julie dog

[imported_julie]

Hi Greg

I adjusted the contrast slightly. It did not take much to make it look very weird indeed.

I then spent a stupid amount of time trying to get the blue out of the dogs tongue. I tried a skin pin but that didn't work. i then just adjusted the blue curve but ran into trouble with increased saturation in the greens and in the dogs coat. Couldn't decrease it in rgb. Is that possible.

Then I had a cup of tea and a deep breath.

Went back into lab and got a little bit of decrease.

Sharpened a little using smart sharp which is new for me. May have underdone it but I don't like the look of over sharpened.

Question time. There seems to be a lot of discussion about numbers this time course. Numbers just don't mean anything to me. I know they are numbers, but I have trouble assigning meanings to them. I love the hue clock and the visual representation of the curves but I just cant seem to make the numbers represent things. I also tend to make judgements around my aesthetic values, I know what I do won't please everyone but it should please me. Is this going to create problems for me.

Julie (the numerically challenged)

[ggroess]

Question time. There seems to be a lot of discussion about numbers this time course. Numbers just don't mean anything to me. I know they are numbers, but I have trouble assigning meanings to them. I love the hue clock and the visual representation of the curves but I just cant seem to make the numbers represent things. I also tend to make judgements around my aesthetic values, I know what I do won't please everyone but it should please me. Is this going to create problems for me.

Julie (the numerically challenged)

Julie...Art's postings are similar to yours in that the numbers are the central issue.  They are worth a read if you have not read them yet..  The numbers are really sign posts for you not necessarily destinations.  What the numbers will tell you if you take another sip of tea and another deep breath... is which way you need to move and in a general sense by how much.

The Hue clock is showing you a few things...
1) The Hue Angle, represented in degrees, Same as the HSB color scale.
2) The Saturation, Represented by the length of the arm on the clock.  Longer arm more saturated color.
3) The numeric values for the color space you are working in. 

Trying  to make something with the numbers requires a destination to get to.  If you know the RGB values for a specific color or item then they would be the destination to get your numbers to go to. In Lab you can get a sense of the type of color cast you have by assessing the numbers Positive numbers are warm colors; negative numbers are cold colors.  But again a destination is required to make something of the numbers.

I understand the desire to correct by aesthetic means. I use it to get me close on fast projects.  The trouble is and I am not always sure my monitor is correct in it's calibration. How would I even know if I look at it every day and things look right??  If I send out a file for printing and the color looks bad in the print but great on the monitor I might have a problem.  Then numbers help you to know that the file is right even if the monitor is not.  The only problems will be when you ramp up the color or send the files out for printing.

I am not a calibrationist...I calibrate the monitor because I have had issues in the past; and I have found that they are non-existent if I keep the monitor calibrated.

If you do not use them for specific color targets and stick to checking neutrals you will have 95% of the problem solved.

[ggroess]

Let's talk about the image as posted for a minute in relation to your question about the numbers...

In my screen shot I placed a hue clock on the black nose of our fine doggie....
So what is the hue clock showing me....Shot2.jpg

The Hue Angle tells me the nose is yellow
The Visual square tells me the nose is black.
The numbers tell me the B channel in LAB is warm...Since B channel is yellow/blue  I know the image is too yellow.  The number I need it close to zero so it is neutral.

In Shot 1.jpg I have made an adjustment to the B channel and brought the nose closer to a neutral black.

In this case the visual information and the hue angle information do not agree and I really need to pay attention to that...I have a strong yellow cast in the image....Since Grass and Golden  dogs are mostly yellow it is easy to ignore this...But it's real and the image looks better to have it removed. 

I did move the point between the screen shots...I did not like the correction the stronger values produced...The cast was not as bad as the sample shows me...This is where the aesthetic comes into play...

Greg

[mikemeister_admin]

Greg, I don't understand why you would adjust colors in LAB since you have no control over individual colors.  If you wanted to just adjust the red, how do you do that in LAB?  Wouldn't it be better to make all color adjustments in RGB since you can adjust each individual color?

[ggroess]

True enough...
I can unfortunately do both....and I can isolate red out of the A and B curves as needed....But I do not have a yellow channel in RGB.  Adjusting the Blue channel is my only option and it can make a mess out of things as well...

For me; for the example shown, it was faster and easier to adjust the B channel of LAB since the cast was overall the image and not tied to brightness...

Greg

[mikemeister_admin]

But how would you know to decrease the yellow instead of increasing the blue?  I also remember reading that we rarely ever adjust the individual colors in LAB.

[ggroess]

That was a visual decision based on the hue clock shown in the first shot. 

The B channel being positive tells me it was yellow...
If I chose the nose to be a neutral, I want the A and B to be Zero.

Rarely, does not mean that I cannot...It can be very difficult to do LAB color corrections.  Lab is a very coarse space.  Fast changes are not necessarily the best changes...I really used this example to show julie that the numbers can be better than using your eye or the hue clock...Not absolute...just effective...I hope.... ;)

[imported_julie]

Hi Greg
Sorry i have disappeared for a while again. Work went out of control, I had to prepare a talk for a professional study day and the house was being painted. Hopefully I now have some more time.

About the dog. I knew there was a yellow cast but I couldn't figure out how to get rid of it. I was in RGB and didn't think to leave it. so if I move the angle up the side like you did does that desaturate equally over the image.  I can see how the numbers give informationbut the hue clock gave me the same information i.e. its yellow not black. Will I be able to get good information by looking at what is on the hue clock, numbers and colour, or will I need to understand and remember all the technical information to really get this

Julie

[ggroess]

The hue clock will tell you those things...

Sliding the end point of the A channel in LAB moves the neutral.  Since it was too yellow overall and I have no neutral to set upon I moved the entire curve.  This reduces the yellow across the entire image It did not really desaturate it too much because I did not really flatten the curve from both ends.  The net effect is to move the neutral and all the points across the entire curve.

If I had a known neutral I would set a neutral point there and both the A and B curves would be affected. 

Greg

[mikemeister_admin]

Julie,

"Question time. There seems to be a lot of discussion about numbers this time course. Numbers just don't mean anything to me. I know they are numbers, but I have trouble assigning meanings to them. I love the hue clock and the visual representation of the curves but I just cant seem to make the numbers represent things. I also tend to make judgements around my aesthetic values, I know what I do won't please everyone but it should please me. Is this going to create problems for me."

I too am in exactly this same place, and I was so glad to hear that I am not the only one struggling with these issues.  Thank you!