What is the "grain" filter?

Q
Posted By
quickcur
Oct 19, 2006
Views
797
Replies
6
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Closed
Hi,

Does anyone know how the Adobe Photoshop "grain" and "grain film" filters are implemented? What is the Math behind them?

Thanks,

qq
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MR
Mike Russell
Oct 20, 2006
wrote in message
Does anyone know how the Adobe Photoshop "grain" and "grain film" filters are implemented? What is the Math behind them?

Adobe does not publish the details of how their software works, but in general grain can be added in at least two different ways. One is to add noise to the image, with the amount of the noise controlling the graininess of the final image. This does a good job when for example, you need to match the grain of a photograph to hide a retouched area. You can experiment with this effect using Photoshop’s Gaussian noise filter.

Another way to add grain is to multiply the image by a pattern. The template can be a pattern created by scanning an actual piece of film, or a mathematically generated pattern consisting of noise clumped together to simulate a grain texture. To experiment with a screen like this, the center of each grain is pure black, fading out to white at the edges. Fill a new layer with the pattern, and set the layer mode to Multiply.

Here is a free action that simulates a grain effect – you may find it interesting to step through the action and see what it does: http://www.turningturnip.co.uk/photoshop/actions/photo-grain -actions.php —

Mike Russell
www.curvemeister.com/forum/
J
j
Oct 20, 2006
Mike Russell wrote:
wrote in message
Does anyone know how the Adobe Photoshop "grain" and "grain film" filters are implemented? […]

You digimaniacs had best learn what film looks like or you are banned to wannabe status forever. Learn up.
MR
Mike Russell
Oct 20, 2006
"j" wrote in message
Mike Russell wrote:
wrote in message
Does anyone know how the Adobe Photoshop "grain" and "grain film" filters are implemented? […]

You digimaniacs had best learn what film looks like or you are banned to wannabe status forever. Learn up.

LOL. You have a point. Someday the only way we’ll be able to see film grain is in a museum, next to the Daguerreotypes.
—

Mike Russell
www.curvemeister.com/forum/
Q
quickcur
Oct 20, 2006
Mike Russell wrote:
wrote in message
Does anyone know how the Adobe Photoshop "grain" and "grain film" filters are implemented? What is the Math behind them?

Adobe does not publish the details of how their software works, but in general grain can be added in at least two different ways. One is to add noise to the image, with the amount of the noise controlling the graininess of the final image. This does a good job when for example, you need to match the grain of a photograph to hide a retouched area. You can experiment with this effect using Photoshop’s Gaussian noise filter.
Another way to add grain is to multiply the image by a pattern. The template can be a pattern created by scanning an actual piece of film, or a mathematically generated pattern consisting of noise clumped together to simulate a grain texture. To experiment with a screen like this, the center of each grain is pure black, fading out to white at the edges. Fill a new layer with the pattern, and set the layer mode to Multiply.
Here is a free action that simulates a grain effect – you may find it interesting to step through the action and see what it does: http://www.turningturnip.co.uk/photoshop/actions/photo-grain -actions.php —

Mike Russell
www.curvemeister.com/forum/

Thanks. So how about those "options" in the "grain" filter? I am especially interested in the "vertical" option. It works very well to make a photo looks old.

Thank you again.

qq
MR
Mike Russell
Oct 20, 2006
wrote in message
[re PS’s grain filter]
Thanks. So how about those "options" in the "grain" filter? I am especially interested in the "vertical" option. It works very well to make a photo looks old.

I’m not saying Photoshop does it this way, but an effect similar to this one can be made by scaling Gaussian noise. Create a one pixel high image full of noise, with the width equal to your final image. Then scale it vertically to match the height you need. Multiplying it with another layer with plain noise in it will give an effect similar to vertical grain.

Photoshop is capable of just about any effect if you keep at it and experiment. Also, look at the work of others with free actions, etc, from Adobe exchange and similar places.
http://www.adobe.com/exchange/
—
Mike Russell
www.curvemeister.com/forum/
JM
James McNangle
Oct 21, 2006
"Mike Russell" wrote:

Another way to add grain is to multiply the image by a pattern.

I periodically print business cards for several members of the family, and recently developed a template in Photoshop. When I first started printing cards I got some nice blue grey deckle finish card, but when I went back to get some more the nearest they had was a greenish grey, which I didn’t like as much. However I still had some matching blue grey paper, and the other day I wondered what would happen if I scanned it, and used the resulting image as the background for the cards.

After a bit of experiment I discovered I could delete the original white background from my master template, and then insert the image of the card underneath the text. I then printed the cards on glossy photocard. This gave quite an attractive result, and the recipient wondered if I had laminated the cards in some way, as they looked as if they were on deckle finish card but had a shiny finish.

James McNangle

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