Today I’ll talk about the effect of Filmulator’s Film Area parameter on the perception of a photograph.
The way Filmulator works is by iteratively developing the film in steps (consuming developer from the active layer unevenly over the image), then simulating diffusion within the active developer layer, then diffusing between the active layer and the ‘reservoir’ of inactive developer, and repeating. It also performs agitation once to completely mix the active layer and reservoir.
The Drama slider controls the diffusion between the active layer and the reservoir of developer. The higher the Drama, the less replenishment of developer there is, thus the depletion of developer becomes more severe around the highlights. The Overdrive switch kicks it into high gear by additionally disabling the agitation, strengthening the effect.
On the other hand, the Film Area slider controls the radius of the blur used for lateral diffusion of the developer.
- If you set the Film Area small, it means that the diffusion is large relative to the image size; this enhances larger scale image detail. Because of the more thorough mixing within the layer, the highlights are not darkened as much and you maintain more global contrast given the same Drama setting.
- If you leave the Film Area at the default setting, it provides a good balance between the enhancement of fine detail and the enhancement of larger details.
- If you increase the Film Area, diffusion is much smaller relative to the image size. This limits the exchange of developer between dark and light areas to a small scale. Global contrast can be significantly more strongly affected given the same Drama, so you may want to avoid Drama over 60 or 70 lest you get an extremely flat, crunchy look.
Here’s an example with constant drama (70), whitepoint fixed to an appropriate value and varying film size. Try viewing the images both zoomed out and fullscreen with your face up close.
Small film size:
Default film size:
Large film size:
Large film size with increased contrast (further lowered whitepoint):
95% of the time, I don’t touch the Film Area slider. When I do, it’s usually when the main features in the image are small, like with panoramas.
The other main reason to change the Film Area is depending on how large the image will be when it’s viewed. I’m pretty sure this is actually an interaction with the way your eyes perform their own global contrast reduction: the eye’s tone mapping has its own halo size (fixed angle of view) and Filmulator works best when its halos are the same size as the eye’s.
If the halos are the wrong size, then you notice them and that gives the “Bad HDR” look. But if the halos in the presented low dynamic range image match exactly the halos you would see in the real scene, then the photo can really trick your brain into perceiving the original brightness range.
If you look at the example images, you’ll see that the large format one with boosted contrast looks best if you view it fullscreen and stick your face up close to it, viewing from a distance of ~1/2 the image diagonal. By comparison, the small format one has some areas that look oddly dark (the peaks of the stone walls) and others that are oddly too bright.
On the other hand, the small format one has the most pop if viewed small like on a cellphone or zoomed out (> 3x the image diagonal), while the large format one looks flat and lifeless, even the version with boosted contrast.
And from a moderate distance (distance = 1x to 1.5x the display diagonal), the default film size tends to look the best.
So in summary, pick larger film sizes for larger display media, and smaller film sizes for smaller display media.