The Photoshop Blend-if sliders are a great way to interactively blend two images based on luminosity ranges.

I sometimes use it to wear away an image of a painted graphic against an underlying wood grain or brick texture, to make it seem as if the paint is very old. When I do this I often wish I had a layer mask to use to control the blend, so I could take it into, say, Maxwell, and make a layered material with the wood rough and the paint smooth.

Here's one way to preview the composite using the Blend-if sliders and extract the underlying luminosity mask into a layer mask.

Snow Warrior


A computer generated vehicle commissioned by Chicago photographer Robert Randall as part of a larger Snow Warrior composition of his. Maya, ZBrush, Photoshop, Maxwell.



Probably one of the more complex CG models I've made. It's a digital prop commissioned by photographer Matthew Cherry.


There's quite a bit of detail in the model. It was designed to hold up in a high resolution medium format composition.

Pygmalion & Galatea

Clear Plastic Bag as a Soft Filter



Essential Everyday brand resealable quart freezer bag, single ply, flat across lens. Nikkor 50 mm 1.4 on a Nikon D3s - basically it's the old 'pantyhose across the lens' soft filter except with a sheet of clear plastic.

Some M Verta Maxwell Rendering Commandments

I have a rule: if a feature is going be used, it's going to be mapped.

I don't use solid colors; I don't use a single roughness value; I don't use a single layer opacity value; I don't use fixed angles.

Nothing in reality is perfect - no solid color is absolutely solid; no surface is absolutely uniformly rough. The greasy specular stuff exists on virtually every material I make, because it's on everything I touch. Sometimes it's more subtle than other times, but you simply can't overestimate the value of all these little imperfections. It goes without saying that my geometry is always similarly imperfect. I don't have perfect angles; I don't duplicate objects without heavily modifying the copies. I don't use snap aligns, I don't even model to ortho snaps. I do it by hand and by eye, and in my attempts to be perfect, the models are always gloriously imperfect, as reality is. Even the most rigidly machined product has visible inconsistencies and tolerances. It's the layers of ambient complexity, building up, which help sell the final image.

Another of my Rendering Commandments: Thou Shalt Not Use Thy Eye to Judge Materials. Use reference photos, only. Remember, in Maxwell, we are not recreating reality, we're recreating photographed reality, and a camera sees the world differently than our eyes do. I have this little toy car sitting next to me in my office. Looking at it with my eye, it looks different than the render does (not night and day, but still...). But take a picture of it, and it matches the render precisely. I have a number of HDRIs that I subject my materials to, which I have come to trust, and in the end, because Maxwell is recreating the look of low-dynamic-range capture devices (cameras), their images have to be our guides.

- Mike Verta, Maxwell Forum
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Texture Experiment: Salt and Soapy Water


A solution of salt, dish washing liquid, and water, spread across a vertical dark colored board and dried with a hair dryer. The dryer seemed to produce much better results than simply letting the board air dry on its own.

"One Stop"

Changing a lens opening by "one stop" means either doubling or halving the amount of light that passes through the lens. By definition a .30 log neutral density filter will absorb 50% of the light passing through it (i.e. -1 stop)

If a cinematographer opens up "one stop" he is doubling the amount of light passing through his lens. To compensate he could put a .30 ND filter in front of his lens and be back where he started. If he's shooting under perfect conditions and opens up one stop and exposes a motion picture negative film such as 5247 then twice as much light will hit the film as should. To compensate for a one stop overexposure in the lab the gamma, or contrast, of the film must be considered.

The gamma of all contemporary motion picture color negative camera stocks is around 0.65. This means that for a one stop increase in exposure, the resulting density increases by .30 ND times the gamma of 0.65 which is .195. One laboratory printer point is 0.025 ND. Dividing .195 by .025 yields 7.8 printer points. Therefore to compensate for a one stop overexposure by a cinematographer one must increase the light in the printer by 7.8 printer points to make a print of the proper density.

If a cinematographer asks for the timing of a scene to be "one stop darker" he probably means, "make the scene look as if I stopped down one stop." So to accommodate the wishes of the cinematographer one should add 7.8 points of density.

If an optical house cameraman says that he shot the dupe neg "one stop overexposed" and asks the lab to compensate, the request is quite different: The optical cameraman is probably using 5244 intermediate stock which has a gamma of 1.0, so his resulting density increased by .30 ND times the gamma of 1.0 which yields .30, or 12 printer points, since .30 divided by .025 is 12.

- some wisdom from the old optical printer days in Hollywood.


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