Hue Blend Mode Confusion

Question

Hello,
  In reading about the Hue blend mode, I have come to understand (perhaps erroneously) that given two layers (T)op and (B)ottom, that if the Blend Mode of T is set to Hue, then the hue information in T will be blended with the saturation and luminosity in B, which essentially means that the hue information in B is replaced by the hue information in T. However, in running some experiments, I've noticed that when dealing with a very simple document comprised of two layers only, that setting the Blend Mode to Hue also changes the saturation and brightness.
Here are the steps to duplicate the observed phenomena using two regular layers:
Create a new blank document.
Fill with the color that corresponds to the HSB values (0, 70, 50).
Add a new layer above the existing layer (blend mode Normal).
Fill the topmost layer with the color that corresponds to the HSB values (230, 70, 50).
Using the Info panel, the HSB values for the document should read as (230, 70, 50).
Change the Blend Mode of the topmost layer to Hue.
Using the Info panel, the HSB values for the document should read as (230, 70, 50), but instead read as (230, 66, 53).
And here are the steps to duplicate the observed phenomena using a regular layer and an adjustment layer:
Create a new blank document.
Fill with the color that corresponds to the HSB values (0, 70, 50).
Add a Hue/Saturation adjustment layer (blend mode Normal).
Adjust the Hue value in the Properties panel for the Hue/Saturation adjustment layer to be -130.
Using the Info panel, the HSB values for the document should read as (230, 70, 50).
Change the Blend Mode for the Hue/Saturation layer to be Hue.
Using the Info panel, the HSB values for the document should read as (230, 70, 50), but instead read as (230, 66, 53).
The results in both (for me) are identical. Am I misunderstanding the Hue blend mode?
Thanks,
Matt
Photoshop Info:     13.0.1 x64 Extended
OS:                        Windows 7 64-bit
CPU:                      Dual Xeon E5440
RAM:                     16 GB
Video:                    Nvidia GeForce GTX-580

Answer 1

Hi Chris,
  Thanks very much for your straightforward and helpful answer. So, it would appear that my simplistic understanding of the Hue blend mode as 'replacing' the hue of the underlying layer(s) is incorrect. Would a fair rendering of what the Hue blend mode actually does be as follows?
"The Hue blend mode will perform a direct replacement of the hue in the underlying layer(s). The brightness and saturation of the underlying layer(s) will not be affected *unless* the resultant hue, saturation, and brightness 3-tuple would result in an illegal HSL combination, in which case the saturation and brightness of the resultant pixels will be altered to bring the HSL values into compliance."
Also, is there a way for the Info panel to display HSL values?
Thanks again,
Matt