Questions about B&W filters

darinwc · Jul 3, 2009

My last roll of B+W film was taken at a concert in a park. Shooting up onto the stage forced the inclusion of large amounts of sky that were way, way brighter than the subjects. The exposures were fine due to spot metering. But the pure white sky in the background was dissapointing.

So, i'd like to try some black and white filters, most notablty either yello or red. One thing that I noticed though is that looking through the filters it doesnt seem to have much of an effect. I guess my question is more about 'visualization' than use. Why is it that looking through the filter doesnt seem to have much of an effect?

Rol_Lei Nut · Jul 3, 2009

Because your eye doesn't have the same response as B&W panchromatic film.

(I'll leave the more accurate technical answers to the next posters...)

Peter De Smidt · Jul 3, 2009

What film are you going to use?

Q.G. · Jul 3, 2009

If the the filter has an effect, you will indeed see it when looking through it.

Yellow, orange or red filters can make a blue (!) sky darker.

Hazy skies however are hardly effected at all.

So the sky must be a nice saturated blue, or else, no fun using any of these filters.

ntenny · Jul 3, 2009

Q.G. said:
Hazy skies however are hardly effected at all.

Red will tend to cut the haze (because the longer wavelengths scatter less), infrared still more so. So I wouldn't go as far as you have, though it's certainly true that the sky-darkening effect of filters is stronger in the absence of haze.

A red filter is generally considered kind of extreme for natural-looking landscapes, but in the sort of application the OP describes it might be about right to make the sky an appealing, darker background, IMHO.

-NT

Rol_Lei Nut · Jul 3, 2009

O.k., seeing the lack of "more accurate technical answers", a polariser will "give you what you see" though completely dependant on where the light source(s) are (what you see through the viewfinder is what you'll get).

Yellow, Yellow-Green, Orange and Red (in that order) will darken a blue sky with B&W (the effect is not visible through the viewfinder).

Exposures can vary greatly according to what kind of lightmeter your camera has.. You'll need to investigate that to get accurate exposures with coloured filters.

Sirius Glass · Jul 3, 2009

Consider using a polarizer which will darken the sky, saturate the colors depending on the location of the Sun relative to the camera, and cut back on reflections and glare.

Steve

Q.G. · Jul 3, 2009

Rol_Lei Nut said:
O.k., seeing the lack of "more accurate technical answers",

What, what, what?
"If the the filter has an effect, you will indeed see it when looking through it." is an acurate as-technical-as-it-can-be answer.
(It really is)

Rol_Lei Nut said:
Yellow, Yellow-Green, Orange and Red (in that order) will darken a blue sky with B&W (the effect is not visible through the viewfinder).

Why yes, it is! Very much so.
Skies will be blue tomorrow in your part of the world. So take the opportunity to have a go with filters and see!

Q.G. · Jul 3, 2009

A polarizer may work, and it may not. Even when skies are deep blue.
When you're shooting B&W anyway, better use a yellow or orange filter. They always work ... when skies are blue.

Personally, i dislike polarizers because they produce dull images (as in: without sparkle. Not as in: boring. Or ... ? ).

Rol_Lei Nut · Jul 3, 2009

Q.G. said:
What, what, what?
"If the the filter has an effect, you will indeed see it when looking through it." is an acurate as-technical-as-it-can-be answer.
(It really is)

I really hope that you don't have B&W vision... Though dogs often seem quite happy with it...

Q.G. · Jul 3, 2009

So you think that you need to have black and white vision to see that a red filter darkens a blue sky?
If so, do get out tomorrow and have a look.

Rol_Lei Nut · Jul 3, 2009

Q.G. said:
So you think that you need to have black and white vision to see that a red filter darkens a blue sky?
If so, do get out tomorrow and have a look.

Last I looked, it made it look strangely red....

Q.G. · Jul 3, 2009

And that makes it impossible for you to recognize that it also was darker?
I'll perform a PubMed search. Maybe someone found a cure for that condition already.

pentaxuser · Jul 3, 2009

Try a red and a polariser together for a more dramatic effect if you shoot the sky at right angles to the sun. I use the word more dramatic advisedly as in Northern lattitudes such as the U.K.(50-60 degrees) I have never noticed it give an over the top near black look suchg as you get with IR film.The effect is really noticeable as you turn the polariser and find that the clouds really stand out. I don't think I'd bother with the polariser if there aren't any clouds. An orange will simply darken a clear blue sky which is better than ending up with a white sky but only marginally so.

A solid blue cloudless sky as a light or mid grey does very little for me. Fortunately we are seldom afflicted with such a phenomenon in the U.K. :

pentaxuser

keithwms · Jul 3, 2009

darinwc said:
One thing that I noticed though is that looking through the filters it doesnt seem to have much of an effect. I guess my question is more about 'visualization' than use. Why is it that looking through the filter doesnt seem to have much of an effect?

To fully estimate the effect of the filter, you need to overlay the sensitivity curve of the film with the transmission curve of the filter. Then all will become clear.

Although the sensitivity curve of your film does not exactly match that of your eye, you can usually estimate a filter's effect by eye... if you are using a typical pan film. If you are using an ortho film or IR film or whatever then of course all bets are off.

Here is something related that may amuse you...

http://hyperphysics.phy-astr.gsu.edu/hbase/vision/candle.html

Note also that the eyes (and brain) are remarkably adaptive and will conspire to do their very best to counteract any filters etc. you put in front of your eyes or changes in the colour temp or intensity of the illluminant light. I doubt this happens on a quick enough timescale to matter in this case, but I'd not be surprised to hear that the eye adaptively reduces the contrast we perceive in a scene. E.g. something like the Chubb illusion.

Christopher Walrath · Jul 3, 2009

For the effect differing color filters will have on different wavelengths, think of a clock. We have three primary colors; red, green and blue. We'll put red at 12 o'clock, green at 4 o'clock and blue at 8 o'clock. There are three complimentary colors; yellow, cyan and magenta. These colors bridge the gap between the primary colors. Yellow resides between red and green at 2 o'clock. Cyan resides between green and blue at 6 o'clock. Magenta resides between blue and red at 10 o'clock.

Now a color correction filter will allow light of a similar wavelength to pass through or transmit through the filter while blocking other colors to an increasing degree until you work your way around the wheel to that color's complimentary color (P.C. Red- C.C. Cyan, P.C. Blue- C. C. Yellow, P.C. Green- C.C. Magenta). So if you employ a red filter, it will allow more red light to pass and block out your green light and will have the most impact on blue. If you use a blue filter it will transmit blue light and block out your reds. Yellow filters will raise your yellows and greens and block down your blues, though not to the degree a comparable red filter would.

That's the basics. Hope it helps.

Mike Richards · Jul 4, 2009

It's the Angle

Q.G. said:
A polarizer may work, and it may not. Even when skies are deep blue..

Depends largely on the angle of sunlight. It needs to be as orthogonal as possible to the sunlight to get the effect. If the sun is behind you, virtually no effect.

Q.G. · Jul 4, 2009

And even if at right angle, the effect of a polarizer on the sky may be visible in a small part of the image only, depending on the angle of view of the lens.

Re the visibility of the effect when looking through the filter: just look through it and you will see whether it has one or not.
These contrast filters are not 'fine tuning' thingies, but rather coarse affairs.
Coarse enough not to be able to trick our eyes.

You can even judge whether any of these have an effect on the sky by looking at the sky without filter. If deep blue, the effect will be strong. If a lighter blue, a moderate effect. If a hazy light blue, the effect will be minimal. If rather white than blue, no effect at all.

Questions about B&W filters

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