Re: Coolmint frequency question

["Lee Tarpley" <tarpley@xxxxxxxxxxxxxx>]

Gavin,
> I recieved this email in the early hours of the morning, and its bugging
> me, so I thought I'd get the "experts" on the list to see what they make
> of it.
>
> His reference is to http://www.coolmint.co.uk/infrared/guide/
>
>
> ---------------- Begin Forwarded Message ----------------
> Technically one of the things you say in your rough guide is a falacy.
> Now, don't be offended. I'm just being analy technical. But 700nm+ means
> a lower frequency. Because the wavelength is longer it takes a longer
> time for a cycle to complete. I forget what the frequencies are for
> infared but I assure you that they are way BELOW the visible light
> spectrum

Quoting from the Coolmint Guide first page (with my upper case added for
emphasis):

"Looking at the above table the visible spectrum, the one which we can see
with the naked eye, ranges from 400nm (violet) to approximately 700nm (red.)
Infrared phototography deals with the invisible spectrum up to 900nm.

You'll see the various spectral ranges of the films, regular film records
light up to about 680nm, extended red films go up to about 720nm whereas
infrared films cover the range up to 900nm, the infrared spectrum kicks in
about 700nm, A WAVELENGTH BELOW WHAT THE HUMAN EYE CAN SEE, this is where
things start to become interesting!"

This phrase is confusing, and I'm guessing is the source of the e-mail
discussing frequency. The 700 nm is near (or barely within?) the cutoff of
the visible. How about rewording to something like "Wavelengths longer than
700 nm cannot be seen by the human eye. This region of the spectrum is where
things start to become interesting!"

Lee Tarpley






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