Cheers.

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Why it will work

by Oz_Media In reply to Yeah that's what I'm gett ...

I market products based on facts and performance. Most take the easy route, market a product on the sheer basis that you carry a product.

"Hi we have this"

I am not the only person working with this particular line here, but I am the only one that will drive it, which is why the manufacturer is now explaining to others why their territory has been opened up to competitors, such as me.

I have a reputation on offering viable, cost effective solution to fill client needs. This is opposed to offering products.......and that's it.

I have had to work hard in the past to sell in competitive markets, learning/understanding what it takes to shine above the rest.

Most will say "Here's a brochure, I sell these."

I will find out weaknesses in other products, that are being sold as strengths or tiptoed around.

I then sell based on my own products merits, not the other products weaknesses. But by illustrating my strengths, the client starts to question their own product lines and asks the manufacturer for answers. When they get no substance and my offering stands on its own, the tides change.

I have not mislead anyone, in fact the absolute opposite, I have simply informed people of what is important in MY products line. THEY do the dirty work of finding out their existing product line falls short or has been misrepresented.

I find this type of sales approach gets easier each year, as more and more people do less and less work to move a product.

When the customer calls them and says, "you offer a frequency range on your speakers but your graph and specs don't show the decibel curve, what are your stats based on?"

The sales rep usually says something stupid or nothing at all. They often make up a spec, like 24dB, not understanding the question and shooting themselves in the foot or they don't know and can't get answers, again making them look unqualified or simply avoiding the answer.

I find educating clients as to what is important and what is relevant, instantly has THEM scoping people out and questioning validity of their own claims. If that is based on info they were fed by a competitor, that competitor is history real fast.

It is easy as **** actually, exactly why I love what I do, it's effortless, get a good product that stands on its own and watch people stumble and trip trying to compete with facts.

That's why I always say its often easier to sell higher priced, quality items than it is to sell low priced junk just because it is cheaper.

Phew wordy or what?!?!?

It's a passion, sorry.

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