FDPiech
25th January 2007, 02:57 PM
This technique works on any image, color or B&W
Setting the correct white and black points in our images doesn't need to be done by eye. In fact it's much smarter for us to set them by the numbers and take the guess work out of it. Not only will we be sure that our image will fall within what our printer or processor can produce, but it makes fixing color casts in our images much easier.
Lets look at the wonderful image by Shawn.
http://www.piechdesign.net/tutorial_img/WBPoint_001.jpg
A very fine window light shot of a young boy, but it's very grey. Our blacks are all not quite black, and our whites are all not quite white. While this image will print as a nice image, lets set our black and white points and bring out the full beauty of the light he's captured here.
First let?s add a Threshold Layer. Threshold shows us our image in 2 colors. Black and white. If we move the slider to the right, it shows us more highlights. If we move it to the left we see more shadows. We are going to use this to set some points with the color picker tool so we can adjust the black and white.
Let's add the layer: <Layer><New Adjustment Layer><Threshold>
http://www.piechdesign.net/tutorial_img/WBPoint_002.jpg
At 128 our image looks like this
http://www.piechdesign.net/tutorial_img/WBPoint_003.jpg
Let's move the slider on the threshold over to the right and find the first NON-SPECULAR point that shows up on our subject. What do I mean by non-specular? I mean the brightest point in our image that is not a bright reflection. Do NOT pick a point like say... the eyes catch lights, or a glare on someone?s eye glass frames.
In this image that point is right down on his sleeve.
Click OK on the threshold dialog to accept.
http://www.piechdesign.net/tutorial_img/WBPoint_004.jpg
So lets pick our color sampler tool, set it for a 5x5 sample and then click it in one of those white spots down where his sleeve is.
Now we have our white point selected.
http://www.piechdesign.net/tutorial_img/WBPoint_005.jpg
Let's pick our black point now.
Double click on the threshold layer in out pallet again and lets move the slider to the left and find what the blackest point in our image is. Here we can see that it's right on the edge of the stripe on the back of his shirt.
Click OK on the threshold dialog to accept and put another control point in one of those black squares.
http://www.piechdesign.net/tutorial_img/WBPoint_006.jpg
Now that we have selected the brightest point and the darkest points in our image, we have no more need for the threshold layer. Drag it down to the trash can on our layers pallet and get rid of it.
Now lets look at our info pallet. In a normal setup, it's in the same frame as the Navigator and the Histogram. See the values for the two points we selected?
We are going to use these numbers along with a curves layer to set these numbers. What numbers do we want to make them? Well, a good rule of thumb is to have the white point values all be at or near 245 and your black values all to be at or near 15. If you set your points in this range, you should be able to get good, full range prints.
http://www.piechdesign.net/tutorial_img/WBPoint_007.jpg
Here we can see that our white point only makes it up to 200, and our black point only makes it down to 25. We're loosing 45 points of highlight and 10 points of shadow. Ok... So lets fix it.
Add a curves layer to your image. <Layer><New Adjustment Layer><Curves>
We are going to work on each of the color channels themselves. This will allow us to be sure that our white and black is neutral. Why do you ask? Having neutral white and black points will solve MANY image color problems and the ones that it doesn't solve, it will make easier to correct.
Select the Red Channel, and click the little box on the shadow side of the graph then use the arrow keys to move that point left, right, up or down. Watch the info pallet while you do this, you'll see the value in the red value of the shadow point changing. Change it until you get it as close as you can to 15.
Now select the Green Channel and do the same thing...
And finally the Blue Channel.
We now have our black point set to a neutral black.
Black Point:
http://www.piechdesign.net/tutorial_img/WBPoint_008.jpg
Now I work my way backwards through the channels but this time picking the highlight box in each graph and adjusting the white point values until I get each one as close to 245 as I can.
White Point:
http://www.piechdesign.net/tutorial_img/WBPoint_009.jpg
Now let's look at our image again. Look at how much modeling we've brought out in this image. Look at our info pallet. Notice how our black points are now showing 17?
http://www.piechdesign.net/tutorial_img/WBPoint_010.jpg
This is not uncommon. Adjusting the white points has added some value to our black point. Just pop your curves layer back up and adjust the black points to be 15 again.
http://www.piechdesign.net/tutorial_img/WBPoint_011.jpg
And here is our final image.
http://www.piechdesign.net/tutorial_img/WBPoint_012.jpg
This is a great technique for getting the full range out of any image you wish to print of display. It's also a great
way to fix a lot of color problems.
Show us your Before and After images and let us all know what you think!
Setting the correct white and black points in our images doesn't need to be done by eye. In fact it's much smarter for us to set them by the numbers and take the guess work out of it. Not only will we be sure that our image will fall within what our printer or processor can produce, but it makes fixing color casts in our images much easier.
Lets look at the wonderful image by Shawn.
http://www.piechdesign.net/tutorial_img/WBPoint_001.jpg
A very fine window light shot of a young boy, but it's very grey. Our blacks are all not quite black, and our whites are all not quite white. While this image will print as a nice image, lets set our black and white points and bring out the full beauty of the light he's captured here.
First let?s add a Threshold Layer. Threshold shows us our image in 2 colors. Black and white. If we move the slider to the right, it shows us more highlights. If we move it to the left we see more shadows. We are going to use this to set some points with the color picker tool so we can adjust the black and white.
Let's add the layer: <Layer><New Adjustment Layer><Threshold>
http://www.piechdesign.net/tutorial_img/WBPoint_002.jpg
At 128 our image looks like this
http://www.piechdesign.net/tutorial_img/WBPoint_003.jpg
Let's move the slider on the threshold over to the right and find the first NON-SPECULAR point that shows up on our subject. What do I mean by non-specular? I mean the brightest point in our image that is not a bright reflection. Do NOT pick a point like say... the eyes catch lights, or a glare on someone?s eye glass frames.
In this image that point is right down on his sleeve.
Click OK on the threshold dialog to accept.
http://www.piechdesign.net/tutorial_img/WBPoint_004.jpg
So lets pick our color sampler tool, set it for a 5x5 sample and then click it in one of those white spots down where his sleeve is.
Now we have our white point selected.
http://www.piechdesign.net/tutorial_img/WBPoint_005.jpg
Let's pick our black point now.
Double click on the threshold layer in out pallet again and lets move the slider to the left and find what the blackest point in our image is. Here we can see that it's right on the edge of the stripe on the back of his shirt.
Click OK on the threshold dialog to accept and put another control point in one of those black squares.
http://www.piechdesign.net/tutorial_img/WBPoint_006.jpg
Now that we have selected the brightest point and the darkest points in our image, we have no more need for the threshold layer. Drag it down to the trash can on our layers pallet and get rid of it.
Now lets look at our info pallet. In a normal setup, it's in the same frame as the Navigator and the Histogram. See the values for the two points we selected?
We are going to use these numbers along with a curves layer to set these numbers. What numbers do we want to make them? Well, a good rule of thumb is to have the white point values all be at or near 245 and your black values all to be at or near 15. If you set your points in this range, you should be able to get good, full range prints.
http://www.piechdesign.net/tutorial_img/WBPoint_007.jpg
Here we can see that our white point only makes it up to 200, and our black point only makes it down to 25. We're loosing 45 points of highlight and 10 points of shadow. Ok... So lets fix it.
Add a curves layer to your image. <Layer><New Adjustment Layer><Curves>
We are going to work on each of the color channels themselves. This will allow us to be sure that our white and black is neutral. Why do you ask? Having neutral white and black points will solve MANY image color problems and the ones that it doesn't solve, it will make easier to correct.
Select the Red Channel, and click the little box on the shadow side of the graph then use the arrow keys to move that point left, right, up or down. Watch the info pallet while you do this, you'll see the value in the red value of the shadow point changing. Change it until you get it as close as you can to 15.
Now select the Green Channel and do the same thing...
And finally the Blue Channel.
We now have our black point set to a neutral black.
Black Point:
http://www.piechdesign.net/tutorial_img/WBPoint_008.jpg
Now I work my way backwards through the channels but this time picking the highlight box in each graph and adjusting the white point values until I get each one as close to 245 as I can.
White Point:
http://www.piechdesign.net/tutorial_img/WBPoint_009.jpg
Now let's look at our image again. Look at how much modeling we've brought out in this image. Look at our info pallet. Notice how our black points are now showing 17?
http://www.piechdesign.net/tutorial_img/WBPoint_010.jpg
This is not uncommon. Adjusting the white points has added some value to our black point. Just pop your curves layer back up and adjust the black points to be 15 again.
http://www.piechdesign.net/tutorial_img/WBPoint_011.jpg
And here is our final image.
http://www.piechdesign.net/tutorial_img/WBPoint_012.jpg
This is a great technique for getting the full range out of any image you wish to print of display. It's also a great
way to fix a lot of color problems.
Show us your Before and After images and let us all know what you think!