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Newbie: difference between Hue, Cast, Color balance and C. Temp?

 
 
Aerticulean Effort
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      12-05-2004
David J Taylor wrote:
> http://www.velocityreviews.com/forums/(E-Mail Removed) wrote:
>
>>In message <(E-Mail Removed)>,
>>"David J Taylor" <(E-Mail Removed)> wrote:
>>
>>
>>>I regard Hue adjustment as rotating things round a colour circle, and
>>>therefore as something which should be reversible. Depends on which
>>>program does the adjustment? My perception probably comes from too
>>>much involvement in colour TV!

>>
>>Photoshop's hue/saturation control will shift red to blue and leave
>>blue where it is, for example.

>
>
> Oh, in which case it's not operating how I would expect a hue control to
> operate. To me, hue is something which is measured in degrees (0..360)
> and would wrap round, so you could /not/ shift red without shifting blue
> as well.
>
> Cheers,
> David
>
>

It depends on relative or absolute shift

absolutely shift red to blue (and leave blue & green unaltered)

relatively shift red and blue (relative to each other and leave green
unaltered_

relatively shift the color triangle by mapping R -> B B -> R G -> G
and so forth (maybe even allowing G -> Y)

Aerticeus
 
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ABC
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      12-06-2004
In short, does it mean:

Hue is to change the colour by turning a colour wheel, so that the
color become the neighbouring one

Cast is to add a chosen colour tint---I can add a red cast, right?

Colour balance is to change cast by sliding it between blue to
yellow. Same for C. temp.

Or is that wrong??

I use photoimpact 10. It has one control for color balance and one for
cast. There must be something that makes them different.

ABC
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bob
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      12-06-2004
ABC <(E-Mail Removed)> wrote in news:nhd7r0loq6lc5ocp4unj361j2ap47gv6le@
4ax.com:

> In short, does it mean:
>
> Hue is to change the colour by turning a colour wheel, so that the
> color become the neighbouring one


Hue is a particular shade of color. Red is a hue, blue is a hue.

> Cast is to add a chosen colour tint---I can add a red cast, right?


Cast implies too much of a color. If you put a yellow filter in front of
your lightbulbs, then your photos will have a yellow cast.


Bob

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bob
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      12-06-2004
(E-Mail Removed) wrote in news:(E-Mail Removed):


> Even if all tools worked as you thought, hue would still be in a
> different class than color balance tools, as there is no way to go from
> 0,255,0 to 0,0,255 in any of them.


Can you explain why you think that?

If I make a graduated fill from 0,255,0 to 0,0,255 that fills left to right
across a selection, then the info tool reports H,S,B at 120 degrees, 100%,
99%, at the left edge, and 204,100,62 at the right edge. The H value goes
up sequentially, while the S value dips and rises, and the B value
generally falls.

To my way of thinking, the hue works the way David describes, not in some
other way that you seem to think.

Bob


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JPS@no.komm
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      12-06-2004
In message <Xns95B6E4485DE1Cbobatcarolnet@216.196.97.142>,
bob <(E-Mail Removed)> wrote:

>(E-Mail Removed) wrote in news:(E-Mail Removed):
>
>
>> Even if all tools worked as you thought, hue would still be in a
>> different class than color balance tools, as there is no way to go from
>> 0,255,0 to 0,0,255 in any of them.

>
>Can you explain why you think that?


Can you explain what it is that I "thought". Judging from your
response, you did not understand what I wrote.

We were talking about software functions that change the RGB values of
pixels. I said that hue adjustment was in a different class of
operations than color balance tools.

Color balance tools change scaling. You can't scale any number greater
than zero to zero, and you cant scale zero to sny number that is not
zero.

>If I make a graduated fill from 0,255,0 to 0,0,255 that fills left to right
>across a selection, then the info tool reports H,S,B at 120 degrees, 100%,
>99%, at the left edge, and 204,100,62 at the right edge. The H value goes
>up sequentially, while the S value dips and rises, and the B value
>generally falls.
>
>To my way of thinking, the hue works the way David describes, not in some
>other way that you seem to think.


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JPS@no.komm
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      12-06-2004
In message <(E-Mail Removed)>, I,
(E-Mail Removed) wrote:

>Color balance tools change scaling. You can't scale any number greater
>than zero to zero,


Well, you can if you scale it *by* zero, but that is not a normal color
balance operation.
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David J Taylor
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      12-06-2004
Aerticulean Effort wrote:
[]
> It depends on relative or absolute shift
>
> absolutely shift red to blue (and leave blue & green unaltered)
>
> relatively shift red and blue (relative to each other and leave green
> unaltered_
>
> relatively shift the color triangle by mapping R -> B B -> R G -> G
> and so forth (maybe even allowing G -> Y)
>
> Aerticeus


If you are using the normal definition of Hue (as in HLS, HSV etc.) then
there is no such thing as absolute or relative shift as you describe it.
Neither is there any way in which altering the Hue will leave /any/ colour
unaltered.

Perhaps some programs introduce the concept for special effects or
marketing?

David


 
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ABC
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      12-06-2004
On Sun, 05 Dec 2004 21:12:42 -0600, bob <(E-Mail Removed)>
wrotd:

>ABC <(E-Mail Removed)> wrote in news:nhd7r0loq6lc5ocp4unj361j2ap47gv6le@
>4ax.com:
>
>> In short, does it mean:
>>
>> Hue is to change the colour by turning a colour wheel, so that the
>> color become the neighbouring one

>
>Hue is a particular shade of color. Red is a hue, blue is a hue.
>
>> Cast is to add a chosen colour tint---I can add a red cast, right?

>
>Cast implies too much of a color. If you put a yellow filter in front of
>your lightbulbs, then your photos will have a yellow cast.
>

Good definition. But can adjusting Hue also change 'Cast'?

What exactly does the Hue adjustment do?

ABC
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ABC
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      12-06-2004
On Mon, 06 Dec 2004 04:26:52 GMT, (E-Mail Removed) wrotd:

>Color balance tools change scaling. You can't scale any number greater
>than zero to zero, and you cant scale zero to sny number that is not
>zero.

Oh, what on earth is that??


ABC
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