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DPP: Part 1 – Workflow: Exercise 3 – Histogram

The aim of this exercise is to increase my familiarity with, and understand of, the histogram.  I have previously posted my learnings on the camera histogram here, however I’m completing this exercise in any case to refresh the knowledge and ensure there’s nothing important I’ve missed.  However, this exercise isn’t expected to be an in-depth analysis.

The objective is to shoot the three most basic categories of scene by contrast – low contrast, average contrast and high contrast – with three images of each; an average exposure and then one each at one f-stop higher and lower.

I expect that the resulting histograms will show the graph shifting on the tonal scale – with increased “clipping” at the dark end (when at a stop higher – i.e. darker) and the light end (when a stop lower – i.e. lighter).  For low contrast the graph will have a concentrated area of tones, for average contrast a reasonably even spread across the range of tones and for high contrast peaks toward the dark and light ends of the range.

So, here are the shots:

Low Contrast

Average Exposure

White and cream – you can’t really get much lower contrast than that…

Low Contrast Average Exposure (f/8)

Low Contrast Average Exposure (f/8)

Here it is with histogram and clipping; it’s hard to see but there are some spots of black which are clipping; in the plug holes.  Dark tone clipping is blue in Lightroom:

Low Contrast f/8 with Colour Histogram

Low Contrast f/8 with Colour Histogram

Lightroom shows the colour range on the histogram with a grey area for the exposure, which was difficult to compare to what I had been seeing on the back of my camera:

Colour Histogram for Low Contrast f/8

Colour Histogram for Low Contrast f/8

So I converted it to black-and-white so it then just showded the tonal distrubtion; this looked more-or-less identical to what I was seeing on the back of my camera and – as predicted – showed a bunched up graph for the low contrast image:

BW Histogram for Low Contrast f/8

BW Histogram for Low Contrast f/8

One f-stop Higher

So the image is brighter:

Low Contrast f/5.6

Low Contrast f/5.6

Still some extremely small clipping areas in the black area.  As expected, the graph has essentially shuffled toward the brighter tone direction.

BW Histogram for Low Contrast f/5.6

BW Histogram for Low Contrast f/5.6

One f-stop Lower

Low Contrast f/11

Low Contrast f/11

More noticeable clipping can be seen in the plugs – where before it was barely visible.  What is interesting is that the dark clipping isn’t evident on the histogram; I’m thinking this is becaue as a proportion of the image they are very small so will barely register. The graph has shifted the opposite direction as predicted for the darker image.

BW Histogram for Low Contrast f/11

BW Histogram for Low Contrast f/11

High Contrast

Average Exposure

So a picture of a camera with black parts on a cream/white background:

High Contrast f/8

High Contrast f/8

The histogram shows what I expected – peaks toward the top and bottom of the tonal scale.  Some clipping can be seen at both ends as the camera can’t expose the image in a way that avoids it.  A small speck of red for bright tonal clipping can be seen at the top where the lens meets the camera body.  The blue for low tonal clipping is obvious:

BW Histogram for High Contrast f/8

BW Histogram for High Contrast f/8

One f-stop Higher

So the brighter version next:

High Contrast f/5.6

High Contrast f/5.6

The graph has moved to the right, with less nuance to the brighter tones, while the darker tones have spread out as there’s more detail and variation to the dark tones; what was spikey has been rounded off and spread out for the dark tones, while the opposite has occurred for the light tones.  More red bright tonal clipping is evident in the same place as before.  There is a very small amount of dark tonal clipping, but it can barely be seen below:

BW for High Contrast f/5.6

BW for High Contrast f/5.6

One f-stop Lower

And now darker:

High Contrast f/11

High Contrast f/11

The dark tonal clipping is extremely evident now, and the graph has moved left – but with the dark tones bunching up to a significant spike.  The bright tones have spread out – with a barely visible amount of clipping visible in red on the image:

BW for High Contrast f/11

BW for High Contrast f/11

Average Contrast

Average Exposure

So the last image is a fairly average contrast image – though there are a couple of spots of very dark and very bright areas.

Average Contrast f/9

Average Contrast f/9

Only the very dark areas are clipping.  The graph is reasonably well spread out, but the black of chair, table and bag have meant there are more towards the dark tones than light; still this does show how something with a good spread would register across the range:

BW Histogram for Average Contrast f/9

BW Histogram for Average Contrast f/9

One f-stop Higher

The brighter image:

Average Contrast f/6.3

Average Contrast f/6.3

Some minor dark tonal clipping, but the white in the background means there’s mainly bright tonal clipping.  The dark tones have spread out becoming more nuanced, the light tones have bunched up and become spikey, as observed with the high contrast image.:

BW Histogram for Average Contrast f/6.3

BW Histogram for Average Contrast f/6.3

One f-stop Lower

The darker image:

Average Contrast f/13

Average Contrast f/13

A lot of clipping for the dark area – with the dark tones bunching up considerably.  The brighter tones have spread out and become flatter – again as noted with the high contrast image:

BW Histogram for Average Contrast f/13

BW Histogram for Average Contrast f/13

Conclusion

For the most part, I’ve observed what I expected to; however there’s a couple of key points I’m taking away that hadn’t really occurred to me before (but, perhaps, are obvious when you think about it):

  • Firstly; the change in nuancing on the graph can show where detail may be lost due to how an image is exposed ; so the brighter and darker parts becoming spikey if the exposure is losing detail in those tones.
  • Secondly; clipping isn’t always obvious as small clipping can be difficult to spot as it’s such a small portion of the image.
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