From: JEFFREY PAULL (email suppressed)
Date: Tue Jul 14 2009 - 13:07:00 PDT
If your B&W stock is "Blue Sensitive" it's not sensitive to yellow or red light, so you can use an amber coloured safelight - a real safelight, not just an amber or yellow bulb.
Hi-Con stocks are usually "blue sensitive".
If your B&W stock is "Orthochromatic", it is sensitive to blue and green light waves, so a (real) safelight colour is red.
If your filmstock is "panchromatic" - most regular camera stocks - it's sensitive to light of all colours,
but there is a slight dip in sensitivity to green light, so your (real not just green) safelight is dark green.
Camera stocks are also much much more sensitive to light than lab stocks, so this panchromaic green safelight
is very very dim.
Kodak describes sensitivity in their bulletins for each stock. They also graph the sensitivities for thr spectrum of wavelength.
No safelight is utterly safe. There are minimum distances you must follow so as not to fog
your stock even tho it's a safelight.
fogging from not-quite-safe safelight (or tiny light leaks into the darkroom, is insidious.
Remembr that safelight fogging would be from both the unsafe safelight AND the added actual exposure light, so regions of the frame that are barely exposed,
are more influenced by safelight fog than heavily exposed regions.
If the image will be a negative, the shadow tones with little actual exposure light will be strongly influenced by the slight fogging light
of the unsafe safelight. So, when printed, the shadow tones will be a bit lighter than usual, so the black parts (the D-max) not so black.
If the image will be a positive print film, the highlight areas of the positive will receive little exposure trough the highlight parts of the NEGATIVE.
So the highlight parts become compressed and a bit grey and unsparkling.
Where either stock receives a lot of exposing light in a part of the frame, the slight safelight fog has much less influence.
There used to be so-called "desinsitizers" which you used before the developer step
that made the stock much less sensitive to darkroom light.
Although these desisitizers used to come in packets you dissolved in water,
these days you'd probably have to make the desinsitizer bath from scratch.
But Google "photographic desensitizers" and see if any of the chemical companies still make it.
Colour stocks require total darkness.
JP
On Tue 14/07/09 14:05 , Myron Ort email suppressed sent:
> Is this sodium lamp (598nm) a practical darkroom safelight for color
>
> and b&w film stocks? I am looking for a practical way to see what I
>
> am doing while making photograms on movie film stocks.
>
> Are there other practical solutions to this.
>
> Myron Ort
>
>
>
>
>
>
>
> On Jul 14, 2009, at 2:34 AM, Pip Chodorov wrote:
>
>
>
> > The positive stock expects the orange mask. There is a
> tiny
> > stalactite in the sensitivity curve that corresponds
> precisely to
> > this frequency of light. In the darkroom we can work
> with a sodium
> > lamp of the same color - 598nm - under which positive
> stock will
> > not be fogged.
>
> >
>
> >
>
> >
>
> > At 14:12 -0700 13/07/09, ev petrol wrote:
>
> >>
>
> >> the main stumbling block seems to be the orange mask -
> how does
> >> that work usually folks, how do the labs deal with it
> to get a
> >> good pos?
>
> >> cheers! Moira
>
> >
>
> >
>
> >
> __________________________________________________________________
> > For info on FrameWorks, contact Pip Chodorov at (address suppressed)
> om>.
> >
>
>
>
>
>
> __________________________________________________________________
>
> For info on FrameWorks, contact Pip Chodorov at (address suppressed)
> om>.
>
>
>
>
>
__________________________________________________________________
For info on FrameWorks, contact Pip Chodorov at <email suppressed>.