An illustration of the effect of filters on black and white photography.

[stellarfieldanomaly]

Zuiko 50mm F1.2 - (Probably) Fomopan 400 (possibly) expired(overexposed 1 stop to compensate) - Rodinal 1:25 - gif created by @monsterrobotics

The above images were shot moments apart, on the same file, with the same lens.

The only difference is that one was shot straight through the lens, while the other was shot through a circular polarizer and deep red filter.

The difference in softness is most likely a result of poor focus or scanning on my part, however you will notice a pretty drastic difference in the distribution of shadows and highlights across the frame.

The darkening of the sky as well as the almost complete removal of the reflection on the ice are the result of the circular polarizer. A polarizer (to simplify wildly) uses a type of optical filter to remove a given angular orientation of light from the image. In practical terms, this means a polarizer can remove reflections from a scene, and by rotating the polarizer you can remove a given angle of reflection. This is most intuitive with reflections like in the ice above, but remember that the blue/white color of the sky is a result of light scattering (read: reflecting) off of the atmosphere itself, a properly rotated polarizer can create a deep darkness in the daytime sky, especially when pointed at a 90 degree angle to the direction of the sun.

If you really work at it you can produce extremely dramatic black skies during broad daylight. 

The red filters effects are more noticeable, but harder to quantify. As a general rule of thumb, in outdoor black and white scenes a colored filter will serve to increase contrast. The color of the filter will determine to what degree. The above was shot through a deep red filter, this results in an apparent brightening of the slightly orange sandstone cliff and exposed wood on the tree limbs, while also darkening the dark sky and pale blue ice.

When the trees still have leaves on them, you can get extremely dark results from foliage even when the leaves are in direct sunlight.

Both of these techniques are central to my personal style of photography as I really value the extreme contrast you can achieve.

Of course, some of these results can be achieved in post(and both the linked images and the film images are post processed to my own tastes), especially the effects of the red filter. However I feel there is value to achieving the results you want in camera, it's more committal, intentional and especially with the polarizer cannot be fully replicated in post, as the physical arrangement of the light hitting the sensor is changed, not just it's color or gamma.

What do you think, do you use filters in your own work? 

[pepper]

This is a great illustration of filters on black & white, I learned a lot from this so thank you! I haven't really messed around with filters much but it's definitely on my list of things to try out. Maybe next time I go to the shop I'll pick up a polarizer filter 

I usually just keep a skylight on my lens, mostly because I dislike using a lens cap so I'll just keep the skylight on it and throw the camera in a bag with no lens cap 

I have experimented a little with an Infrared filter, though! I got an R-72 filter and put it on my Canonet rangefinder, and went out to shoot a test roll of Rollei IR. Here are the results, these are just from the contact sheets so not very high resolution:

Some mushrooms using Rollei Infrared, R-72 filter, Canonet QL17 GIII, these were done with a tripod and stepping up shutter speed, I think at f/5.6-ish (should've written it down  )

And this is the same mushrooms with a straight lens (skylight, I suppose) with HP5+ 400 on my OM10:

And finally this is the shot I chose to print, from the IR roll, at full resolution (well, "full resolution". it's a scan so I can never scan the actual print's depth into a digital format) 8x10 off my optical enlarger:

It's interesting to me that the IR filter made the trees in the background appear darker, and the leaves feel softer and richer. The mushrooms themselves have different parts popping with lighter tones than the normal shot, and the shot overall has more contrast but still feels soft? I dunno. I prefer the IR shot between the two examples here though!

I haven't really had the chance to play around with infrared as much as I'd like, but I wanted to share what I have anyways!

[stellarfieldanomaly]

@pepper

I definitely recommend a polarizer, it's such a useful tool! I didn't even get into the effects it can have on color photography, it can increase apparent saturation by removing specular highlights from plant leaves among other things.

I have never done infrared personally, but I want to at some point. I am constantly fighting the demon on my shoulder telling me to get my ZF converted to full spectrum. Your results are interesting, the foliage is darker than I would have expected. I think the reason might be a lack of direct sunlight, from what I've seen direct sunlight IR results in a lot of reflected IR from the chloroplasts in plant light, making them show as a luminous white in photos. I imagine that might be a bit of an issue in the PNW though haha. Another factor might be the IR sensitivity of Rollei IR seems to be 650-750nm while your filter seems to cut anything under 720nm, but that should still leave a usable if small amount of IR light through, the tripod was definitely the right call!

All that said I like the rendering on the the canonet lens, the focus falloff is very smooth.

I can't imagine not using a lens cap haha, but I have some reasonably rare lenses so maybe I'm more precious with them.