Pogue exposes the digital cam megapixel scam as a "big fat lie" and he's right

Pogue exposes the digital cam megapixel scam as a "big fat lie" and he's right

Summary: The New York Times' David Pogue has written the story that I've wanted to write for about three years now but never got to (mostly because consumer tech isn't my primary beat). Pogue has very articulately pointed out that there's a point of diminishing returns when it comes to the number of megapixels digital camera vendors are trying to sell you.

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TOPICS: Hardware
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The New York Times' David Pogue has written the story that I've wanted to write for about three years now but never got to (mostly because consumer tech isn't my primary beat). Pogue has very articulately pointed out that there's a point of diminishing returns when it comes to the number of megapixels digital camera vendors are trying to sell you. The manufacturers in this space are crawling all over each other to you offer you more megapixels for less money. Chances are though, like the car that does 0-60 in 4 seconds (something you'll never really need in reality), having something in the neighborhood of 5-7 megapixels will suit everyone but the pros and some "pro-sumers" just fine. Pogue does a brilliant job of proving this by twice testing the public's ability to appreciate the megapixel difference in the final product: a printed photo, enlarged.  Writes Pogue (registration may be required):

But one myth is so deeply ingrained, millions of people waste money on it every year. I’m referring, of course, to the Megapixel Myth.

It goes like this: "The more megapixels a camera has, the better the pictures."...

...I created three versions of the same photograph, showing a cute baby with spiky hair in a rowboat. One was a 5-megapixel shot, one was 8 megapixels and one was 13 [and had them blow up to poster-sized 16x24 inch prints]....

...[From a crowd of people that took the test] only one person correctly identified which were the low-, medium-, and high-resolution prints. Everybody else either guessed wrong or gave up, conceding that there was absolutely no difference.

Some of Pogue's readers challenged him. But the results were hardly different when he repeated the test with a slightly different methodology (also challenged). Although Pogue recommends the 5-7 megapixel range, he points out that he has seen photos from 4 megapixel cameras that look sharper than ones taken with an 8 megapixel camera.

So, how can this be? Well it really comes down what you do with all those pixels. Pogue made an incredibly important point when he blew his pictures up into poster-sized prints. For example, my 6 megapixel Nikon D70 can take a 3008x2000 pixel photograph. When all those pixels are finally displayed somewhere (on paper or on a screen), the sharpness of the image will be determined by how those pixels were ultimately treated. For example, if I try to print it on a poster that covers the entire wall of my son's bedroom (and I have a printer that can do that), the enlargement process will compensate by adjusting each pixel (and adding others) to a point that the image will look blurry or pixelated. 

What Pogue proved in his test is that even if you enlarge a 5 megapixel photo to fit into a 16x24 inch poster, it looks just as good as if you enlarge an 8 or 13 megapixel image even though the latter image has more raw pixels to work with (in other words, fewer pixels to stretch, if stretching is even needed to fill the 16x24 frame).  

Now comes the question of what most people do with the pictures they take. Hardly anybody I know ever enlarges their photos to something bigger than the biggest page size their printer can handle. In fact, most people do one or two of the following with the photos they keep: (1) print a 4x6, (2) print a 5x7, and/or (3) save it for viewing on the computer (from their hard drive, a CD/DVD, or a photosharing service on the Web).  Believe it or not, in ALL of these cases (especially the digital viewing case), for most people, 3 megapixels will do. In fact, most of the pictures I take (many of which I load onto ZDNet) are taken at my D70's 3.3 megapixel setting and some are even taken at the 1.5 megapixel setting!  

Consider this. If the most you think you'll ever do with your digital photos is look at them on your computer or share them on the Web, 99 percent of all digital photo viewing is done in a way that when the image is displayed, it's only taking up a fraction of the display. Then, take into consideration what resolutions most people have their entire display set to. Most people are set to 1024x768. At 786,482 total pixels, that's not even one megapixel. In other words, at 1024x768, you can't even view an entire 1.5 megapixel image without shrinking it to fit into your display. Go ahead, take a 1.5 megapixel image and try viewing it Firefox. In its full-screen mode, Firefox will automatically downsize it to make it fit in its window and give you a magnifying glass as the cursor so that you can return it to full size with a single left-click. When you're done clicking, you won't be able to see the entire image because it's to big to fit on the display.

OK, so you're runing your monitor at 1280x1024? That's 1.3 megapixels. (still way less than 3 or 4 megapixels). 1600 x 1280? That's 2 megapixels. Now take your typical photosharing service or any one of the photo applications that get used on the Windows or the Mac and 100 percent of the time, they default to shrinking images. For example, when you get to Flickr.com's image level page, Flickr actually shrinks (as do other services) images to be 500 pixels wide (dynamically auto-adjusting the height based on whatever the original image's aspect ratio was). A 500 pixel wide image is viewable in it's entirety at most of the commonly used resolutions (including the once popular 800x600 resolution). So, it was a good choice by Flickr. More importantly, to do this sort of shrinking, photosharing services must drop pixels. In other words, no sooner did you go out and buy that that 13 megapixel camera only to find out that your favorite photosharing service will throw out most of that data before it presents your pictures in the service's default viewing size.

The point is that as more and more people skip the idea of printing their pictures, the importance of having more than four or five megapixels is even further diminished.  

So, when might you need more megapixels? Well, again, it comes back to what you're going to do with them. If you routinely crop your photos with a digital photo editor (eg: Adobe's Photoshop), then, both the pixel dimensions of the final product and how you're going to output the final product matters. If, for example, you started with 6 megapixels as I did when I took a picture of two bald eagles fighting in the air (see right, one eagle is talons-up) but, after cropping, ended up with a photo that's 168x132 pixels (the dimensions of the photo to the right), there isn't a whole lot more that can be done with this image. If I tried the Pogue test and stretched all 22,176 pixels of this image to fill a 16x24 inch poster, you probably wouldn't even recognize the subjects in the photos as birds (they'd be so blurry). But, if I had more original pixels to work with, I probably would have gotten better results (provided none of the blurriness is attributed to bad optics, the wrong aperature/ISO/shutter speed settings, or my inability to hold the camera still). 

Here, for kicks, is what the same image looks like at 470 pixels wide (width in inches on your monitor will depend on your display's dot pitch, another factor in sharpness):

To expand what was once a 168 pixel-wide image into a 470 pixel-wide image without having a bunch of white space between the original pixels, Photoshop had to reach into its bag of tricks to synthesize new pixels and insert them into the image. It does this by inspecting the original image and making decisions based on what it sees. But, if I had more megapixels to work with from the getgo, such pixel fabrication probably woudn't have been necessary (or at least not as much). 

Anyway, given how pixelated the above enlargement is, you can imagine how much worse it would look if we attempted to enlarge it to something poster-sized. Likewise, you can imagine the sort of tricks Photoshop would have ending up doing if all I gave it to work with was 1.5 megapixels. The above enlargement would have been far worse. That's why, when I saw this arial dog fight taking place and took note of how far away the eagles were (approximately 250 yards), the first thing I did was moan about not having my 500mm zoom lens with me. The second thing I did was crank the D70 up to its 6 megapixel setting (a setting I almost never use). I knew in advance that this is a picture that'd I'd be looking to crop because this is what I saw in the D70's viewfinder:


Now you know why a 500mm zoom lens would have come in handy. Short of having a good zoom lens, more megapixels for post-photo editing is probably the next best bet in terms of extracting good close-ups out of a far-away shot. Which brings me to my next point.

Two other features that you may notice when comparing digital cameras are their optical and digital zooms. With optical zoom, your lens is doing all the work and the ability to do good zooming will depend on the lens' optics. But with digital zoom, your camera is literally cropping what it sees before you take the photograph, and then its resizing that cropped image to match the whatever pixel dimensions your camera is currently set to take its pictures at. Much the same way Photoshop did some tricks to turn my 168 pixel-wide cropped photo into a 470 pixel-wide image, a camera's digital zoom does the same thing which is why its results will sometimes be on par with what happens after un-digitally zoomed photos are cropped and enlarged with a photo editor.

So, the basic question is what's going to happen with all the pixels? If the most that's going to happen to them is that they're going to be viewed on a computer or on a 5x7 print, 4 megapixels (heck, even 3) is actually more than enough. If you're going to be cropping and enlarging photos, then it might make sense to go with more megapixels. How many more? It's hard to judge. Only you know the sorts of pictures you think you'll be taking and to what extent you might be cropping and/or enlarging them.

Finally, as Pogue pointed out in his piece, there are so many other things that contribute to final photo quality that it might make sense to devote your time and/or the money you save (by going with fewer megapixels) on those. For example, the built-in flash on many cameras invariably does a fair job of lighting your subject, but not the sort of job that a high quality flash can do. With Nikon's wireless flash technology and its SpeedFlash external flashes, I've seen what otherwise might be a mediocre photo turned into a gorgeous shot simply because of the better lighting.

Update: I posted a part II to this blog entry. See The exception to the digital cam scam.

Topic: Hardware

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43 comments
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  • Those aren't birds...

    That's a hawk dropping a cardboard cutout of Bullwinkle.

    ;)
    ejhonda
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  • The best advice for digital camera use.

    READ THE MANUAL !

    Yes, I know it sounds like a "well duh" statement but I'd bet 4 out of 5 people have never read the manual or figured out how to really use the tool in their hands.
    No_Ax_to_Grind
    • Actually, RTFM doesn't work

      I have several digital camera manuals here and they're all terrible. They're perfect at telling you how to set the camera to the different megapixel settings (as well as adjust every other setting). But there's no explanation that goes along with these step by step how-tos that explains the reasons you'd want to make those changes.
      dberlind
      • Well, I have to give you that one.

        I agree, they tell you how but now why you would do it. But then, do non-digital cameras do a better job in this area? I don't ever recall any manual explaining "why" you would change the F-Stop.
        No_Ax_to_Grind
        • Some suggestions.

          There were some excellent explanations in the Kodak photography guides complete with images showing the effects on depth of field as the lens aperture was changed. Even my old Nikon S3's manual had an excellent explanation though some oddities in the translation process could confuse the unwary.

          Hmmm... anyone else here own a Nikon rangefinder at any point in time? Anyone else seen a SPX other than the one in the Kodak museum in Rochester?

          OTOH, with an SLR with a depth of field preview button, you can watch the effect on depth of field as you change the aperture. Some Nikon and Canon digital SLRs offer DOF preview, others don't.

          As for megapixels? They're important but the signal to noise ratio in the sensor is often overlooked in the rush to smaller sensors with higher pixel numbers. As is the effect of sensor size on both signal to noise ratio and the diffraction airy disk to the circle of confusion.

          Perhaps I should admit to still remembering what HD curves are.

          Check the following URL for more information with better explanations: http://www.normankoren.com/Tutorials/MTF7.html
          DNSB
      • RTFM works fine

        The Fine Manual is written to support the fine camera's operation. It is the how. The why is available from other sources.

        I.e., knowledge of photography, which is an art and a science, is something that the camera operator needs to acquire elsewhere. I recommend "The New Zone System Manual" by Minor White for an explanation of why. Among others, Ansel Adams used this system, which is primarily a discussion of how to produce a good quality negative and so may seem to not be applicable to the digital camera era. It is.
        fuzzy2k
  • Additions

    A few nitpicks:

    There is no 1600x1280, it is 1600x1200

    The effect of extreme pixelization taking place when taking a smaller image and artificially asking the program to make it larger is called "interpolation".

    It should be stressed that as you said one of the largest advantages to larger megapixel count is the cropping without loss that it affords you. The large white lenses seen on the sidelines of sporting events are Canon L series lenses, almost all are what are fixed focal length lenses, or prime lenses. They are unable to zoom to any degree which means that with the subjects moving around often large amounts of cropping is required to make the image usable.
    foxylockxy
  • This is comparable to CPU measurements

    Since a couple years ago CPU's were measured the same way. The bigger the number the BETTER the cpu? Right? Wrong.. AMD proved itself in those years by have a CPU that would have a lower mhz rating yet outperform or perform at par with Intel equivalents.

    Same goes for Cameras, the people that don't know a mega pixel from a pixel will always go for BIGGER is better, its not a scam. Sales people just tend to push more expensive items, thats all. If you went in and a 3MP camera cost $500 and a 5MP cost $25, I'm sure the sales person would PUSH the $500 dollar model simply because he could rattle off one thing or another that would set the 3MP apart.

    My 2 cents.. I always tell people, read reviews of a camera, make sure it does what you want it to, don't buy for MP size.
    jakex3@...
  • Optics are more important than the ccd

    You briefly touch on it when you mention zoom, but any microscopist can tell you, the quality of your image is vastly more affected by the quality of your lens than it is by small differences in the sensor (going from 5 to 8 megapixels). If you have a crummy lens, you won't get high quality pictures no matter how good your ccd. Which is why phone cameras are such a waste of time. Why spend more for a 3 mp phone camera when it's always going to be limited by a crappy, tiny, plastic lens?
    tic swayback
    • So true.

      Scott Kelby makes this very clear in his book "The Digital Photography Book", which
      is a well of knowledge easily laid out and aimed at the non-professionals (most of
      us!). It is not a manual, but full of insightful tips that stopped me in my tracks -- and
      I've been shooting for years. If you are using a DSLR and want sharp images, spend
      the money on the glass.

      For the record -- I found the manuls for my DSLR Nikon and Fuji to be very
      complete, as far as manuals go.
      999ad@...
      • cameras

        As someone once said 'Its not size that counts - its what you do with it that matters.'

        My digital SLR can do 5meg pix, but I very rarely use it as that. One meg or less is fine for most stuff.

        Pogue is correct.
        kjrider@...
      • i agree

        When I started using SLR film cameras decades ago, many writers in the photo mags made the same statement. Spend your money on the best possible lenses you can afford. The body just holds the film and the shutter. I got the same advise from the local press photographers I knew.

        As far as learning about cameras, the manual are good starting places. You have to use the camera to know what to do by instinct when the Perfect Picture is presented. This used to be expensive when using Kodachrome and Tri-X film. People who use digital have it easy and cheaper. IF they understand why the pictures they DELETE are bad. Anyone can take pictures. It takes skill, a ready eye, and lots of experience,(training and just taking lots of lousy pictures) to take PHOTOGRAPHS.
        pfyearwood
    • no, but the Megapixels are not the most important

      An appropriate lens is important, but beyond a certain quality more is not better, you just get more resolutoin than the imager can take adavantage of.

      More important that Megapixel count (beyond, say 3MP) are sensitivity and dynamic range. Sensitivity should be high (so that noise is low) and dynamic range should be high (so that the broadest range of 'shadow' and 'highlight' can be captured with detail).

      Fuji has made some real strides here, making half of their pixels super-sensitive (for a low noise image) and the other half low sensitivity (for high dynamic range, they take over when the other ones start to "burn out"). This makes for images that are more "film like" in their low noise and high dynamic range.
      baldwinleo@...
    • No, not always true.

      Surpizingly, the size (not pixels) of the CCD is criticaly important. How to explain? Ok, imagine the CCD is .2 inches, that means the lens must focus the light down to a .2 inch area. Now compare that to a CCD that is .5 inches, the lens doesn't have to compress the light beam nearly as much.

      Manufactures can cut costs by using a small CCD and then using the lens to try and compensate. In most cases that works out so so, but in many cases (at the end of the focal limits at either end) the problem can be very noticable.

      As a general rule, the larger the CCD the better quality of the images.
      No_Ax_to_Grind
      • CCD size

        Or the situation with my "8 megapixel" camera in my cellphone. A quick calculation says the minimum aperture to avoid diffraction effects is f2.8 while the maximum aperture to avoid aberration effects is f4 (based on the sensor diagonal size). This lens has NO sweet spot between the two limits. Not to mention being a chunk of plastic which when I tried taking pictures outdoors in bright sunlight gave me results which, being kind, were unacceptable by the standards of a 1950's Kodak Brownie. A Brownie whose images were printed by a colour blind technician.

        By comparison, my old Nikkor 50mm f2.0 lens has a sweet spot from f3.5(aberration) to f11 (diffraction) taking photos of resolution charts which matches pretty closely to the theoretical numbers for a 43mm diagonal "sensor". I do have to admit that resolution charts while they make for great discussions often show little resemblance to the results of real world photographs.
        DNSB
    • Phone cameras

      The most important use for phone cameras might well be candid shots; Saddam Hussein's hanging being the most notorious example, but also shots made for legal purposes, or to expose alleged abuse.
      John L. Ries
  • i'ts always been a numbers game.

    Whilst I agree that it is the lens that is more important that having 5 or 8 megapixels, the average consumers just does not care.

    Talking about your lens on your 5 megapixel camera to your neighbour with his 8 megapixel camera isn't going to work.

    Even though having a 52" screen doesn't make the TV programs any better than next doors 48" screen (it could even have a worse picture), its that extra 4" that count. And you know it.

    :-o
    Bozzer
  • It may not be megapx, but it's about glass and sensor

    Most consumers could give a crap about quality...and couldn't spot it, anyway. They want a camera that they can just point, shoot, and not get blur. They don't really even care about noise and color issues.

    I had a Canon Digital Elf. What a piece of total crap. It was 5mp. At ISO 400 (required to take pictures w/o a flash and its highest setting), the pictures were horrible. I upgraded to a DSLR (Nikon D70s), and the results are night and day. You get what you pay for.

    Spending $500-$1000 for a lens and $300 for a decent flash makes a huge difference as well.

    One of the major issues with p&s is the fact that the flash is next to the lens. Are they kidding? You should be able to pop it up about 6 inches or something. Oops... no red-eye anymore.

    Also, issues with p&s is size of lens. Do you really think you can let that much light into that little lens? Why do you think an 85mm 1.4 lens is like 4 inches in diameter.

    P&S is good for one thing... capturing the moment.

    He's a good rule of thumb. When you go to buy a p&s, buy the one with the largest (diameter) lens. From what I've witnesses in p&s, bigger (physical size) is better. Get a DSLR and stop crying.
    numbers987654321
    • Speaking of Digital SLR...

      This is something that's bugged me for a while now. Maybe a more experienced photographer can enlighten me. What is the point of using SLR on a digital camera, when a digital viewfinder already accomplishes the same task as the SLR mechanism? Is an optical view much better than a digital one? I would think one would want to preview the output rather than the input to the imager anyway. Just curious...
      sethhoyt@...