Traditional filters vs. channel mixer

[keithdunlop]

Has digital processing of scanned B&W film replaced the need for traditional colored filters?

In my wet darkroom days, I would shoot landscapes with a red filter if I wanted that really dark Ansel Adams sky. But with digital processing of scanned negatives, is that even necessary anymore -- can't the effects of colored filters on B&W film simply be replicated on the computer by mixing channels?

Or is anyone still using B&W filters on film prior to scanning?

 

[f16sunshine]

It can if you are talking about scanning and converting a color negative or positive film and mixing channels for B+W conversion .
Once exposed, a B+W negative image is set in terms of the colors it responded to.
No red filter=less contrast in the sky etc..

 

[Godfrey]

Has digital processing of scanned B&W film replaced the need for traditional colored filters?

In my wet darkroom days, I would shoot landscapes with a red filter if I wanted that really dark Ansel Adams sky. But with digital processing of scanned negatives, is that even necessary anymore -- can't the effects of colored filters on B&W film simply be replicated on the computer by mixing channels?

Or is anyone still using B&W filters on film prior to scanning?

If you're shooting color negative film, yes: color channel manipulation gives you the same if not more control over the rendering of different color into monochrome tonalities. The filters that the channel mixer cannot do more than simulate are polarizer, neutral density, and infrared-pass filters. These fundamentally change the light that is being recorded in ways that manipulating channels do not accommodate.

If you're shooting B&W film, the film itself is setting the color channel relationships by its own spectral sensitivity. You only have control over the resulting contrast curve and intensities. So you still need B&W filters in the capture phase of making photographs when working with B&W film.

G

 

[keithdunlop]

But if my B&W film scan is an RGB file, don't I have control over the channels?

 

[Chris101]

But if my B&W film scan is an RGB file, don't I have control over the channels?

Changing the channel mix will result in a colored image, not control over the contrast based on the original colors. The colors are lost once the image is recorded on B&W film, right?

 

[Takkun]

And changing contrast digitally only affects the relationships of the shades captured by the scanner. If you want to darken a blue sky, for example, the file doesn't know that it was blue--just a particular shade of gray, that may be the same shade as something else in the picture.
The film sees only luminance values--for example, if I were to photograph a light gray building with a blue sky (which incidentally is much of what I'm doing these days!), the film is only seeing two things that are about as bright as each other--and I'm sure you understand what the end result of using a contrast filter is. The difference is that BW film, or the M Monochrom for that matter, only see the brightness, so there's no way to change separation by color after the fact. And the scanner in turn just sees how dark or light the negative is.
Color film, like everyone else said, can be manipulated digitally since you still have color information to selectively manipulate in post.

So essentially digital capture obviates the need for filters in BW. But traditional film is still film.

 

[nongfuspring]

But if my B&W film scan is an RGB file, don't I have control over the channels?

Nope. The great thing about digital is that you can adjust contrast in certain areas but not others, dodge, burn, etc. much easier than in the darkroom, but those filters are still useful.

But more broadly both in terms of colour digital and film, I'm not 100% sure if colour filters are entirely useless now either. Sometimes I experiment with colour filters on my fuji to produce effects that would ordinarily blow out certain colour channels had I just done everything in photoshop.

 

[Godfrey]

But if my B&W film scan is an RGB file, don't I have control over the channels?

If you're scanning B&W film into an RGB file, all you're doing is scanning the same grayscale image data into three color channels. There's no information to differentiate red from green from blue ... so no filtration affecting the color to monochrome translation is possible.

G

 

[JoeV]

Keith;

When scanning B/W film, there's no color information left on the emulsion to filter via channel mixer.

Perhaps you're thinking of using channel mixer with a color digital file (derived either through scanned color film or a digital capture), in which case channel mixer can affect a color-selective monochrome output.

However, for optimal results, it's best to filter for the monochrome output in-camera, using filters on the lens, even when shooting digital capture. This is because choosing a monochrome output from only one of the three original color channels (say, red) you'll find post channel mixer that the selected channel's histogram will be underexposed, thereby causing a loss of tonal rendition in the highlights.

Another way to affect proper single-channel exposure in-camera is to use manual exposure compensation while monitoring the in-camera histogram, ensuring the desired output channel is adequately exposed.

The problem here is that the typical photographer who's entered into the craft post-film era has little clue about these things, and thinks all things are fixable in post, absent any forethought at time of capture. Garbage in, garbage out, and all that.

~Joe

 

[charjohncarter]

When I was dumb enough to think that I could get a good B&W image out of a digital file, I went through the channel mixing nightmare. In the end it was easier to just shoot B&W film, and then either shoot color film or digital for color. That was ten years ago, and maybe things have changed for the better, but now I don't want to even think about going through that hell again.