What Is Lens Sharpness and How Is It Measured?

If you’ve ever wondered how to assess the sharpness of a lens or perhaps read an MTF chart and been curious as to how it’s made, check out this short video that quickly runs you through the basics.

If words like modular transfer function, sagittal, meridional, and field curvature seem a bit daunting, don’t worry. Ted Forbes does an excellent job of breaking down how lenses function and how their characteristics can be measured objectively in order to be assessed and compared.

Lens performance is an incredibly subjective field, and many photographers will prefer images from lenses that have arguably worse MTF charts, simply because of how a lens’s characteristics might lend themselves to what a photographer is trying to achieve. And as Forbes notes, photographers can be very passionate about their gear, so his video is prefaced by a couple of disclaimers in the hope that he doesn’t upset anyone.

If this video didn’t sufficiently tickle the geek in you, be sure to check out the blog over at Lens Rentals, such as this article by the company’s founder, Roger Cicala, that compares the Sigma 35mm f/1.4 DG HSM Art, the Tamron 35mm f/1.4 SP Di USD, and the Zeiss Milvus ZE 35mm f/1.4. Grab your pocket protector and enjoy.

How important is lens sharpness to you? Leave your thoughts in the comments below.

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michaeljinphoto's picture

For my work, sharpness is pretty important and it's right up there with distortion as one of my major concerns. For my personal work, it tends to bug me less. I have a few super sharp lenses for when I'm specifically looking to take really detailed shots, but most of my favorite lenses to use are not all that sharp by modern standards.

Mr Reeman's picture

Loved this explanation (most of which was known to me) it laid out fundamental but import considerations in an easy to take in way. My own lens collection vary greatly in quality and cost (mainly tracking my increasing disposable income) however my sharpest lenses are not always the newest or most expensive. I feel Quality Control has been slipping for some manufacturers and lenses that should have never left the factory have and entered via the grey market. Sharpness will always boil down to a melange of technique, chosen aperture (for a given lens), light quality (soft/contrasty/etc) and post processing (self control?). However starting with a lens that is known or proven to be a performer really helps. However fashions in photography are (in my world of the art of photography - non commercial) mean that currently any sharpness is destroyed almost completely for an ethereal result. Such fashion and fads are a swinging pendulum and this is already changing.

Great article Ted, thanks.

Was farm reflection scene at 6:06 shot using a black mirror?