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’s E mount camera. 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.
In forum discussions of the service, there’s inevitably the question (usually phrased emphatically as a statement of fact) of whether one would be better off selling the lens and rebuying it in the new mount. After all, the cost of the conversion service is not insignificant (and also not readily available publicly). So, the first order of business is to understand the cost of conversion and how it compares to simply selling the lens and buying it again new.
I wrote to Sigma USA, as their mount conversion page suggests, to get quotes on the couple of lenses I was interested in converting before sending them. Once I sent them in, I got a service order with actual estimate. It’s worth pointing out there was a difference between the email quote and the estimate once Sigma had the lenses in-hand.
| Lens | Email Quote | Actual |
|---|---|---|
| Sigma 35mm f/2 DG DN | $230 | $250 |
| Sigma 100-400 f/5-6.3 DG DN | $250 | $350 |
I also did some price research. I looked at how much similar condition copies were going for, if I were to sell the lenses and re-buy. I also got quotes from MPB for good measure, as the lowest-effort, lowest-return option for selling them. This way we can compare the cost of conversion to the cost of the lens new, used, and what I would likely sell it for. The table below has those estimates, as well as the new price.
| Lens | New | MPB Quote | Rough Used |
|---|---|---|---|
| Sigma 35mm f/2 DG DN | $700 | $265 | $450 |
| Sigma 100-400 f/5-6.3 DG DN | $1000 | $330 | $650 |
The mount conversion is not cheap, but it’s not terrible (around 1/3 of the price of the lens new), but it is nothing compared to the cost of selling to a company like MPB and rebuying new, so I didn’t consider either of those options. But if I were to sell the lenses and then rebuy in roughly the same condition used, the different is probably just minor overhead costs per-lens.
This is the thought behind a lot of the sentiment around this service from people responding to forum discussions: that selling and rebuying the lens used is basically cost-neutral.
However selling and rebuying used on classified type of forums and sites has non-monetary costs like time and effort, and carries some risk with it. It is generally not my favorite activity. And that assumes you can find similar condition lenses in the alternative mount, which is not always the case. The Sigma 35mm f/2 seems in short supply in any mount. It seems like a lot of churn to engage in, especially for lenses I already have.
There’s also the “why get these converted when you could buy a ___ lens instead”, and on that question, I find both of these lenses to be the best balance of what I care about (on the spectrum of size/weight/image quality) for what they are in both mounts.
The mount-conversion service
So… I proceeded with the conversion service! For science (and convenience). I filled out the online repair form specifying a mount conversion from L-mount to E-mount, printed the resulting page, packaged up the lenses as well as I could, and shipped them to Sigma America (insured for the new replacement cost). I included only the front and rear lens caps, and kept the hoods, and kept both the rubber ring and tripod shoe ring for the 100-400.
Looking at the tracking delivery time, it took approximately 3 hours after Sigma received the lenses to provide me with an invoice (this is a turn around time that gives me a lot of confidence if I ever need to have any Sigma gear serviced… which I haven’t to date).
It also took 1 week, door to door, for the two lenses. I sent them on a Tuesday, received the invoice on Wednesday. The following Monday afternoon I got notice that they were being shipped back, and had them delivered Tuesday. When I got them back, I was eager to take a look to try to understand what had been done.
Before I get to that though, there is something I was curious about with the process. I assume the back part of the lens barrel (which appears to me to be a solid piece) has to be replaced since L-mount and E-mount have different depths and diameters. On both lenses, this appears to be one solid piece. On the 35mm, the serial number itself is on this piece, so I was curious if they were replacing this, does it get re-engraved on the replacement part of the barrel? Is the serial number different? What does this mean for warranty registration, etc? The serial number is in the middle of the lens on the 100-400, so if the mount-end of the barrel is being replaced I wouldn’t expect it to change.
For these two lenses, this “service” simply exchanged my L-mount lenses for E-mount lenses. When I received them, I noted that the serial numbers on both lenses were different. Sigma confirmed when I asked about warranty implications (if I need warranty service, I just have to reference the order number for this service). They said otherwise it would’ve been a 2-month trip to Japan to change the mounts on the lenses. My assumption is that they don’t talk too in-depth about this to preserve options based on what they have available.
I’m actually quite fine with this? Effectively I paid 1/3 the cost of the lenses new to exchange it for a different mount, and continue receiving warranty coverage for the lenses.
For lenses I love, that I bought a while back, that I want to continue using on the new system I’m moving to? I think that’s a pretty good deal considering the level of effort and risk involved (virtually none), and the turnaround time (during the holiday season too).
Would I do it again?
I’m not completely leaving L-mount yet, but if I do, I have a couple other Sigma L-mount lenses that I would consider bringing with me (the 24-70mm f/2.8 Art II). I would definitely use this exchange service again.
I can’t promise that my experience would be universal, but since there’s not really any first-hand information out there about this service, it felt important for me to write about my experience. If you, like me, your priorities lie more along the low-effort and low-risk sides of the triangle, rather than the low-cost side, then I think it makes a lot of sense. The quick turnaround made it even better — I was fully prepared for it take a couple weeks. If you, unlike me, are looking for the lowest-cost way to swap, maybe with more effort or risk, this isn’t it.
Hopefully, dear reader, you found this useful.
Update
About a month after I wrote this up, I did use the service again, to convert my Sigma 24-70 DG DN II Art lens from L-mount to E-mount. The turn-around time was even quicker (<1 week) than for the previous two lenses, and (and this is why I’m writing an update) the lens mount was converted it was not exchanged for a lens in the destination mount. It was converted instead. The E-mount lens I received back has the same serial number as the L-mount lens I sent in, and it was the same minor scuffs on the filter ring. The cost of converting the 24-70mm f/2.8 DG DN II Art was $345.
What I can conclude is that, in the US at least, right now, Sigma may either exchange a lens or convert it as part of their Mount Conversion Service, depending on whether they can do it in their service center or whether it will need to be returned to Japan to convert.