Monday, February 17, 2020

Steering wheels ~ examples of film-like grain in digital photography

I realize that sometimes it helps to see real world examples of some of the concepts and ideas I share here.

To illustrate how film-like grain can change the emotional response to how we view images I selected a series of classic car steering wheels.

As a first pass I had processed a few of them in color and liked the results.  But when I processed them in black and white, there was always "something" missing.  Now that I better understand film-like grain and it's "purpose" or "role" in how we see things I can see my earlier mistakes.

So I reprocessed my earlier images using first Rawtherapee to get the monochrome scale correct (green-yellow digital filter and curves modifications) and then through the Gimp (G'Mic-Degradations-Add Grain - Tri-X 1600 - Overlay blend mode).

So, without further ado, here is a series of classic car steering wheels from the 2016 traversee de Paris estivale.

 [Suggestion - click on an image to get to the Flickr page, then enlarge to 100percent to see the grain.  Back out the resolution and see how it "feels."  The effect will be subtle.]

la Traversee de Paris ~ 2018 (BW redo)

la Traversee de Paris ~ 2018 (BW redo)

la Traversee de Paris ~ 2018 (BW redo)

la Traversee de Paris ~ 2018 (BW redo)

Saturday, February 08, 2020

The role of film (or film-like) grain in photography... [part two]

Properly adding film-like grain to a digital image takes into account how silver halide prints actually behave. 

If you carefully study silver halide prints you may notice two things.

First, the grain structure is not even across the field.  There is less visible grain in the highlights and shadows.  It is primarily the mid-tones that show grain structure.  This is an effect of film.

Second, the highlights tend to "bloom" or "glow" ever so slightly.  This is the effect of light passing through print paper gelatin top layers and very gently scattering as it passes these layers.  The effect is indeed gentle and might not be noticeable at first glance.

With this as background, here is a process for adding film-like grain to a digital image using the open source software image processing package called the Gimp.  You can adapt this approach using Photoshop or other software that allows the addition and manipulation of layers.

Highlight "bloom" or "glow" -
  • Copy base image to a new layer
  • 1 pixel Gaussian blur upper layer (if you don't like the way this looks, try different blur radius' to find the effect you like best)
  • Add a "Grayscale layer mask"
  • Adjust curve of mask to allow just the highlights to show the 1 pixel blur
  • Flatten the image

Grain (two approaches) -

I use one of two ways to add grain to an image.  The first is using the G'Mic "Add Grain" function.
  • Open G'Mic - Degradations - "Add Grain" 
  • Select the film type that appeals to you
  • Note the blend mode selection (we will come to this shortly)
The second is building a grain layer from digital noise.  This is useful when applying grain to smooth images with large contiguous tone areas.  The G'Mic Add Grain function sometimes gives an obvious non-random repeating pattern in this specific case which we want to avoid.

Using the base image processing software (not G'Mic) -
  • Add a new layer with medium tone gray
  • Add digital noise to the gray layer
  • Gaussian blur the gray layer 2 to 3 pixels (observe the effect at 100% enlargement to find the effect that most closely matches film grain)

Set blend mode -

The selection of the blend mode is critical to how your digital image will correctly mimic film grain structure in a print.
  • Select "Overlay"
Flatten your image if the tools haven't already done so for you and you're finished.

Here is a look at the output of the highlight "bloom" steps and illustrates why setting the blend mode is so important.

Comparison ~ Digital Film Grain Simulation

Coming back to the real world, here is a failed attempt that I made by not correctly setting the blend mode.  The "grain" looks too harsh in both the highlights and shadows.  Old silver halide prints never look like this.

Emulating Tri-X film "look"

Here is another real world example, this time of how correctly setting the grain layer blend mode can look.  As in the above image, the Tri-X 1600 G'Mic "Add Grain" function was used.  But as you no doubt easily can see, the difference between the two images is quite noticeable. 

Look carefully at how the "grain" behaves in the highlights and shadow areas.

la Traversee de Paris ~ 2018 (BW redo)