LINKS:
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UNDERSTANDING DIGITAL EXPOSURE:
Part 1: Exposure Reduction for Highlight Retention
Part 2: Digital Exposure & Noise
Part 3: When Blocked-up Shadows Aren’t Really
Part 4: Take a Balanced Approach to White Balance
Part 5: Dynamic Range
Part 6: Extending the Tonal Range
Part 7: What’s the Real Difference Between RAW and JPEG?
GENERAL:
1) COST-EFFECTIVE PHOTOGRAPHY
2) CONTROL THE RANGE OF FOCUS
3) IMAGE INTERPOLATION
4) LOSE THE DEAD SHOTS
5) SCANNING 35MM FILM
6) THE RAW vs. JPEG DEBATE…
7) IS PHOTOGRAPHY EASY?
8) MUST EVERYTHING HAVE AN ADOBE SLANT?
9) A CAMERA TO PAINT WITH
10) WHAT'S THIS COMPOSITION THING ABOUT?
Understanding Digital Exposure
5. DYNAMIC RANGE
By applying heavier processing in-camera it’s possible to get images that appear to need little or no work in image-processing software. In DSLRs we can set JPEG contrast, colour and sharpening parameters. But this approach tends to set limits on creative interpretations of an image in software.
It could be argued that it’s best to set a DSLR to produce properly exposed, more neutral JPEGs so that tones, contrast, sharpness and colour can be subtly manipulated later. Typically it's best to avoid extremes either way with sharpening and contrast. I enjoy fine-tuning each converted JPEG image in software, but I can understand why that approach won't appeal to everyboby.
If we’re shooting with advanced compacts, we find ourselves working with a reduced exposure latitude due to the smaller sensor’s more limited dynamic range. This will usually restrict image-manipulation techniques, but there’s still scope for effective creativity.
In my opinion, dynamic range is a much misused term. We should concentrate instead on what we can do with the tones we have recorded. The term is surely more relevant to imaging technicians than the dedicated photographers who visit this site.
Knowing all there is to know about dynamic range won't help you get better images with your camera. Not one jot. You'll be concentrating on doing all you can with exposure to make the most of the tonal range in the scene. Typically you'll be trying to avoid noisy images. Dynamic range is meaningless too when you're working in software – you'll still be working with the tones the camera captured, wanting to keep them smooth and noise-free.
You don't need to learn about the complexity of modern engine design before you go for a drive.
Dynamic range is an expression of any medium’s maximum and minimum capabilities. Dynamic range in photography is the tonal capability inherent in the medium being employed. Really, dynamic range isn’t relevant. We end up with the tones we end up with anyway. With these tones from our chosen medium as a starting point we can get on with creating an image that works for us.
So, really, it may be more helpful at the start if beginners think of dynamic range only in the context of the medium they are dealing with – a sensor, a film, a screen representation or a print. Once a digital image is recorded, its tonal range is fixed, having been constrained by the sensor’s dynamic range. The basic raw data cannot be extended further. (How much of this data we need to create appealing images is open to debate, but that’s another subject.)
High Dynamic Range imaging software is simply a dedicated tool for extending a scene’s tonal range by using two or more images. It would be more appropriate and meaningful in this context if “HDR” software routines were called Extended Tonal Range Imaging since the dynamic range has already been set in place by the sensor or film that was used to capture the original files.
As discussed elsewhere, electronic sensors favour the shadows but have frustrating highlight limitations that must often be accommodated in some way, at the time of shooting and/or later in software.
The dynamic range of larger-than-compact sensors hasn’t changed much over the years. In-camera image-processing software is certainly advancing. I remember reading an early review of one of Nikon’s very best DSLRs – the impressive D3, as hi-tech as you’ll ever get. At the time the reviewer gave it a very high score but noted its accuracy with midtones meant that “care should be taken to avoid highlight detail burning out… 3D Matrix [evaluative] metering tends to deliver accurate midtones, with the result that highlight detail can get lost; …‘old-fashioned’ precautions (slight negative exposure compensation or selective metering) are still the best way to hang on to the highlights” (Amateur Photographer Magazine).
The Nikon D3
He’s right.
Cautiously reduced exposure is still the best solution to handheld digital highlight problems. Manufacturers can’t calibrate the built-in DSLR exposure meters to favour brighter tones because not all photographers will be significantly manipulating images in software. Photojournalists, for example, will want camera-processed JPEGs that can be sent with the minimum of fuss to newspaper offices and other sources where they can be used immediately.
But what about dedicated amateurs like ourselves?
Well, I for one would strongly recommend buying Elements or Paint Shop Pro PHOTO and learn how to use the most powerful features we can find, like Curves and Levels and Layers. If we have intelligently held as much brighter tone detail as possible we can take a good look at any shadows to see where they may need opened up a little.
A couple of years ago I exchanged a few emails with Ken Rockwell, after having a good read though all the material on his site. I found him to be very knowledgeable – knowledge he backs up with very impressive unprocessed JPEGs.* He made a few really useful recommendations to help me on my way.
I don’t pretend to fully understand a lot of the more technical stuff associated with digital imaging, and quite frankly I’m not that interested. I'm after the more practical information that helps me manage my images more creatively. I'm happy as long as can get vibrant, reasonably sharp 12x8s and bigger.
But according to Mr Rockwell (who comes in for more than his fair share of negative criticism, much of it groundless, petty and personality-related), film “has a huge advantage in recording highlights...” Sensors, on the other hand, are inherently held back by amplification and sampling electronics that “won't be fixed soon...” (I'm beginning to wonder if they will ever be fixed!)
Incidentally, he also points out that although a JPEG has 8-bits per colour channel and RAW 12, because of how a JPEG is written the two are the same in the shadows: “…the full 12-bit resolution in the dark areas is preserved by the non-linear coding.” Or, to put it another way, after “log and gamma conversion” JPEGs have full bit-depth precision in the shadow levels.
For the ordinary amateur photographer, like me, these technical details may amount to mere gobbledegook. But it probably helps to explain why we can have so much control over shadow detail, especially in images captured by DSLR sensors that have better light receptors. Full-frame is ideal and arguably worth saving for if image-editing is important to you. However, we should note that in practice it's likely that working with RAW data will allow us open up shadow details even further if necessary.
This is good news. It means in certain situations creative DSLR users can expose with the more significant lighter tones in mind rather than depend on an exposure meter’s mid-tone bias that may well harm highlights.
By thinking intelligently about exposure and consulting the histogram when possible, we can often capture DSLR images with a tonal range that can be fully exploited in software. We can selectively edit areas within the frame, without causing visible data damage.
A slight reduction in exposure can extend creative possibilities.
* See HERE too for a photographer who shoots JPEG
