View Full Version : Light sensors can be key to better digital photos

21st November 2006, 10:55 AM
Light sensors can be key to better digital photos
November 19, 2006


Cheap digital cameras are the wonders of our age. Combining one with a PC and printer, you can create photo masterpieces that would once have required a multithousand-dollar processing lab to handle traditional film.

There's one little secret about digital cameras that the average consumer hears little about: Most sub-$500 cameras deal poorly with low-light situations and motion.

Given a sunny day outdoors, or flash photography indoors, the photos are terrific. Try the artsy stuff - indoors, natural light and shadows, no flash - and you're often disappointed. Autofocus systems lose their grip on reality. People with shaky hands have blurry shots. Same with moving objects. If you want to make those kind of shots, you need an expensive SLR (single lens reflex) camera.

There's a specific reason for that: The SLR has a bigger sensor, postage-stamp sized or larger, and can thus collect more light, with the space between pixels more clearly defined. The typical point-and-shoot camera, on the other hand, has a sensor the size of your fingernail. Even with the same number of pixels as an SLR, this small sensor simply can't collect as much light and record as much definition.

To compensate for low light levels, manufacturers amplify the electronic signal coming from the camera sensor. Like turning up a cheap AM radio too loud, that can generate noise, which is visible as grainy artifacts. At that point, the camera's internal programming may try to compensate by applying a de-noising filter, which in turn gets rid of the graininess - but also erases details. Often, the photo can't be used. There's an alternative approach that a lot of professionals use - and that you can try for free. (It will waste, at most, an afternoon of your time): Use an aftermarket de-noising program on your PC.

Your current image-editing program probably has some ability to take out noise. But the specialty programs generally do a better job, particularly with the output from older cameras that have less-powerful processors and less sophisticated de-noising algorithms.

Start by downloading and installing a copy of Noiseware Community Edition, available at Imagenomic.com. This is the freebie version of a program that's been around for a few years and is popular with serious photographers. The basic tradeoff with any de-noising program is between detail and noise. Noiseware lets you tune this by hand and compare "before" and "after" versions before you commit to saving the revised file.

The biggest limitation is that it saves only in compressed jpeg format; but the various for-fee versions (starting at $29.95), including a Photoshop plug-in, add additional formats and features.

If you decide to spend money on a de-noising program, you might also want look at Noise Ninja ($34.95 and up at picturecode.com). It comes only in a trial version that overlays a grid and watermark to prevent you from using the output.

Check out the sample photos and FAQs on both sites.

Just as with film, the light gathering ability of camera sensors is equivalent to film speed and is measured in ISO: The lower the number, the less light sensitive and the less noise generated by amplifying the signal. Point-and-shoot cameras start out at 50 ISO and may be struggling to produce usable shots at 200; by contrast, even cheap SLRs give decent results at 1600. An external de-noising program can usually make a 400 ISO shot look like 200, a 200 like a 100, and sometimes even better.

You can try these programs on your current photo collection, but you may also want to adapt your photo-shooting style to them. (Alternately, cameras that don't support raw files - known as digital negatives - can usually be set to minimize in-camera processing.)

In our last column, we showed you how to work with raw files, which can bypass all in-camera processing, including dubious de-noising systems. With your format set to raw, experiment with your camera's manual controls. Turn off the flash and try higher ISO settings - and see what Noiseware can do with the resulting output.

Stabilizing small sensors

This year's big buzzwords in point-and-shoot digital cameras are "image stabilization" - using gyroscopes or electronics to reduce the natural shakiness of human hands. A virtual tripod, so to speak.

The idea, of course, is to improve on some of the problems native to the small sensors on consumer cameras. (Expensive single lens reflex, or SLR, cameras have used stabilization for years on long telephoto lenses.) If the camera doesn't shake, the lens can stay open longer and collect more light without blurring the shot. All else being equal, a stabilized camera should be able to shoot at lower light levels, and use lower ISO settings - hence less noise. Good.

What stabilization won't do is freeze motion. Your camera may be rock steady but that doesn't slow down a leaping receiver at the Super Bowl. That would require more traditional photographic solutions - faster lenses, higher ISO speeds - which points us again to digital SLRs.

Still, we're at the point where it's worth paying more attention to low-light performance than pixel count. Indeed, there's been some suggestion in the trade press that manufacturers may be approaching the point of diminishing returns by cramming 10 million pixels on a small sensor. If you're buying a new camera this year, you can get a good idea of low-light performance by reading the reviews (with lots of sample photos) and forums on sites like my personal favorite, Digital Photography Review (dpreview.com). Also worth a look: Popular Photography (popphoto.com) and Steve's Digicams (steves-digicams.com).

21st November 2006, 11:23 AM
Interesting article Auntie Zain, thanks for sharing. Sememang nya low light condition adalah situasi yang mencabar, need a fast lense and a very steady hand.