Having Mega-pixels, our notion of Quality and Print


Let’s be honest about this: the notion of Mega-pixels has been shaped by the marketing engine of all the camera manufacturers in this world. One can’t really blame them. How well could a person or a manufacturer communicate with you how good the quality of the picture is in the shortest possible terms?

Answer: Mega-pixels.

Imagine one pixel represents a coloring box of a picture. The more boxes one has, the more refined the picture it will be. It is therefore simple to equate the number of boxes with the refinement one sees on the print of the picture or the screen.  Hence people aim for the largest mega-pixel (MP) count that a camera could have in its sensor. Pretty easy really.

That’s why Nikon’s D800 sensor has a whopping 36MP to say that it has the highest refinement when it comes to representing the picture taken. No argument with that.

However there are practical limits to how much a refinement can be represented on a piece of paper. The most basic way to represent how much a printer can show refinement in a picture is via Dots Per Inch or DPI (in old tech talk). It should be PPI or Pixel Per Inch now.

The thing is this: If the amount of image refinement of say 36MP is used to print on a paper media that is smaller than the intended size, then the extra information would be downsized to match the PPI of the print. Let’s use the below graph taken from West Coast Imaging.

As you can see, the way west coast imaging define photographic quality prints is of those that has at least 200+ PPI and if most of us print A4 size or 8 by 12 inch, that would mean 4 MP would be enough. So what happens if you use a 36MP sensor to print A4 size? That means for 9 Pixels in the sensor would represent 1 Pixel or Dot in the print media. In that case, it would mean that the computer has to let go of 8 pixels worth of data and downsize it to fit the media.

Of course one would argue that having more information would bring about a more accurate representation of the image. Again, I have no arguments against that.

BUT, having more data via more MP can only mean one thing: a deluge of unnecessary data being kept and more so when RAW file formats are being used.

So when one comes across MP, then these questions has to be asked, what is the size of the print you usually do when you do it (if you eventually do it?). And how much would one want to upkeep huge image sizes for the sake of maybe printing the size that you would want?

I personally would print the largest at 70cm by 100cm or 27 inch by 39 inch. And using the graph, the best sensor to have would be from 63MP onwards. Again, is that justifiable by cost versus perceived quality?

When I mean by perceived quality, it means one cannot see the differences in terms of quality when one sees a picture in its entirety. So by this statement, pixel peepers won’t be happy at all. But the majority of us look at the whole picture to see what we are shooting and usually 150 DPI/PPI is good enough. And back to the chart, 150PPI would result in using a sensor size of 22MP. For me, I can settle for 120 PPI because I don’t see a huge difference when I view the whole picture from a distance of 1m and so 16MP is good enough for what I do 99% of the time.  I would also say for those who likes to post edit, 4 pixels to represent 1 pixel on print of A4 is more than sufficient information to do it with high quality.

So the rest of the time? I share pictures via the Internet and the resolution of the screen is 1080pixels x 1920pixels = 2MP.

Hence to the question on why Lytro only have 1MP JPEG output which is good for a 5R print.

The key thing about Lytro is that its output and its intended use, is for the computer screen which is 1080 pixel tall by 1080 pixel wide which is the native resolution of the Lytro output of 1MP. Since it is only logical that refocusing and perspective shifting effects can only be seen on the screen and not in print (yes, you can’t shift on paper prints), then having any output bigger than 1MP is not necessary.

At the moment there is no two way about this. For every picture Lytro takes, it will take in on the average of 20MB of data. This is to allow the camera and its ecosystem to have the necessary information needed for the user to refocus and also to do perspective shifting. And the same data will be used for 3D viewing in the future. In some ways perspective shifting IS a form of 3D effect. And to demand 2MP worth of information for a JPEG output would at least mean doubling of data needed to do what the camera is doing at the moment.

So to have 1080 by 1080 picture on the screen, be it Living room TVs or the desktop monitor, it is more than sufficient for its intended use.

If a potential buyer is put off by Lytro’s seemingly anaemic JPEG output of 1MP, then the potential buyer has missed the point of the Lytro totally. And for that, I would rather recommend a simple point and shoot that has 10MP at least with no refocusing and perspective shifting feature.

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