why wont color replacement brush work on this image?

[VectorCat]

The attached image appears to fulfill the requirements of the color replacement brush, but I can not do any actual color replacing as I can in other images.

Is there something about this image that prevents the color replacement brush from working on it? 

Thank you 

[walt.farrell]

Other than it being white, you mean? 

The misnamed Color Replacement Brush just replaces the Hue, leaving the Saturation and Luminance unchanged. 

So, here's an experiment for you to try: 

1. Set the Color panel to HSL slider mode, and the color to White.

2. Leaving the Saturation and Luminance sliders alone, move the Hue slider around. 

Did the color change at all? 

 

[VectorCat]

Hi, Walt;

I tried your experiment but nothing happened. Should it have?

 

thank you

[walt.farrell]

No, because when S = L = 100% then changing Hue has no effect. And as the Color Replacement Brush changes only the Hue, it has no effect on a white object either. (You would also find it has no effect on a Black object, I think.)

[PaulEC]

Depending on the result you want, you could try either using a Recolour Adjustment, or paint with a normal brush, on a new layer above with the Blend Mode set to Multiply. (You could just paint directly on your picture with the brush set to Multiply, but if you paint on another layer it's easier to correct if you make any mistakes.)

[VectorCat]

6 hours ago, walt.farrell said:

No, because when S = L = 100% then changing Hue has no effect. And as the Color Replacement Brush changes only the Hue, it has no effect on a white object either. (You would also find it has no effect on a Black object, I think.)

Walt; 

While you and I as humans would say that the N95 photo is of a "white" mask, if that image were truly white, we wouldn't see anything but white. But in fact we see colors or tones that are not white - albeit very close to white. Not as colorful as a photo of an amazon parrot, but it is an RGB image and I'd think that Photo could change whatever pixels are there. Perhaps vibrant colors are required for the "Color Replacement Brush" to truly shine. If I look very closely, I can see a color of my choosing being imparted, but it's faint, probably because, as you intimated, it isn't a colorful enough image from the software's point of view..too many tones for which the R, G and B are pretty close to each other. Just thinking out loud here..

maybe PaulEC's suggestion to use the regular brush in Multiply will get me where I need to go.