How to adjust green / magenta balance in very dark densities only / Photoshop CS2

[John Salim]

Hello all,
I need to adjust the magenta / green colour balance right in the dark areas near black level. It must not affect any other levels.

The 'shadows' adjustment in Image>Adjustment>Colour Balance is not suitable because it affects the mid tones.
I've also had a go using curves, but can't adjust it precisely enough.

In essence, I want to adjust and see a neutral 'greyscale' but with a little magenta in the darkest parts.

Any tips most welcome,
John S

 

[Patrick Robert James]

Select/Color Range/Shadows. If that isn't narrow enough, then use /Sample Colors and select the area with the eyedropper and move the Fuzziness down or up until you get what you want.

Hope that helps you.

 

[Mr Bill]

Hi, I don't use Photoshop anymore, so can't verify, but... I would probably use "curves." Regarding the precision, I THINK that fine adjustments were available by single taps on the keyboard arrow keys.

Going from fuzzy memory, I think there may have been an option to actually enter numbers for each point. If that option is not there, and you are computer-savvy, you could try making a rough curve, with as many set points as you need, then "save" that curves file (use an easy name to search on). Then, outside of Ps, try editing the curves file; you will probably have to decipher the format, but I THINK (very fuzzy memory) that a simple text editor may do it. (If not, a hex editor, along with an understanding of his to use it, might be needed?) Note that the curves file might be "hidden" so a little digging might be necessary. Back in the day, in my "day job" I made plenty of such corrective "curves," and I THINK that I did a number of them for use in Photoshop (my memory could be wrong on this, though; we did a lot of our own custom software).

I'm guessing that you don't have an editor for ICC profiles. If you DO (they used to be pricy) you could make edits to your input profile to push/pull specific colors around. This takes a lot more knowledge about the 3D color space you edit in (such as CIELAB or some version of HSV?), so if not already conversant with these, probably not worth digging into. But it is a far more powerful way to control color. Best of luck.

 

[Bob Carnie]

This can be done easily in LAB but it would take hours to explain and above the pay grade of most people using Photoshop.. Google Dan Margulis he is on Kelby Training and his methods are those I learned that do indeed solve this problem
Sorry I cannot be more specific.

 

[Bob Carnie]

Or learn Capture One.

 

[ced]

Try via gradation and use the dark pipette which will set a new dark point and neutralise at that point.

 

[nmp]

Hello all,
I need to adjust the magenta / green colour balance right in the dark areas near black level. It must not affect any other levels.

The 'shadows' adjustment in Image>Adjustment>Colour Balance is not suitable because it affects the mid tones.
I've also had a go using curves, but can't adjust it precisely enough.

In essence, I want to adjust and see a neutral 'greyscale' but with a little magenta in the darkest parts.

Any tips most welcome,
John S

Masking with use of Color Range is one way (Msg # 2).

Another way is to use "Blend If" in "Blending Options" dialog. Double click on your Color Balance layer and you will have a pop-up for it. In the "Blend If" section at the bottom, you can move around sliders to limit the color balance to whatever range you want. You can also control the transition zone by splitting the sliders. Look up a good resource to learn how exactly it can be done as I am sure I will botch it up if I tried to explain in detail.

:Niranjan.

 

[Prof_Pixel]

Should be easy with Curves

 

[jim10219]

Curves is a good option. Usually you can get the color right with just the curves tool unless you’ve got an awkward situation where something was so messed up, that to make the curves work would require too sharp of an adjustment to the curves to get a natural color in the scene as a whole. This usually occurs in situations where you either completely blew the exposure, development, or scan. It can also happen in situations with extreme contrast or something that caused an unnatural color cast in just a certain area. About the only time I’ve had to do this when I didn’t screw something up is in astrophotography where you might not be able to expose the film long enough to expose the foreground without getting star trails. In any case, your best option in those situations is to either create a new layer with just the parts you want to edit, or create a mask layer doing the same, so you can edit the selected parts separately without effecting the rest of the image.

 

[John Salim]

I've tested these adjustments again using 'curves' but this time rather than than grabbing and adjusting the curve, I tried the 'drawing' option.
This again can't be used with accurately ( trying the hand draw a *line with a mouse ain't easy ! ).

I found by inserting many grab points ( in the *line parts that mustn't be adjusted ) I can grab and move the curve without affecting the rest of the *line.
Unless anyone knows of a way to lock parts of the *line ?

* line = the diagonal line ( curve )

Thanks everyone
John S

 

[jim10219]

The trick with the curves tool is to keep the curve as smooth as possible. The fewer points, the better. It’s also a good idea to set the upper and lower bounds with the arrows on the bottom of the graph. And remember, they are all relative to one another. So sometimes it’s easier to drop the red and blue than bump the green up. It takes a lot of practice to figure it all out, but once you do, it’s a pretty powerful and quick tool to get the colors you want.

And you’re right. To lock a spot, just drop a point on the line. However, as you’ve probably noticed, it can’t truly be locked independently from the rest of the line. If it starts getting too convoluted, you’ll get unintentional dips and bumps. And remember, you want a smooth curve. I usually just set the upper and lower bound, and then place one point somewhere in the middle to adjust. I almost never use more than three points, unless making a curve for an alternate process negative (in which case I still try to keep it as smooth as possible).

And like I said before, if you have just one section that needs serious work while the rest looks okay, you’re best off just masking that off, or creating a separate layer so you can adjust it individually. In some cases, you may need to do several layers. I often find it helps to feather the edges of the layers a few pixels to keep a hard line from forming. This too takes practice to get good at.

Photoshop is one of those programs that many people know how to use, few people know how to use it extremely well, and only a handful are truly experts at. You could dedicate a lifetime to that program and still not learn everything there is to do and how to do it well.