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Red filter on B/W...


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#1 Adam Frisch FSF

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Posted 26 September 2005 - 07:38 PM

I might be about to embark on a film shot on 5231 or 5222. I'm familiar with the use of red filters to enchance skies and generally approach a near-infrared look. But I have a couple of questions:

Having a red filter in front of the lens changes the wavelenght and therefore the focus of the lens slightly. Is this significant enought to have to be adressed? And if I filter behind the lens in collimated light instead, does the same thing apply?

Also, does anyone have real life experiences with using the red 23, 25 and 29 filters on B/W and can give some recommendations to which one should be preferred?

Thanks.
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#2 Mike Williamson

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Posted 26 September 2005 - 10:48 PM

I have not heard of anyone making focus compensations when using red filters. I remember using a Red #25 to good effect in my first student films, but I haven't used either of the other two. It's my impression that the #25 is the most commonly used of the red filters. It seems you would want to test these filters out yourself and look at different levels of exposure compensation, as different exposures should produce different effects.

Also, if you have the "Cinematography Screencraft" book, Kaminski talks briefly about his filter choices and compensations on "Schindler's List", probably the AC article would have some info as well. I remember him using a Red #25 and also some orange filters maybe. I'd be tempted to dig into the old school books too, Malkiwiecz' "Film Lighting" or something like that, to hear from the guys who knew B&W filters.

Can you tell us about the project, Adam? Is it going to be a real B&W feature? I'd love to have the opportunity to shoot a feature on B&W film, but I'm afraid I won't ever be able to. Best of luck with the project!
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#3 Adam Frisch FSF

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Posted 27 September 2005 - 06:23 AM

Thank you, Mike.

No, unfortunately it's not a feature, it's just a short. Those features seem elusive... :(
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#4 Tim J Durham

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Posted 27 September 2005 - 06:45 AM

I might be about to embark on a film shot on 5231 or 5222. I'm familiar with the use of red filters to enchance skies and generally approach a near-infrared look. But I have a couple of questions:

Having a red filter in front of the lens changes the wavelenght and therefore the focus of the lens slightly. Is this significant enought to have to be adressed? And if I filter behind the lens in collimated light instead, does the same thing apply?

Also, does anyone have real life experiences with using the red 23, 25 and 29 filters on B/W and can give some recommendations to which one should be preferred?

Thanks.

<{POST_SNAPBACK}>

Hi,
The focal plane is changed only with infrared film. That's what the red dot was for on still cam lenses. I've used all three of those red filters for stills photography and they really jack up the contrast so you need to plan for that.

For skies, you can get maximum cloud/sky seperation with a red 29/polarizer combo. It's pretty dramatic. Skin goes white, anything red goes black (lipstick) so be aware of make-up. Green filters also have interesting effects if you're shooting a lot of foliage.
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#5 Adam Frisch FSF

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Posted 27 September 2005 - 07:13 AM

Skin goes white, anything red goes black (lipstick) so be aware of make-up.

<{POST_SNAPBACK}>


Thanks, Tim.

But are you sure lips go black? I thought they being red and going through a red filter would brighten them?

Would you say that the red filter adds contrast overall or is it just perceived that way because skies go darker?
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#6 John Pytlak RIP

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Posted 27 September 2005 - 09:41 AM

Most lenses are designed to have minimal chromatic aberration over the VISIBLE portion of the spectrum, 400 to 700 nanometers. So focus adjustment for a red filter is usually not necessary. The correction in the infrared is needed because the lenses were not normally designed for infrared photography.
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#7 Tim J Durham

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Posted 27 September 2005 - 03:00 PM

Thanks, Tim.

But are you sure lips go black? I thought they being red and going through a red filter would brighten them?

Would you say that the red filter adds contrast overall or is it just perceived that way because skies  go darker?

<{POST_SNAPBACK}>

Strange but true. There's some tipping point below which red goes black. Pink lipstick does not react the same way. Red filters DO add contrast. I don't remember the filter factors and mired shift business, but it's all listed on the sheet you get with the filters. Then with push processing, you can get some crazy contrast. You really gotta want it, though, because the shadows will have little detail if any.

I actually gave up using on-cam color filters for B&W photography because I could do the same thing in the darkroom with my 4x5 color enlarger head and totally control it. I could just dial in any amount of red/green/yellow (or was it red/blue/yellow?) I wanted. It wasn't died in the wool. I suspect there is some post effect that is equivalent.
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#8 John Pytlak RIP

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Posted 27 September 2005 - 03:22 PM

I actually gave up using on-cam color filters for B&W photography because I could do the same thing in the darkroom with my 4x5 color enlarger head and totally control it. I could just dial in any amount of red/green/yellow (or was it red/blue/yellow?) I wanted. It wasn't died in the wool. I suspect there is some post effect that is equivalent.

<{POST_SNAPBACK}>


:blink: I assume you mean you are printing monochrome images onto a panchromatic paper from a color negative, where you could select the color record you are printing? AFAIK, you can't enhance the clouds in a B&W negative image by simple color filtration during printing if they were not imaged on the negative in the first place.

Using a red filter when printing a color negative will image the red sensitive layer, which has the best contrast between white clouds and a cyan sky.
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#9 Tim J Durham

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Posted 27 September 2005 - 04:28 PM

:blink:  I assume you mean you are printing monochrome images onto a panchromatic paper from a color negative, where you could select the color record you are printing?  AFAIK, you can't enhance the clouds in a B&W negative image by simple color filtration during printing if they were not imaged on the negative in the first place.

Using a red filter when printing a color negative will image the red sensitive layer, which has the best contrast between white clouds and a cyan sky.

<{POST_SNAPBACK}>

Hi John,
No I was printing from B&W negatives using an enlarger with a dichroic color head which projected color-filtered light (a red, a green and a yellow) into a light mixing chamber- NOT a "color film" head, that's a whole different ball of wax- then the mixed light is projected through negative and enlarger lens onto polycontrast B&W paper (I used Ilford Gallery- sorry. But always Kodak film!). It is/was similar to this one only a 4x5":

http://www.adorama.com/BE6730.html

and I could dial in the desired amount of contrast. The color mixing chamber design replaced the set of filters that were inserted below the enlarger lens which was a bad idea from the beginning. Dust issues, scratches, etc.

It was infinitely variable and I found the results much better doing it this way. Just shooting the film for accurate exposure usually with a polarizer outdoors. I expect there are many more variables to consider when shooting motion picture film and so this example may not perfectly convey.
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#10 Dominic Case

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Posted 27 September 2005 - 06:36 PM

Having a red filter in front of the lens changes the wavelenght and therefore the focus of the lens slightly.

In the interests of nit-picking, I should point out that the filter does NOT change the wavelength of anything. What it does is selectively remove some wavelengths (those typically below around 600nm) and pass the rest.
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