Sliders clarified

It is all too easy to be overwhelmed by the array of sliders when opening up Lightroom (LR) or Adobe Camera Raw (the sliders are more or less the same) and it is easy to adopt a “muddle through” workflow, I should know because I have been doing this for years!
The proverbial “penny” dropped last year while watching an instructional video, sadly I forget which one, which explained how LR sliders worked. I did know that when LR was designed with a logical top to bottom workflow what I didn’t understand was how properly use the three critical sliders; Exposure, Contrast and Clarity.

It is no accident that the very first thing you see in the Library and Develop panels is the Histogram, so before I go on I’ll get a wee bit techy and explain some terms.
The Histogram is a representation of your picture showing all the instances of each tone of your picture. The Histogram starts at pure black zero tonal value on the left, through to pure white at 255 tonal value on the right. Tones in the middle are called mid-tones, tones between the middle and the first quarter are called shadow tones and between the shadow and the left hand side are the Black tones. Conversely, tones between the middle and the third quarter are highlight tones and between that and the right hand side are the White tones.
(You can see which slider moves which part of the histogram if you hover the cursor over the histogram and you will see a slight change in the background colour and a corresponding change in one of the sliders backgrounds.)
Each slider is designed to work on that particular portion of the histogram although they can interact with other sliders.

To start with Have a look at the following histogram.


Showing where the various sliders operate on the Histogram

 The eureka moment came when I understood which parts of the Histogram were affected by the Clarity and Contrast sliders.

Clarity Contrast

Clarity works by moving the mid-tones in or out, while Contrast works by shifting the highlights and shadows in or out.

The sliders and what they do…

  • Exposure
    Adjusts the Mid-tones and not the Highlight Tones
  • Contrast
    Adjusts the bits at the ends of the Histogram
  • Highlights
    Adjusts the top quarter, the lighter portion of the tones
  • Shadows
    Adjusts the lower quarter, the darker portion of the tones
  • Whites
    Adjusts the highlight tones towards pure white
  • Blacks
    Adjusts the shadow tones towards pure black
  • Clarity
    Adjusts the contrast on the mid-tones
  • Vibrance and Saturation
    Adjusted to taste.

Ultimately the sliders in the Basic module are only a way of manipulating a Curve, as you would find in Photoshop, indeed the next box down in LR is called Tone Curve and operated in much the same way as a Curves adjustment except you get to see which part of the curve you are affecting.
Note that the Curve and the corresponding Lights slider are highlighted.

Tone Curve

Tone Curve

Let’s look at a picture.

Transferring the Histogram onto the picture

Transferring the Histogram onto the picture

Getting things almost right  to start with.

Life is made that little bit easier when you get the exposure right in camera and not relying too much on LR being able to rescue a badly exposed picture.
My preferred shooting mode is to Full Manual, adjusting the ISO, usually 200, the aperture, I favour f/8 and selecting a shutter speed depending on the focal length of the lens or for effect.
Now the most important thing that I do when I make the picture is Expose to the Right (ETR).  This is so important, get this correct and editing photos is simple because the less time that you spend editing photos the happier you will be.

Dumb light meter

Light meters are sophisticated but they should never be implicitly relied upon as manual adjustment in the form of aperture/shutter speed adjustment or EV (Exposure value) adjustments are needed. The major factors to remember with light meters that while they see a white object it exposes for an equivalent of light coming from something that is only 18% grey or to put it another way something that is 78% white, under exposing a predominately white or  over exposing a predominately black subject. This is where the ETR method comes into it’s own, you don’t need to think of giving a +2/3EV adjustment for a white object, all you need to do is adjust the EV dial (or shutter/aperture settings) to get the histogram as near to the right as you can without clipped highlights.

More teccy stuff – The camera can only record from 0 to 255 tones, that’s a fact. Anything less or more than that is piled up at an end of the histogram and is termed a Clipped tone. It contains no useful information, other than it is pure white or black. The trick is to avoid having clipped tones to start with and this is where ETR comes it. You adjust your camera so that when you take a test exposure or look at a live histogram, if your camera has this, there is nothing piling up at the right hand end of the histogram. If you look at the above Histogram (for the Clarity adjustment) you well see a gap between the far right and the beginning of the histogram, a level bit and then the start of the histogram proper. Critically, it is slightly under exposed, by not being a bit further up the histogram but that’s OK as you can fine tune this in LR, the level bit is the Specular Highlights, which are points of lights from reflective surfaces or in this example the snow off the hills in the background. The Histogram starts properly with the Highlight tones round about where the white cross is on the fuselage.

In exposing to the right, I made a compromise in that I accepted a degree of clipped blacks, which are on the main wheel tyres. Generally I do not worry too much about clipped blacks as I know that in this instance I can adjust them in LR.

Back to the Histogram. I like to look at the RGB Histogram, it shows the distribution of Red, Green and Blue (primary colours) and Cyan, Magenta and Yellow, (secondary colours.) The Luminance Histogram just shows the overall lightness of the scene and not which channel is clipping. You can see from the above example a large blob of Blue in the shadow area and in the Highlight area and a large blob of yellow in the mid-tones, which comes from the grass. Believe it or not but most tones in the grass are yellow and not green.
One last techy bit. Pure black is 0, pure white is 255. The same goes for Red, Green and Blue, this is why saturated colours such as yellow do not reproduce all that well because Red and Green (make yellow) at or very near 255 loses tonal values and more importantly the picture will not sharpen properly because of these clipped tones.
Generally a maximum value of 242, 5% less than 255 is a good place to have your maximum tones, where a degree of detail is to be had in what is an almost blown out part of your picture. Lightroom expresses the Histogram as 0 to 100%, so 95% is OK.

So to finish editing this picture and getting back to LR, starting at the top…

before after

Before and After LR adjustments

It did not need any Exposure Adjustment (no adjustment to the mid-tones was requited), the Contrast was OK (there were tones at the blacks and whites) as the Histogram was roughly evenly spread, I bypassed the Highlights, Shadow sliders and adjusted the White slider so the specular highlights were not showing as clipped (it would not hurt if they were) and then made a small adjustment to the Clarity, to increase the visual “pop” of the image and a little bit of Vibrance to cheer up the grass.
When you adjust the Clarity slider, it often pushes the highlight and shadow tones into the clipped regions, so in this case I adjusted the Blacks to lift the clipped tones a little
You can see the difference between the before and after picture above.
I hardly bother with the last slider which is Saturation. I should have as in this case it made the grass that bit greener and more visually pleasing (I done this on the final image below.)

In a normal picture the lack of contrast will make or break a picture. All too often aviation photographers are afraid of shadow tones, so they will unnaturally lift these to muddy shadows, for fear of getting a rejection but contrast gives photos “pop” and I’m not bothered what a screener may think of my photos any more.
When I say “normal exposure” I mean to say there are exceptions to the rule and it really depends on what the photographer wants from a picture and some may be naturally High or Low Key pictures (High is where there is a lot of light tones and no darks and Low Key is the reverse, lots of darks and little or no lights.)

Composition wise, the crop was adjusted to retain the wing shadow (as a lead-in line to the engine) and come close into the tail giving it a form of diagonal composition (and another lead-in line) and the height reduced, so the bottom third ran along the airfield horizon. It was exported out of LR into Photoshop CC, where the white blob was removed from under the prop and also the wind sock in the background was cloned out and job’s a good un’

G-FOKR Fokker E.III, Scone

G-FOKR Fokker E.III, Scone

I’ll continue this series but there is one thing for sure….Mair tae come

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