It really depends on atmospheric conditions and on your definition of the word "darken" In summer we have very blue skies in inland Australia and a yellow filter can really darken the sky, closer to the ocean or in winter, when the sky isn't as blue a yellow filter will do very little.

I rarely use filters (apart from ND) and amen to your comment about heavy handed photographers with the AA sky. I think the reason the older guys really went after sky darkening was a reaction to ortho films that made blue skies white, pan films came along and they wanted all the dark skies they could get, the darker the better.

Quote Originally Posted by jnanian View Post
hate to say this but yellow filters don't really darken the sky at all, maybe a tiny bit
maybe enough to make clouds seem like they are there a bit more, but if your objective
is to darken the sky, a yellow filter won't really do that ...

the person i was responding to was talking about how in nearly 50 years of professional photography
he really found no use for using filters, and i pretty much agree with him .. unless it is for a specialized purpose
like contrast control with paper negatives, or making ilford SFX film do its thing ...
i find the use of filters by a lot of "landscape" photographers to be heavy handed in the very least
and a lot of the time kind of hackneyed and clichéd ... cheezy velvia nudes at slot canyon ...

but what do i know ...