Why 24-26 megapixels is just about right

When cameras were analog, people cared about resolving power – but of film. Nobody purchased a camera based on resolution because that was contained in the film (and different films have different resolutions). So you purchased a new camera only when you wanted to upgrade features. Analog cameras focused on the tools needed to capture an optimal scene on film. Digital cameras on the other hand focus on megapixels, and the technology to capture photons with photosites, and convert these to pixels. So megapixels are often the name of the game – the first criteria cited when speculation of a new camera arises.

Since the inception of digital sensors, the number of photosites crammed onto various sensor sizes has steadily increased (while at the same time the size of those photosites has decreased). Yet we are now reaching what some could argue is a megapixel balance-point, where the benefits of a jump in megapixels may no longer be that obvious. Is 40 megapixels inherently better than 24? Sure a 40MP image has more pixels, 1.7 times more pixels. But we have to question at what point is there too many pixels? At what point does the pendulum start to swing towards overkill? Is 24MP just about right?

First let’s consider what is lost with more pixels. More pixels means more photosites on a sensor. Cramming more photosites on a sensor will invariably result in smaller photosites (assuming the sensor dimensions do not change). Small photosites mean less light. That’s why 24MB is different on each of MFT, APS-C and full-frame sensors – more space means larger photosites, and better ability in situations such as low-light. Even with computational processing, smaller photosites still suffer from things like increased noise. The larger the sensor, the larger the images produced by the camera, and the greater the post-processing time. There are pros and cons to everything.

Fig.1: Fig: Compare a 24 megapixel image against devices that can view it.

There is also something lost from the perspective of aesthetics. Pictures should not be singularly about resolution, and sharp content. The more pixels you add to an image, there has to be come sort of impact on the aesthetics of an image. Perhaps a sense of hyper-realism? Images that seem excessively digital? Sure some people will like the the highly digital look, with uber saturated colour, and sharp detail. But the downside is that these images tend to lack something from an aesthetic appeal.

Many photographers who long for more resolution are professionals. People who may crop their images, or work on images such as architectural shots or complex landscapes that may require more resolution. Most people however don’t crop their images, and few people make poster-sized prints, so there is little or no need for more resolution. For people that just use photos in a digital context, there is little or no gain. The largest monitor resolution available is 8K, i.e. 7680×4320 pixels, or roughly 33MP, so a 40MP image wouldn’t even display to full resolution (but a 24MP image would). This is aptly illustrated in Figure 1.

Many high-resolution photographs live digitally, and the resolution plays little or no role in how the image is perceived. 24MP is more than sufficient to produce a 24×36 inch print, because nobody needs to pixel-peep a poster. A 24×36” poster has a minimum viewing distance of 65 inches – which at 150dpi, would require a 20MP image.

The overall verdict? Few people need 40MP, and fewer still will need 100MP. It may be fun to look at a 50MP image, but in all practical sense it’s not much better than a 24MP. Resolutions of 24-26MP (still) provide exceptional resolution for many photographic needs. It’s great for magazine spreads (max 300dpi), and fine art prints. So unless you are printing huge posters, it is a perfectly fine resolution for a camera sensor.


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