AIM: Space Hunter DeepSpace filter

Accurate Image Manipulation for Desktops

DeepSpace Filter
Filter Name | Space Hunter
Compatibility | Adobe Photoshop 5.0 and later.
Required RGB working-space | This filter works correctly only in the AIM working-space (Trinitron, D6500 and gamma 1.0) that is the output space of the filter. Incorrect working-space gamma is indicated by a superimposed gray cross-bar in the preview image.
Description | Provides gamma control, color temperature correction either by correlated color-temperature slider or gray sampling using a probe, color-space conversion saturation and hue adjustment. Colorimetry is absolute in CIE xyY.
Installation | Download and copy all files from the zip archive into the /photoshop/plug-ins directory.

Setup

Open a higher bit-depth image (or convert a 8-bit/channel image to the 15-bit mode, then enter to the filter dialog and press Alt+g to open the Define screen settings -dialog. Enter the system gamma space that is the gamma value from the Adobe Gamma utility (or from other system calibration utility) not the gamma value from the RGB setup.

This one-time-only step is needed in order to have the image in the preview box to appear correctly.

Sliders | Gma (.01) | File Gamma. Used for linearization of the image. Adjust only the tonal range with Gma. Especially look at the deep shadows, areas that appear as pure black indicate too low gamma linearization, increase the Gma value. Airy or thin or washed out apperance indigate too high gamma linearization, decrease the Gma value. Slider value is 100x.

CCT (K)

Correlated Color Temperature, in Kelvin from 2200K to 12000K. Used for balancing color-cast due to illumination. In case the gray probe is active this control is disabled.

If the image is already edited (of unknown color-temperature) it may be much better to use the probe.

If the image is not already edited this control usually gives much more natural apperance than the probe.

Note that the output color temperature is fixed ( to D6500) so this control appears to effect in reverse, in other words the CCT value of the slider is the color temperature of the image before correction to D6500.

Use PV Modes 4...7 to help in adjusting the gray balance.

Sat (%)

Adjust the saturation, carefully, 50% increase is rather much.

This control can totally damage the image if adjusted too heavily. Some images can be saturated very much some only little, this also depends on the amount of the white-point correction that is needed.

Use the PV mode 3 to evaluate the clipping at highlights and if necessary use the WP slider to give headroom for the saturation enhancement.

Hue° | Adjust hue in the range -60° ... 60°. This control should be regarded as the last resort, it takes the chromaticity of the image out from the specified color-spaces. However for artistic purposes it may be very good.
S radius | Gray sampler radius. E.g. radius 5 is the average of 5x5 pixel area.

PV mode

Preview mode. There are 7 preview modes.

1. Shows saturation map. This can be used for gray balance evaluation.
2. Shows clipping at shadows. Shows the location of the pixels that will be clipped to level 0. The intensity of those pixels shows the clipped amount.
3. Show clipping at highlights. Shows the location of the pixels that will be clipped to maximum level. The intensity of those pixels shows the clipped amount.
4. Shows gray areas of the image.
5. Shows more gray areas of the image.
6. Shows even more gray areas of the image.
7. Shows still more gray areas of the image.

The preview modes 4...7 show the filtered result with areas that have high color saturation masked with black. So, only the greyish image areas are visible. Very useful for color balance.

Clipping display in preview options 2 and 3 are color coded. White means that the image information of the pixel is completely clipped. Red means red channel is clipping, green means green channel is clipping blue means blue channel is clipping, cyan means both the green and blue channels are clipping, magenta means both the red and blue channels are clipping and yellow means both the red and green channels are clipping.

The preview modes are active only when the PV mode check box is checked.

Use the preview modes to evaluate and estimate the effect of the various operations.

WP ev(.01)

White-point adjustment in ev. 100 means one ev or one f/stop. -100 means -1ev or -1 f/stop.

Some image enhancement operations will peak some of the color channels of some pixels to the maximum level value. WP control is used to give headroom for the operation by expanding the range. It can also contract the range, use it when there is tail in the histogram.

Use carefully, it will clip when when contracting and scaling up too much will make the image to appear un-naturally.

Use the PV mode 3 (show clipping at highlight) when adjusting the the WP control.

Sat x5 | Multiplies the saturation amount by 5. This is special function, useful e.g. for data mining behind a saturation mask.
Check Boxes | PV mode | Enable/Disable the Preview display. When this option is selected the preview mode is active and the selected preview operation is applied over the filtered result.
Selection Dropdown | Choose the input color-space of the image. The output space is always Trinitron. E.g. Some scanners and digicams have the CIE RGB color-space.

Color Sampler

The probe adjusts the color temperature of the image. Drop the probe on a surface that should appear as gray (but currently has a color cast). Using the probe will disable the CCT slider.

Read the Filter Formula Efficient Use -page about the issue when using the sampler.

Use PV Modes 4...7 to help in adjusting the gray balance.

Usage

Useful as the first step in editing images of unknown working space and generally for hue, saturation and white-balance corrections.

1. Adjust the gamma for natural tonal range.
2. Adjust CCT for good gray balance. If it can not be found then drop the gray probe on an image area that was gray in the real-life.
3. Increase the saturation if necessary.
4. Step through the dropdown entries, trying evaluate what entry gives the most natural colors (this is it, space hunting).
5. use the Preview option 3 to evaluate if the corrections require headroom, if it does use the WP slider

Author | Timo Autiokari.
Homepage | Accurate Image Manipulation for Desktops
Usage Right | Free.
Distribution Right | Distribution is prohibited.
Filter Engine | FilterFormula v 1.13, by ATS/Graphics (extended version for 16-bit images).