Colour rendition index and b&w film spectral response

steveo_mcg

steveo_mcg

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I'm looking at LEDs for the shed/shop/studio and one thing I'd not thought of before is the colour index (ie how white the light is) of LED's; most tend to favour blue so they look brighter without having to run as high power.

My guess is that one of two things will happen, either it'll be fine and the image will be as close to correctly exposed as I ever manage or the exposure will be all over the place depending on the meter and the film being used. For example something with a tendency to blue may be over exposed under cheap LEDs.

I reckon my options are buy the expensive bulbs which claim a full spectrum output, use a couple of rolls of film and check the response is acceptable under a normal LED or.... Don't suppose anyone has already done the leg work?
 
Looks like I might need to do some tests then.

Anyone know where I could get a colour chart for such things?
 
I've got a GretagMacbeth colour checker card which you could borrow to save the expense of buying one for a one off if you'd like to - it's about A4 size.
 
And possibly a silly question, but are we talking exposure on black and white film, colour film or digital? The difference in film speeds between daylight and artificial light for black and white films (as given by the makers) are really very small.
 
StephenM said:
I've got a GretagMacbeth colour checker card which you could borrow to save the expense of buying one for a one off if you'd like to - it's about A4 size.
Click to expand...

that would be great thanks.

StephenM said:
And possibly a silly question, but are we talking exposure on black and white film, colour film or digital? The difference in film speeds between daylight and artificial light for black and white films (as given by the makers) are really very small.
Click to expand...

b&w film primarily. I expect most comparisons in the past between daylight and artificial light have been with incandescent which by its nature produces a full spectrum light whilst LEDs can have a very narrow output spectrum and still look fairly white.
 
I should have picked up on the thread title and not asked a silly question :banghead:

PM your address and I'll post it.
 
Spectral response of B&W film is very variable.
All the chemistries will respond to UV, but some films contain layers to block most of this.
Very early films had no response to green let alone red.
More recently B&W films are usually 'panchromatic' seeing all the colours we see (as well as some UV) but 'orthochromatic' films are still available these don't respond to red (but see blues & greens) so can be processed with a red safe light...

Within any class of film there is more subtle variation too.
 
Light fittings arrived, I've got an old halogen Mr16 just trying to get the cheapest led to compare it with before I get the dearer hight cri ones.

Don't suppose lumen output or beam angle really matters that will be sorted by the exposure.
 
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