B&W and Red or Coloured Filters.

[arith]

When I was a kid I had a red filter for my camera, it was red coloured and I seem to remember it made red things lighter, although I might have got that wrong.

The School had a Hasselblad with a yellow filter on it, wasn't allowed to remove it, the teacher said it improved skin tones.

So given the digital filters seem to make a colour lighter, for instance a red filter makes red lighter, are these the same filters we used in the past because intuitively I would have thought a filter reflecting red would make the red in the image darker?

How do coloured filters work in B&W?

[Shadowman]

I have an old skylight filter and it was designed to absorb UV light, add a touch of warmth to scenes captured with film; which would reduce blue haze in airy scenes. My digital camera has a series of filters that can be applied to an image, but they don't seem to do anything for me visually, perhaps if I compared the histogram I would see a difference.

[Mike Buckley]

How do coloured filters work in B&W?

Whether shooting with black-and-white film and using colored filters or shooting digitally in color and then converting to black-and-white, the color of the filter makes that color in the color image appear the brightest in the black-and-white image. It makes the color that is oppositely positioned on a standard color wheel chart the darkest in the black-and-white image. The other colors appear less bright or less dark than the two colors already mentioned depending on how far away they are positioned in the color wheel from those two colors.

[arith]

Cheers John and Mike, still don't understand how it works though. Would a red filter appear cyan, if it was red it would reflect red light and thus make film darker.

[Inkanyezi]

Ideally, the filter should not reflect any light at all, if it is an absorption filter. A red filter absorbs green and blue, hence the image is mainly formed from red light. The filter is red when you look through it.

There are also dichroic filters that have another working mechanism. They reflect the light they are not supposed to let through. Hence a red dichroic filter will indeed reflect cyan. Dichroic filters are usually not used as camera filters, but they are very common as colour filters in additive printing equipment.

With a digital camera, coloured filters are not needed, as we have three colour channels to choose from, and if we want a B&W image filtered red, we can just take the red channel and exclude the other two. All colour filter effects can be composed from our three colour channels.

[arith]

Cheers That is what I wanted to know Urban.

[William W]

. . . How do coloured filters work in B&W?

Black and White and Contrast Filters:



Black and White and Toning Filters:



Black and White and R72 Filter (IR):



WW
All Images ©AJ Group Pty Ltd Aust 1996~2015, WMW 1965~1996

REF: HERE and HERE

[IzzieK]

The best explanation so far in this post, William....and to complete it with examples is a bonus...

[arith]

Fantastic reply Bill, I had no choice but use B&W at school and I haven't used it since really. I did nothing as good as your image above, in fact I didn't do landscape unless told to and most the instruction was in portrait photography, but I haven't the room or money for that, and I don't think I could interact with the models like Duffy did, I couldn't insist that they sing for instance.

Anyway, a bit off track, thankyou for your explanation.

I was excited by Urban's explanation because I remember my red filter was red, and I didn't remember I was looking through it, not at it. So now I know

[William W]

Thanks Izzie. Thanks Steve.

*

It was actually Urban's answer "With a digital camera, coloured filters are not needed . . ." which triggered my memory that I had made those Toning and Contrast samples years ago.

The Contrast and Toning samples are typical of the features which are contained in Canon EOS Cameras, (but other cameras are very similar) and my samples were made with an EOS 20D.

The additional image, (Sunrise at the Beach), used a Physical Filter on the lens (Hoya R72) and was made with a Fuji X100s.

*

. . . most the instruction was in portrait photography . . .

One of the reasons, probably the main reason, for using a Contrast Filter for B&W Portraiture was (still is) to 'bring out' the Skin Tones: but another reason was to create contrast in the CLOTHING, when the sitter chose the 'wrong' colours to wear.

As a side note and picking nits: I have noticed that generally folk who have worked with B&W Contrast Filters (and Film printing) are far more sensitive to the nuances of and more critically analyse Digital conversions from Colour to Black and White.

WW

[IzzieK]

Well, William...at least with your detailed explanation, I took out my colour chart and my old set of filters and am able to determine what I was looking at, not just guess which ones are good for what. I didn't learn that while I was in films as I realized now I should have started learning then ... not too late as long as I wake each day with a smile on my face as usual...

Thanks.

[William W]

That's good. And you can apply that theory in the Digital Darkroom when converting colour to Black and White.

WW

[William W]

Cleaning out some of my old tutoring files, I just found this (complete with the typo 'shoot').

It is a similar topic of Filters, but for Colour Temperature correction - in this case for 'enhancement' of the Portrait to one's individual taste:





The above is an example of applying Post Production in Photoshop and using the "filters" as described.


***


This is (a larger version) of the original Image:




WW

All Images ©AJ Group Pty Ltd Aust 1996~2015, WMW 1965~1996

[IzzieK]

Good illustration...thanks for sharing...this is a great teaching tool...

[jcuknz]

Cheers John and Mike, still don't understand how it works though. Would a red filter appear cyan, if it was red it would reflect red light and thus make film darker.

But a filter does not reflect but rather absorbs which is the problem with your approach to the subject.