Table of Contents

• Image Quality And Large Aperture Lens
• The Advantages of a Very Large Aperture
• You Don’t Need F1.4 to Get Background Blur
• A Few Important Nuances

Image Quality And Large Aperture Lens

One might think that a lens with a very large aperture is automatically the best option available, but that is not entirely true.

In general, extremely fast apertures involve compromises in image quality.

As an example, I will quote a sentence from a 1980s Leica brochure:¹
“The performance of the Leica R Summilux F1.4 matches that of the Leica R Summicron F2.”

It is also worth noting that the F2 version focuses as close as 0.45m, while the F1.4 version is limited to 1m.

And today, the F2 version costs on average three times less than the F1.4 version.

The Advantages of a Very Large Aperture

The main advantage of a very large aperture is the added flexibility it provides while shooting, as well as a shallower depth of field.

So unless, like me, you enjoy night photography and want a little extra margin in low light, there is often little reason to spend two or three times more on a 50mm F1.4 lens instead of a 50mm F1.7 or F2 lens.

You Don’t Need F1.4 to Get Background Blur

A 50mm lens at F2, or even a 135mm lens at F3.5, is more than capable of producing beautiful background blur, or “bokeh” as it is called in Japanese.

Likewise, for portrait photography, it is generally best to avoid shooting too wide open (for example f/2.8 on a 50mm lens) when using a manual-focus lens, in order to reduce focusing errors.

A Few Important Nuances

Of course, there are budget-oriented 50mm F2 lenses with poorer image quality than some 50mm F1.4 lenses.

Likewise, I imagine the performance gap between fast and slower lenses has narrowed considerably over the past few decades.

1. Page 32 (in french) https://www.summilux.net/documents/LeicaR4-Brochure-150dpi.pdf ↩︎