B&W Color Balance Under the Forest Canopy

dancqu · Sep 13, 2007

I suspect that there is a considerable distortion of the
available light's color balance at the forest floor where
little if any direct sunlight may be visible.

The usual B&W films are color balanced for tungsten but
wonder if a light yellow filter filter goes far enough towards
muting the preponderant available blue. Would an orange
filter be more correct? Also, yellow or orange, would
filter factors need to be increased in such a blue
blue-green environment? Dan

Chuck_P · Sep 13, 2007

As I run what you are saying in my head, I'll think it through by just speaking it.

The color temperature in the forest shadows will be bluer. Shadows illuminated by sky alone will be bluer, therefore, any blue absorbing filter such as the yellows, orange, or reds will serve to reduce the shadows to even lower values by decreased negative density and thus darker print value. To compensate you would have to increase the exposure, but then be concsious of where your highlights are on the scale. I think, if I understand you correctly, that an increase in exposure to support the shadows is needed, not an increase in the filter factor. IMO, the factor should remain the same, but I'm not completely experienced in the use of filters, so I'm out on a limb here, IDK. Someone is bound to correct me, which is good.

Chuck

Chuck_P · Sep 13, 2007

I should have said...shadows illuminated by blue sky alone, will be bluer.

An overcast day, of course, will have much less blue.

MurrayMinchin · Sep 13, 2007

Under the forest canopy there is no preponderance of blue light. To have blue shadows you need them filled in by the blue of the sky...under the forest canopy you can barely see the blue sky, therefore it cannot be filling in the shadows. The light is scattered and reflected from a preponderance of green/brown surfaces.

At least that's the way it is here in a temperate rainforest from my vantage point on the forest floor. Near the top of the canopy the shadows would probably get bluer, but its hard to set up my 4x5 over a hundred feet from the deck

Murray

John Koehrer · Sep 14, 2007

Chuck1 said:
An overcast day, of course, will have much less blue.

Less?

Vaughn · Sep 14, 2007

dancqu said:
I suspect that there is a considerable distortion of the
available light's color balance at the forest floor where
little if any direct sunlight may be visible.

The usual B&W films are color balanced for tungsten...snip Dan

They are? Anyway, having done B&W under 300 feet or so redwoods for the past 30 years, I have never worried about it a bit. And unless one is doing some strange highly detailed scientific study, I see no reason to give it a second thought.

Vaughn

Ed Sukach · Sep 14, 2007

The ambient light of an overcast day, and in shadows, will have a ~ higher color temperature (to something over 10,000K) - be "bluer" than direct sunlight, ~ 5500/ 6000K.

Given the spectral sensitivity of modern black and white films, I would determine filtration by the "look" of the finished product, not color temperature.

Chuck_P · Sep 14, 2007

Ed Sukach said:
The ambient light of an overcast day, and in shadows, will have a ~ higher color temperature (to something over 10,000K) - be "bluer" than direct sunlight, ~ 5500/ 6000K.

Given the spectral sensitivity of modern black and white films, I would determine filtration by the "look" of the finished product, not color temperature.

Looks like I went out too far on that limb afterall. At least I had a disclaimer . Thanks Ed for the correction.

Chuck

dancqu · Sep 15, 2007

Vaughn said:
They are? Anyway, having done B&W under 300 feet or so
redwoods for the past 30 years, I have never worried about
it a bit. And unless one is doing some strange highly detailed
scientific study, I see no reason to give it a second thought.
Vaughn

Apparently the manufacturers of film have never managed to
make film as red and or green sensitive as it is blue sensitive.
So the spectral sensitivity is balanced across a band around
2800K tungsten.

As for filtration under the canopy my only concern is image
fidelity. For example I've photos where a trail of rock and
earth is less seperable from surrounding green flora than
I judge true to the scene. Dan

Roger Hicks · Sep 15, 2007

dancqu said:
Apparently the manufacturers of film have never managed to
make film as red and or green sensitive as it is blue sensitive.
So the spectral sensitivity is balanced across a band around
2800K tungsten.

As for filtration under the canopy my only concern is image
fidelity. For example I've photos where a trail of rock and
earth is less seperable from surrounding green flora than
I judge true to the scene. Dan

Dear Dan,
Um...

Film is inherently sensitive to blue/violet/ultraviolet. Dye sensitization extends that to green/yellow (ortho), orange/red (pan) red and even near IR (hyperpan, extended red).

Filtration allows you to differentiate and pair of reasonably different colours. This is not the same as 'being sensitized to tungsten'.

In fact, if you think about it, as tungsten is much redder than daylight, and many films are fractionally slower to tungsten than to daylight, the statement that B+W films are 'sensitized to tungsten' comes very close to sheer nonsense.

Cheers,

Roger

Ole · Sep 15, 2007

Some films are slower in tungsten lighting, some films are faster. There is no "General Truth" to any statement about sensitivity, just a lot of lesser "special truths".

Vegetation also varies a lot in spectral reflection, so I can't give general filter advice: sometimes a light blue gives better separation, sometimes orange or even warm-up, and other times not even deep red will do the trick. Confound this even more with the different spectral sensitivities of different films...

Roger Hicks · Sep 15, 2007

Ole said:
Some films are slower in tungsten lighting, some films are faster.

Dear Ole,

Very true, and the figures are almost never given nowadays. Either way, for pan/hyperpan films, it's seldom more than 1/3 stop. Of the figures I've seen, more are faster to daylight than tungsten, though T-Max films seem generally to go the other way. That still doesn't alter the fact that 'sensitized to tungsten balance' is effectively meaningless when referring to monochrome.

Nor does it alter the fact that filters lighten their own colour and darken their complementaries. Different shades of green may be unpredictable; but take green foliage and brownish earth (or indeed brownish tree-trunks) and green or orange will lighten the one and darken the other.

Cheers,

Roger

dancqu · Sep 15, 2007

[QUOTES=Roger Hicks]
"Dear Dan, Um... Film is inherently sensitive to
blue/violet/ultraviolet. Dye sensitization extends
that to green/yellow (ortho), orange/red (pan) ..."

Our usual B&W Films are sensitized well into the red.
When so the green through red sensitivity is well below
the film's inherent blue and shorter wave length sensitivity.
Manufacturers have failed to bring emulsions up to blue speed.

"...the statement that B+W films are 'sensitized to tungsten'
comes very close to sheer nonsense." Cheers, Roger

Good thing I didn't say that. I wrote, "...spectral sensitivity
is balanced across a band around 2800K..." All that is needed
to confirm is a look at any manufacturer's film data sheets. If
blue speed were possible across the spectrum we would
have much higher speed emulsions. Dan

Vaughn · Sep 16, 2007

dancqu said:
As for filtration under the canopy my only concern is image fidelity. For example I've photos where a trail of rock and
earth is less seperable from surrounding green flora than
I judge true to the scene. Dan

But how did they meter? If the flora and earth/rock meter the same, then of course they blend in together. A red ball will pop out visually to the eye when sitting on green grass, but if they metter about the same, then in B&W the ball will not pop out visually on the film. Not really about panachromatic B&W film's responce to color, but the intensity of light reflected off the ball and the grass.

Now, the amount of light objects are reflecting might change due to the color balence of the light hitting them, but your meter will tell you that. Your brain is differentiating between the earth and the flora on the basis of color...but your film is differentiating between them based on the amount (not color) of light reflecting off of them.

In your example, you may wish to use a filter to seperate the values of the earth and the foliage -- green to lighten the flora relative to the brown earth...or an red/orange filter to darken the flora relative to the earth.

Vaughn

CBG · Sep 16, 2007

dancqu said:
I suspect that there is a considerable distortion of the available light's color balance at the forest floor where
little if any direct sunlight may be visible.

The usual B&W films are color balanced for tungsten but
wonder if a light yellow filter filter goes far enough towards
muting the preponderant available blue. Would an orange
filter be more correct? Also, yellow or orange, would
filter factors need to be increased in such a blue
blue-green environment? Dan

Consider the chance you are thinking this out waaaay too much. Sure, thought is good in general, but there's a time and place, and it aint now.

Just go shoot "the forest floor" and see what you get. If you are shooting flowers or something with a strong color, against a contrasting colored background, filtration will be useful for special effect, but the forest is bland color wise, and generally will not respond usefully to any color balance corrections you may impose, other than to make your exposures longer.

Forest light never stopped Wynn Bullock, A.A., Weston and co, and they all got amazing images without worry about the exact spectrum of the forest light. Heck, you can get pretty far with color film in the woods without elaborate color correction. Maybe a uv/sky filter or a modest warming filter would be fine.

Had you a very accurate color meter system, I'm sure you could discern some sort of very modest slant to the spectrum at the forest floor, but with any BW film having a fair claim to being panchromatic, there will be no show stoppers whatsoever if you shoot with no filtration.

The worst issue is likely to be contrast if the day is sunny, since any patches of direct sun will be far above the predominant brightness. I love gray days.

Best,

C

bjorke · Sep 16, 2007

Latitude, type of foliage, density, and weather conditions are all pretty changeable variables in this question. Better to test.

MurrayMinchin · Sep 16, 2007

I'm old school...take one photograph as you would normally, take one with the experimental filtration/exposure/development/whatever, take notes, print them both as proof prints, then compare.

This serves two purposes; it gets you out photographing and it gives you real life results you can hold in your hand

Murray

dancqu · Sep 16, 2007

dancqu said:
Our usual B&W Films are sensitized well into the red.
When so the green through red sensitivity is well below
the film's inherent blue and shorter wave length sensitivity.
Manufacturers have failed to bring emulsions up to blue speed.

If B&W films had across the spectrum sensitivity equal to their
blue sensitivity we would have Daylight B&W film. To use indoor
a blue-ish or cyan filter would be needed.

Daylight B&W film might be possible. As it stands a blue
de-sensitizer would need be found. Dan

Ole · Sep 16, 2007

Dan, take a look at the sensitivity curves for Ilford FP4+.

It has reduced blue sensitivity compared to most other films.

A "blue de-sensitizer" is easy: Yellow dye. I don't know if that's what Ilford uses, but I like the colour response of FP4+ better than other films I've tried for most outdoors work.

MikeK · Sep 16, 2007

Vaughn said:
They are? Anyway, having done B&W under 300 feet or so redwoods for the past 30 years, I have never worried about it a bit. And unless one is doing some strange highly detailed scientific study, I see no reason to give it a second thought.

Vaughn

My biggest problem shooting in forests has nothing to do with spectural response of the film but with the extreme contrasts. Dark shaded areas with patches of bright sunlight bursting through - magic stuff.

I have begun to experiment with overexposed XP2 in my 6x12 back - the images from my trip to Weott were really good - even sold a panoramic last weekend at a local show. The other benefit of XP2 is has really good reciprocity characteristics - handy when you can get into multiple second exposures.

By the way - I will be heading up to Weott & the Matole Road for the second part of my field trip - love that area

Mike

Vaughn · Sep 16, 2007

MikeK said:
My biggest problem shooting in forests has nothing to do with spectural response of the film but with the extreme contrasts. Dark shaded areas with patches of bright sunlight bursting through - magic stuff.

I have begun to experiment with overexposed XP2 in my 6x12 back - the images from my trip to Weott were really good - even sold a panoramic last weekend at a local show. The other benefit of XP2 is has really good reciprocity characteristics - handy when you can get into multiple second exposures.

By the way - I will be heading up to Weott & the Matole Road for the second part of my field trip - love that area

Mike

That's why when I printed silver gelatins, I always photographed on overcast days (that's the advantage of living here...step out side, check the weather, and if it feels right head into the redwoods!) Now that I carbon print, I look for that sun coming through the redwoods as the process eats up that contrast for lunch!

I prefer the redwoods 40 miles north to the redwoods 40 miles to the south (Weott). Mostly because there is no poison oak to the north! but the redwoods on the flood plains along the Eel River are beautiful.

When will you be heading up this way?

Dan, A blue-desensitizer for film is availible -- it is called a yellow filter.

Vaughn

MikeK · Sep 17, 2007

Vaughn said:
That's why when I printed silver gelatins, I always photographed on overcast days (that's the advantage of living here...step out side, check the weather, and if it feels right head into the redwoods!) Now that I carbon print, I look for that sun coming through the redwoods as the process eats up that contrast for lunch!

I prefer the redwoods 40 miles north to the redwoods 40 miles to the south (Weott). Mostly because there is no poison oak to the north! but the redwoods on the flood plains along the Eel River are beautiful.

When will you be heading up this way?

Dan, A blue-desensitizer for film is availible -- it is called a yellow filter.

Vaughn

Probably the last weekend of October. In the summer I usually stay at tge Hidden Springs Campground - but this time it will have to be the Burlington.

I will probably be leaving Walnut Creek early Friday morning and should arrive around 1:00 PM in the afternoon. Will stay through lunch time Sunday before heading back.

You are right about the poison oak - its all over the place as well as the mosquitoes. I was eaten alive the last afternoon I was there. I was OK setting up the 4x5 and tripod and had made about three shots when they decided I was a free meal - but that goes with the territory.

Mike

dancqu · Sep 17, 2007

CBG said:
Consider the chance you are thinking this out waaaay
too much. ....... Just go shoot "the forest floor" and see
what you get. Best, C

I've scrubbed 1ea, Uv, Y8, Hoya Orange and Y/G and
a color film blue. Also I've dusted off my ETRSi and
loaded it with Acros 120. As soon as the dentist
and bad weather are out of the way I'll head
for the woods. Dan

Vaughn · Sep 17, 2007

dancqu said:
I've scrubbed 1ea, Uv, Y8, Hoya Orange and Y/G and
a color film blue. Also I've dusted off my ETRSi and
loaded it with Acros 120. As soon as the dentist
and bad weather are out of the way I'll head
for the woods. Dan

You might as well toss in a polarizer filter, also. I read that tip on some forum somewhere for use with color...esp slide film. The leaves reflect the light from above, which tends to be bluer than the surrounding light -- so by reducing the reflections from the leaves, one gets rid of the blue cast they can have. Of course, adding a couple stops or more to one's exposure under a forest canopy is not always a desirable thing!

Have fun and good luck with the dentist!

Vaughn

Roger Hicks · Sep 17, 2007

dancqu said:
[QUOTES=Roger Hicks]
"...the statement that B+W films are 'sensitized to tungsten'
comes very close to sheer nonsense." Cheers, Roger

Good thing I didn't say that.

Dear Dan,

True. You said 'balanced for tungsten' (post 1) which is equally meaningless -- which is why I forgot the exact words you used.

Cheers,

Roger

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