Setting Black and White Points

Unbrok3n

In my recent quests to learn and master curves, Ive come across many (some here on dgrin) articles. Most say its a good idea to set the black and white points so that the pic can use its full range, and the output to the printer is better.
However, in another forum, an experienced ps'er said that manually setting them manually (as in the "make your pictures pop" tutor here) isnt necessary. That as long as the "black point compensation" box is checked under color settings, everything is all set.
What are some "pros" thoughts on this? I can link to what he said and linked to if necessary. Id like to know as much as possible about this.

Thanks!

pathfinder

Unbrok3n wrote:

In my recent quests to learn and master curves, Ive come across many (some here on dgrin) articles. Most say its a good idea to set the black and white points so that the pic can use its full range, and the output to the printer is better.
However, in another forum, an experienced ps'er said that manually setting them manually (as in the "make your pictures pop" tutor here) isnt necessary. That as long as the "black point compensation" box is checked under color settings, everything is all set.
What are some "pros" thoughts on this? I can link to what he said and linked to if necessary. Id like to know as much as possible about this.

Thanks!

Jason, I saw your question in your previous thread, and have been giving it some thought. I was hoping one of the pre-press pros might have an answer for us. Alas....

I learned to set Black and White points from a video in the Online Epson Print Academy several years ago, and I have seen similar recommendations by several authors as well, Scott Kelby being an obvious one. But when you asked why, I had to stop and think, and do a bit a research to formulate an answer.

I will start by saying that I am not a pre-press professional, nor am I a professional user of Photoshop. I am an enthusiastic amateur photographer who has used Photoshop since PS Version 5, about 8 years ago. So there are folks here with far more authority than mine who are invited to correct any of my errors in fact or opinion.. I do my editing in Photoshop regularly on a calibrated monitor, and my prints, whether from Smugmug via EZPrints, or from my personal Epson 3800, closely match my screen images when examined carefully under controlled illumination from an Ott-light. To me, this suggests that what I see on my monitor and what I print are faithful digital images. What I see is truly what I get.

I looked at your link from dpreview where it was asserted that you did not need to set a white or black point, and I think that I respectfully disagree.

If one's goal is to prepare images for the web as video content and never make a print, then maybe it is less important, but most of us here anticipate seeing our images on paper at some point I believe..

One of the references I found most useful in this discussion is Ewe Steinmueller and Juergen Gulbins's "Fine Art Printing for Photographers" which I recommend to any one with a serious interest in fine ink jet printing.

I want to begin by suggesting that you go to www.outbackphoto.com/booklets/resources/fap/ and download the Printer Ramp3 tiff white point and black point test ramp , and several things will become clearer. Clear any default values for the black and white points in your Levels command, so that the numbers in the boxes match the pixel data displayed in the Info palette. It is highly recommended that you do this exercise on a calibrated monitor - it will not be as meaningful on a monitor that is not calibrated properly.


While digital files can have 255 unique steps in the R,G, and B channels as 8 bit images, one cannot see 255 distinct levels on a monitor, let alone on paper.

Once you have downloaded the printer test ramp, how close to zero on the black scale can you distinguish any detail on your monitor? I am certain you cannot see the difference between 0 and 2, or possibly, even 4. On my calibrated Cinema Display, ( I recalibrated just prior to this post ) I believe I can see down to about 8-10 and up to about 253 on the white scale. I will be able to use these values for my default black and white points when we get done with this exercise.

Now, when one sets a black point by using the Threshold command in Photoshop, you are ALSO neutralizing any cast in the darkest colors by making the darkest pixels neutral and black, with all three channels being forced equal.. Likewise, setting a white point on the lightest pixels that you wish to retain visual contrast and detail in, also converts those pixels to a neutral white, since all three channels will be equal at 250,250,250 or whatever value you pick.

Finally, print out this test ramp on your printer, and get an idea what you can actually distinguish on a printer page as opposed to a backlit monitor.

When I print out this test ramp I have difficulty discerning below box 4 in the blacks, but I can see detail in box 253 in the whites, when printed on glossy paper. Matte will usually have even less shadow detail. This is a pretty good range for and inkjet printer.

Now I will go back and enter 8,8,8 and 250,250,250 and save them as defaults for my custom black and white points as I know I can see these on my monitor, and I can print them with my printer, Voila!

To do this, to to Curves, hit the Options button and click on the Shadows black box area - a new Menu box titled "Select target shadow color" opens up - enter 8,8,8 in the R,G,B boxes and click OK. Now go back to the previous "Auto Color Correction Options" box that is still open, and click on the white box for highlights. When the "Select Target highlight color" box opens, enter 250,250,250 in the R,G,B boxes and click OK. Now click on Save as defaults in the still open "auto color correction options" box, and then close the Curves box.

If your monitor and printer values are different than mine, use them. Mine were just suggested for this exercise, although they are the correct values for my workstation and printer.

BinaryFx

Unbrok3n wrote:

However, in another forum, an experienced ps'er said that manually setting them manually (as in the "make your pictures pop" tutor here) isnt necessary.

BPC attempts to map/scale wider source values into a more limited destination space, so that shadows are not plugged (the black in print is not as dark as black in RGB, so with no BPC the shadows may tend to fill in).

BPC and endpoint editing are interrelated, although they do not replace each other. If your source tones are dark enough, BPC will account for the difference...if the source is not darker than the destination, it should not apply and the tone will be reproduced as close as possible to the source in the destination.


Stephen Marsh
http://members.ozemail.com.au/~binaryfx/

arodney

Black Point Compensation is a "fix" in the Adobe color engine for a hole in a real old ICC profile issue. It really has nothing to do with this discussion. You always want it on. It either does nothing (because the profiles are correctly mapping black) or it fixes this issue the profile should have provided in the first place.

Ekaj

I prefer to use the gray point instead of the black and white points because you only have to set one point, and it takes half the time.

pathfinder

If you have taken the time to use a true neutral grey card that should read 128,128,128 I would agree that is a great way to set your color balance. WhiBal and BalanceSmarter have business's based on this tactic. I even wrote a thread about using a gray card to set a custom white balance here

My problem, is that if I have not included a true neutral gray card, it is hard to always find such a point in an image that I can use to balance with. Just 'some shade of gray' won't really optimize an image, even if it corrects the color temperature.

Tango

pathfinder wrote:

Jason, I saw your question in your previous thread, and have been giving it some thought. I was hoping one of the pre-press pros might have an answer for us. Alas....

I learned to set Black and White points from a video in the Online Epson Print Academy several years ago, and I have seen similar recommendations by several authors as well, Scott Kelby being an obvious one. But when you asked why, I had to stop and think, and do a bit a research to formulate an answer.

I will start by saying that I am not a pre-press professional, nor am I a professional user of Photoshop. I am an enthusiastic amateur photographer who has used Photoshop since PS Version 5, about 8 years ago. So there are folks here with far more authority than mine who are invited to correct any of my errors in fact or opinion.. I do my editing in Photoshop regularly on a calibrated monitor, and my prints, whether from Smugmug via EZPrints, or from my personal Epson 3800, closely match my screen images when examined carefully under controlled illumination from an Ott-light. To me, this suggests that what I see on my monitor and what I print are faithful digital images. What I see is truly what I get.

I looked at your link from dpreview where it was asserted that you did not need to set a white or black point, and I think that I respectfully disagree.

If one's goal is to prepare images for the web as video content and never make a print, then maybe it is less important, but most of us here anticipate seeing our images on paper at some point I believe..

One of the references I found most useful in this discussion is Ewe Steinmueller and Juergen Gulbins's "Fine Art Printing for Photographers" which I recommend to any one with a serious interest in fine ink jet printing.

I want to begin by suggesting that you go to www.outbackphoto.com/booklets/resources/fap/ and download the Printer Ramp3 tiff white point and black point test ramp , and several things will become clearer. Clear any default values for the black and white points in your Levels command, so that the numbers in the boxes match the pixel data displayed in the Info palette. It is highly recommended that you do this exercise on a calibrated monitor - it will not be as meaningful on a monitor that is not calibrated properly.


While digital files can have 255 unique steps in the R,G, and B channels as 8 bit images, one cannot see 255 distinct levels on a monitor, let alone on paper.

Once you have downloaded the printer test ramp, how close to zero on the black scale can you distinguish any detail on your monitor? I am certain you cannot see the difference between 0 and 2, or possibly, even 4. On my calibrated Cinema Display, ( I recalibrated just prior to this post ) I believe I can see down to about 8-10 and up to about 253 on the white scale. I will be able to use these values for my default black and white points when we get done with this exercise.

Now, when one sets a black point by using the Threshold command in Photoshop, you are ALSO neutralizing any cast in the darkest colors by making the darkest pixels neutral and black, with all three channels being forced equal.. Likewise, setting a white point on the lightest pixels that you wish to retain visual contrast and detail in, also converts those pixels to a neutral white, since all three channels will be equal at 250,250,250 or whatever value you pick.

Finally, print out this test ramp on your printer, and get an idea what you can actually distinguish on a printer page as opposed to a backlit monitor.

When I print out this test ramp I have difficulty discerning below box 4 in the blacks, but I can see detail in box 253 in the whites, when printed on glossy paper. Matte will usually have even less shadow detail. This is a pretty good range for and inkjet printer.

Now I will go back and enter 8,8,8 and 250,250,250 and save them as defaults for my custom black and white points as I know I can see these on my monitor, and I can print them with my printer, Voila!

To do this, to to Curves, hit the Options button and click on the Shadows black box area - a new Menu box titled "Select target shadow color" opens up - enter 8,8,8 in the R,G,B boxes and click OK. Now go back to the previous "Auto Color Correction Options" box that is still open, and click on the white box for highlights. When the "Select Target highlight color" box opens, enter 250,250,250 in the R,G,B boxes and click OK. Now click on Save as defaults in the still open "auto color correction options" box, and then close the Curves box.

If your monitor and printer values are different than mine, use them. Mine were just suggested for this exercise, although they are the correct values for my workstation and printer.

wow, you rock Jim, now this should be put into a "how to" sticky.

pathfinder

Thanks, Aaron. Let's wait and see if we can get some of the real heavy weights to weigh in here, first.

I do know that Marc always sets a black and white point when editing his images, as he did, when we were at his printing workshop.

Unbrok3n

Thank you everybody who has contributed so far!
Im starting to get a better handle on this issue, but still have a ways before I can "master" it.
I only print/ plan to print on smugmug, so I dont know if that has anything to do with how extreme I get here.
But all in all, I really appreciate your time!

Ekaj

pathfinder wrote:

If you have taken the time to use a true neutral grey card that should read 128,128,128 I would agree that is a great way to set your color balance. WhiBal and BalanceSmarter have business's based on this tactic. I even wrote a thread about using a gray card to set a custom white balance here

My problem, is that if I have not included a true neutral gray card, it is hard to always find such a point in an image that I can use to balance with. Just 'some shade of gray' won't really optimize an image, even if it corrects the color temperature.

I use photoshop's threshold layer on a difference blended, 50% gray filled background copy, not a gray card. I have found I can isolate a neutral gray in almost every photo I have used this on.

I have only recently learned this technique from an artist I hold in very high regard, so I don't know all the limitations yet. But, this has helped me immensely.

Cheekygeek

I'm a newbie at this, so please correct me if I'm off base, but what would be wrong with setting the Black/White points in LAB Color using (Layers -> New Adjustment Layer -> Levels…) and moving the end points into the histogram on the Lightness channel? Then move on to the curves for the color adjustments.

Here is a (striking) example of a before/after image using such a technique:
http://blogs.tech-recipes.com/qmchenry/2008/02/16/photoshop-lab-color-enhancements-nyc-from-above/

Heh. After looking at more of the blog above, I see that it is a fellow dgrinner's blog. (I've seen those images in LAB Color discussions here already: the Wisteria and the Leaves).

arodney

Cheekygeek wrote:

I'm a newbie at this, so please correct me if I'm off base, but what would be wrong with setting the Black/White points in LAB Color using (Layers -> New Adjustment Layer -> Levels…) and moving the end points into the histogram on the Lightness channel? Then move on to the curves for the color adjustments.

The conversion into Lab for one. Why?

Here is a (striking) example of a before/after image using such a technique:
http://blogs.tech-recipes.com/qmchenry/2008/02/16/photoshop-lab-color-enhancements-nyc-from-above/

What's striking to me is that the after image doesn't look very good to me!

pathfinder

arodney wrote:

The conversion into Lab for one. Why?



What's striking to me is that the after image doesn't look very good to me!

I am inclined to agree, Andrew.

Would care to be list your reasons for your opinion? I think that might be more educational for all of us.

BinaryFx

I think most of the "pro/con" issues are contained in these links:

Some links to other discussions on Lab editing:

http://www.alternativephotoshop.com/phpBB3/viewforum.php?f=7&sid=0f1665d3b78ca970902a433258e8f5d9 (colour correction forum)

http://www.ledet.com/margulis/ACT_postings/ColorCorrection/ACT-LAB_intuitive.htm

http://www.ledet.com/margulis/2007HTM/ACT06-LAB_opposing_color.htm

http://www.ledet.com/margulis/ACT_postings/ColorCorrection/ACT-LAB-damage.htm

http://www.ledet.com/margulis/2007HTM/ACT06-LAB_Conversions.htm

http://www.ledet.com/margulis/ACT_postings/ColorCorrection/ColorCorrection.htm


Regards,

Stephen Marsh
http://members.ozemail.com.au/~binaryfx/
http://prepression.blogspot.com/