Quote Originally Posted by Noble View Post
Have you ever used filters?!

It's not a matter of transmitting or absorbing. It is a matter of scattering the light. The sky is blue simple because whatever is in the sky scatters blue rays more.

Go up on an elevated area such as a really tall building or a mountain and then take a landscape picture with some fine grain film with a deep red filter (3 stops of compensation). Then take the same picture without the filter. You will be able to see a lot more detail with the red filter. Once you filter out the scattered blue light you will get the more direct red light. Now take the picture with the blue filter. Details will be obscured.

I read about red filters cutting through haze but I didn't realize how dramatic the effect was until I tried it for myself. I took the pictures on a clear bright day and you could still see a difference. Try it with a red filter AND a polarizer. It's even more dramatic. Bring a tripod and cable release.

The benefits of a red filter particularly a strong red filter cannot be duplicated with a digital camera or photoshop. It really is one of the unique tools of analog photography.
Gee, I think I might have used a filter a time or two in my 30+ years of photography... I also studied physics of light and optics as an adjunct to my other university studies. I think I have a fairly good understanding of what filters do.

Anyway, all flippancy aside, I think we are saying fundamentally the same thing; I just think you have missed the gist of the OP's original post.

And yes, the blue sky is from scattered blue light, but in a transmission spectrum of water or clouds or fog, you will find that the longer wavelengths are absorbed more, resulting in a higher color temperature (i.e., more blue).

The original question was about "enhancing" fog, not "eliminating" it. I agree, that a yellow or red filter will do exactly what you say it will. And, a blue filter would do just about the opposite, i.e., lightening and "enhancing" the haze; that is, making it more apparent.

Note that there is a fundamental difference between shooting a scene with haze in it that is otherwise lit with "normal" sunlight and shooting from within the fog (which is what I believe the OP was addressing). Use of a blue filter in this case will just overexpose the film a bit, since the factor for the filter is not based on the color temperature of the light coming through the fog. It will no appreciably enhance the foggy effect.

Hope this clears things up,