Post Tab ‐ Post‐Processing Effects - ApertureViewer/Aperture-Viewer GitHub Wiki

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The Post-Processing Tab (labeled "Post") in the Aperture Phototools Suite (APS) is where Aperture Viewer truly shines, offering a revolutionary real-time image mastering pipeline directly within the viewer. These controls allow for sophisticated adjustments to High Dynamic Range (HDR) rendering, tone mapping, color balance, saturation, and various artistic effects, rivaling the capabilities of dedicated photo editing software like Adobe Camera Raw or Lightroom – all live, as you view the world.

[!IMPORTANT] The settings in this tab provide powerful, real-time adjustments to the final rendered image. Experimentation is encouraged! All these settings are saved as part of Aperture's comprehensive Graphic Presets.

HDR & Tone Mapping Settings

These settings control the High Dynamic Range rendering pipeline and how the wide range of scene brightness is mapped to your display.

Enabling HDR and Tone Map Selection

  • Enable HDR:
    • Function: Checkbox to toggle the High Dynamic Range (HDR) rendering pipeline.
    • Purpose: Enabling HDR allows for more realistic lighting, better handling of bright highlights and deep shadows, and is a prerequisite for most effective tone mapping and post-processing adjustments.

[!NOTE] Most controls in the Post-Processing tab, especially tone mapping and exposure, are most effective or only active when HDR is enabled.

  • Tone Map:
    • Function: A combobox to select the tone mapping algorithm used to compress the HDR image data into a range suitable for your display.
      • Khronos Neutral: Aims for a neutral, perceptually accurate tone mapping.
      • ACES (Academy Color Encoding System): A film industry standard known for producing cinematic and natural-looking results with good color fidelity, especially in highlights.
  • Tone Mix:
    • Function: Controls the blend between the original scene lighting (pre-tonemap) and the selected tone mapping algorithm's output. 0.0 means no tone mapping effect (raw HDR or SDR if HDR is off), 1.0 is the full effect of the selected tone mapper.
    • Range: 0.0 to 1.0.
    • Default Reset Button (D): Resets to 0.0.

[!IMPORTANT] By default, Aperture Viewer's graphics presets set "Tone Mix" to 0.0. This is a deliberate choice to provide users with an unadulterated base image for their own post-processing adjustments, rather than enforcing a specific "look" from a tone mapper. You can increase this value if you wish to utilize the selected tone mapper more strongly.

Tone Adjustments

These sliders provide fundamental control over the tonal range of the image, similar to basic adjustments in photo editing software.

  • Exposure:
    • Function: Adjusts the overall brightness of the image.
    • Range: 0.0 to 4.0 (slider optimized range; spinner allows wider).
    • Default Reset Button (D): Resets to 1.0.

[!NOTE] This "Exposure" control is the standard viewer setting. Its behavior might differ slightly from the "Exposure" slider in Adobe Camera Raw, particularly in its default value and scale.

  • Contrast:
    • Function: Increases or decreases the difference between light and dark areas in the image.
    • Range: -100.0 to 100.0.
    • Default Reset Button (D): Resets to 0.0.
  • Highlights:
    • Function: Recovers detail in or darkens the brightest areas of the image.
    • Range: -100.0 to 100.0.
    • Default Reset Button (D): Resets to 0.0.
  • Shadows:
    • Function: Recovers detail in or lightens the darkest areas of the image.
    • Range: -100.0 to 100.0.
    • Default Reset Button (D): Resets to 0.0.
  • Whites:
    • Function: Adjusts the white point of the image, affecting the very brightest pixels. Similar to "Highlights" but targets a narrower, brighter range.
    • Range: -100.0 to 100.0.
    • Default Reset Button (D): Resets to 0.0.

[!NOTE] The effectiveness of the "Whites" slider can depend heavily on the presence of very bright elements in the scene. It may require tuning for optimal results.

  • Blacks:
    • Function: Adjusts the black point of the image, affecting the very darkest pixels. Similar to "Shadows" but targets a narrower, darker range.
    • Range: -100.0 to 100.0.
    • Default Reset Button (D): Resets to 0.0.
  • Crush Blacks:
    • Function: Lifts the black point, making the darkest areas of the image appear as a shade of gray rather than pure black. This can create a faded, vintage, or cinematic look.
    • Range: 0.0 (no crush) to 255.0 (blacks become white, an extreme effect).
    • Default Reset Button (D): Resets to 0.0.

[!TIP] This is a key control for achieving specific artistic styles. Subtle use can add depth and a filmic quality by revealing a hint of detail in what would otherwise be clipped blacks.

  • Crush Point:
    • Function: Defines the point on the tonal curve where the "Crush Blacks" effect begins its fade or transition. It influences how smoothly the blacks are lifted.
    • Range: 0.0 to 0.25.
    • Default Reset Button (D): Resets to 0.0.

Color Balance & Saturation Settings

This section provides tools for adjusting the overall color balance and intensity of colors in the scene.

Color Balance Mode

  • Mode Selection (Radio Buttons: Shads, Mids, Lites):
    • Function: Selects which tonal range (Shadows, Midtones, or Highlights) the color balance sliders below will affect.
  • Preserve Luma (Preserve Luminance):
    • Function: When checked, color balance adjustments will attempt to maintain the original brightness (luminance) of the affected pixels, changing only their color tint. When unchecked, color adjustments might also alter brightness.
    • Default: Checked (On).

Color Balance Sliders

These three sliders adjust the color balance towards complementary colors within the selected tonal range (Shadows, Midtones, or Highlights).

  • Cyan / Red:
    • Function: Shifts colors towards Cyan (negative values) or Red (positive values).
    • Range: -100 to 100.
    • Default Reset Button (D): Resets to 0.
  • Mag / Green (Magenta / Green):
    • Function: Shifts colors towards Magenta (negative values) or Green (positive values).
    • Range: -100 to 100.
    • Default Reset Button (D): Resets to 0.
  • Yellow / Blue:
    • Function: Shifts colors towards Yellow (negative values) or Blue (positive values).
    • Range: -100 to 100.
    • Default Reset Button (D): Resets to 0.

Saturation & Luminance Weights

  • Saturation:
    • Function: Adjusts the overall intensity of all colors in the scene. 0.0 results in a black and white image. 1.0 is normal saturation. Values above 1.0 increase saturation (oversaturate).
    • Range: 0.0 to 2.0.
    • Default Reset Button (D): Resets to 1.0.
  • Vibrance:
    • Function: Intelligently boosts less saturated colors more than already saturated ones, and has less effect on skin tones. This can make colors "pop" without looking overly artificial.
    • Range: -100 to 100.
    • Default Reset Button (D): Resets to 0.
  • Lum Red / Lum Green / Lum Blue (Luminance Weights):
    • Function: These sliders control the contribution of the Red, Green, and Blue color channels to the overall luminance (brightness) calculation, especially when converting an image to black and white (by setting Saturation to 0). Adjusting these weights changes how different colors are translated into shades of gray.
    • Ranges: -1.0 to 2.0 for each.
    • Default Reset Buttons (D): Reset to NTSC standard weights (Red: 0.299, Green: 0.587, Blue: 0.114).

[!IMPORTANT] To effectively use Luminance Weights for black and white conversion:

  1. First, set Saturation to 0.0.
  2. Then, adjust the Lum Red, Lum Green, and Lum Blue sliders to achieve the desired grayscale tonal balance.
  3. If desired, you can then bring Saturation back up slightly for a tinted monochrome or heavily desaturated color look. These weights have no visible effect if Saturation is at its default of 1.0 or higher with full color. Their primary impact is seen at low saturation levels or in pure black and white.

Effects Settings

This section includes effects for sharpening and adding film grain.

  • Sharpening:
    • Function: Adjusts the sharpness of the overall image using a Contrast-Adaptive Sharpening (CAS) algorithm.
    • Range: 0.0 (no sharpening) to 1.0 (max sharpening).
    • Default Reset Button (D): Resets to the value defined by the current Aperture Graphics Preset (often around 0.4).

[!NOTE] The current implementation of sharpening might have a subtle effect. Excessive sharpening can introduce artifacts.

  • Grain Amt (Grain Amount):
    • Function: Controls the intensity or visibility of the simulated film grain effect.
    • Range: 0.0 (no grain) to 100.0.
    • Default Reset Button (D): Resets to 0.0.
  • Grain Rough (Grain Roughness):
    • Function: Adjusts the size and texture of the film grain. Higher values can create a coarser, more pronounced grain.
    • Range: 0.0 to 100.0.
    • Default Reset Button (D): Resets to 0.0.

[!TIP] Film grain can help to de-emphasize the "digital" look of computer graphics, add texture, and can be particularly effective for vintage or moody aesthetics. It can also help to mask banding or other minor artifacts in gradients. [!NOTE] The film grain implementation is effective but may evolve in future updates for even more nuanced control. Discussions are underway to potentially add other effects like Vignetting and Texture Overlays/Watermarking to this section, which would likely necessitate UI changes like accordion-style panels to accommodate more controls.