Questions upon questions....

[ggroess]

ok...well we are going to try to play don't break the ice in reverse...I'm feeling like I am half way there so...let's see if we can connect the dots and break through the wall. 

I have an idea and I'm going to work on it a bit. I will try to have something for you soon...

Greg

[ggroess]

Ok...Let me try this...If I miss the mark I get another swing....

Art,
In order to understand the numbers and the hue clocks and the channel grids I think we have to tip it on it's side for a minute...Let's start with the hue clock.  See Item #1 below in the second attachment.  There are 2 parts to the CM hue clock.  There are the numbers and there is the hue clock itself.  We, for lack of a better term have always called this the hue clock. 

The hue clock portion is created by using the actual hue angle of a given color.  (Whew...what the heck was that...) Hue is the color component of any given color that makes it red or green or yellow.  The HUE is defined like the color wheel.  shot3.jpg  The color is defined in degrees around that circle.  Red is both 0 and 360 degrees.  The hue clock in CM uses this definition and extends it with a bit more data.  The letters around the clock give you a visual reference for what color you are seeing It's less precise but faster. 

The hand of the hue clock points to the hue color in degrees and is a fast reference to what color we are actually seeing.  Lastly on the hue clock the length of the hand shows you how saturated the color is...  A short arm is a light tone a long arm is a dark tone and a dot is usually a neutral.

Ok, now the numbers.  Let's just look at the Red channel again. In this sample the Red = 204.  Notice the hue clock is between red and yellow.  This as you know is the red color value for the sample point.  So now on to #2 on the picture.

Looking at the #2 area of the picture...I have turned the Channel grid on it's edge to show the curve line as a horizontal.  I want you to think of the curve line as a number line; with the number 255 (white) on the left and the number 0 (Black) on the right. All pixels in the image have a value somewhere on this line.  The color sample is located at 204 on that line at the point of the arrow.  So, If I want to see where to adjust the curve for this color I have to find 204 on the line.  The same would be true for Green and Blue on their respective grids. I can use the color worm, the mark command, or the numbers on the edge of the grid to help me find the point. 

So the sample in the hue clock really does point to the adjustment on the curve directly.  #1 leads you to #2.  They are the same thing just shown in different formats #1 is fast and visual; it helps you figure out what to fix. #2 is precise and adjustable; this is where you actually make the adjustment.

I'm hoping you are still with me...On to #3

Which way to move....
It depends on what I want to do.  If I want to make the color darker...More red...I move the selected point towards a lower number.  In this case if I move the point up; (above the curve line) then numbers on the edge of the grid section are going down in value and the color will get darker. 

The value in the hue clock #1 will go down as well reflecting the new color value from on the curve line.  You will notice that as you move the curve the color worm you marked will move along the curve line.  This is because the sampled point has to stick to the curve line; It cannot exist anywhere else.  If the curve bends the point has to move.  The numbering system along the edge of the curve is the new value after your move. It is the "target" or destination how ever you want to think of it... So in #3  if I move my 204 point up to the 185 line the color will get darker.  As the number gets closer to 0 the color gets darker.

OK so how far do I move.

The amount of the move is also related to what you want to do.  If you are trying to make a neutral color;  you move only so far as to make the number value equal the G and B values back on the hue clock.  If you are just trying to "warm" up the image you move until you are satisfied with the warmth...

[mikemeister_admin]

Which way to move....
It depends on what I want to do.  If I want to make the color darker...More red...I move the selected point towards a lower number.  In this case if I move the point up; (above the curve line) then numbers on the edge of the grid section are going down in value and the color will get darker. 

The value in the hue clock #1 will go down as well reflecting the new color value from on the curve line.  You will notice that as you move the curve the color worm you marked will move along the curve line.  This is because the sampled point has to stick to the curve line; It cannot exist anywhere else.  If the curve bends the point has to move.  The numbering system along the edge of the curve is the new value after your move. It is the "target" or destination how ever you want to think of it... So in #3  if I move my 204 point up to the 185 line the color will get darker.  As the number gets closer to 0 the color gets darker.

OK so how far do I move.

The amount of the move is also related to what you want to do.  If you are trying to make a neutral color;  you move only so far as to make the number value equal the G and B values back on the hue clock.  If you are just trying to "warm" up the image you move until you are satisfied with the warmth...

Okay, so I think I have the concept up to this point.  This part I don't get.  First, looking at the red channel grid, the point that you marked....the 204 that the hue clock is indicating....you say that if you move the point up, it will get darker.  Why doesn't it get darker if you move it down?  If you look at the color that is on the outside edge of the grid, it shows that things get darker whether you move the point up or down, so why does it get darker if you move it up, but not if you move it down?  The numbers along the grid go down whether you move the curve up or down.

Another of the many things that I don't understand is when we are told that we need to remove a color cast.  We look at the hue clock and it says....to use the numbers in your clock....R=204.....G=152.....B=112.  Which one is the color cast?  Then, if we adjust whichever one is the color cast, then what about the other two?  If we want the picture to be red, then don't we need to do something to the last color that is left after we adjust the color that is causing the color cast?

Maybe those numbers were a bad example, since a color cast wouldn't have a high number.....it might be something like, R=204.....G=14.....B=12.  If we determine that blue is causing the color cast, and we adjust it down to 0, what about the green?  Doesn't that have to be adjusted also?

[ggroess]

Okay, so I think I have the concept up to this point.  This part I don't get.  First, looking at the red channel grid, the point that you marked....the 204 that the hue clock is indicating....you say that if you move the point up, it will get darker.  Why doesn't it get darker if you move it down?  If you look at the color that is on the outside edge of the grid, it shows that things get darker whether you move the point up or down, so why does it get darker if you move it up, but not if you move it down?  The numbers along the grid go down whether you move the curve up or down.

For a minute let’s look at the images shown  as streets on the map…

Shot 1 shows the grid with a point at the intersection of  160th Lane  (East West) left / right…and 160th Street (North / South) Up / Down.

In Shot 2;  I am going to move up to 114th Lane but stay on 160th Street.; a vertical move that darkens the sample because the value goes down.  Notice the circled sample point has stayed close to my adjustment point . and lands at 114 with my adjustment point landing at 116.  The sample is what matters here because that is what I am measuring and that is what I want to change.  I can care less about where the adjustment point lands.  It’s just a tool to move the curve.  This is the result of an up down move.  The curve point is above the center line and the point has dropped in value.

Shot 3 is the same move but in an east west direction.  The sample point is circled and as you can see moving the adjustment point from 160 the street to 116th street gives us a totally different result…the sample stays on the curve line and by moving the adjustment right you move the sample point down which in this case makes the sample number go higher; 202 in this case…again the adjustment point does not matter to me as much as where the sample point is ending up.  I have moved my adjustment point right from the blue dot to the location shown. 

Another of the many things that I don't understand is when we are told that we need to remove a color cast.  We look at the hue clock and it says....to use the numbers in your clock....R=204.....G=152.....B=112.  Which one is the color cast?  Then, if we adjust whichever one is the color cast, then what about the other two?  If we want the picture to be red, then don't we need to do something to the last color that is left after we adjust the color that is causing the color cast?

In the case you have listed the color cast that would be visible a Peach color…the two lower numbers Green and Blue are darker in color (lower numbers) and therefore the weaker colors in this sample.  There are three ways to remove this “cast”  You can go which ever way you need to and the result is different depending on the need.  The result  is based on the brightness.  If you raise the G and B up to 204 you get a very light shade of gray.  If you lower the  Red to 152 and raise the blue to 152 you get a medium gray.  If you lower the Red and Green to 112 you get a slightly darker medium gray.  All three are possible and depend on what I am sampling.  This is the heart and soul of a color correction By the numbers…Which we cover next week.  In RGB this is one of the best ways to get rid of color casts in the shadows and highlights…It is possible to have different colors based on mixed lighting…for instance daylight mixed with florescent.

Maybe those numbers were a bad example, since a color cast wouldn't have a high number.....it might be something like, R=204.....G=14.....B=12.  If we determine that blue is causing the color cast, and we adjust it down to 0, what about the green?  Doesn't that have to be adjusted also?

Color cast can be visible to some people at a difference of 2 to 3 on the color scale.  In the case you have listed the color would be a dark blood red and you would certainly notice it….Usually the numbers are much closer together and you are looking at things you want to be neutral.  So for the drummers you want the street shadows to be neutral or close to neutral…as an example…

Good Stuff...
Greg