Lenses

What’s important in a lens

As an amateur photographer, I have been up and down the list of focal lengths, in primes and zoomes, more times than I’d care to admit. I always seem to arrive back at 35mm though. I feel like I’m always searching for the next 35 though. When you’re a photography enthusiast it’s very easy to fall into reading about lenses, watching videos about lenses, and subsequently buying lenses. Especially in Leica M-mount, where the choices—especially in 35mm—are overwhelming and span the 70+ year lifetime of the system, you can easily cycle through buying and selling several different lenses of the same focal length.

It’s tempting to ask, in exasperation, which lens is the best? Because I’ll have that one. Unfortunately, it’s not an easy question to answer. You have to decide what’s important to you in a lens, what isn’t, what you can live with, and what you can’t. Because they’re all compromises. And unlike a Canon R-mount camera, where you have two choices, Leica Lens List lists over 90.

How do you know what’s important to you? I can’t tell you that, but I can tell you what I’ve arrived at for myself, as told through four 35mm lenses that I like very much. So this is a sort of review (of what I care about) of the Voigtlander 35mm f/2 APO-Lanthar, the Voigtlander 35mm f/2 Ultron, the Light Lens Lab 35mm f/1.4 Aspherical, and the Leica 35mm f/1.4 Summilux-M ASPH FLE II.

I am a huge fan of Sigma’s optics and cameras, but I recently decided to consolidate some of my camera gear and switch to a Sony E mount camera (α7R V). But I wanted to continue using some of the Sigma lenses I have and love.

For a number of years Sigma has offered a mount conversion service to convert Sigma lens you already own from one mount to another, as long as the lens is offered in the destination mount. It’s an intriguing prospect in the abstract, being able to switch systems and not rebuy all new lenses. However, there doesn’t seem to be a lot of information out there from people who have had experience with it. I decided to give it a try, and write about my experience, breaking down the price I paid, the time it took, and to compare alternatives and provide some rationale for why I personally decided to use the service in late 2025.

Update: see below for an update based on my experience of converting another lens, my 24-70 II.