Questions about white's and black's

[FeatherMonkey]

As the title really, as I tend to underexpose I've been trying to get out of that habit.

1 My understanding is overexposed white's/highlights will clip, underexposed black's/shadows will is this correct?

2 Am I aiming for the deepest and tiny shadows, and the brightest and again tiny highlights to clip?

3 Regards white balance. Now generally I know I can change this pp. This is more specifically with flash am I better creating a custom white balance from a white object in the flash exposed scene? Suppose I'm not quite sure what I'm achieving here certainly I'm finding the balance is closer to true. I'm just not sure if I'm doing something that could just be done in pp workflow

 

[tirediron]

Over-exposed highlights will 'clip', under-exposed shadows will 'block'; either way, it means the same thing. You've lost all detail in that area of the image, and you're only ever going to get white or black (or detail-less shades of gray if you muck with it). As to which is better, it depends on the image. If I'm shooting a sunset, and there are some people on the beach in the foreground, then correctly exposing the setting sun will probably render the people detail-less black blocks, so in that case I would let the highlights go, whereas if I was shooting a scene in bright sunlight where I wanted detail, I would expose for that and not worry so much about the shadow. There are techniques which can be used to enhance both issues. As for WB, if you know the "temperature" of your flash (usually close to daylight; 5500k) it's not quite as important, but I always shoot a colour target regardless. You can create a custom WB, but to be honest, I find it easier just to shoot a white/grey target and correct to that in post.

 

[Ysarex]

There are always exceptions of course but the basic rule is that you do not want to clip diffuse highlights and you do want to reach black.

There are two kinds of photo highlights and black is black. Highlights that are either reflections and/or light sources are specular highlights. They should clip -- reach pure white. Non-reflective highlights are diffuse and should retain color and detail.

Examples of specular highlights would be polished metal, glass, a mirror, etc. Examples of diffuse highlights would be white clouds, white fabric like a tee shirt or wedding dress, yellow flower petals.

Here's a photo example -- two different versions of the same photo:

Note the inset histogram. In this version of the photo (created by camera software) the diffuse highlights are clipped. Large sections of the white wall in the background and the highlights on the truck fender and hood are all clipped and you can see in the histogram the graph piling up against the right side -- that's clipped highlight data.

The photo also contains a lot of solid (clipped) black -- tire wheel wells and under the truck for example. The graph piles up against left side indicating clipped blacks.

Here's the 2nd version of the same photo:

The histogram does not pile up against the right side and the diffuse highlights are not clipped. There is a specular highlight in the photo and it is clipped but it's too small to record in the histogram at this file size. The Ford emblem on the side of the truck is polished metal and it's pure white.

Notice the different treatment of shadows and blacks in this photo. The histogram does begin to pile up against the left side (pure black). It should. It would be ridiculous for this photo to not contain some solid black. But the amount of shadows that reach solid black is much less than in the photo above. Compare for example the shadow on the ground under the front of the truck and the shadow in the wheel well.
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Setting a custom WB is never a bad thing. To do that follow the instructions for your camera but make sure and use a good WB target. White paper and other "white" stuff laying around is not a good target. Either use a commercial target like a WhiBal card or use white Styrofoam.

Joe

 

[WayneF]

1 My understanding is overexposed white's/highlights will clip, underexposed black's/shadows will is this correct?

Highlights hitting the right 255 edge in the histogram are clipped, meaning they are gone. There is nothing above 255. Meaning there is no detail possibly visible in these clipped tones. Post processing can reduce 255 to a lower value, but it cannot recover what was clipped.. that detail is gone. Watch the three RGB histograms for this, the one single gray histogram is worthless for seeing clipping (only a math contrivance, not real data). See: Two types of Histograms

Underexposed dark tones may be pretty black (no detail visible), but they are not "clipped". They can be boosted in post processing. Basically, that's all ISO does, is to increase the levels. We can do the same in post processing (I'm really speaking of Raw, JPG does not have much range for this).

(post processing can clip either white or black end. If PP sets White Point to 50, making it be the new 0, then all detail below the original 50 is lost. The camera does not ordinarily do that. Exposure cannot be below zero. Different methods of Contrast can clip both ends, but the camera contrast does not do those methods.)

2 Am I aiming for the deepest and tiny shadows, and the brightest and again tiny highlights to clip?

That combination is called dynamic range. Sometimes compromises are necessary. Low ISO is your best shot, along with skill in setting the right exposure to straddle the range. But it also depends on the camera sensor. The latest models excel over the older models, so a new camera can be the best advice.

3 Regards white balance. Now generally I know I can change this pp. This is more specifically with flash am I better creating a custom white balance from a white object in the flash exposed scene? Suppose I'm not quite sure what I'm achieving here certainly I'm finding the balance is closer to true. I'm just not sure if I'm doing something that could just be done in pp workflow

Custom white balance is only feasible for many pictures in a fixed lighting setting, like maybe a studio session. We cannot do that for walk around pictures in different lighting situations (too awkward and time consuming).

Flashes have different color at their different power levels. Speedlights are more blue at low power, and most studio monolights are more red at low power. Attempts to categorize it otherwise are pointless. Flash color varies with power level.

White Balance in bright sun is the easiest, usually no real problem, bright sun is known and does not vary, camera usually gets that right. Everything else is a problem. Some situations are a big problem. But WB can be made easy.

The easy way to handle White Balance, flash or otherwise, is to use a white card (good example, Porta Brace White Balance Card, $5 at B&H. Or the WhiBal card is good, more cost).

Include that in your scene (maybe just in the first "test" picture"), in the SAME lighting.. Then in post processing, use a good White Balance tool to just click it and correct the color cast in all pictures in the same lighting.

See: White Balance Correction with or without Raw

If shooting raw, see the video at: Why shoot Raw

 

[FeatherMonkey]

Thanks tirediron, Ysarex and WayneF that's helped loads just to expand these where a few images that instigated the topic just so that I can confirm I've got it. Sorry about repetitive subject they're just always there...

So I fixed the white balance in pp.
So this a bluey original caused by the flash

After fixing WB
No card so chose greys from beak

This is just clipping(White highlights on top of head) But is it artistic or just bad?

This clips hardly on subject but I suspect falls into doesn't matter(clipping in background), has a colour cast not fixed in this pic.
How would you of stopped the colour cast happening?

Also I presume from my limited knowledge these are acceptably exposed?

Many thanks Stef

 

[Ysarex]

Thanks tirediron, Ysarex and WayneF that's helped loads just to expand these where a few images that instigated the topic just so that I can confirm I've got it. Sorry about repetitive subject they're just always there...

So I fixed the white balance in pp.
So this a bluey original caused by the flash

After fixing WB
No card so chose greys from beak

Bird beaks can be pretty neutral -- good choice without a card.

This is just clipping(White highlights on top of head) But is it artistic or just bad?

There is no highlight clipping in the feathers on the top of the bird's head. If you're using some tool that indicates clipping there you need a new or better tool. The photo however does not reach a black point and it would be improved to do so.

This clips hardly on subject but I suspect falls into doesn't matter(clipping in background), has a colour cast not fixed in this pic.
How would you of stopped the colour cast happening?

You prevent the color cast by getting a proper white balance. If the photo is in mixed light that task becomes complicated and editing become necessary.

Diffuse highlight clipping is bad unless the photo is an exception (eg. product photographed against white). If it's in the background it's just less bad -- it still matters and should be avoided. In this photo there appears to be clipping lower left however whatever that is the bird is perched on looks like it qualifies for "shiny" and so the highlight would be specular. Although a specular highlight may not be a "technical" error it can be distracting and as such still be undesirable -- in this case it is.

Also I presume from my limited knowledge these are acceptably exposed?

Many thanks Stef

Exposures look acceptable.

Joe

 

[FeatherMonkey]

Thanks again Ysarex found the clipping marking threshold was set at 95% ... A little unusual not quite sure on whether there is many Darktable users on the forum.

This is really helping loads, I take it when you say black you mean rgb 0,0,0(reached by tweaking levels on black by 0.1% lowest I can) getting a little confused here by the histogram now..

Having tweaked threshold to 97%-3% Doesn't that imply it's over exposed now?

 

[Ysarex]

Thanks again Ysarex found the clipping marking threshold was set at 95% ... A little unusual not quite sure on whether there is many Darktable users on the forum.

This is really helping loads, I take it when you say black you mean rgb 0,0,0(reached by tweaking levels on black by 0.1% lowest I can) getting a little confused here by the histogram now..

Having tweaked threshold to 97%-3% Doesn't that imply it's over exposed now?

You won't find many DarkTable users here or anywhere. I use it but not heavily since I have to boot Linux to use it. I have only good things to say about DarkTable however. It's superb software and if it were a commercial product that I could purchase and use on my Win systems I'd buy it immediately. (It is not however good enough to get me to buy an Apple product

I'd set the clipping warning thresholds to 0% and 100%. Don't use Levels in the automatic mode -- keep it in manual. Adjust the highlight slider until you see clipping (red) indicated and then back off just until the last red pixel disappears.

Black on the other hand is your friend -- get there, but just touch it.

Don't forget about the gamma (grey point) slider -- adjust it to personal preference.

NOTE COMPLICATION: DarkTable's Levels adjustment operates on the L channel of your photo and I assume the clipping warning is then likewise responding to the L channel. That means it is still possible to be clipping single color channels even when the clipping warning indicates no clipping. You can toggle individual RGB channels in the histogram to check for this and reduce channel saturation as a solution. There may be a better way to address this but I'd have to do some research.

Joe

 

[FeatherMonkey]

Can't thank you enough Ysarex my learning curve in post processing jumped a great leap yesterday thanks to your input with darktable(I really didn't expect any assistance there). I'll have to pause the learning with the camera and tighten my pp a little more now, seeing a marked improvement already from this thread.

Many thanks to the others that participated also.

 

[Braineack]

the two black point photos look identical on my monitor.

 

[FeatherMonkey]

It was off you can see me tweak earlier I thought the same but couldn't pick 0,0,0 from the pupil till I moved the black point.