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Poll: Megapixels vs. camera sensitivity

If you squeeze more megapixels onto a sensor of a given size, a camera works worse in dim conditions. So what's better, more megapixels or higher sensitivity?

LAS VEGAS--The camera companies keep telling me the megapixel race isn't over, but I'd like to see if you have a different opinion.

I'm one of those people who doesn't believe more megapixels necessarily makes for a better digital camera. Sure, at least theoretically having more megapixels permits larger prints and tighter cropping, but it also can impose penalties such as image noise, lousy low-light performance, smeary noise-reduction artifacts, and other drawbacks. There's a trade-off here. Poll

Megapixels vs. Sensitivity
It's hard for camera makers to resist increasing new models' megapixel count, but smaller pixels on the sensor can mean higher noise that worsens performance in dim conditions and lowers overall sensitivity. Which would you rather have, more megapixels or better sensitivity?

10 megapixels and ISO 3,200
12 megapixels and ISO 1,600

View results

So it's time to vote now for what you'd benefit from more in a camera: more megapixels or higher sensitivity. Click the button to register your opinion and explain yourself below in the TalkBack section if you want to make your case in more detail.

Camera makers seem unable to resist the temptation of higher megapixels in compact cameras right now, marching on past 10 megapixels to 12. But in the SLR domain, where buyers are more sophisticated and larger image sensors provide more leeway, there are some interesting trade-offs going on.

Most interesting to me right now is Canon's approach. Its entry-level EOS Rebel XSi is a 12-megapixel model, but one step up the ladder is the 10-megapixel 40D. The Rebel's XSi top sensitivity is ISO 1,600, but the 40D offers 3,200.

Canon and Nikon provide another contrast with their top-end models. Canon's $8,000 1Ds Mark III offers 21 megapixels, while Nikon's $5,000 D3 has 12 megapixels. The 1Ds Mark III reaches ISO 6,400, but the D3 can go to 25,600 in a pinch. (Although these are top-end models, Canon's $4,500 1D Mark III, with 10.7 megapixels and maximum ISO of 6,400 but a smaller image sensor than the D3, is probably a more direct comparison with the D3.)

Now that we're beyond the 2-megapixel era, I'd prefer better sensitivity over a couple extra megapixels. I find myself much more constrained by dim conditions or fast-moving subjects such as children and wildlife than by insufficient pixel quantity. I've blown up my 8-megapixel camera's images to 20x30-inch prints without trouble.

Take a pixel peep at the cropped photo I took with the Nikon D3 of a BMW racing by on a Las Vegas track at about 80 miles per hour. The picture won't be gracing the pages of Sports Illustrated, but using ISO 6,400 let me freeze the action with a 1/8000 shutter speed, and the full image looks fine.

I recognize it's not a simple case that sensitivity is better than megapixels, and clearly some people may have different priorities. If you're in controlled studio conditions and shooting stock photos, a market that sometimes pays by the pixel, more pixels is probably helpful. And lacking a mammoth telephoto lens, I do sometimes wish I had more pixels left over after I crop heavily to better show a bird.

This is a 100 percent crop of a photo I shot with a 12-megapixel Nikon D3 at a shutter speed of 1/8000 sec., f/7.1, at ISO 6,400, with Nikon's new 24-70mm lens. Sure, there's lots of noise and the colors aren't as vivid as they could be, but ISO 6,400 will let you freeze the action of a BMW racing past at about 80 miles per hour (which means the top edge of the wheel is going about 160mph). This crop is from the in-camera JPEG. Stephen Shankland/CNET Networks

Optical resolution is another issue. Lower-end and sometimes even expensive lenses can lack sufficient sharpness to really take advantage of all the pixels on the sensor.

Gratuitous megapixels have other drawbacks besides noise. Image processors that convert sensor data into a JPEG have to do more work--especially with the double whammy that they often must use more sophisticated but power-hungry noise-reduction work.

Perhaps most obviously, more megapixels means memory cards and hard drives fill up faster. Sure, storage is cheap, but what if what you're storing is bulkier but no better?

There are signs that the industry is moving beyond its megapixels-uber-alles worldview. When Panasonic unveiled a number of compact cameras at a press conference Tuesday at the Photo Marketing Association trade show here, the company took pains to emphasize all the attributes besides megapixels it hopes to use to sell cameras.

You know where I stand on the issue. Let's hear your voice.

Update 8:30 a.m. PST: Here's my response to the issue of sensor size raised in some TalkBack comments.

Increasing the sensor size while holding megapixels constant can let manufacturers improve sensitivity, too. However, that's another trade-off because larger sensors cost a lot more to manufacture. I chose the 12 megapixel/ISO 1,600 vs. 10 megapixel/ISO 3,200 comparison because it's a real reflection of choices Canon had in its Rebel XSi vs. 40D.

It's not practical for Canon to fix the sensitivity problem simply by dumping smaller APS-C sensors and moving to full-frame. The cheapest full-frame camera today, Canon's 5D, costs at least $2,100 with no lens, which is hardly competitive in the entry-level SLR market.

It's easier to vary sensor size in compact cameras where the built-in lens can be matched to the sensor. (Indeed, Canon increased the sensor size slightly from the PowerShot G7 generation to the G9.) But the same cost trade-off applies there too, and compact camera buyers are even more price-sensitive.