[LRflex] Re: Was: Concentration; Now: Colour of light. (HELP!)

Hi  David !

The yellow lights you refer to are, in my modest opinion, low pressure sodium 
(natrium), discharge lamps.

The light emitted is monochromatic i.e. all the luminous energy is emitted at a 
single wavelength of approx. 5900 Angström (or in a very, very narrow bandwith 
centered on that wavelength).

The main advantage of this light source is its very high efficiency, up to 190 
lumens per watt (to be compared to 20 lumens/watt for quartz halogen filament 
lamps).

Its main drawback is that its use is limited to places where colour recognition 
is not important (roads, tunnels ...). E.g. a red object will appear black or 
very dark brown under this light source.

All the best !

Etienne






  ----- Original Message -----
  From: David Young
  To: leicareflex@xxxxxxxxxxxxx ; leica@xxxxxxxxxxxxx
  Sent: Wednesday, July 16, 2008 4:03 PM
  Subject: [LRflex] Was: Concentration; Now: Colour of light. (HELP!)


  At 15/07/2008, you wrote:

    Hi David,
    Very interesting scene of the mill. I see you had some concern about the 
light? Best advice I can give on this type of situation?
    It’s there and that’s what it looks like on film or digi, so why try to do 
anything with it? Which I assume you mean to bring it to a better eye ball 
balanced look as you remember.
    However, forget it, shoot it and get the right exposure that is far more 
important. Everyone in the world will be quite amazed at your ability to shoot 
under the kind of conditions you described and show.
     Steel plants, refineries and you name of this ilk,  when it comes to these 
type of operations are lit differently. So its much better getting a proper 
exposure and composition than being concerned about the colour of the light.
    That is of course unless you have a lighting crew of dozens who’ll strobe 
light the plant! J That’s when you can think about light balance. J
    Real life light? Heck just go with what’s there on a perfect exposure, 
smile and walk away with a beautiful photograph as you’ve done here. J
    ted



  G'Mornin' Ted!

  You mentioned the light ... your advice being just to "shoot and go".

  But, the light I was referring to, was not the light in the photo of the 
concentration mill (which I was able to correct, within reason)... but to the 
light on the Ball/Sag Mill side.  This is the light you can see filtering 
through at the far left, in the concentration shot, I posted.

  http://www.furnfeather.net/Temps/Concentration.htm

  The light on the Ball mill side is provided by some sort of lamps, the likes 
of which I've not seen before.  The images have a yellow cast similar to that 
provided to daylight film when shot under tungsten light, but much more so.

  Experimentation has shown that the colours can be restored to some semblance 
of what I remember by reducing the colour temperature to 2000 Kelvin  (my RAW 
software, Silkypix, will not permit going any lower).  However, if I do this, 
although the colours come closer to what I saw, they take on a surreal look. 
While the mill's walls are starting to come close to their "natural" colour, 
the greens are still too weak, and the yellows much too strong.  Not to mention 
that in spots, they disappear all together, when they really were there, in the 
mill!

  I have posted three versions of one shot in the ball/sag mill.  The left is 
as taken (3292 deg. K.),  the center one is the best I've managed, so far, with 
a colour temp of 2000K and, for comparison, a b&w image, at the right.

  All are at:

  http://www.furnfeather.net/Temps/SagMill.htm

  So, Ted, although you say get the perfect exposure, smile and walk away ... 
would you provide the shot on the left to a client?  I don't feel that I could.

  I would appreciate any help from the digi-wizards on the list who understand 
these things.  How do I make the colours at least near natural?

  Many thanks.


  ---


  David Young,
  Logan Lake, CANADA


  Limited Edition Prints at: www.furnfeather.net
  Personal Web-site at: www.main.furnfeather.net
  Stock Photography at: http://tinyurl.com/2amll4



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