What I look for in a lens.

Sharpness and Pixel Counts. Does it matter?

You have heard it being said, “Sharpness is not everything.” Or “All lenses are sharp.” Some Photographers also recon: “8MP is all you really need.”

I disagree. If that was the case, photographers would not spend any more on lenses than what the cheapest entry level lens provides. Instead the professionals make use of some of the finest lenses out there and often recommend you to buy a cheaper body but spend more on glass. Why is that?

First of all, you can add huge amounts of blur in post-production, but you can’t make a blurry image much sharper.

Secondly you can trade some of your sharpness or detail for reduction in noise, better dynamic range, and for zoom or cropping, but you need to start with ample amounts of sharpness.

But why did they say these things? Perhaps they said these things at a time when high resolutions and sharpness did not matter as much as it does today.

Let’s look at a timeline of technology over the last couple of years.

post190-resolutions

Note: The 50% dotted lines indicate the resolution of a lens giving us at least 50% sharpness. Certainly if you had the Canon 5D or 5D mk II cameras between 2008 and 2012 you had way more resolution than you needed for your website or for display on any computer, mobile phone or TV. However, since 2014, things have changed a bit with 4K devices becoming commercially available. For a short time period, the results from Canon would not be enough to make full use of a 5K iMac.

post190-resolution ratios

In 2008, your camera might have had 5 times the resolution needed by your display, but this gap is closing fast. How long before we see 8K display devices? For how long will your images that you create today be considered of good enough quality to be displayed on those devices?

If you plan to print large images instead of displaying them on devices, then image quality matters and a sharp, high pixel count matters anyways. You will want as much sharpness as you can get and as little as possible aberrations and diffraction.

If you do not plan to print large images and only want to show your images via the internet, on today’s mobile phones, then your smartphone is generally more than capable to achieve what you need and you do not need a dedicated camera or lens. You can happily stop reading and snap away at those selfies, they won’t matter any longer than a couple of minutes anyways. They served their purpose to show you at this point in time.

How many pixels is enough? Go to the next page to find out.