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Thursday, March 30, 2017

New Video on The Histogram


This is my first attempt at a Video Tutorial.  Feedback on overall watchability would be greatly appreciated.

Tuesday, February 21, 2017

The General Controls - Getting the basics right.

These “General” controls are the single most important segment of raw development.  Often times called the exposure controls, they deal most directly with the information stored in the raw file.  They control how much of the captured data we have available to work with, they are an important influence on how we perceive our photos overall. Getting this section "Right" ultimately controls just how successful your photo will be.

I will discuss the controls From the top of the controls window to the bottom. Note this is part 2 of an ongoing series of articles. This article will cover only what ACDSee calls the "General" controls and White Balance.  The rest of the Raw development tools will be covered in subsequent articles.

Color and Black and White Sub Tabs


These tabbed controls don’t really do all that much other than desaturate or re-saturate the image with whatever color controls were current at the time the B&W tab was activated. Getting Killer B&W Photos with ACDSee

Curiously though, I have found this tab useful for luminance noise control. I suggest you review my article entitled "A Quick and Easy Noise Reduction Technique"


Exposure

We all understand this control brightens and darkens a photo, but what this slider control actually does is allow you to adjust exposure to as much as an EV of -2 of under exposure, to an EV of +2 on an over exposure. The value settings on this control appear to be a 1:1 comparison of the EV numbers, though ACDSee never says that directly. In my tests, sliding the control to the left to a - .5 corresponds to setting an EV of -5 on the camera that the difference is irrelevant in my eyes.

Two points you need to remember regarding the exposure control.

If you need more than an EV spread of -2 to a +2, your ability to set your camera accurately for your desired effect must be questioned. If you are THAT far off on your exposure you have done something wrong, or your camera is broken.

If you find yourself setting this control consistently to, say, an EV of -.5 (or whatever value), then maybe you should consider adjusting your camera to always underexpose to a value of -.5. Getting it right at capture time is always better than adjusting it later.

Yes we understand that it makes the photo brighter, but what does Exposure actually DO to the photo? 
Try an experiment look at this Histogram of our test photo.  I refer you to the first article in this series for an explanation of the Histogram

NOTE: With all photos, just click on them to see larger versions
Examine the histogram of the photo we are working with. Note how the shadows mostly reside about 20% to the right of the far left, and that the highlights, while fewer (curve is shorter), also reside about 20% to the LEFT of the far right.  This indicates that there are few shadows and highlights that are so dark or light that there is no detail showing in them.  And it is a well exposed photo with not much contrast to it.

Now, slide the Exposure control to the right, note that everything the curve represents slides to the right, and what appears to be the left most anchor point for the start of the shadows also moves to the right. If you move the slider to the left, everything moves to the left, including the shadow anchor point.

Highlight Enhancement - This control is somewhat misunderstood. What it does, is darken the highlights while ignoring the mid-tones and shadows. It allows you to set the exposure control properly for the shadows and mid-tones and then selectively darken the highlights only so that you don’t lose the detail in them.

Try a little experiment. Take a photo that you want to work with, and move the EXPOSURE control a bit too far to the right. Notice how the brightest highlights start to go completely white. Also take note of the Histogram. Note how the curves are sort of pushed to the right. The part of the curves that represent shadow (the left side) in the histogram stay about as tall as ever while the mid-tone curves get a bit shorter. But in both cases, the shadow and highlight portion of the curve gets “fatter”as it slides to the right. Also note how the highlight portion of the curve not only is pushed too far to the right, but that portion of the curve gets skinnier and taller.

What you are seeing is ACDSee trying to brighten the shadows and mid-tones by pushing them to the right of the histogram, Naturally, since we are using the overall exposure control this forces the highlights to an ever brighter position. Leave the Exposure control at the ‘too far to the right’ position you have selected.

Now, let’s look at the Highlight Enhancement control. By sliding the control to the right, the highlights start to darken a bit, though the shadows and mid-tones don’t change all that much. In the Histogram, notice that the portion of the curve on the far right starts to get shorter and fatter as it moves back to the left. But curiously, while the shadow and mid-tones portion of the curve change shape a little bit, the ‘anchor point’ on the left where the shadow portion of the curve starts to take shape doesn’t move at all. Basic black is already set and isn’t going to change. Any changes to the photo will have to work around that anchor point for the shadows.

So, what we have demonstrated is that Highlight Enhancement tries to shift the Histogram BACK to the left without adjusting the left most anchor point, and the net effect is that the shadows and mid-tones are affected less by this adjustment than are the highlights.



Fill Light Control - Oddly, this control is very similar to the exposure control, BUT what it does is respect the shadow anchor point as set by the exposure control. So in other words, the leftmost anchor point as set by the exposure control never changes as you slide the Fill light control to the right, everything else is pushed to the right.

Contrast Control - This is an interesting control from a Histogram perspective. What it does when you slide the control to the right (i.e. increase contrast) is squeeze the middle portions of the curve down and push the extreme left and right sections of the curve to their respective edges of the histogram. In other words, it decreases the intensity of the mid-tones and increases the intensity of the shadows and highlights.

When you slide the control to the left (i.e. Decrease contrast), what occurs is that the intensity of the shadows and highlights decreases and the intensity of the mid-tones increases.



Saturation Control - This control is similar to brightness but deals with color purity, instead. When you slide the control to the left, the color seems to go away, when you slide the control to the right, the color becomes deeper. In a photo there are 3 colors that combine to make all the other colors. Red, Green, and Blue. if there are a lot of pixels in a given primary color, that curve will be tall. Each color has a value from -100 to +100 with the default of zero (0) .

A value of +100 for a given color means that as much of that color has been added as possible, and the curve for that color gets fatter.

A value of -100 means the all the color for a given color has been reduced to nothing, so the color channel curves start to merge with the overall luminance curve set by the exposure control. As a result, the photo now appears to be black and white.

When set to -100, the curve doesn’t go away, because the pixels set to zero are still designated as belonging to one of the 3 primary colors. they just happen to be set to -100 and all that remains is the relative luminance.

Changing the saturation value of a primary color won’t change the number of pixels assigned to a given color, it will just change the level of saturation, so the height and width of each color channel moves closer or further away from the curve representing Luminance.



Vibrance Control - The ACDSee Pro help file claims that Vibrance adjusts the intensity of the colors in the same way as saturation, but that skin tones are less affected. The text doesn't really mention other already lightly saturated objects though many people have always assumed it worked equally well on any lightly saturated object.

It does seem to protect skin better than non skin objects in a photo, but I'm not sure if that is some sort of illusion. Logic tells me it should work equally for any lightly saturated object, but I just don't know for sure, since the difference is most noticeable for protecting skin when increasing saturation overall.

Vibrancy seems to work LESS, on less saturated colors, but the effect is much less noticeable when moving the slider to the left (DE-saturating) than it is moving to the right (adding saturation). Its effect is SO much less noticeable when de-saturating that it fooled me into thinking it wasn't working. If I were to want to de-saturate more than just a VERY tiny bit and still prevent significant change to skin tones, I might consider using a development brush to protect the skin tones completely.

I tested the Vibrance control on a series of photos where the range of skin tones was very wide, from the palest 'white', to the darkest 'black', and everything in between. Apparently, even the darkest skin isn't all that saturated overall, because I felt Vibrance protected very dark skin about as well as the lightest skin. But again, when de-saturating the protection effect was minimal

The effects of the Vibrance control is VERY subtle. You will want to be very careful and selective in its use.

Clarity Control - This is both a useful tool and an incredibly sweet confection! What Clarity does is add or remove contrast to the mid-tones only, leaving the highlights and shadows alone.

Many people think of it as a sharpening control. I know this because when I was writing about sharpening earlier, LOTS of people wrote me asking why I didn’t include Clarity in the discussion.

True, Clarity can increase the illusion of sharpness, but so can contrast in general. In fact Sharpening is really no more than the technique of adding contrast to the edges of the objects. So why ISN’T clarity considered a sharpening tool instead of a general or exposure tool? Primarily, in my eyes, that is because it simply doesn’t care about the edges of objects. It will increase or decrease contrast to every mid tone it sees, edge or not.

Let’s take another look at our sample photo and its histogram:




Note how there aren’t a lot of highlights or shadows in the photo. It is mostly mid tones. Now look at the histogram, almost nothing of the curves actually reach the extreme left or right of the chart. The area of the most shadow is roughly 20% closer to the right edge of the chart than the left. And it seems the highlights don’t really even make it to the right edge! They stop about 80% of the way from the left edge to the right. I would say, that for the most part, this is a photo with very little washed out highlights or solid blacks. Just about everything resides in the mid tones area.

Just for fun, try a little experiment. With your favorite photo, invoke the clipping view (That little triangle icon just above the Histogram and below the word “Tune”) and slide the Clarity tool all the way to the right. Notice you won’t see much clipping, if any. (In my sample photo I don’t see any.), Now reset the Clarity slider and move the Contrast slider all the way to the right.

There’s a huge difference, isn’t there? What is happening is that by concentrating on just the mid-tones, very little of those mid-tones are forced into either the highlights or shadows. And THAT is what makes Clarity such an important and useful tool. We can either add or remove contrast in just those tones that carry most of the photo’s information.