Printing clipped hightlights

[David PZ]

Just a basic question. If you don't adjust clipped highlights downward until the white triangle in the upper right corner of the histogram turns black, does this mean that ink will not print those areas at all or make up a color to print there?

 

[Tony Jay]

No colours will be made up.
The colour (255, 255, 255) which is white will be represented by paper white - no ink is laid down.

Tony Jay

 

[David PZ]

Thanks Tony. So I'll just reduce highlights until the red disappears. Actually, the red areas do not necessarily represent areas that are supposed to be white. I am looking at one image of a human portrait with some bamboo branches in it and I see red spots on her face as well as on some of the bamboo branches. I suppose red simply indicates that there is no detail present?

By the way, when the white triangle in the histogram disappears, small red spots may still be seen. I suppose they won't matter much visibly to the print. Also, I've learned to go negative a little bit more with the highlights because otherwise, the white triangle often shows up again when I reopen the image.

 

[Tony Jay]

Yes, to add more detail to my first post, whenever any singles colour channel has a value of 255 this is deemed as blown.
Whether one tolerates areas of an image as blown is an image-by-image proposition.
An area that really is a specular highlight should be allowed to blow.
In a portrait, however, having areas of exposed skin that are blown is rarely a good idea.

Tony Jay

 

[David PZ]

Hi Tony, I went on my portrait again. (1) With the original as shot, I need to set Highlights on the face to -20 to make the white triangle disappear. (2) Then I clicked Auto Tone and like the result. The Highlights went to -2 and red spots on her face showed up, but her entire face looked perfectly natural. After all, the portrait was taken on a not very bright day out of direct sun. So I don't see why there would be unprintable areas which are not even white. (3) To correct the situation, I had to set Highlights to -90 to make the white triangle disappear, and the result looked somewhat less lively.

So would you go with (2) and ignore the red warnings? Come to think of it, before I even had LR, I had this image printed at a local lab on an Epson inkjet printer some years ago without any editing, no correction of any sort and the print did not show any spots on her face white without any ink. How can we explain this?!

 

[David PZ]

Tony, also do you check the channel values with the WB dropper? I went on my portrait, read the red areas and none of the channel readings topped100, so can they be blown? Did I really miss something?

 

[Tony Jay]

David, without seeing what you are seeing it is difficult to comment definitively about an image - especially from a subjective point of view.
However, I personally think that aesthetics always trumps numbers.

Lets clear up some details, to make sure that we are on the same wavelength - when looking an image in Develop (without softproofing activated) then channel luminance has values between 0 and 100 and is expressed as a percent - this is why you report the white balance dropper tool reporting values between 0 and 100 for each channel.
As soon as softproofing is activated then channel values switch to 0 to 255 which is supposed to represent the 256 levels that an 8-bit image file gives one - in fact with a raw image file there are in fact many more levels per channel but the convention persists.
(This explains my reference earlier to pure white as 255, 255, 255.)

I checked on some images of my own to see whether there was a problem where the clipping warnings were present and yet the cursor or white balance eye dropper showed that area as non-clipped - this did not happen.
So I cannot directly explain your observations in this regard.

I think the only way for a another party to try and judge some of what you are referring to is to have the same image in Lightroom to see exactly what you are seeing.

Tony Jay

 

[David PZ]

OK, Tony. It was my mistake in not realizing that I was reading %. In soft proofing, I found I didn't even need to use the wb dropper. Everything you said checked out. Only I was wrong, unknowingly. I appreciate your help, thanks again.

 

[David PZ]

I'd like to state my new understanding. The red color showing clipped highlights only means that at least one of colors is blown. And only if all three are blown, you have pure white and no ink will be printed. (I suppose, in that case, you would be able to spot the no-ink spots easily.) On the portrait I mentioned that was printed with clipped areas on the face and still looked OK, I believe it's because not all three channels were blown. Kindly correct me if I am again wrong.

 

[Tony Jay]

David, I think that is about it - and well done for figuring stuff out!

Tony Jay

 

[David PZ]

Just a last question, Tony. In practice when there are no specular highlights to consider, do you always reduce highlights until the white triangle in the histogram disappears when preparing an image for printing?

 

[Tony Jay]

Yes David, most of the time, but one does need to consider the overall aesthetics of the image - occasionally one does find an image where it seems appropriate that the highlights are left to blow somewhat.
There is no technical answer here - it is all a season to taste affair.

Tony Jay

 

[Johan Elzenga]

You also have to consider that a pure white pixel is not 'wrong' by definition. It's just as valid as a pixel of any other color. The only problem is that you don't want to have a cluster of pure white pixels, because that means loss of detail. If you hold the Alt-key while moving the Whites slider, Lightroom will show you where the white pixels are. A few white pixels scattered all over the image is no problem whatsoever. The same number of pixels all clustered together in one place could be a problem.