More Megapixels Does Not Mean More Quality

[Ben Stafford]

While the megapixel war has more or less cooled off, there are still sales people out there who are pushing the "more megapixels is better" line to first time digital camera buyers or digital camera owners who are upgrading from older digital cameras. I see this just about every day on our forums where people, when comparing a 6 megapixel camera to a 8 megapixel camera, that the 8 megapixel camera is the one to go with.

A great analogy for the whole progression of the ever-increasing megapixels is the computer processor industry. For a while, it was generally accepted that a faster (faster clock speed) processor meant a faster computer. Then, as different architectures were introduced, a processor could achieve the same, if not better performance, at a slower clock speed. Also, processor speed has progressed more quickly than what computer applications need, so we now have processors that are much faster than what most people use them for. If you just browse the web, do some word processing, and email, many of today's current computers are much faster than is needed.

A similar progression happened with digital camera sensor resolution, where, for a while, more megapixels were better since the rest of the camera also improved - better lenses, better image processing, etc. Then, the resolution out-paced what people really need. Quite simply, having more megapixels means that you can create a larger print (or that you can do more cropping and still have enough data left for a full-size print).

The size at which you can print depends on a couple factors, including the capabilities of the printer. According to this page at Microsoft's site (and you can find plenty of other references out there with some Google searches), their minimum recommended printing resolution is 240 ppi (pixels per inch). At 240ppi, a 5 megapixel image can create a maximum print size of 8.1 x 10.8 inches. With a higher quality print resolution (300ppi), you would need an 8 megapixel image to be able to print an 8x10, but a 3 megapixel image is all that's needed for a 4x6.

However, the mathematical requirements for a large print may be completely irrelevant as the differences in print quality may not even be noticeable to the untrained eye. Recently, David Pogue, a tech columnist for the New York Times, took the same image and made three 16x24 prints at a photo lab. One image was the full 13 megapixels, one was 8 megapixels, and one was 5 megapixels. He put up the posters in Times Square and asked people walking by if they could figure out which print was which. During his test, about 95% of the people could not tell the difference. One person correctly figured it out, but she was a photography professor. You can read more about it on his blog.

Why More Is Not Necessarily Better

In addition to producing more image data than you need for your uses, higher-megapixel sensors are not always of better quality. Typically, within a camera product line, the physical dimensions of the sensor stay the same from model to model. To achieve a higher resolution, more "photosites" must be packed onto the same size sensor. Advances in manufacturing and sensor technology allow this to even be possible. However, when the photosites become more densely packed onto the sensor, they start to affect each other - electrical signals can affect neighboring photosites.

Another downside to high-megapixel cameras is simply the file size of each image. While actual storage space is cheap these days, it will take longer to transfer images and it makes it harder to transfer full-size images to friends, family, and photo-sharing sites.

It's not all Doom and Gloom

Luckily, camera manufacturers know the consequences of packing more pixels onto a small sensor package and actively work to minimize any ill effects. Imaging processors are constantly improving, manufacturing processes are always improving, and the rest of the parts of the camera are getting better.

Bottom line - don't think that more megapixels means better image quality. Don't let that sales person talk you into a better model than the one you were planning to buy just on the basis of resolution. If you never print anything larger than a 4x6, you won't need anything larger than 5 megapixels. If you do a lot of cropping, then do consider getting a higher megapixel camera as there's more data there for you to crop.

 

[NetBrakr]

I Knew it! Couple of months ago, I was trying to convince this person about megapixel and quality. Thanks Ben!

JC

[Wail]

Excellent article.

I hate it when people talk of MP as if it's the God of picture quality. I had always wanted to ask a number of questions on this matter, I will post my questions on another thread as it will go off topic from here; never the less, one part of these questions is ...

What is the maximum MP an "average" person would ever need?

Given what an average person needs a camera for, knowing roughly what the pictures will be formatted into (frames, prints, large wall mounted frames, PC screen viewing, and TV viewing) .. what would you consider to be the maximum MP any average person would need?

I figure that anything more than 12 MP is a waiste of memory & processor resource. But I would love to hear other's input on this too.

[Ben Stafford]

I typically tell people that if they only make 4x6 inch prints, that 5MP is enough. It's also probably good enough for the occasional 8x10 (especially given the test that David Pogue did that you can read about in the main article).

There are, of course, plenty of other factors. What is the "average" person? Do you like to do a lot of cropping? Cameras also have JPEG compression settings, where a 5MP image with high compression (smaller file) will be noticeably lower quality than a 5MP JPG image created with low compression.

If you're talking about displaying on a TV, or photo frame, or something with a display - resolution is *much* lower. Your 1280x1024 computer monitor is technically only 1.3MP

[bTaryag]

But this is the way of the world. Until the masses are educated, I 10mp piece of trash will fetch more than a 5mp that takes awsome pictures.

You can't blame the camera manufacturers, because their business is to make money so they'll keep on marketing the 10mp model, and you can't blame the people because that's all they think is important, because that's what the marketing has convinced them..

Which came first, the chicken or the egg?

[Wail]

But I do believe that MP count will come to a stop very soon as we reach a point of deminishing return ... just imagine if manufacturers kept pushing up the MP it will soon reach 20 MP yielding a picture size of 30+ MB ... even if we have the abundance of storage for all that it would take a "relatively" long time to write the file to the chip / memory.

However, just as with CPUs ... consumers have now come to understand that MHz isn't all that it was meant to be .. and even a lower MHz of a C2D is far better than a higher MHz of a regular P IV.