HSL vs. HSB

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Level 1

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HSL vs. HSB

I've checked the Aperture manual and the discussion forums, but I haven't found an explanation. . . what is the difference between HSL and HSB, such as when using the Loupe? L (luminance?) and B (brightness) report different numbers for a given pixel, but what exactly are the two measuring? And which of these corresponds to the percentages on the Levels histogram?

- Hal -

24" iMac, Mac OS X (10.5)

Posted on Jul 20, 2008 2:20 PM

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Answer 1

rwboyer

Level 4

3,170 points

Jul 20, 2008 3:34 PM in response to Pastor Hal

Hal,

HSL and HSB are standards based color models both based on the hue, saturation, value model. The numbers are a little different because the B and the L are calculated differently but these models are not specific to Aperture. the HSL or HSB value that Aperture displays for a given sample will be the same as that model in any other application. Chalk it up to YACM™ (Yet another color model)

RB

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Answer 2

Pastor Hal Author

Level 1

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Jul 21, 2008 10:49 AM in response to rwboyer

Do you know which values are used in the histogram on the Levels brick (i.e. the percentages at the bottom of the histogram)?

- Hal -

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Answer 3

rwboyer

Level 4

3,170 points

Jul 21, 2008 3:45 PM in response to Pastor Hal

Hal,

Neither but HSL is closest. Just out of curiosity why is this important to you? Are you trying to accomplish something specific?

RB

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Answer 4

Pastor Hal Author

Level 1

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Jul 22, 2008 5:34 AM in response to rwboyer

Actually, yes. What I want to do is to adjust the brightness of a specific tone (or range of tones) with Levels. I've been using LightZone for my image editing, and this is one of the great features of that program that I miss in Aperture. The closest it seems that Aperture can come to doing this is through the quarter-tone controls in Levels. If I can use the loupe to find the brightness of a pixel or group of pixels, I can set the top triangle of a quarter-tone levels control to this value and adjust the brightness of those tones in the image.

So an approximate value from the loupe will work well enough for this, though I find it odd that the levels histogram doesn't correlate with either standard brightness measurement.

If there is a better way to accomplish this same thing in Aperture, I would love to know what it is.

- Hal -

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Answer 5

Jul 22, 2008 7:09 AM in response to Pastor Hal

Here's a little trick:

In the Enhance brick you'll find the Tint controls. If you choose any of the eyedroppers and pass it over the image, you'll see a yellow line moving around the Histogram (The main Histogram not the one in the Levels brick) as you move the dropper. This will tell you where on the histogram a certain area falls.

I'm not telling you to use the tint controls to change the tint DON'T CLICK. You're just using it to obtain info.

DLS

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Answer 6

rwboyer

Level 4

3,170 points

Jul 22, 2008 7:13 AM in response to Pastor Hal

Hal,

I wouldn't get hung up on the numbers thing too much, your eyes work great when making adjustments. if you just use the RGB setting the fourth "L" value at the bottom of the loupe is the value in the consolidated histogram.

RB

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Answer 7

Pastor Hal Author

Level 1

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Jul 22, 2008 7:40 AM in response to rwboyer

Excellent! Thank you, RB and DLS, for the tips.

- Hal -

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