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jfrancis
08-06-2009, 08:52 AM
http://www.creativevideo.co.uk/public/product_images/altimage/19%2006%2020081213868207photoflex_ac-gridm%20copy.jpg

Playing around in Maxwell to investigate the effect of gridding softboxes.

http://www.digitalartform.com/archives/2009/08/softbox_with_eg.html

Link NSFW if nude gray-shaded Poser figures are considered NSFW

mister3d
08-06-2009, 09:21 AM
Huhuh, that's funny. Those dgrids exist to limit the intensity of light afaik. Am I right? What practical sense does it make?
I had similar research once, but not very successfull. http://forums.cgsociety.org/showthread.php?f=21&t=565061

The only thing I'm interested to try is barndoors with arealights.

THe problem is sped. Until we have realtime raytracing, using such things is too expensive.

jfrancis
08-06-2009, 09:31 AM
No, the dial on the side of the light is what you mainly limit the intensity with.

Grids limit the angle of the spread.

For example:

The Alien Bee brand Honeycomb Grids come in four angles of beam width: 10, 20, 30 and 40.
http://www.alienbees.com/hg4x.html

So a gridded softbox is a large area light with barn doors that are flush to the light, soft, and in the form of a grid, instead of the large doors a large area light would need.

jfrancis
08-06-2009, 09:35 AM
THe problem is sped. Until we have realtime raytracing, using such things is too expensive.

I don't care much about speed. I'm mainly making stills and digital matte paintings.

mister3d
08-06-2009, 09:53 AM
Do you see any changes in shadow forming with such grids?
Though I would really just scale the spotlight.
Anyway, that's an interesting research, thanks for sharing. :)

jfrancis
08-06-2009, 04:59 PM
I think there is a shadow difference, and a light wrap difference.

With a large area light, rays from one side of the area emitter will see places on the object that rays from the other side will not see, so you'll get softer light-to-dark shading.

A spotlight is I think a kind of point light, when you get down to it. So the shadows should be hard (unless you takes steps to soften them) and the light-to-dark transition on the object should be contrastier.

Maybe I'll try barn-dooring the area light next, just to see what that does. I assume it will be like no grid for a while, with soft light-to-dark transitions on the object (what the late Dean Collins always called 'shadow edge transfer (http://www.google.com/#hl=en&q=%22dean+collins%22+%22shadow+edge+transfer%22&aq=f&oq=&aqi=&fp=-Pw1cEIpNGU),' -- although for some reason I never warmed up to that term), soft figure shadows on the wall, and a sharp falloff (depending on the length of the doors).

Anyway. It's just messing around to see what happens.

israelyang
08-07-2009, 06:59 PM
YES, many people think in 3d soft shadow = soft light, but it's not. Blurring a shadow map is just a fake. Only something like an area light in a raytracer will give you a soft light and it still depends on the size of the light and its distance to the subject to really show its effect. Using a spot light with soft shadow properties will still give you a hard light but with a blurred soft shadow.

Also using barndoors or flags on the area light will probably give you the same result as with the eggcrate since both things are just redirecting the light rays to be more directional.

What I'd like to see is the use of a black screen (negative light). For example the light source is a large area light over the subject, like in an overcast day. And large black screens are set up on 2 sides of the character off camera to block the ambient light and thus result in a more contrasty lighting. But I guess this is redundant in 3d since we can easily scale the arealight down...

By the way Joesph a very nice blog you have. I have learned a thing or 2 from your postings.

mister3d
08-07-2009, 08:47 PM
What I'd like to see is the use of a black screen (negative light). For example the light source is a large area light over the subject, like in an overcast day. And large black screens are set up on 2 sides of the character off camera to block the ambient light and thus result in a more contrasty lighting. But I guess this is redundant in 3d since we can easily scale the arealight down...

By the way Joesph a very nice blog you have. I have learned a thing or 2 from your postings.
It's called a light blocker. I used it in my scenes. Despite blocking direct light, it can be used to limit GI reflection, as black absorbs.
There are not so many lighting devices:
reflectore
diffusers
light blockers (also include gobos)
light color gels

In 3d we are not limited with a size of a source, so we don't need diffusers. Also we are not limited with setting a light's color, so we don't need light color gels.
Basically what makes sense are reflectors (for which we can use just area lights) and light blockers (black planes).
I'm not sure about using light tools which change directionality of a light, such as fresnel lens or grids or barndoors... for now. As I'm about a compromise between speed and quality.

jfrancis
08-07-2009, 09:30 PM
I, on the other hand, like to use Maxwell to model and better understand my real world light modifiers, like white and silver beauty dishes (http://www.digitalartform.com/archives/2009/03/silver_beauty_d.html), so that I can use them better even in photographic images that contain no CG at all.

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