how many megapixels are enough?

How many megapixels do you need? Do most of your images remain in digital form, displayed on the web? Or do you create large prints for display?

As camera sensors grow in resolving power, greater demands are placed on lenses. A kit zoom lens that resolved just fine for a manufacturers 6 MP model might not rate so well on a 10 or 12 MP model. More resolution also means larger file sizes and increased data storage needs. With current cameras able to resolve well enough for many applications, is there a need for increasing numbers, other than for advertising purposes?

It will be interesting to see where Digital SLR design goes in the near future. Just a few years ago Nikon was fully committed to the smaller APS-C sized sensors and stated clearly that they had no intention of ever producing a full frame DSLR. Now they have two of them, the D3 and D700. Sony is not far behind with the coming release of their full-frame 24 MP sensor (watch Sony closely, folks, they’re a huge company with tons of resources). Olympus, on the other hand, has committed to a sensor half the size of full-frame with the 4/3 format. And they all produce high quality images.

Regardless of future directions taken by manufacturers, it’s assured we’ll be getting more impressive specifications with each new model release. Yes, some of the companies have taken a misstep here and there but, overall, the ball is rolling downhill pretty fast on innovation. Take Canon, for example, with the Digital Rebel.

Popular Photography has a current DSLR shootout: Five Top Cameras Compared, posted both on their website and featured in the August 2008 issue of the magazine. Just out of curiosity I looked at the specs of the Canon Digital Rebel XSi and then flipped through the archives in order to find a similar shootout from 2006. In January 2006 they called a similar article the Hotshot Shoot-Out, which featured the Canon Digital Rebel XT. In between these two versions there was also the XTi model from Canon.

So how much has this camera evolved in the two and a half years from XT to XSi? At a glance there don’t seem to be earth-shattering changes, just constant refinements. But, taken as a whole, the improvements are impressive. Let’s walk through some specs, courtesy of Pop Photo:

Canon Digital Rebel XT (Jan. 2006) vs. Canon Digital Rebel XSi (Aug. 2008)

Roughly the same list price: XT was $880 with the just adequate 18-55mm kit lens. The XSi is listed at $900 with a much improved 18-55mm lens with image stabilization. Very big improvement.

The LCD screen has tripled in size, going up from 1.8” to 3”. Major improvement.

The megapixel count, the thing most people look at first, has jumped from 8 MP to 12 MP, a sizeable step. Color depth has also jumped from 12-bit to 14-bit A/D conversion, a wonderful spec at this price.

The friendly sensor also cleans itself off now, saving post-production time spotting out dust. Nice.

A thing that doesn’t show on Canon’s spec sheets but does in created images is the resolving power of the sensor. According to Pop Photo, the best the XT could resolve was 1800 lines per inch. The XSi? 2265 lines, a 25 percent improvement. Heck, the XSi still resolves 2160 lines at ISO 1600, better than the XT’s best effort at ISO 100! Major gains have also been made in noise reduction.

Compared to 2006, the latest Canon Digital Rebel is easier and faster to use and creates sharper images with increased resolution and less noise…all for the same price. Adding up the individual feature improvements points out huge gains on paper. And we’re just talking a couple years here, not 4 or 5 or even 10 years.

But, at the end of the day, do these improvements result in better images for most photographers? Or maybe an improved user experience? The larger LCD screen certainly does make things nice.

What are the certain features and improvements that compel you to buy a new camera? Are megapixels the most important thing?