Menu

Posts Tagged ‘cctv wiki’

How many MegaBytes in a GigaByte?

Wednesday, January 14th, 2009

Google logoHard disc drives continue to get larger all the time, especially when you need them to record megapixel CCTV cameras 24hrs per day.

As unlikely as it seems, we are now headed towards 2 TeraBytes on an SD card!

We’ve covered this topic of MegaBytes, GigaBytes, TeraBytes and PetaBytes before, but we realise that it still confuses people, so we just thought it might be worthwhile mentioning Google’s inbuilt converter and calculation functions for those that aren’t already aware of them.

If you want to know exactly how MegaBytes compares to GigaBytes (or whatever), just type your query into Google’s search box in the following format:

500MB in GB

Google’s first ‘search result’ will be:

500 megabytes = 0.48828125 gigabytes

You can use this for any conversion using:

KB = KiloBytes

MB = MegaBytes

GB = GigaBytes

TB = TeraBytes

PB = PetaBytes

It also works for other conversions:

4 pounds in kilos

4 pounds = 1.81436948 kilograms

2 feet in cm

2 feet = 60.96 centimeters

Google will also tell you the current time in most World Cities:

time Brisbane

10:18am Wednesday (EST) – Time in Brisbane, Queensland

Brisbane, California 4:18pm -1 day PST

Hope that’s handy to know?

IRE and Lux Light Levels

Monday, January 12th, 2009

IRE for CCTV Lux

What does IRE mean when quoted with Lux light levels for CCTV cameras?

We’ve noticed that many people seem to be a little baffled by this mysterious occasional mention of the term IRE, so we thought we’d just write a quick article to explain it in lay terms for you.

There is a good technical explanation over on Wikipedia, but as often happens it is a bit too technical if you are starting from the point of having no idea!

IRE stands for Institute of Radio Engineers, but that’s not important, you want to know what it means.

Well, keeping this within terms easily understood by lay-men:

The squiggly line above represents a composite video signal.

We refer to a good signal as being 1 volt peak-to-peak.

The Institute of Radio Engineers came up with the term IRE to represent the composite video signal in percentage terms i.e. 100IRE equals 100%, a full (good) signal.

Now the buyer beware bit. Just about the only time you see IRE quoted is when a manufacturer is trying to apply specmanship i.e. they are claiming that their camera can ‘see’ in very low light levels, but in fact it only does so poorly, and produces a less than good composite video signal.

For example 0.05 Lux (30IRE) means that in light levels measured at 0.05 Lux the camera will produce an image, but it’ll be a poor one, with a composite video signal level at only about 30% of what it should be. Effectively this would be a fairly useless image, and perhaps the camera is only really useful down to a higher lux level of say 0.5 Lux …

Of course, due to our human tendency to ignore the bits we don’t understand, it makes for quite clever marketing really; most folk just read the specification, see the incredible ‘see-in-the-dark’ capability indicated by the very low lux light level claimed in the specification and proceed to buy the camera.

To gain a better understanding of relative lux light levels take a look at our free chart.

Lux Light Level Chart

Monday, December 1st, 2008

Lux light levels chartLux levels are quoted by all IP camera manufacturers to indicate the low light level capabilities of their cameras.

The problem is that the lux scale means nothing to most of us, and we are often asked to give an indication of just what is meant by 1.0 lux or 0.01 lux.

Somehow, us saying “quite dark” or “very dark” never seemed very satisfactory!

We checked with Wikipedia:

The lux (symbol: lx) is the SI unit of illuminance and luminous emittance. It is used in photometry as a measure of the apparent intensity of light hitting or passing through a surface. It is analogous to the radiometric unit watts per square meter, but with the power at each wavelength weighted according to the luminosity function, a standardized model of human brightness perception. In English, “lux” is used in both singular and plural.

That’s that cleared up then! 😉

We don’t really think that the information on the Wikipedia page is quite what our CCTV camera enquirers are looking for, so we’ve created our own lookup lux chart with indicative pictograms to give you a visual representation of relative lux light levels.

Click the link to view the chart as a pdf – Lux Light Level Chart.

We hope that’s helpful?

You might also be interested in our article on IRE and Lux Levels.

If there’s any other CCTV terminology that we can de-mystify for you then please feel free to get in touch and let us know. You can use the comments below or visit our IP CCTV Forum.