Tried to read the documentation on this topic, but it was not fully explained (at least that I could figure out).
I note that the histogram will show a different result, based on whether HSV-V or HSL-L colour space is used, albeit slightly. I also note that Show Clipped Highlights may not reflect the Histogram, depending on the Colour Space for the tool. As example, an image I am working on, does not show any Histogram clipping in HSL-L, while it does in HSV-V, and the Show Clipped Highlights shows a small clipped area. I realize Show Clipped Highlights is also dependent on Preference Settings.
So, my question(s) - Is the Show Clipped Highlights/Shadows based on HSV-V? Or is Colour Space immaterial to this tool (I assume it has some bearing)? What is the value (no pun intended) of HSL-L versus HSV-V? And, should one keep the Histogram to HSV-V to perhaps better correlate with Show Clipped Highlights/Shadows? Or does that (last question) matter at all?
Marv
Histogram and Clipped Pixels
Moderator: jsachs
Re: Histogram and Clipped Pixels
Show Clipped Highlights is based on RGB -- there is a second set of buttons that lets you switch between Any Channel Clipped and All Channels Clipped. If Any Channel Clipped is selected, highlights are indicated anywhere the R, G or B channel exceeds the threshold defined in Preferences. If All Channels Clipped is selected, highlights are indicated only if all three channels exceed the threshold. Any Channel Clipped marks areas that are full saturated -- All Channels Clipped marks pure white.
HSL is highlight clipped only if all channels are clipped (255), i.e. the color is white.
HSV is highlight clipped if any channel (R, G or B) is clipped (255), i.e. the color is as saturated as it can be.
HSV or HSL are shadow clipped only if all channels are clipped (0)
The HSV and HSL histograms can, depending on the image, be very different. HSL only maxes out for pure white while HSV maxes out if R, G or B are maxed out. So for example, a very deep red flower may have its R channel clipped at 255 but the HSL L value is closer to 128.
Using Any Channel Clipped is a good way to see if any of the channels is maxed out -- this may indicate loss of detail for certain areas of intense color.
Using All Channels Clipped is a good way to tell if highlights are totally burned out all the way to white.
I have included this information in the help file for the next release.
HSL is highlight clipped only if all channels are clipped (255), i.e. the color is white.
HSV is highlight clipped if any channel (R, G or B) is clipped (255), i.e. the color is as saturated as it can be.
HSV or HSL are shadow clipped only if all channels are clipped (0)
The HSV and HSL histograms can, depending on the image, be very different. HSL only maxes out for pure white while HSV maxes out if R, G or B are maxed out. So for example, a very deep red flower may have its R channel clipped at 255 but the HSL L value is closer to 128.
Using Any Channel Clipped is a good way to see if any of the channels is maxed out -- this may indicate loss of detail for certain areas of intense color.
Using All Channels Clipped is a good way to tell if highlights are totally burned out all the way to white.
I have included this information in the help file for the next release.
Jonathan Sachs
Digital Light & Color
Digital Light & Color