Blend Modes: Is the math correct?

[Sullyman]

I have a question.....

When performing some steps that I have mimicked from Photoshop using blend modes (using the same image) the resulting image never matches the result in Photoshop. Now is this because the math behind the layer modes differ or because the color profile that I'm using in Designer/Photo (default) differ from Photoshop (default)? What could I be overlooking?

[gdenby]

Perhaps both, but from what little I know of the blend mode math in each programs, it seems the equations are probably somewhat different. I suppose it might be something like: In one program, color values above a certain threshold are added by x% to the underlaying layer. In the other program, colors above a slightly different threshold are added y%  to the underlying layer. 

[jenkm]

1. The blend modes do not depend on the color profile, they operate with color values i.e. just numbers and not what color they represent.

2. I think there is no difference in the blend modes math, at least significantly visible.

 

So perhaps, you are using Fill (in Photoshop) instead of Opacity, or Convert to Profile vs Assign Profile when you open the file.

[Sullyman]

On 12/21/2017 at 5:45 AM, Yevgeny Makarov said:

1. The blend modes do not depend on the color profile, they operate with color values i.e. just numbers and not what color they represent.

2. I think there is no difference in the blend modes math, at least significantly visible.

 

So perhaps, you are using Fill (in Photoshop) instead of Opacity, or Convert to Profile vs Assign Profile when you open the file.

Fill and Opacity layer changes are not being made in the process, just the change of the layer's mode.

[jenkm]

@Sullyman Can you post a screenshot or describe which mode you're using and how.