Doing the math. Which is more sensitive to visible light?

[DoorMan 0]

I'm really trying to get my head around all this stuff and have spent a large amount of time on this one. This is my first quection here and I tried to figure it out alone to no avail.

 

0.05 Lux at F1.2 (30 IRE, SAGC)

 

Or

 

0.15 lx (50IRE, F1.3,AGC 30dB)

 

Assuming the AGC's line up perfectly between the two and the Color Temps are identical. That is to say, are the f ratings gonna bring these into line as equals with regards to IRE if changed the lenes around? Which setup is brighter?

 

Thanks all!

[DoorMan 0]

Atleast I think that's all you guys would need? Am I missing some basic look-up tables to help determine this?

[DoorMan 0]

Responding to my own thread again.

 

Nevermind I found it. It's a pretty simple equation really. I hope it proves as real world useful as it should for my purchases.

[kensplace 0]

I guess it depends on if the specs are actually accurate in the first place....

[DoorMan 0]

I guess it depends on if the specs are actually accurate in the first place....

 

Yes not too many companies rate their products with all of these specified. I'm hoping that the one's I'm looking at will infact be accurate enough to assume a decent real life replication.

 

I've heard told the one's who do spec this way are the more trustworthy of manufacturers. Not the one's rating thier cameras with several thousand dollar lenses and such.

 

Sony is one the the two..

 

Anyway figured I'd ask all the experts here.

[Jeroen1000 0]

Share what you have learned please:)I I'd say the 30IRE one has the better specifications. IRE has something to do with light intensity I believe...the lower the number the lower the light conditions. The one camera is able to producte an image at 50IRE while the other one needs even less light, in this case 30 IRE.

[DoorMan 0]

50 IRE is a better image than 30 IRE produced by the camera. IRE is kind of slang when describing anything but an analog too. This is a decent article explaing the variables in play.

 

http://www.mintron.com/HTM/Q&A/Q&A%20revised%20version(Sep.07)/Basic%20questions/Q1-Minimum%20illumination%200.0001%20lux.htm

[rory 0]

specs rarely mean anything, unless its coming from a big brand like Ge, Bosch etc. and even then its a stretch.

 

only way to tell is buy them and put them side by side .. sucks but thats pretty much it.

[DoorMan 0]

At Megapixel IP Cam rates you could spend several thousand dollars to test them out. That really hurts the wallet.

 

I know they all lie, and the Japan mfg's use standardized test methods. Only to embellish them in the end but they should atleast be more uniform in real world results. But specifying like this:"Buy my camera it is .001 Lux" is unproveable. When spec'd like the above ,with all varibles listed, the verification can be done (if anyone really cares to that is).

 

In the end it is buy and try it...and yes it does suck at $500 to $900 a pop. Just wanted to know how to run this math to determine the better cam of the two is all...I believe I do have it.

[rory 0]

check out faceplate sensitivity.

Manufacturers should include this in their specs, but rarely do.

 

and here are some threads that may relate to this topic:

 

http://www.cctvforum.com/viewtopic.php?t=4227

http://www.cctvforum.com/viewtopic.php?t=11439

http://www.cctvforum.com/viewtopic.php?t=11783

 

and .. well too much info:

http://www.cctv-information.co.uk/i/Light_Transmission_Through_Lenses

[ak357 0]

At Megapixel

I know they all lie, and the Japan mfg's use standardized test methods. Only to embellish them in the end but they should atleast be more uniform in real world results. But specifying like this:"Buy my camera it is .001 Lux" is unproveable. When spec'd like the above ,with all varibles listed, the verification can be done (if anyone really cares to that is).

In the end it is buy and try it...and yes it does suck at $500 to $900 a pop. Just wanted to know how to run this math to determine the better cam of the two is all...I believe I do have it.

 

I hear your pain

buy light meter and start comparing yourself ( few hundred bucks and fun to use

[DoorMan 0]

Rory,

 

What a great compilation of posts and link. This really is helpful to someone of my limited knowledge. Now that last link is filled with all the right info for some intellegent research not simply relying on blubs of short attention span info I've been running into. If my eyes weren't bleeding from the info contained in the post I'd read on throught the site you linked tonight.

 

Time to fire up MathCad and have some fun with all that info..

 

Thanks alot for this.

[DoorMan 0]

ak357,

 

I was looking at those and probably will get one. Is the Exetech a decent one?

 

Geez now I gotta research light meters.......where is that coffee....

[ak357 0]

ak357,

 

I was looking at those and probably will get one. Is the Exetech a decent one?

 

Geez now I gotta research light meters.......where is that coffee....

 

I would recommend the one on my pix

here is why

Wide range to 20,000Fc or Lux with high resolution to 0.01 Fc/Lux

[DoorMan 0]

Thanks!

[Biphase 0]

Extech makes nice meters....jsut picked up a LUX meter as well.

[cglaeser 0]

Lux ratings are pretty much useless without the shutter speed. Consider the data sheets for the following hypothetical cameras?

 

Camera A - 0.05 lux

 

Camera B - 0.5 lux

 

Which camera would you select for a night security camera? Before you answer, let's reveal more information.

 

Camera A - 0.05 lux @ 2 s

 

Camera B - 0.1 lux @ 1/50 s

 

Operating Camera A with a shutter speed of 2 s is pretty much useless. Virtually all motion except for growing mold will be blurry. So, if we operate Camera A at a more reasonable 1/50 s, then the minimum light required would be 5 lux, which is considerably more light than is required by Camera B.

 

In other words, the lux ratings commonly listed in security camera data sheets are pretty much useful without the associated shutter speed.

 

Best,

Christopher