What’s the Best FStop? Do You Need to Stop Your Lens Down?

If you told me years ago that nearly every lens on the market made today would be super sharp wide open, I’d be elated. But if you also told me that lenses could be too sharp, I wouldn’t believe you. I mean, how is that possible? Years ago, you’d just consider the best fstop on a lens based on sharpness. These days, that’s not necessarily the case. Photography has changed, and people want something different. So, with over 12 years of testing lenses under our belt, we’re going to talk more about the best fstop and how it’s changed over the years.

How It Used to Be: The Story of the Best Fstop

When I first started The Phoblographer over 12 years ago, lenses were much different. They were mostly developed for film cameras and then ported over. Very few were developed with the idea of being digital first. Back then, you used to have to stop the lens down to get to the best fstop. On full-frame 35mm, it used to be around f8 to f11. It varied based on which medium format option you were using, but you’d try to get the same equivalent. This also applied to APS-C and Four Thirds sensors. 

Shooting a lens wide open set you up for a host of problems back then:

  • Your lens would be very soft wide open, which is nice these days.
  • Your lens might have a bunch of color fringing, which can be seen as lens character these days.
  • Vignetting was abound, which is now easily correctable.
  • You’d also probably not get your subject in focus because DSLR and Film SLR autofocus wasn’t so great.

Then things changed.

And Then the Zeiss Otus Line Happened

I remember there was a short period of time where a lot changed. A bunch of tsunamis and storms destroyed lots of factories out east. Then, oddly enough, the industry bounced back with good optics. They came to Zeiss and Sigma first. The Zeiss Otus lens lineup was pretty much unbeatable. The Sigma Art lens lineup was also unbeatable for image quality. Then Sony got it, Tamron caught on, Nikon, Tokina, etc. Optics became a ton better.

This was interesting because Zeiss started to market that you didn’t necessarily need to stop the Otus lens lineup down. They showed the press tons of MTF charts where the Zeiss 55mm f1.4 Otus lens would have equivalent sharpness of the nearest competing lenses. However, the Otus was doing it wide open while the competition was doing it at f5.6 or f8. It was remarkable technology, if not incredibly flawed. Zeiss did what they do with an insane price tag, no weather sealing, and a few other things. Then Sigma’s 50mm f1.4 Art started to outdo the Otus. Sigma has always been strong with clinical image quality at the cost of build quality, character, and autofocus speed. It was the same back then as it is today. 

So by all means, back then, Zeiss began to say that the best fstop is shot wide open. That started to change the rest of the industry. Combine this with the rising megapixel count on camera sensors and improved flash technology and you’ve got a winner.

Today, What Is the Best FStop?

Today, it’s hard to find a lens that isn’t sharp wide open. Lensbaby purposely does this, and that’s awesome, but all other camera and lens manufacturers strive for sharp wide-open performance. The best fstop and all it means has changed since then. There used to be the idea of the sweet spot, which referred to when the lens was at its sharpest. And today it’s more about a balance between pleasing bokeh and sharpness. It depends on what sensor format you’re using, but generally, most photographers think the best fstop is either wide open, f4, or f5.6. Lenses are super sharp wide open, and honestly, most of us on staff rarely have good reason to stop down unless the exposure calls for it. High megapixels on camera sensors mean more value is given to a lens. Combine that with flash and what specular highlights do, and you’ve got a winner. 

Overall still, the best fstop is the one that fits the exposure. Need to stop down to f8? Then do it. Need an f1.4 aperture? Use it! These days, lenses are so good you don’t need post-production considering what cameras are capable of doing.

Chris Gampat

Chris Gampat is the Editor in Chief, Founder, and Publisher of the Phoblographer. He also likes pizza.