May 2009 Archives


Something I was noticing. If you posterize a color image (maybe somewhat in the vein of the Shepard Fairey Obama image) you seem to get more 'intuitive' results by posterizing in Lab color space.

The RGB image posterized to 4 levels each of R, G, and B, and each set of bands in each channel fall in different places, which causes what I consider to be some unexpected color combinations.


The little padlock symbols in the Photoshop Brush Palette probably don't do what you think they do.

Logic would dictate that locking an attribute, scatter, for example, would make it impossible to accidentally uncheck scatter on that brush.

Completely wrong.

If you lock scatter on one brush, then every other brush in Photoshop also becomes a scatter brush.

Good function. Poor implementation. I'd at least go for some kind of 'global' symbol - not a padlock. Padlocks have a different meaning.


I was playing with spirals, possibly as a prelude to making a spiral photo mosaic, and noticed some interesting aspects of them.

A spiral in a polar coordinate system unwrapped into a rectangular coordinate system becomes a series of diagonals. I figured it would.

A hand drawn, irregular spiral, when unwrapped, still tiles seamlessly. That was interesting.

A tiled, unwrapped spiral re-wraps into a multi-armed galaxy-type spiral. For N tiles there are N arms and each arm wraps N times fewer around the spiral. Also interesting.

Eric Dandurand - Master of Glass

glass_DSC6428_crop, originally uploaded by jfrancis.

The Harmonious Art of Eric Dandurand by Natasha Dalton. Glassblowing photo by Joseph Francis

While driving home to LA from a New Year's in San Francisco, we passed through the tiny town of Harmony, CA (pop 18) where I happened to photograph master glass artist Eric Dandurand. That photo was recently published in Journal Plus, Magazine of the Central Coast, May 2009, p 12


Scar13 Hula Mosaic Tapa Cloth 2, originally uploaded by jfrancis.

Scar 13 dances in a grass hula skirt. I've rendered her in patterns reminscent of Polynesian Tapa cloth.

As an experiment I created a LAB color space image with the A and B channels taken from the original photo and the L channel replaced by the mosaic.

Make a Maze in Photoshop


You can make fairly complex patterns in Photoshop by randomly shuffling simpler patterns. This is a Photoshop reprise of material covered for Maya here.


This 'maze' is composed of 4 randomly shuffled tiles.


The tiles are interchangeable. They all connect in the middle of each edge.


Each tile was defined as a pattern and filled as a repeating sheet.

I also made a 16 x 16 image of noise, blew it up 'nearest neighbor - no interpolation' to match the sheet sizes, tone-leveled it and posterized it to 4 values: black, dark gray, light gray, and white.

(click image for a much closer look)

I magic-wanded (non contiguous, with 0 tolerance) each of the 4 gray levels and turned them into layer masks. This caused the tiles to randomly 'shuffle.'


The maze tiles with itself, even if rotated in increments of 90 degrees.

In computer graphics this technique is called texture bombing.


Instead of matching grays to random tiles, I matched them to hand drawn patterns of appropriate values, and create an artistic dither or simple photo mosaic.'


I hand drew symbols of appropriate brightness (using Filters > Blur > Average to gauge the average intensity of the image) My hope was to create a portrait of the model Scar 13 in Hawaiian wardrobe that looked as if it were made from Tapa Cloth.

(click image to see full size)

I used the Threshold tool and a set of known values (in this case of 16 zones I went from from 0/15*255 to 15/15*255 -- see 1:43 video for a rapid spreadsheet solution). I selected, magic wanded, and layer masked ever smaller, brighter areas as I rose level by level through the Photoshop layer stack.

What I ended up with is a bit like overstrike ascii art from the 1970's, which is what this process produces when tile values correspond to mosaic tile values. So if that's something you want, here is a method for 'eyeballing' a custom one just for yourself. (The work is mainly in creating a set of correctly weighted tiles) When I first started playing around with photo mosaics in the early 90's I originally experimented with Chuck Close-style abstract painted targets and swirls. I was reminded a lot of those days while I painted these Tapa cloth tiles. : )

UPDATE 5/28/2009

So I was visiting Filter Forge to see if I could implement this 'maze' pattern and maybe earn myself a free copy of the $300 plugin, when I noticed there was a similar (but simpler) pattern already there called Truchet tiling, which uses only a pair of triangles, or the arc pair tile above. I think I like mine better. :)

UPDATE 6/19/2009

It occurs to me you can use the Photoshop dissolve blend mode to create the random noise patterns.

UPDATE 9/23/2009

I had imagined generalizing this into interlocking tile illustrations for a game or children's mural. I noticed on boingboing tonight that someone was also thinging along those lines.

Makers 5x5 tile game

UPDATE 1/1/2010

While researching Japanese patterns for an upcoming image of mine I came across a NYT article on the repeating Truchet-style patterns of Japanese artist Asao Tokolo. Quite interesting.

The Post-Materialist | A Pattern's Math Magic


I'm going to start keeping track of online sources of fonts that look interesting. Some free. Some not free. The main criteria will be, do I want to 'bookmark' this link? They are in no particular order.

Fontex free fonts

Walden Font Co

Font Diner

House Industries

HPLHS Vintage Fonts

Old Fonts Texas Hero

P22 Type Foundry

Dieter Steffmann - quite an amazing collection of free fonts

Hype for Type (twitter)

17 Remarkably Professional Looking Free Fonts per Web Design Ledger

A list of free fonts assembled bt

25 High Quality Free Fonts for Professional Design from tripwire magazine

20 Free Graffiti Fonts (1 or 2 of which I like)

45 'Outstanding' Free Vintage Fonts (All 45 are not 'Outstanding,' but some are)

The Black and White Adjustment Layer has a nice ability to target and boost or suppress narrowly defined hues. For example, it can affect red without affecting yellow. That's something you can't do with curves.

In this video I'm experimenting not with what kinds of black and white images can be made from the Black and White Adjustment Layer, but what kinds of color images can be made using it.

Technicolor 2-Strip Process in Photoshop

FOLLOWUP: An Experiment with Selective Color Adjustment Layer

I'm curious to see if all I did above was recreate Selective Color the hard way. It looks as though there is some overlap, but Selective Color is not as aggressive in being able to change the image.


Photoshop Black and White Adjustment Layer: A Closer Look

UPDATE 5/31/2009

The Black and White Adjustment Layer

reconstructs the red channel of an image as follows:

R 100% and its 2 red-containing companions, Y and M at 100% - all else at 0%

reconstructs the green channel of an image as follows:

G 100% and its 2 green-containing companions, Y and C at 100% - all else at 0%

reconstructs the blue channel of an image as follows:

B 100% and its 2 blue-containing companions, C and M at 100% - all else at 0%

UPDATE 5/31/2009

The color photography of Madame Yevonde

Editing Audio in After Effects

Is still a bit of a mystery to me. I had created a screencast in pieces using a cheap microphone that creates a baseline silence that is anything but. My first thought was to cross-fade the 'silences' to smooth the transition from one cut to the next, but I was getting volume dips in the middle of the audio dissolves.


I downloaded some pink noise from and tried some tests.

  • Overlaps with fades gave me me volume drops in the transition.
  • Overlaps without fades gave me volume jumps in the transition.
  • A simple end-to-end butt splice sounded seamless. No pop, even.

So for screencasting, that's good enough for me.

Depth of Light


(A Maxwell Render simulation)

Depth of Light

When the figure and ground are almost the same distance from the light they will be of similar brightness.

To let falloff separate figure from ground, pull the model away from the background and place the light so that it is much closer to the model than to the background. Expose for the model.

see Violations of the Inverse Square Law

UPDATE 7/7/2011

Maya Incandescence



Maya models 'incandescence' by pumping flat cartoon color into an object to mimic light radiating equally in all directions, but it looks like from this photo that even a radiant ball like the sun actually has falloff at the edges.

Maybe Maya should build in a 'facing ratio' light contribution option.

photo credit: (NASA/Thierry Legault)

The little dot the gray arrow points to is actually the space shuttle.



...although when I 32-bit HDR-dim-down a finely-smoothed Platonic solid emitter in Maxwell, I see no signs of falloff. So maybe what I see in the sun photo is due to something other than how many rays from a given area get sent toward the camera.


The Inverse Square Law is not an innate property of light. The ISL is a property of expanding spheres. When light does not expand spherically (as in a collimated beam) or when the source cannot be approximated by a point, then light seems to 'violate' the Inverse Square Law.

Cases where the ISL does not hold.

Umbrellas and softboxes will follow the law quite closely for distances greater than twice their diameter.

To see the Inverse Square Law in action, see Depth of Light

If you have a distortion filter that is reversible you can pre-distort an image, apply an 'art filter' to the distorted image, then un-distort the image. The result? The 'art filter' is distorted, while the image itself seems undistorted.

Unfortunately not enough Photoshop distortion filters are reversible, but I could probably back calculate an inverse displacement to a distortion by applying it to an image of absolute pixel addresses - an idea I partially present here:

Smear Now or Smear Later and
UV Map Now or UV Map Later



UPDATE 5/10/2009

I was reasonably successful in using channel calculations to compute displacement maps that undo other displacement maps. The quality is somewhat limited by things like Photoshop's refusal to displace in higher than 8-bits, but below is a test.


I used Perlin noise Photoshop 'clouds' to displace a photo, then I applied the mosaic filter. Finally I reversed the displacement so that the photo was normal, but made of rippled 'mosaic' tiles.

I reversed the displacement by applying the same displacement to an image of absolute pixel address (the yellow, red and green 'UV' image) and subtracting the undistorted version from the distorted version to get an image of relative displacements.

See Digital Heat Ripple to learn all about how the Photoshop displacement filter works.

UPDATE 5/12/2009


Here is a color version: a CMYK color halftone without using CMYK inks


Half brick offset mosaic. One level is offset, then mosaiced, then re-offset.


Full brick offset mosaic. One level is offset, then mosaiced, then re-offset.

I may do more elaborate work by uv mapping and warping reversible Maya meshes.

UPDATE 6/22/2009


More on Hexagonal / Triangular Grid Mosaics in Photoshop

I noticed that every time you apply certain filters to an image they run differently each time. I thought it might be fun to check out the image stacking in Photoshop's new 'extended' versions.

I chose coarse settings for the pixelate > crystallize filter - course enough to disguise the photo. Below is a stack of 8 such images averaged together. The more you use, the less the filter disguises the original.


Here is a (tedious) method for stacking images without the extended version of Photoshop

High ISO Noise Reduction by Image Averaging

I was playing around with this. For image averaging you don't actually need Photoshop Extended. You can do it in any version of Photoshop that supports 32-bits:

Stack the images in layers. Use the LINEAR DODGE (ADD) blend mode to sum all the layers. You will blow out the image way past white. No worries. Kick into 32-bit mode and dim the sum (no pun intended :D ) back into a usable range. For a true average, dim it by a factor of (1 / N layers)

Fake Depth of Field in Photoshop

(click on image to take a close look)

The obvious method: combine a blurry and sharp version of the same image using a layer mask. In most cases this is good enough, but look how the blur behaves through the transition.

(click on image to take a close look)

Blur through a selected alpha channel instead and the blur radius actually grows in proportion with the brightness of the alpha channel. Nice.

This 'ramping up the parameters' behavior is true in other Photoshop filters, as well.


Actually, Photoshop seems to be inconsistent on this issue.


Some filters, like Ocean Ripple, do not ramp up, while others, like Ripple, do ramp up their strength based on alpha.

What a mess.

(click image to see larger)

Use the Black and White adjustment layer to eliminate col-erase non-photo blue pencil sketch lines from a scan of inked artwork. (or many other pencil colors - experiment with hues other than blue - this approach is more versatile than those methods involving eliminating or copying a single color channel)

(click image to see larger)

Adjust one or more sliders, use mainly the cyan slider in the case of Col-Erase non-photo blue, until you target the precise hue of pencil you need to eliminate. The process occurs interactively as you adjust the slider.

An AND gate can be replaced by an OR gate with both inverted inputs and outputs. Correspondingly, the OR gate can be replaced with an AND gate with both inverted inputs and outputs.

To test De Morgan's transformation, and check out this nice Boolean logic gate applet.

In Photoshop, a MULTIPLY blend mode is equivalent to an AND logic gate. When two images are multiplied, both have to be bright to produce a bright result. If either one is dark, the result will be dark.

A SCREEN blend mode can be replicated exactly by inverting two layers, multiplying them, and inverting the result. De Morgan's rules. This means that if a MULTIPLY blend mode is analogous to an AND Boolean logic gate then a SCREEN blend mode must be an OR gate. And sure enough, it is analagous to one. In a SCREEN blend, if either layer is bright (or if both are bright) then the result will be bright. Since SCREEN mode is derived from MULTIPLY mode using essentially De Morgan's rule, it would seem that SCREEN is a 'better' description of an OR gate than Linear Dodge (Add) is.

It also turns out that the transformation between MULTIPLY and SCREEN works the other way, as well. A MULTIPLY blend mode can be created by SCREENING two negatives and inverting the reult, also as predicted by De Morgan.

DIFFERENCE blend mode acts like an EXCLUSIVE OR (XOR) gate. If either layer is bright the results will be bright. If both layers are bright the results will be dark.

UPDATE 5/4/2009

Josh Tynjala has a really great Flash-based logic gate circuit simulator.


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