The megapixel race, image resolution and print size…
In the last year or so I have started to take a step back as well as a big step forward with my photography and I would like to share the reason why. I started to think about why I continued to seek something more than I already had. I became so caught up with getting a better file, a better output and the biggest possible print size that the heart of what photography is about became a distant memory. Photography is (for me at least) about capturing a moment, creative composition, lighting, timing, expression, story telling and is not about sensor size, megapixel count, dynamic range, AF speed, FPS. Although I do not deny that those things can aid an image, or make it possible to get the image in the first place. I always wanted to ‘future proof’ myself and make sure everything I shot had huge resolution, buy then I asked myself, why?
I can understand the desire for more resolution. Let’s face it, it’s easy to win at top trumps, with those huge numbers, it’s great zooming in on the computer so that you can see every tiny ill placed hair on your face and it allows you to print huge, right? Well, no, not really and here’s why.
Let’s look at this a little more objectively…
The normal viewing distance for a print is roughly 1.5 to 2 times its diagonal measurement.
This allows you to take in the entire image in one view, any closer would mean you’d be only able to look at parts of the image at one time. So let’s say that you are printing a huge image that stretches 60 inches x 40 inches, the diagonal measurement of the print would be 72.11 inches. You can work out the diagonal measurement of any rectangle by using the formula:
Diagonal = √(l2×w2)
In English this means; the length multiplied by the length added to the width multiplied by the width, then find the square root of that number, or just google ‘rectangle calculator’ and get the online people to do it all for you. So, our print of 60in x 40in would be worked out as below:
60×60 = 3600
40×40 = 1600
3600 + 1600 = 5,200
Square Root of 5,200 is 72.11 – this is our diagonal measurement in inches
72.11 inches multiplied by the closest viewing distance (1.5X) gives you 108.17 inches from our 60 x 40 inch print.
Here is the next part of the equation.
The human eye is said to realistically be able to distinguish individual pixels at a distance of around 10 inches on a screen that is 300dpi (dots per inch). You might have noticed, most phones made today are well over this number, some over 600/700dpi. You’d be hard pressed to see those pixels at all, regardless of the viewing distance. As the viewing distance increases, the harder it is to see the pixels, meaning the less pixels you actually need. Looking at an image from 20 inches away would mean you only require a 150dpi image to get the same quality as 300dpi at 10 inches…
Take a look at the illustration above. Looking at a 10×8 print at 282 dpi from 12 inches will give you the same quality image as viewing a 20×16 at 141 dpi from 24 inches. Other than your brain realising that the 10×8 is actually a lot closer to you then the 20×16, the image will appear the same size and the same quality, although its resolution is half that of the 10×8…
Putting this into practice.
If we take a 24 megapixel image, with a resolution of 6000 x 4000 pixels, and printed that image to the 60×40 inch size we started with originally, it would give you a 100dpi print. That might sound very low, however we have already established that this huge image would need to be viewed at around 108 inches away. Let’s just go with 100 inches, to be well on the safe side of the equation… At 100 inches the eye cannot see pixels denser than 35dpi. Well, we have an image nearly three times denser than that, so we could view our image at around 35 inches and still not be able to make out the pixels.
In fact, viewing a 60 x 40 print at 100+ inches means you only need a 6mp-8mp image to get the optimum quality that the eye can see. Sure, if you do then press your face up against it, it’s not going to look as crisp, but why would you do that?
This common sense approach illustrates just how crazy the megapixel race really is. I am hearing folk that are dissatisfied with their 42mp Sony, 50mp Canon or 36mp Nikon…. Why? Well in my opinion people are just obsessed with specs. They’re easy to compare, they’re pretty factual, but in the same breath, pretty meaningless also. At least they are above a certain point.
If you are the type of person that just loves looking at high resolution images, then the above will not sway you at all and there is nothing wrong with that at all. I can even understand the appeal of clicking 10 times on your mouse and still getting a perfect image… The problem comes when people think that high resolution means better photographs, because it does not. At times it means quite the opposite. You need steadier hands, faster shutter speeds, a tonne of storage space, better computer and printing equipment. Our houses and walls are getting no bigger, our eyes are getting no better, so don’t join the megapixel race just for the sake of it.