Overexposing paper negatives outdoors

[Toffle]

I did a search but could not really find what I'm looking for, so please excuse if this has been answered to death.

I've been shooting a lot (a lot) of paper negatives lately and have had really good results working under controlled lighting situations in my studio. (living room) As soon as I move my setup out of doors, however my exposures are very over exposed, even though I am using the same metering process indoors and out.

A few details: I am using an 8x10 Burke and James with a 5x7 back and shooting on single weight Ilford RC glossy paper. My light meter is a Gossen Luna Pro. (In my opinion, none of those details should make the least difference in indoor/outdoor exposure)

I have tried reflected vs incident reading, I have tried metering off the brightness of the sky, (which should have resulted in severely under-exposed paper)... no luck. Everything is coming out 2-4 stops over exposed. The shadows, which should be nearly white on paper, are an almost unprintable mid to dark grey. It's almost as if the paper is being fogged. But why would this be so out of doors and not indoors? (The paper edges where it is protected by the film rails are pure white as expected.) I have checked my bellows and find no light leaks, so I seriously doubt this is the problem.

Can anyone tell me why I should not be getting similar exposures indoors and out? I have wasted far too many sheets of paper on this.

Thanks in advance,
Tom

 

[horacekenneth]

Well as you probably know the paper is sensitive to UV light but I can't imagine that giving you 4 stops difference.

Did you need to compensate for reciprocity in your studio?

 

[Doremus Scudder]

Your light meter reads the entire visible spectrum plus probably a bit of infrared.

Your paper is only sensitive to blue and a bit of green, components that are only a very small portion of incandescent lighting (which I assume you are using). Your meter gives you a reading, but only a fraction of the light it reads is actually exposing the paper.

Daylight has a lot more blue and green in it, plus UV, so the portion of the light read by the meter that is exposing the paper is proportionally more. That means, for the same reading in incandescent and daylight, the daylight will give more exposure than the incandescent simply because the paper is sensitive to more of the daylight and very little of the incandescent light spectra.

You need to test for an E.I. in daylight. You may need to do the same for overcast and open shade as well, since these have even more of a blue/green component.

Best,

Doremus

www.DoremusScudder.com

 

[removed account4]

hi tom

i hate to suggest this
cause i never believed it, but paper can be about asa 24 ...
depending on the light conditions i usually meter
paper at asa 6 ( gloomy ) but more times than not
at asa 24 or so ... i never believed paper was as fast as it is
but once PE suggested ilford rc paper was around that speed
my negatives have been OK ...

it is kind of fun to think that photo paper is as fast as a slow film

good luck !
john

 

[NedL]

I agree with Doremus. I've also noticed that the angle of the sun in the sky makes a much bigger difference on paper negatives than on panchromatic film, and quite a bit more than your light meter will indicate. I think as the sun gets closer to the horizon, the spectrum shifts strongly to the red.

Just a couple weeks ago, I repeated a paper negative pinhole exposure that was perfectly exposed at 3 minutes a few days before. Both days were cloudless and I put the camera in exactly the same spot. I knew it was closer to sunset, so I exposed 7.5 minutes, but the result was very badly underexposed. My camera light meter readings differed by a bit less than 1 stop.

Have fun!

 

[Toffle]

Thanks for all the responses so far.
I'm going to go with... the UV/blue sensitivity of the paper. (for now)
I have been aware of the limitations of paper to reds, but neglected to take the outdoor levels of blue into account.
My interior lighting is incandescent and warm-toned CFLs... probably not a lot of blue there.

John, I have been exposing at ISO 6, and have gotten consistent results indoors, so I'll stick with that.. (for now)

So the next step for me will be to get out and do some tests - I need a consistent factor to judge my exposures, or as Doremus suggests, one for daylight, overcast and open shade.

The series I am working on is a fun set of studies involving a $0.99 magnifying glass for a lens, and contact printing on Ilford Art300, developed in Caffenol. So far I have a number of really nice images. (I have lots of "proper" lenses in my collection, but am enjoying the extreme Galli-esque nature of the cheap lens)

Thanks again, folks.
Cheers,
Tom

 

[removed account4]

hey tom

i think your guess is right .
the cfl isn't much blue,
so your over exposure is about right
and outdoor there is more of everything.
it makes sense that you are over exposing everything by a few stops

good luck getting everything to look the same
with your caffenol, i know you have mentioned things can get "fun"

john