The Megapixel Marketing Myth

Watch out, I'm climbing up on my soap box for a bit...

Walk into any consumer electronics store (or even visit their website) and go to the camera section. Now look at the information by each camera. First on the list is the number of megapixels. Look at your camera phone or your point n shoot. I guarantee it has the number of megapixels stamped on it somewhere. Ask your (non-photographer) friend why they chose the last camera that they did, and I bet number of megapixels is near the top of the list (usually right after price). Why is this? My guess is that megapixels is a convenient number for the marketing department to hype, and more is obviously better, right? Wrong.

(Just to be sure we're all on the same page, the number of megapixels a camera has refers to its resolution - namely, how many pixels are on the camera's sensor. One megapixel = 1 million pixels. When consumer digicams were first released, they clocked in around 1MP. Now, most point n shoots are in the 12-16MP range. More on this in a minute.)

So how many megapixels do we really need? That depends on what you use them for. A surprising number of people use their camera as their main way to share photos. That means that their 14MP images are being shown off at less than 1MP. Talk about overkill. Let's say they do download them to the computer and share them on Facebook (or some other photo sharing site). Facebook recently increased the size of displayed photos to 720p on the long side. Even if you upload a square photo (720x720) for the maximum display size, you're still coming in at 518,400 - just over half a megapixel. Say you show off some vacation photos on the family's big HDTV. 1080p = 1920x1080 pixels, which comes in at 2.07 megapixels. 16:9 is a bit wide for a still camera, so let's take that to a more common 3:2 format - 1920x1280, or just shy of 2.5MP. I'll even agree to a bit of extra so that you can straighten photos or cop in a bit, so let's call it an even 3MP. What about printing, you say? The guidelines I've seen for printing suggest 100-300 dpi, depending on your printer, print size, viewing distance, etc. Taking 100 dpi as a minimum (and it makes a very acceptable print), even 8x10's only require 800 x 1,000 pixels (just shy of 1MP). 3MP is therefore plenty for any consumer camera. 6MP is enough to print 20x30 inch prints at 100 dpi, so even most professionals don't need more than that.

So what's wrong with packing in the megapixels? It can't hurt to have more room to crop in on photos, right? Like with everything else in photography, getting more resolution comes as a trade off. Despite the increase in pixels, sensors in point n shoots are still the same size (about the size of your pinkey fingernail). This means that the actual photo sites (the electronics that make up a "pixel") have to keep getting smaller. Smaller photo sites mean less light is able to enter each pixel. This cuts down on sensitivity, resulting in a lower dynamic range and more noise at higher ISO settings. Despite advances in noise reduction technology and image processing, small cameras just don't handle low light very well. Which means that anyone taking photos indoors winds up nuking the scene with the tiny built in flash, and we all know how flattering those photos are.

At the other extreme, consider the Nikon D3s, which has the best low light high ISO performance of any camera on the market at the moment. How do they do it? They spread a mere 12 megapixels over the relatively vast space of a full frame sensor. Each photo site is therefore nice and large, increasing the dynamic range and sensitivity of the camera. For reference, here's a diagram comparing the different sensor sizes. Most point n shoots have 1/3" or 1/2" chips:



So why doesn't Nikon release a 3MP point n shoot camera that takes great photos in low light without a flash? Mostly because no one would buy it, especially sitting on the shelf next to other cameras that boast 15+ megapixels. It would require re-educating consumers and taking a huge risk, and I just don't see it happening in the near future.

Here are my recommendations (for whatever they're worth) for good resolutions:

- Cell phone cameras: 1080p HD, and no more. Even that is overkill, but I think the benefit of having that image size (and more importantly, that video size) outweighs the disadvantages.

- Point n shoots - 3MP. Like I said, most people will never use more than that.

- DSLRs (crop sensor) - 6-8MP. 99% of photographers will never need more than that, especially as more and more photo consumption moves away from print media and toward the internet.

- DSLRs (full frame) - I think Nikon has this one nailed at 12MP. The high ISO performance of that camera is truly amazing, and I think it's shifting people's focus in the photography world.

So what do you think? Do megapixels matter? Are you excited about the next batch of higher resolution sensors? Or have you had it with the megapixel race, and are ready for camera manufacturers to focus on something else? I think you can guess where I stand.

edit: I wrote the bulk of this post well before the Stevenote at WWDC (the iPhone 4 announcement). Interestingly, Steve Jobs said a few words about this very topic defending why they went with a 5MP chip instead of an 8MP one which is the highest available among current smartphones. Even more interestingly, they went with a back-illuminated sensor, which sets a great precedent for the small camera market.

~S

[title of blog] on flickr