reversing the inverse square law

[cglaeser 0]

How is that BS? They are saying that due to the amount of different cameras in the field, they cannot tell you exactly how their product will perform,

 

The photo industry solved this mix and match problem many decades ago. Photographers could select a camera, lens, flash, and film and get perfect exposure.

 

In the security camera industry, it's trial 'n error and hit 'n miss. Consider the discussions on this forum. Has anyone tested the output of this IR Illuminator? Has anyone tested the low-light performance of that camera? The specifications should address these questions, but they typically don't.

 

Best,

Christopher

[ak357 0]

Can u be plz more specific and explain your point

why u find this to be "spectacular marketing claim"

 

It may be helpful to visualize the inverse square law. Suppose you want to butter your toast with a butter spray gun. Suppose the butter spray pattern will precisely cover a single slice of toast when held one foot from the toast. Now, suppose you want to butter four slices of toast the same time. All you have to do is arrange the four slices in a 2x2 pattern and move the sprayer two feet from the toast. You have doubled the distance between the sprayer and the toast, and 1/4 of the butter is falling into each slice. That is the inverse square law. In other words, there is a relationship between the distance and the amount of butter (light) that falls on a given area. If you double the distance, you reduce the light on a given area by a factor of 2 squared which is 4. If you triple the distance, you reduce the light on a given area by a factor of 3 squared or 9.

 

This law is well known in the field of photography, and such BS would be ridiculed as a joke in photography marketing literature. Security camera manufacturers assume that security camera installers know very little about light, and much of the security camera marketing literature is near worthless. Lux ratings don't mention shutter speed or aperture, IR Illuminators give an arbitrary distance without any mention of assumed camera or lens specifications, varifocal lenses don't mention aperture for the full zoom range, and the list goes on and on. It's pathetic. Security camera installers with a background in photography don't know whether to laugh or to cry when reading these specifications.

 

Best,

Christopher

 

Thx, Chris

I do understand inverse square law well enough

but i like you example

was just curios

[Soundy 1]

FWIW, we used pretty much the same math for calculating SPL coverage/distance of speaker arrays, and particularly compression horns, when I took audio engineering courses. Inverse-square functions make it relatively simple to design an array to provide even-level sound coverage from a single point over a large area... much like the illuminators are doing with IR light. The funny thing is, we did our calculations using the regular inverse-square law, straight up... none of this reversing BS.

 

That's the stupid thing about this: in order to get even illumination, they're USING the inverse-square law to design the illuminators - enclosure, reflectors, lenses, all of it factors in. Adding "reverse" on there is just pure marketing BS.