Sigma Lens Mount Change Service

This could well be of interest to some:

http://www.sigma-global.com/en/lenses/cas/service/mcs/index.html

Unfortunately it only seems to be available on their new range of lenses and the lens has to be already available in the mount for which you wish to change.

I was all ready to buy the new Sigma 120-300mm f2.8 and tpay out for a Pentax conversion but it's not possible

Despite the service only appling to their new line of lenses, I personally think it is a very good idea. Sigma are putting forward some great options that know other lens manafacturer currently provide.

What are they charging for this service though? I would have thought in most cases it would be more expensive than selling your lens and then purchasing another in your new mount?

I'd be really impressed though with a lens that could fit say two different manufacturers bodies say Pentax and Canon, Nikon and Sony or whatever...or even better a body that could take lenses from more than one manufacturer without requiring an adaptor. There's room in the market for a new camera body manufacturer with this as their USP.

The latter point about multiple mounts on a camera is a very old idea, but I'll bet the manufacturers wouldn't like that at all. That is, even if technically possible at a realistic price level.

First they are releasing very interesting and high performing lenses that compete with camera manufacturers' top lenses (think 35mm 1.4 art, 18-35 1.8....)

Now this idea that would mean your investment in lenses is protected as you can change your bodies in the future.

In a world were bodies are commodity and changing continuously, they are turning around the business model: you choose your lenses, not your bodies..... Interesting

What is the depreciation like on new lenses though these days. One reads of so many
anecdotes (admitedly taken at face value) where the seller claims to have sold at virtually no loss or even in some cases made a small profit. Lenses don't seem to behave like cars which automatically drop in value the moment you drive it off the forecourt.

Almost Everything depreciates the moment you buy something new. Sigma are well on the ball the new 24-70 f/2 looks amazing as does the 135mm f2. Might be a wake up call for the camera manufacturers to reduce their prices. The reviews for Sigmas Art range are just so positive.

It's wonderful news for Canon and Nikon users with Sigma lenses who can now upgrade to a Pentax K-5

I believe this can be the case if you buy used lenses and you know when to buy /sell. Top lenses keep their second hand value quite well. But if you buy new you generally will lose when reselling, with some exception (price increases, exceptional deals, etc.)