There seems to be an overwhelming obsession with megapixels these days.
It’s always the first number reported when a new camera is released, and many people still think it indicates the quality of the camera’s photographs.
Well, unfortunately that’s not the case. There is no direct correlation between number of megapixels and image quality. We all have a natural desire to sum up a product with one number, but with a camera that’s impossible.
So, what do megapixels really mean?
Megapixels refer to the number of pixels in the final image. It simply tells you how large you can print your photo without having to enlarge it.
Here’s a table that matches a few megapixel values to the maximum size print they can produce:
As you can see, even a 10 megapixel camera can get you large poster-size prints!
Other advantages of megapixels
Although megapixels have no direct correlation to image quality, there are two advantages of having a lot of megapixels, that will indirectly give you better images:
Cropping. Having a lot of megapixels gives you more freedom when cropping images, because you simply have more pixels! You’ll be able to crop an image and still maintain a good resolution. This could be useful when you max out your zoom lens and your subject still doesn’t fill the frame.
Resizing. If you use the proper resizing method (or better yet, use the best method, Lanczos, available in the GIMP), then reducing the size of your image can actually help sharpen it too. Having a lot of extra megapixels will allow you to take advantage of this special form of sharpening, while still keeping a large enough resolution for your desired print size.
How many megapixels do you need?
It depends on your end goal: will you be printing large poster size images? Do you crop your photos often? If so, then you’ll probably want at least 10 megapixels.
But, if you just want to snap photos, post them on the web, and occasionally make smaller sized prints (i.e. less than 13×19″), then you’ll be just fine with 6 megapixels!
I recently read an interesting article at the Online Photographer that explains how most people would be perfectly fine with a 3 megapixel camera. Sounds shocking at first, but when you consider how most of us just snap our photos and share them online, resolution really isn’t super important in most cases. As the author of the article points out, “if a digital photographer never make prints, what in the world does he need a lot of megapixels for?”
What really matters is the quality of each pixel, not the quantity.
Of course, most SLRs these days come with at least 10 megapixels, so they’ll all give you those large print sizes, but when you’re debating between a 10 MP camera and a 15 MP camera, just remember that those 5 extra megapixels have nothing to do with image quality.
For more information on the “megapixel myth” check out this article by Ken Rockwell.
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About the Author: Steve Berardi is a naturalist, photographer, computer scientist, and founder of PhotoNaturalist. You can usually find him hiking in the San Gabriel Mountains or the Mojave Desert, both located in the beautiful state of California.
Honestly, even the MP:Print ratios you lay out above are not absolute. I’ve had *stunning* 16″x20″ prints made from my aging 5MP Olympus C5050Z camera. Mind you it was an action shot with quite a bit of blur, but what needed to be sharp was sharp. (Very low-res version posted here.)
What matters most IMO, is composition, then light, then lens. MP is way down the list, unless you’re using an old Apple QuickTake, but even those could cough up a good image under the right circumstances.
Higher MP on smaller sensors (ie point and shoot camera size) can actually DEGRADE photo quality by adding alot of extra noise in to the photo.
Did you actually cite Ken Rockwell as a source? Holy mackerel. That’s spooky.
The megapixel rating is actually important to different photographers in different ways. A portrait photographer with a 10 MP camera will be using 10,000,000 dots (pixels) to capture the face of a 5’5″ 102 lb girl. A landscape photographer will be using the same # of dots to capture a 4 mile wide valley with a 40 mile line of sight, with trees in it.
To the landscape photographer, the megapixel rating is important in the same way it is in satellite imagery: spatial resolution. Every pixel in every image represents area. On a portrait of a model, there are 10 million pixels covering a 2’x3′ area. On a landscape, there are 10 million pixels covering a 200 square mile area.
Sure, when it comes down to it, 10 million vs 20 million pixels may not seem to matter, but it doubles your spatial resolution. That’s pretty significant for landscape photog’s. So, if the pixel-quality of greater megapixel sensors could be the same as current lower-megapixel sensors, wouldn’t it be advantageous to go for the greater megapixel count, for archive and the potential for large-print use?
Peter, that is what this article tells.
It’s useful for large prints, but not as much otherwise.
Its very hard for most people to accept that it may not matter how many pixels regardless of what the subject is.. the end result is or should be a form of art and there are no rules. However there is an old saying ‘less is more’ and than can be true even when talking about pixels.