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Tuesday, November 21, 2006

David Pogue Riles People Up

David Pogue's excellent adventure.


Mike Comments: As several people have pointed out, both privately to me and in public comments, Mr. Pogue's trial, though interesting as far as it goes, doesn't appear to mean much. The best interpretation of his test methodology, which he's not entirely clear about, is that he's taken one 13-MP file and down-rezzed it to sizes equivalent to 8 and 5 MP, then made prints of the same size—hard to tell from the above, but they look to be somewhere on the order of 15" to 20" square, something in there.

The real issue is not just "5 MP is as good as 13 MP"; it's a good deal more subtle than that. As is fairly well known by now, a number of factors play a part in image quality and digital image enlargeability. Not only the size of the sensor and the pixel pitch (i.e., the size of each individual photosite), not only at what point and to what degree Bayer interpolation is applied and how the up-rezzing or down-rezzing is implemented, not only the size of the final print and the interaction between the printer's resolution and droplet size and that of the picture file, but even the subject matter...a picture of a baby, for instance, has a much lower demand for resolution than, say, a landscape with a lot of bare trees at infinity distance. As we know, when you up-rez digital files you lose detail, but—unlike the case with film—you maintain perfect smoothness in areas of broad color. It stands to reason, then, that pictures that depend on areas of broad color will fare better when up-rezzed than pictures that depend on fine detail.

As with film, all the determining factors tend to define not one predetermined, set "quality," but a range of possibilities, from "fine" to "not-so-good." And all those ranges overlap. Mr. Pogue's trial is one possibility; another might be to make broad-daylight pictures of the same subject with a 1/1.8" 5-MP sensor digicam, an APS-C 8-MP entry-level DSLR, and a full-frame 24x36mm 13-MP sensor Canon 5D, then make three prints from each: one 4x6", one 13x17", and one 40x60". And then perhaps do the same, but with pictures shot at 1600 ISO. With exponentially more visual data to evaluate, it might not be possible to get good survey results from passers-by on the street, but you'd see a bit more clearly what the ranges of possibility are from each sensor.

And, I would venture to guess, the fact that ordinary people couldn't readily tell the difference between the 4x6" broad-daylight prints from the 1/1.8" 5-MP sensor and the full-frame 13-MP sensor would not be quite enough to conclude that 5 MP is as good as 13 MP. Nor would it be entirely defensible to compare the 40x60" ISO-1600 prints and conclude that 13 MP is better than 5 MP for all people and all purposes!

Also, it's not wise to forget the hidden "equipment" each of us now uses that is just as important as the camera: our software, coupled with our abilities to use it. A skilled technician with inferior software might be able to make better prints than a newbie with Photoshop. Even "leveling the playing field" by giving all the files to an experienced technician to print wouldn't exactly be fair, because what owner of a 5-MP digicam would be using the exact same software and printer as a high-end DSLR photographer?

The upshot, I think, is that it's impossible to compare "just" megapixels and nothing else, because every possible way you could choose to conduct such a comparison subsumes several other choices and assumptions. And those choices and assumptions will determine, as much or more so than the simple megapixel count, the outcome of the test. —MJ


Blogger Ken Tanaka said...

Haw! I'm not at all surprised by either Pogue's results or some of the badly informed (photo-forum-like) flak he received. I've proved this to myself many times.

Could a skilled (digital) photographer distinguish between the prints? Maybe, but not certainly. Could a man-on-the-street distinguish them? Certainly not, nor would s/he give a rat's caboose. But that won't stop him/her from buying the camera with the colorful "10 Megapixels!" sticker plastered to its body. And that's the bottom line in the consumer digital camera biz.

Thanks for noting this, Eolake! Good fun!

12:44 AM  
Blogger Engin Kurutepe said...

Well, although interesting this test is obviously flawed. It is not the same to downsample a 13mp image to 5mp and to take a 5mp image in the first place. The 13mp image has gone through bayer interpolation and does not contain full possible resolution of 13mp. When this image is downsampled to 5mp, the downsampled image will contain most of the information contained in the original image. And this downsampled image will be much superior to an image originally taken an 5mp because it didn't go thorugh bayer interpolation at 5mp.

2:36 AM  
Blogger Just Plain Hugh said...

A 13 megapixel sensor really only resolves about 3.25 megapixels worth of information what with the Bayer sensor and the anti-aliasing filter

A fairer test would be to make a 4 and a 1 megapixel print from a 13 megapixel camera.

The limiting factor with any camera over about 6 megapixels is the photographer, unless the camera is on a tripod camera movement is a much bigger factor than anything else.

10:14 AM  
Anonymous Anonymous said...

If Pogue's article makes people realize there's more to choosing a camera than simply buying more megapixels, he's done what he set out to do. Most folks, including I'll bet the overwhelming majority of his NY Times readers, just want to make nice pictures of the kids, and do so with a minimal outlay of cash and effort. Talk to them about "Bayer interpolation," and they'll head for the aspirin aisle.

10:31 AM  
Blogger Robert Roaldi said...

Our culture trains us to buy more than what we need. The societal default is to ask for more, all the time.

Think of all-you-eat buffet restaurants.

Look at the performance-oriented automobiles we buy. There isn't a driver in ten thousand who has the skill, let alone the gumption, to drive their cars at those vehicles' handling limits. But it doesn't stop people from buying the illusion.

The photo test was perhaps not 100% valid. But it was as valid as a lot of people need.

We are affluent. We have a lot of money and we like to spend it. There are bedroom drawers all over the world filled with several generations of reasonable-to-top quality 35 mm cameras and lenses that hardly anyone uses. They will soon be joined by almost just as many digicams of one type or another. People like to buy cameras, but they do't necessarily like to take pictures.

The digicam marketing frenzy has very little to do with photography. But, the high sales volumes helps bring down the prices of the equipment so that the average photographer can afford them so it's useful in that sense.

2:41 PM  
Blogger Carl Dahlke said...

If you're going to talk quality you have to ask quality for what?, and judged by who?

A big factor in how peple judge images is the extent to which the viewer has learned to see quality differences. Differences that may be obvious to a fine art photographer who has spent years refining their prints may be literally invisible to a viewer who has never spent time working with images.

Most people can't tell the difference between a silver gelatin print and a platinum print without a bit of education. And once they learn to see the difference - well then they are a different person. Education changes perception.

Unless you are in a context where quality matters, the quality discussion is beside the point. My parents were satisfied with snapshots of their life that were technically totally wretched. They were not creating "pictures" they were creating "memory hooks". The appearance of the pictures was incidental to their function. And since appearance was incidental the quality they produced never changed.

If you are in a context where quality matters, then the technical quality can be judged mostly in terms of what you are trying to achieve. A catalog shooter may care a lot about very accurate color and not so much about resolution that will not make a difference to the small catalog prints.

If you are a "fine-art" photographer then technical quality matters mostly if technical deficiency gets in the way of realiZIng your vision. Does the resolution matter? Depends on your vision. Sometimes it matters a lot and sometimes not at all.

To tie all this back to Pogue's experiment.

I would suspect that his results were perfectly accurate. If you didn't care about the pictures he showed you and you weren't an experienced viewer - why would you see any differences?

12:16 AM  
Blogger Bob said...

I'm amazed at how many people praised this test. If the question were, "How large a file should I send to my print lab?" the results may have been meaningful.

But Pogue was claiming his tests could reveal something about the differences (or similarities) between cameras with large or small MP counts. He should have had a chat with a scientist or engineer before publishing this sort of misleading information.

I believe the average person can't reliably distinguish $10/bottle red wine from $60/bottle red wine. However, I would NOT test my theory by sending digital files downsized at various resolutions to some print lab. But if I did, I would expect those who understand wine to ridicule me.

Pogue's so called test did nothing except convince many people that his opinions should be ignored, or at least be regarded as highly suspect.

2:25 PM  

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