Tuesday, December 16, 2008

Plugged In: Shooting for quality: A snapshot of digital cameras

Editor's note: No new cameras of consequence were introduced at the annual photo marketing show in March, so the cameras listed here should be current through about July.

Christmas is nearly upon us and, because digital cameras have become one of the most common gifts for Christmas, I’ve decided to discuss how to buy digital cameras in this pre-Christmas issue.

There are some major facts and misconceptions about buying digital cameras that I’d like to address first, because understanding them should result in more informed purchases and usage.

The basic technical knowledge required for highest-quality digital photography is the same as with traditional film cameras — correct exposure, good focus and depth of field, proper contrast and tonal quality, good color balance, avoiding blurring due to camera shake, using an optically sharp lens and all the rest. Even a high-end digital camera will not turn an indifferent film photographer into the next Ansel Adams, although it can help a knowledgeable photographer avoid some pitfalls.

A digital camera’s sensor acts very similar to traditional film, particularly high-contrast slide film. Except when using very large-sensor professional cameras, using higher ISO sensitivity ratings usually results in poor color and tone separation in shadows and highlight details, and in higher image noise that looks and acts just like film grain. As ISO settings increase, these problems gradually degrade image quality until it becomes unusable. This happens very quickly with small sensors that pack too many pixels into too small a space, causing serious electronic interference between adjacent pixels on the sensor.

A higher number of megapixels (MP) advertised for a particular camera does not guarantee higher sharpness and image quality, despite attempts by marketing departments to convince consumers otherwise. The megapixel race basically dupes consumers into buying this year’s model. Pros know that a good 10MP camera, used properly, can produce high-grade professional images. Given the current state of the art in digital sensors and electronics, there is an optimum megapixel level for each type of digital sensor.

Just as film cameras that used larger negatives usually produced better-quality photographs, digital cameras that house larger sensors will usually produce better-quality images than those with smaller sensors, particularly at the higher ISO sensitivities needed in dim light, when using high magnification telephoto lenses and when you’re taking high-speed action shots. Remember that unlike film, a digital sensor cannot be changed for something better — you’re stuck with it for the life of the camera.

Sensing a difference
The smallest sensors are usually termed 1/2.3-inch or 1/2.5-inch. These usually have the lowest image quality and are primarily useful for very compact casual cameras and compact cameras that mount high-magnification zoom lenses. Eight to 10 megapixels is usually about as much as can be rationally fit on these small sensors. Any more and you’ll usually start losing image quality, rather than gaining it.

Midrange sensors are usually listed as 2/3-inch, 1/1.6-inch, 1/1.7-inch or 1/1.8-inch. These sizes once were also used in higher-quality consumer cameras, but are now mostly found in high-end compact cameras intended for serious use. When used in good light at their lowest ISO settings (about ISO 50 to 200), high-end compact cameras using midrange sensors can take professional-quality photographs. Ten to 12 megapixels is about the useful limit for top-grade cameras using midsize sensors. Some of the more expensive compact cameras claim to squash 14 to 15 megapixels onto a small or midrange sensor, and I’m sure that even higher numbers are on the way. In such cases, image quality is often worse than in earlier models with fewer megapixels.

Most digital Single Lens Reflex (dSLR) cameras use what’s termed an APS-C size sensor that’s about half the size of traditional 35mm film but still several times larger than a midrange sensor. An APS-C sensor is capable of providing excellent quality photographs under a much wider variety of lighting conditions and high-speed photography compared to a high-end compact camera. A dSLR camera usually has a faster operating speed, often taking three to six frames a second when needed. Fifteen to 16 megapixels seems to be the reasonable upper limit for large APS-C sensors at the moment.

At the upper end of price and performance are the so-called “full frame” professional-grade cameras, whose 35mm film-sized frame sensor operates well, even in low light and at faster shutter speeds. However, even when comparing these mega-thousand-dollar cameras with relatively big sensors, lower megapixel sensors using larger pixels still produce better-quality images.

Zoom lenses with long zoom ratios, such as 15X, are more expensive and seem to appeal to less knowledgeable buyers. However, it’s truly difficult to wring good optical quality across a wide zoom range. Stick with zoom lenses whose zoom ratio is 6X or less — preferably less. You’ll get a lot more optical quality for less money. “Kit” lenses bundled with entry-level digital SLR cameras are often less sharp than high-end compact cameras, like the Canon G10. Do your homework and check the review sites listed below before making a purchase.

Lens sharpness remains critical but impossible to gauge by looking at a camera or reading ads. You should research potential purchases by checking some serious digital camera review sites. I’ve found that the best overall comparative camera reviews are found at www.imaging-resource.com, www.dcresource.com, www.steves-digicams.com, www.dpreview.com (British) and www.cameralabs.com (New Zealand).

The best inter-changeable lens reviews are at www.photozone.de (German), www.dpreview.com and www.imaging-resource.com. By far the best comparison of the digital sensors found in high-end cameras is at www.dxomark.com (French). All of these resources are English language sites.

Although all current digital cameras can save pictures in a compressed, ready-to-use JPEG file format, using JPEG compromises your ability to later correct and enhance photos and usually reduces overall quality and resolution. A camera that allows you to optionally use an uncompressed “RAW” file format is much more flexible and can capture the highest quality images.

However, you will need RAW-capable software, of which Adobe Photoshop Elements 7 is the least expensive, usually about $80 at Costco. Adobe Photoshop Lightroom ($299 list price) is a very modern, wonderfully intuitive and high-quality program that really shines with RAW images. Lightroom is fast becoming the choice of professional photographers. It’s still sufficiently easy to use and inexpensive so it’s also well-suited for any photographer who wants to get the most out of a higher-end camera. All digital SLR cameras, and a few higher-end compact cameras, have optional RAW file format capability.

Know your need
Generally, digital camera models are aimed at specific users, including:
Casual family snapshots that will be displayed on smaller computer monitors or digital photo frames and will rarely be enlarged much beyond standard 4-by-6 or 8-by-10 prints. My recommendations for compact casual cameras include the Canon A590 IS, the Pentax W60, the Kodak z1085 IS, and the higher-end models in Sony’s W series, such as the Sony W120.

The best buy is the Canon A590 IS. Panasonic’s FX150 is a worthy high-end casual camera with the bonus of optional RAW files. Best buys for high-magnification, long-zoom ratio cameras include Kodak’s z1012 IS or, if you also want a RAW file option, the Kodak z1015 IS or the Panasonic FZ28, whose 18X Leica lens is considered unusually good. Unfortunately, the lower-end consumer models from Nikon and Olympus tend to get rather poor reviews.

Business users such as engineers, contractors, government agencies and attorneys who need to document specific evidence easily and with sharp detail. Suitable entry-level dSLR cameras include the Pentax K200d (it has the best kit lens), the Canon XSi (EOS 450D), and the Olympus E520. Semipro quality compact cameras for professional users are pretty much limited to the Canon G10 and the Panasonic LX3.

Lower-level but still decent-quality compact cameras with good lenses and midrange sensors include the Fuji F60fd or Fuji S100fs, the Nikon P6000, the Panasonic FX150 and the Kodak z1085IS.

Frequent travelers and vacationers who need decent quality in a very compact, versatile camera. Consider the Canon SD880 IS, the Canon SD990 IS or the Panasonic TZ-5.

“Enthusiasts,” including hobbyists, serious photography students at the college and university level and fine art photographers. Cameras in this range are often considered “semipro” models. The only semipro-level compact cameras worth considering are the 15MP Canon G10 and the 10MP Panasonic LX-3. Both are polished models. There are several very good digital SLR cameras in this range and so many lens options that you really should check some rigorous reviews before making a purchase.

One of the best is Nikon’s new D90, whose image quality and usability seem superb, especially with Nikon’s new, very sharp 16mm-85mm lens. I also like Pentax’s quite rugged, weather-sealed K20d with the older but still excellent 16mm-45mm F4 and 28mm-105mm F 3.2 lenses. The Pentax lenses are often the sharpest available in their price range, assuming you get a properly assembled copy. Canon’s new 50D is also highly regarded, but check out whichever Canon lens is sold with the body — the newer versions are fine but the older optics had a deservedly bad reputation. The image quality of Sony’s entries in this category, the A300 and A350, has been unfavorably compared to the similar Pentax K20d and Canon 50D.

Although professional photographers will sometimes use a semipro model like the Nikon D300, the Pentax K20d or the Canon 50D, serious working pros often prefer full frame digital SLR cameras. The least expensive full frame camera bodies are the Canon 5D Mark II, the Nikon D700, and the Sony A900, which range between $2,700 and $3,000, without a lens.

Unless you’ve got the proceeds of your most recent bank robbery still stuffed in your mattress, purchasing a full frame digital camera is probably beyond the needs and the means of anyone who can’t legitimately deduct it.

Local attorney Joseph Kashi received his bachelor’s and master’s degrees from MIT and has been writing and lecturing about technology throughout the U.S. since 1990 for American Bar Association, Alaska Bar Association and private publications. He also owned a computer store in Soldotna between 1990 and 2000.

1 comment:

Blogger said...

Like watching live sex cams? You won't forget BongaCams.