So, I have this image:

Click to view attachment

I really like it, but when I went to print it, following all the recommendations in the From Camera to Print tutorial, I ended up with blown-out highlights and a green shift in the brightest part of the flam, which, as you can imagine, was less-than-ideal. I would like suggestions for processing that will allow me to preserve the color and luminosity relationships in the screen image without introducing colorshifts or blown-out areas in the print.

I am printing on the Fuji lightjet at Pikto, using their profiles and a fully color-managed workflow.

The "green shift" is channel blowout. Fire and California poppies are common causes of this problem.

When you overexpose in most scenes, you get that detailless sort of blown highlight you see. But as you likely know, the sensor reads red, green and blue data indepenently.

Now, the orange flames break down as mostly red, some green, no blue. As you increase your exposure more and more, the red channel "limits out" or "clips" before anything else. If each channel could, say, be a number from 0 (dark) to 100 (lightest), then the red gets to 100 before anything else. Maybe in your case it "wants" to be 120, and green "wants" to be 40, and blue "wants" to be 5, but the sensor can only report numbers from 0 to 100.

So, you get 100 red, 40 green, rather than 120 red, 40 green.

This changes the ratio of red to green, which shifts your image green.

You might be able to play some games with copying channels to fix the problem, but in any case, the effect you see is a function of how digital cameras (and other sorts of sensors, you could see effects sort of like this with slide film) work, and the fact that you, in some sense, "overexposed" the image.

Hope this helps...

--Joe

Can you recommend a tutorial or book that presents a work-around for the issue?

Would selectively desaturating green in the blown-out areas fix the issue, or do I need to bring the tonality of the highlights down so that there is no clipping in the print?

I would like a general method of fixing this, as I print rarely, in lots, so iteratively fixing a print is not really a great option for me.

The only article or anything I've ever seen that talks about restoring clipped channels is from this site:

http://www.luminous-landscape.com/tutorial...e-clipped.shtml

Again, that's a technique for "faking up"/"restoring" an image damaged by channel blowout, and is probably only worthwhile as a last resort.



Nope. You still wouldn't have detail--in the example I gave the "clipped" areas have values anywhere from 100...120, and now all you have is "they got clipped to 100". The "information" about what pixel is what color is lost, and your best remaining choice is to fake it (roughly the technique in the article above).



If you can do that, either by reshooting, or if there is enough unclipped data in the RAW file, then, yes, this will be a start. (Now the rest of your image might appear "underexposed" to your taste, but you can selectively bring that up in PS to taste.)



The best you can do is to shoot "dark enough" in the first place, and then perhaps bring up the dark areas of the image selectively to restore some level of appropriate tonality. per-channel histograms give you that ability, and in fact, that is their primary value.

In one's dream world, cameras could have better dynamic range, and that would help some. But I'm not waiting up for major improvements in that area.

Best,

--Joe

Joe,

Thanks--that is a lot of help. I will do some layers and curves work to get some detail back into the clipped region before I print it again.

How about a monitor softproof?
I did it with a profile from my lab and no green. When I print the colors are close to my softproof,.
I suppose there is some problem in your workflow.

Jacopo

If this was shot raw you may be able to undo some or all of the channel clipping by doing a second conversion with EC dialed down, then blend using HDR techniques using the image itself as a mask. This is what I did for this image.


- DL