White Points and Black Points...

ront

I hope that this is the correct forum to place this question and I hope that I can explain it also!!
I have both LR 2.5 and CS3. I have mainly used LR for about a year now and have just started trying to learn more about CS3. I have a Sony a700 camera and shoot mainly in cRAW.
There is a lot of this stuff that is still about as clear as mud to me so please bear with me:).
I have been reading a bit about setting white and black points in curves in CS3. How does this compare to WB in Lightroom? Are they doing the same thing? If not, how do the two of them work together? If I load one of my cRAW photos in CS3, it first has to be converted in ARC where changes can me made to the photo if desired. Then it is placed in CS3 where I can apply the white and black points. Then what?
My guestion probably makes little to no sence at all, but I will start here.

Thanks for any input at all, Ron

Miguel Delinquento

Ront, in LR, setting the white point is the same as using the Exposure slider. Just hold down the Alt/Option key until you see the first signs of blown highlights. The Blacks slider is the same for the black points.

M

BinaryFx

Ront, WB in the raw converter is setting the global white point/balance for a single light source. If there are multiple light sources of different temperatures, then the WB eyedropper will only account for one source. Although WB can affect tone, it is mostly about setting the camera colour response to be "neutral", this is basically a colour component move. This is independent of setting exposure (white point) and shadows (black point).

The white/black and gray eyedroppers in Photoshop are for setting these three points - highlights, shadows and neutral midtone. Generally, these three points will set both range and colour balance in the one move, however with blending modes such as color and luminosity, one can independently control the range/tone and the colour without overly affecting the other component. Generally, one gets better results manually adjusting the white/black and neutral points of the image instead of using the curves eyedroppers (which are "OK" if one is in a hurry).

If the WB is correctly set in the raw converter, one may or may not need to adjust the individual channel curves in Photoshop (Adobe raw converter curves do not work on separate individual channels, which is roughly what WB is doing for the light point of the image).

I personally prefer curves in PS to massage the white and black points with the previous use of WB in the raw converter.

Clear as mud?


Regards,

Stephen Marsh

members.ozemail.com.au/~binaryfx
prepression.blogspot.com/

pathfinder

Stephen, if I understand you, you are saying that you frequently, but not alway, do white and black points in Photoshop, in addition to setting white balance in RAW as well ( whether you set the white balance with an eye dropper white balance on the RAW image, or choose a light setting based on the illumination at the time of shooting - tungsten, day light, etc )


I do not do white and black points on all of my images as they come out of Lightroom - many of them do not seem to need additional tinkering with WB to my eye. But, some certainly do need further rendering, and I then use the Threshold command in Photoshop to find an appropriate white and black point, and then set them with the eye droppers in Curves ( or some folks use Layers )

Is this in agreement with your post?


With mixed lighting, other techniques may be needed, curves in RGB or LAB for instance.

Regrading the neutral gray eyed dropper in Photoshop, I do not find it terribly helpful unless I have an image with a known neutral gray to start with - say a WHiBal card. Images without a true neutral gray, do not seem to really balance well by searching for a gray with the Threshold command, for me anyway.

Also, white and black in Lightroom may be relate to maximums of white and black, whereas white and black points in Photoshop should be related to the darkest black and whitest white one can actually print with their own printer and their own choice of paper.

What i mean is that my black point in Photoshop is 5,5,5 which is the smallest step above 0,0,0 that I can see on a step wedge, when printing on my printer. My white point is set at 250,250,250 because I know that I can see 250,250,250 distinct from 255,255,255 or paper with no ink. I have used a stepped gray scale to choose these points based on what I can see printed on my paper on my printer.

DO you choose your white and black point in Photoshop based on what your printer can print on paper, or is it a theoretical choice of numbers?

BinaryFx

pathfinder wrote:

Stephen, if I understand you, you are saying that you frequently, but not alway, do white and black points in Photoshop, in addition to setting white balance in RAW as well ( whether you set the white balance with an eye dropper white balance on the RAW image, or choose a light setting based on the illumination at the time of shooting - tungsten, day light, etc )

Thanks Pathfinder, yes, any shot of importance would get the Photoshop curves treatment, white balance only goes so far and is for a single global light source. Critical areas of the image will still likely need to be massaged with global channel curves and or more selective means.

I do not do white and black points on all of my images as they come out of Lightroom - many of them do not seem to need additional tinkering with WB to my eye. But, some certainly do need further rendering, and I then use the Threshold command in Photoshop to find an appropriate white and black point, and then set them with the eye droppers in Curves ( or some folks use Layers )

Is this in agreement with your post?

We are in basic/general agreement Pathfinder!

LR and ACR set overall colour balance and tonal range, however this only takes one so far. For example, if you establish the correct white balance and then mouse over with the info palette, you may find that other areas that should be neutral are not (either with R=G=B or Lab readouts in the info palette).

I often don't care about thresholding to find the lightest and darkest areas, these are often of little importance...it is the object or scene *critical* "extreme" areas of the image that I am interested in. I am more often interested in getting better contrast and colour in the main subject than I am about plugging or blowing out areas that are not important. This is obviously an image dependent approach.

The human visual system does a similar thing, when you concentrate/focus on a subject in a scene, the rest of the scene "suffers" and the subject is "improved".

This means that I plant a fixed colour sampler in the highlights and shadows, a neutral point and in a known "memory" colour (sky, grass, skin etc). I then inspect the info palette for these samplers, massaging channel curves to get the required values. This is an art, not a science - one may indeed go for "incorrect" info palette values to obtain the result that makes a human observer pleased. I don't let the info palette numbers rule me, however they are often a good guide, unbiased when compared to the ever adapting and changing human visual system.

When one calibrates a monitor, one uses a tool to measure the colour. The info palette is another tool that can be used for an unbiased evaluation.

Regrading the neutral gray eyed dropper in Photoshop, I do not find it terribly helpful unless I have an image with a known neutral gray to start with - say a WHiBal card. Images without a true neutral gray, do not seem to really balance well by searching for a gray with the Threshold command, for me anyway.

Thresholding is only for the endpoints, not a neutral.

Agreed, the gray eyedropper is only for quick and nasty work. One has much better results by placing a fixed colour sampler and then massaging the individual channel curves while watching the readout of the sampler in the info palette. This is also true for the highlights and shadows (not the extremes, the second darkest and lightest areas where you wish to retain detail, otherwise maximize contrast by overshooting the values).

Also, white and black in Lightroom may be relate to maximums of white and black, whereas white and black points in Photoshop should be related to the darkest black and whitest white one can actually print with their own printer and their own choice of paper.

What i mean is that my black point in Photoshop is 5,5,5 which is the smallest step above 0,0,0 that I can see on a step wedge, when printing on my printer. My white point is set at 250,250,250 because I know that I can see 250,250,250 distinct from 255,255,255 or paper with no ink. I have used a stepped gray scale to choose these points based on what I can see printed on my paper on my printer.

As mentioned previously, ACR and ALR set global colour balance via the WB control. The exposure,shadows and tone curve controls are setting *tonal range* and NOT colour balance.

Photoshop is different. Separate channel curves affect both tonal range and colour balance (which is what the eyedropper tools simplify). This is in normal blend mode. To only affect tone, one blends the curve in luminosity blend mode (either by fade or adjustment layer). The same is true for color blend mode, to only affect colour balance and not tone, one uses color blending instead of luminosity or normal mode.

DO you choose your white and black point in Photoshop based on what your printer can print on paper, or is it a theoretical choice of numbers?

When the output device is well known and stable, then I can use known values, more often than not I am using different devices and they may not be stable, so I then aim for values of around 3-5% for highlights and 90-95% for shadows - where detail is required, otherwise I maximize for added contrast, this all depends on the image content, output device and stock, image mood etc.

More on using Photoshop curves in this link to more links:

http://members.ozemail.com.au/~binaryfx/links.html#C

Scroll down to "Curves, Levels & Colour Correction" and explore the direct link to the topic at hand at the "tail" and the entire site content at the "head" of the link.


Sincerely,

Stephen Marsh

members.ozemail.com.au/~binaryfx
prepression.blogspot.com/

pathfinder

Thank you for your discussion of my questions, and reminding me of your links page. For those who are not familiar with BinaryFx page of links he posted, you really should explore them, they are a fountain of knowledge for would be PS users.

ront

Thanks for your input.

Ron