by Guy Lerner
July 1, 2003
Undoubtedly one of the biggest advantages digital cameras have over their film-eating counterparts is noise – or lack of it. But look closely and you’ll see that digital images are far from immune from the ravages of noise, which in many cases degrades their quality significantly. In fact, poorly designed imaging sensors can produce more noise than even the grainiest roll of film, which in today’s digitally driven world, is simply unacceptable.
Fortunately, an ingenious piece of software called Neat Image (available as shareware but reviewed here as version 2.5 Pro+) all but mutes the foul effects of noise in digital and scanned media alike. As you’ll see, it’s quickly becoming the prerequisite arrow for any digital photographer’s arsenal.
What’s Noise?
Noise hardly sounds like a photographic term (pun intended), but it very much
is. In film, “noise” is the “grainy” texture caused by the uneven chemical
composition of the film material; in digital photographs it’s the random (often
multicoloured) texture caused by the circuitry found in all electrical imaging
sensors. In both cases, noise typically shows up best (or worst) in areas of
flat colour (like blue skies), and in deep shadow areas.
As a casual observer, you may not have noticed the noise in your pictures, especially when printed at “standard” drugstore sizes. That’s because noise, like grain, is controlled fairly well by the regular shooting modes (low to medium ISO-equivalent settings in digital cameras and slow to medium-speed film) of your camera, and shows up even less in good light (i.e. bright, sunny days).
But take a shot of the sky at higher ISOs (or with faster film, such as ISO 400 or 800) and zoom in to your pictures on the PC. What at first may look like a perfectly captured image quickly becomes a sea of broken dots (and grain, for scanned film) – long before you’re zoomed in enough to see the pixels of the image themselves. The problem exacerbates when images are required to be printed at sizes upward of A4. It’s then that the noise – imperceptible in smaller prints – becomes distracting and clearly visible, giving the prints a “muddy” or “diffused” appearance.
Taming
Noise
There are several ways photographers control the inevitable noise in their
images before they have to resort to other methods for “cleaning them”. For many
years, professional film photographers have been using slower and slower film
(such as Fuji’s Velvia, rated at 50 ISO) that all but eliminates visible “grain”
from the film surface. Modern technology means that film with speeds up to 200
ISO reveal remarkably low grain, but the inescapable fact remains that film is
“made” of grain.
Digital photographers similarly resort to setting their cameras at very low ISO-equivalent speeds. The lower the ISO, the less sensitive sensors become to the electronic impulses that record the image – and contribute to noise.
Digital noise can also be limited effectively by the size and spacing of the individual pixels on the imaging sensor. The larger the pixels, and the more space between them on the sensor chip, the less susceptible they are to recording noise. (This is why digital SLRs are preferred to compact digital cameras; they have much larger imaging sensors, with much larger pixels spread over a wider area, so they display much less noise at higher ISOs than compact digitals equipped with smaller sensors).
Modern digital SLRs control noise to such a degree that pictures taken at ISO speeds of up to 400, and in some cases 800, show up almost no objectionable noise when viewed or printed, and where noise does creep in, it’s much lower than comparably-rated film. Modern cameras like Canon’s EOS 10D digital SLR, famed for its low-noise reproduction, can produce 800 ISO images with as much noise as ISO 200 film or ISO 200-rated compact digitals!
Keep It Down
But even modern DSLRs fail to produce the ultimate in low-noise imagery, zero
noise. It’s often unfeasible to shoot low-speed film or low-speed digital, even
with a tripod, when available light becomes too low for the sensor to
effectively record an image. That’s when alternative measures to controlling
noise need to be taken.
Enter Neat Image, by ABSoft. For years digital photographers have been looking for ways to rid themselves of noise without affecting the quality of their pictures. Removing noise (and grain from scanned images) often means discarding valuable detail from the picture, detail used to define edges and fill shadows. While the noise is removed, the picture typically ends up looking “washed out” or “plasticky” because vital information has been wiped away by the noise filter.
Neat Image uses sophisticated algorithms to accurately “calculate” the effects of noise on an image, and then works away at ridding the noise away without discarding any other information. This is due partly to the very random nature of the noise, and partly to the software’s ability to “sample” an area of the picture that contains the offending noise. In this way, Neat Image can determine exactly what information needs to be kept and removed from the picture, and goes to work accordingly.
The graphic below perfectly illustrates the effect of noise on an image. The first frame is a 100% unedited crop from a photograph of my son (above), taken with a Canon 10D camera at ISO 800. The “noise” you can see in the shadows and flat areas of skin appears as multicoloured spots that pollute the fine details in the picture.
The picture is then loaded into Neat Image (in this case directly from Photoshop using the Photoshop-compatible plug-in in version 2.5 Pro+), and a small section of noise (containing no other details) is made for the software to work on. Having calculated the degree of noise in the image, the filter is then applied, and the results noted in the third frame.
The
real strength of Neat Image is the ability to “profile” different camera
settings (and different cameras) and save them for use in other images with the
same settings. This is important where areas of flat, featureless noise aren’t
available for the software to sample (sampling an area of noise that also
contains detail can confuse the filter into discarding valuable information from
the image). Once I’d made the calculation for the image above, for example, I
can use it for all images produced by the camera at 800 ISO with fairly
predictable results.
But noise filtering is anything but cut-and-dry. In many cases, complex pictures present complex problems that a basic pass-through simply can’t correct. Neat Image shines again with the level of control it gives you over just about every aspect of the noise removal process.
A quick glance at the control panels in the Photoshop plug-in (the same panels appear in the standalone version, along with options for batch processing and outputting your filtered images) reveals options for modifying almost any parameter used to calculate and effect the noise reduction. These are linked to the colour space model used for the calculations, and range from determining noise levels to specifying noise reduction amounts by colour channel.
Neat Image even goes a further step by offering a sharpening filter tightly coupled with the noise reduction settings, to optimise the edge details of the resulting image. No other software goes to this depth, with this much control, to produce the exact result the photographer is after.
Plug Away
I’ve saved the best for last of course. With version 2.5 Pro+, ABSoft has
finally released a Photoshop-compatible Neat Image plug-in. For me – and many
other photographers that practically live in Photoshop – this “minor” refinement
means I can integrate Neat Image into my existing workflow and take advantage of
Photoshop’s incredibly powerful layering, selection and post-filtering tools.
While
this “feature” isn’t unique to Neat Image, it makes what is already the industry
standard for professional noise reduction the “must have” tool for serious
digital photographers. Imagine all the benefits of applying a uniform noise
reduction filter to an entire image, and then factor in the ability to
selectively reduce the noise in certain parts of your image by filtering only a
predefined and feathered selection in Photoshop!
Before I get swept away in technical jargon, I’ll finish up my kudos to ABSoft by saying that Neat Image has, in one version, become an indispensable part of my processing work. It even has advantages for low ISO images, where noise is almost invisible, by acting as a sophisticated “soft focus” filter, adjustable to my heart’s content.
The Full Monty
If you’re sceptical about anything you’ve read in this hybrid demo/review – as
well you should be – there’s no better way of dispelling your doubts than by
trying the software for yourself. As mentioned earlier, Neat Image is available
as a free, unlimited time version from
www.neatimage.com. The free version has some limitations (it’s not available
as a plug-in, for example, and can only process 8-bit images), but will give you
a good idea of the power of this software without breaking the bank.
I suspect, like me, you’ll be suitably impressed enough to pull out the wallet for the full Monty, the Pro+ version, if only for the Photoshop plug-in.
That said, there are a few things you should know before signing on the dotted line, so to speak. For one, don’t expect miracles to happen quickly. Neat Image is slow, even by the standards it sets itself and the results it produces. On anything less than a 1-GHz PC with enough RAM to keep a small office happy, the software takes over a minute to clean up a high-resolution (6 megapixel) image (the flip side is that it’s plenty fast for cleaning up smaller images for the Web). Try cleaning up a stitched panorama and you may as well call it a day (or night) while the CPU spikes to 100% and hamstrings everything else you’re doing at the time.
I also found the interface, while easy to use, a bit dated for the clean and stylised motifs of modern GUIs. The number of options, while pleasing, can also be confusing, but a handy manual and tutorial are supplied free of charge with the software (even the free version).
Conclusion
Even so, the proof of this software is
in its pudding, and how tasty that is. There’s no other software available that
reaches this level of sophistication at the price. It makes high ISO photography
guilt-free for professionals, and turns otherwise poor-performing digicams into
professional-class tools. Give me a smoother interface and beefed-up
performance, and I’d almost insist that Neat Image be part of every camera
purchase I make from this day on.
I have no hesitation in awarding Neat Image 2.5 Pro+ five out of five Go Inside Magazine Review Lights. Great stuff!
(all green)
Copyright © 2003