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How do you select "neutral"?

Since there is no just "post processing" section, I ask my question here. Mods, feel free to move it to an appropriate section (in fact, I think that we do need a generic "finishing" or "post-processing" section, regardless of RAW or JPEG).

Anyway...

I have a series of pictures of a person on a neutral backround.
However the background is not uniformly lit, so while being all neutral (i.e. almost identical RGB values, or AB values almost zeros), the lightness (L) varies dramatically.

Hence goeth me question: how wouldst thou select something that is "neutral"?
headscratch.gif


Thanks!

PS
I know about magic wand and know my ways around PS CS2 in general :)
 
Nikolai Sklobovsky said:
Hence goeth me question: how wouldst thou select something that is "neutral"?

Calculations is a good tool. Multiply A times its inverse with Calculations to get a new channel. Then use Apply Image to multiply in B and then the inverse of B. Hit the channel with autolevels. Then select the channel and use it as a layer mask on a new layer filled with color. Then set the opacity of the new layer to 50% and use curves on the layer mask to tweak the selection. Then refine it using the lasso depending on your needs.

Things like this are somewhat hit or miss and variations on crafting a selection are often needed.

enjoy,

Sean
 

Dierk Haasis

pro member
I'd use my eyes, a calibrated monitor and several clicks with the grey point eyedropper until I find the most pleasing result. Actually it is even easier when one looks at the RGB values in an info field [like Photoshop's Info palette] and goes for those sample points having almost to exactly the same numbers except for very high and very low values.

250, 250, 250 wouldn't be a good sample as wouldn't be 10, 10, 10; anything between 60 and 180 works for me [8-bit scale].
 
Dierk Haasis said:
I'd use my eyes, a calibrated monitor and several clicks with the grey point eyedropper until I find the most pleasing result.
I had to think thrice, but I assumed he was asking how to select the background and the formula of:

(A*A^-1*B*B^-1)*255
-----------------------------
max(A*A^-1*B*B^-1)

Yields a fuzzy membership mapping (0 is out, 255 is in) modulo some arithmetic issues related to 8-bit versus 16-bit and ICC profiles.

For white balance I agree that just using a calibrated display and your judgement is more than enough. But heck, I shoot with a daylight white balance 99% of the time as I want to see the post sunset blue tones on a landscape. My only problem is that my 550EX is a touch warm with a daylight white balance when using high speed sync.

enjoy,

Sean :0)
 

Asher Kelman

OPF Owner/Editor-in-Chief
Dierk Haasis said:
I'd use my eyes, a calibrated monitor and several clicks with the grey point eyedropper until I find the most pleasing result. Actually it is even easier when one looks at the RGB values in an info field [like Photoshop's Info palette] and goes for those sample points having almost to exactly the same numbers except for very high and very low values.

250, 250, 250 wouldn't be a good sample as wouldn't be 10, 10, 10; anything between 60 and 180 works for me [8-bit scale].

Dierk,

Let me, if I may, modify your suggestion.

If the light is balanced for a known temperature, then that is fine. However one can have 250,250,250 or else 60,60, 60 (for RGB values) in PS when the true value is not in fact all even like that, but there is a colored light shining on your scene.

The only way to get round it is to click on surfaces that are either known to be neutral such as a grey card included in the picture or else try as you suggest sampling varius objects that should be pretty neutral.

Examples of neutral objects would be clean concrete walls or sidewalks, a white table cloth, white paper, white shirt, the white of an eye, white teeth (danger, it might not work since most teeth are yellow/camel color), stainless steel and so forth.

Even if a colored light is shining on the scene, clicking on that target, (that may looks colored and appear 242, 250, 230 but really is neutral, will cause the beauty of the picture to jump out at you.

Let me add that I ALWAYS use WhiBal. It is absolutely a life saver.

Asher
 
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John_Nevill

New member
I have been using a Whibal for few months, but often result to using my eyes.

I intially found the whibal to be very accurate (going by the numbers) but a little warm, especially in evening portraits. I think this is probably more to do with my own colour perception rather than the device.
 

Erik DeBill

New member
John_Nevill said:
I have been using a Whibal for few months, but often result to using my eyes.

I intially found the whibal to be very accurate (going by the numbers) but a little warm, especially in evening portraits. I think this is probably more to do with my own colour perception rather than the device.

I've found it to be just the opposite - slightly cool. It probably comes down to our tastes and perceptions. For me at least, using the whibal is still the fastest way to get things close enough for easy tweaking.

Of course, my whibal has been laundered twice, which might affect the neutrality of its color.
 

John_Nevill

New member
Nikolai,

Having read the original question, could it be done using alpha channel masking. Personally I prefer the lasso tool and feathering, it takes time but feels more controllable.
 

Dierk Haasis

pro member
The WhiBal gives a reference point, actual colour setting has to be done - as was mentioned - to taste. As long as Michael Tapes' claims about the neutrality of his product are right, and I have no reason to doubt them, any observations of 'cool' or 'warm' are down to perception.
 

Michael Tapes

OPF Administrator/Moderator
In general,

One cannot use the numbers to find a neutral point. We are finding what is supposed to be neutral, not what is neutral in the shot. Some of Ashers suggestions are good, some not. Stainless steel would normally produce a specular highlight which is not good. Concrete is mostly good, but white things are generally, not since most white man made objects are not very neutral, like paper, material, etc.

Given that each WhiBal is measured by a precision device to precise specifications, it is never wrong, when used correctly. That gets you accurate color for the space where the WhiBal was. Whether the rest of the photo is in the same light and your perceptions, monitor(!), and likes and dislikes will dictate if you want to tweak it or not. But if you tweak the WB control you throw the profiles ability to properly render ALL the colors (not just the gray) as inaccurate and out of balance. Better to use a different color adjustment control to suit your taste.

Also not all gray card are neutral!
 

Asher Kelman

OPF Owner/Editor-in-Chief
Let me emphasize that my writing above was how to deal with a picture someone else shot and they gave it to me!

I always use a WhiBal. Wouldn't dream of not doing so.

This is what I do. In a shoot, I have the model hold the WhiBal card next to her face and then I take that picture take the card and start my work.

Each time I movel lights, I take another WhiBal shot.

Why? Because I'm lazy and don't wish to spend a minute more than needed processing hundereds of pictures.

In an event, I go around the room and take pictures with whatever light set up, at a number of locations around the room/ location.

Afterward, I sort by location and batch color correct. It is that simple. I don't worry about the mixture of yellow or fluorescant lights.

The problem purple-nosed drinkers who have a long time relationship with vodka, standing next to pasty-faced old ladies with a cake of make up in mixed lighting, will always require custom work for optimal results, no matter what.

However, for 99% of all my work, the method I use works.

Now am I capable of getting white balance on someone elses photos? Yes pretty well, but I hate it!

Asher

BTW, I have no financial interest in any way with WhiBal.

BTW-2, :), I use it with models in the pool too as it is waterproof. A card does not last when wet!

BTW-3 :) They are in the pool, I'm not as my Lumedynes hate wet!
 

Don Lashier

New member
Michael Tapes said:
But if you tweak the WB control you throw the profiles ability to properly render ALL the colors (not just the gray) as inaccurate and out of balance. Better to use a different color adjustment control to suit your taste.
While I agree if your goal is neutral color as in product shots etc., I disagree if your goal is to represent color as the eye perceived it, which frequently isn't spot on neutral. The best example is evening light, but often indoor shots look better/more-realistic if rendered on the warm side. In this case it's much better imo to tweak using the WB controls.

- DL
 

Asher Kelman

OPF Owner/Editor-in-Chief
Don,

Also when using a gel for your lights. Do the WhiBal or grey card first!! Otherwise one is neutralizing the beutiful light one has paid or waited for!!

Asher
 

Michael Tapes

OPF Administrator/Moderator
Many people (not those who posted think that they must select something that IS R=G=B when doing a click WB. of course this is wrong. One must click on something that is known to be neutral, but is not. If it were neutral in the picture, then the WB would already be correct.

Regarding coolness or warmness with WhiBal. yes, of course. While WhiBal is technically extremely accurate, human perception and taste should make the final decision as long as the monitor is calibrated. IMO it is easier to tweak a WB that is technically correct (from using a WhiBal) then one that is just out there.
 
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