Figure 1: Placing control points close together relative to the Spread setting can cause stark contrast in lighting.

Tip #1: Know when to use the smoothness slider

Placing two or more control points close together with respect to the setting of the Spread slider can trigger a sharp contrast in light and dark (see Figure 1). Increase the Smoothness slider to fix the problem while keeping the overall effect faithful to your intent.

Tip #2: Sharpen after, not before

Urban Lightscape relies on edge information to propagate and interpolate adjustments between control points. The purpose of sharpening is to exaggerate edges, but this interferes with Urban Lightscape too. The end result is more grain than you may like, so sharpen after using the plugin, rather than before, if this isn’t what you want.

Tip #3: Save contrast adjustments for later

Contrast adjustment is what Urban Lightscape achieves, but spatially rather than pixel-by-pixel. Increasing the contrast of an image may darken areas that you will later lighten with Urban Lightscape, amplifying noise. Consider deferring your final contrast adjustments until after you have used Urban Lightscape to get the spatial balance right.

Tip #4: Avoid JPEG images if you can

JPEG compression artifacts that are imperceptible to the human eye can still mislead the edge detection used by Urban Lightscape, and degrade its output. Within Photoshop, prefer using the RAW files produced by your camera, if available, rather than compressed JPEG images.

Tip #5: Use the sRGB colour space

The Urban Lightscape Photoshop plugin uses the sRGB colour space internally. Elsewhere in Photoshop, you may be using a different colour space, such as Adobe RGB. This mismatch will degrade the faithfulness of the preview image in Urban Lightscape, usually producing noticeably dull colours. To ensure that you are using sRGB, use the Edit > Convert to Profile menu item in Photoshop, and select "sRGB IEC61966-2.1".

Following the above tips should get you well on the way to getting the most out of the Urban Lightscape Photoshop plugin!

Take this photo (Figure 1) from the Reunification Palace in Ho Chi Minh city. The vase in the foreground is meant to be the focal point of the capture, but it’s also the dullest part of the piece. Global adjustments to brightness, contrast and curves in Adobe Photoshop’s Camera Raw only get me so far (Figure 2). I need to actually enhance brightness locally around the vase, and it is for this sort of adjustment that Urban Lightscape shines.

Figure 1: Original photo as taken off the camera, lighting is dull.

Figure 2: Global adjustments only get so far, the foreground vase is still dull.

Bringing up the Urban Lightscape filter plugin from within Photoshop, I begin by adding the first control point on the vase itself (Figure 3). Double-clicking on the vase and dragging the mouse cursor up increases the light in this area. The adjustment bleeds somewhat beyond the vase into the adjoining carpet on the left, and control points 2 and 3 are placed to smooth the effect, the bright yellow carpet producing a nice contrast with the greens in the vase. The effect around control point 1 is halted at the sharp edge that rings the neck of the vase; control point 4 above lightens its top. Finally, the painting in the background has some nice colour, and control point 5 brightens that up. The spread slider is increased a little to fill the adjustments throughout the picture, giving the final product (Figure 4).

Figure 3: Control points placed on the image to make local brightness adjustments.

Figure 4: The final result after Urban Lightscape adjustments.

A brief parting in an overcast sky set the scene for this shot at Tu Doc tomb outside Hue. While natural light pops the subject (Figure 6) compared to a photo taken just moments before (Figure 5), a dimness creeps in from the right, and in total the foreground has been underexposed, so as not to bleach the sky. Urban Lightscape can be used here to accentuate this spatial contrast of light.

Figure 5: Original snapshot, natural light is poor.

Figure 6: A lucky break in the clouds casts the sun onto the summer house!

A few carefully placed control points achieve this and correct the balance of light to the right for a better composition. The image has been sharpened, and blues and greens further saturated, to finish up (Figure 7).

Figure 7: The enhanced picture after local lightness adjustments.

These two simple examples show three of the main uses of Urban Lightscape: correcting exposure, introducing artificial light sources, and exaggerating contrast in natural light.

See the two photographs in this tutorial on Flickr: The Yellow Room and Emperors and Poetry.

• Performance improvements under Windows.
• Fixed invisible +/- buttons when running under Windows classic theme.
• Fixed some flickering and refresh issues in preview image when running under Windows classic theme.
• Fixed zoom-fit function.
• Fixed gcc 4.6 compile errors under Linux.

./configure --disable-assert CXXFLAGS="-O3 -g" CPPFLAGS="-DNULL=0"

The key addition is the CPPFLAGS="-DNULL=0". A more permanent fix for this will be provided in future versions.

Tintii 2.6.0 is now available for Windows, Mac OS X and Linux, introducing some recent interface innovations incorporated in Urban Lightscape, restoring plugin support for 32-bit Photoshop under Mac OS X, and fine-tuning the behaviour of lightness sliders. It also features a new application icon designed by the team at Creative Freedom.

Detailed changes are:

• New application icon.
• Centred image in preview pane and added textured background.
• Changed lightness sliders to apply multiplicative rather than additive adjustments.
• Added info bar for help messages.
• Separated file types in open and save dialogs.
• Fixed crashes in 32-bit Photoshop on Mac.

The new version is available from the download page.

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Murray, L. M.; Jones, E. M. & Parslow, J. (2012). On collapsed state-space models and the particle marginal Metropolis-Hastings sampler. In review. [arXiv]

Murray, L.M. (2011). GPU acceleration of the particle filter: The Metropolis resampler. Distributed machine learning and sparse representation with massive data-sets (DMMD 2011). [arXiv]

Urban Lightscape delivers sophisticated image-processing via a natural user interface. A simple “double-click-and-drag” paradigm is used to place control points on a photo, and clever edge detection localises and interpolates your lightness adjustments around and between these points. Results are rapid, without compromising on the extra controls needed to achieve subtle refinements.

Urban Lightscape is available for Windows, Mac OS X and Linux. On Windows and Mac OS X it is also available as a plugin to Adobe Photoshop, Adobe Photoshop Elements and Corel Paint Shop Pro. A free 21 day trial is available on Windows and Mac OS X platforms; the software is free and open source on Linux.

Find out more and try it yourself!