Tool radius

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Marpel
Posts: 692
Joined: September 13th, 2009, 3:19 pm
What is the make/model of your primary camera?: Nikon D810
Location: Port Coquitlam, British Columbia

Tool radius

Post by Marpel »

Hello,

Can someone advise what the radius on the paint (and other) tool represents. The only thing I have found in the manual suggests it is the radius of the tool in pixels, however the numbers go up, or down, in increments smaller than a whole number. I would expect 1 (one) would represent a single pixel but how can the radius be anything other than whole pixels (1,2,3 and so on rather than 0.6, 1.7 etc). I'm sure I am missing a simple explanation somewhere.

Thanks in advance,
ksinkel
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Joined: April 2nd, 2009, 11:58 am
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Re: Tool radius

Post by ksinkel »

The radius is the size tfo the tool in pixels. Interpolation techniques allow it to be fractional.

Kiril
Marpel
Posts: 692
Joined: September 13th, 2009, 3:19 pm
What is the make/model of your primary camera?: Nikon D810
Location: Port Coquitlam, British Columbia

Re: Tool radius

Post by Marpel »

Kiril,

Thanks for your reply, however, your answer still leaves me a bit confused.

I was of the impression that a pixel was the smallest measure of an image and that qualities such as tone and colour could not be more finite than one pixel (i.e. a pixel can only be one colour or one tone and you couldn't have, say, half the pixel dark and the other half light).

I experimented with the mask tool and, by zooming deeply into an image, with the transparency, softness and spacing set to zero, tried adding a mask with various sized radius. With anything that I set below 1 (0.2, 0.7 etc), I was only able to get a single pixel. Anything 1 and up to 2, the mask was a 5 pixel cross (like a plus sign). Thinking something changes when generating the mask, I pressed OK and then zoomed into the mask itself and confirmed the comparable masking had been generated. So, if I understand your explanation as it relates to interpolating (I'm only referring to anything less than one pixel because the 1 to 2 pixel result completely confuses me), that any diameter less than 1 is interpolated to 1, what is the value of having a radius of any measure less than 1 or, for that matter, anything other than whole numbers? If the result is a whole pixel(s), why have any fractions at all? I didn't have time to do any checking with the paint tool, so am not sure if the radius fractions work differently and are intended more for that tool.

Thanks
jsachs
Posts: 4203
Joined: January 22nd, 2009, 11:03 pm

Re: Tool radius

Post by jsachs »

Of course you can't paint detail smaller than one pixel.

The radius setting determines the radius of the disc that is painted. This is done by applying the paint color through a mask which is determined more or less by figuring out what percentage of each pixel in the region that is being painted is covered by the disc. The mask is also affected by transparency and softness settings. Thus it makes sense to have fractional radii since this merely adjusts the mask values to account for the coverage of each pixel by the disc. Setting a radius less than 1 simply increases the transparency of the 1-pixel mask since only a fraction of the pixel is covered by the disc.
Jonathan Sachs
Digital Light & Color
Marpel
Posts: 692
Joined: September 13th, 2009, 3:19 pm
What is the make/model of your primary camera?: Nikon D810
Location: Port Coquitlam, British Columbia

Re: Tool radius

Post by Marpel »

Thanks Jonathan,

Makes sense now.
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