[Tracie]

Hi guys

I really want to buy the Sigma 30mm F1.4 for my K5 and have found one on Trade Me website (New Zealands Ebay). However the seller says that it's a Canon Mount lens, does this mean it won't fit my Pentax?

Thanks for any help

[Nass]

Yes. Canon mount is for a Canon

[Tracie]

Ok thanks. It is REALLY difficult to find anything that is a Pentax mount then... Is there some kind of adapter I can buy?

[kenafein]

No you can't use an adapter to go from Canon mount to Pentax. It does work the other way around though.

[DogLover]

Ok thanks. It is REALLY difficult to find anything that is a Pentax mount then... Is there some kind of adapter I can buy?

It's also difficult to find parts for a Rolls-Royce. Just sayin'

[Tracie]

lol

[Adam]

In total there are over 30 current Sigma lenses that can be purchased new for Pentax, so have no worries - there are definitely lenses out there

If you add used stuff to the list then you're probably looking at more compatible lenses than any other manufacturer!

Sigma Lenses - Pentax Lens Review Database

Adam
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[RioRico]

There are a few issues about using non-Pentax lenses: register, mount, and control. REGISTER aka Flange-Focal Distance (FFD) is the distance from the lens mount to the camera frame (film or digital). MOUNT is the hardware for fitting the lens to the camera. CONTROL is the linkage scheme for activating the aperture. These all vary among camera brands.

REGISTER: Longer-FFD lenses mounted on shorter-FFD cameras can focus to infinity. Shorter-FFD lenses on longer-FFD cameras only reach infinity focus after being altered, often with more-or-less extreme surgery; or by using an optical adapter. Leica R, Nikon, and Olympus OM lenses are slightly longer than Pentax PK. Contax-Yashica C/Y, Petri, and M42 lenses are the same as Pentax or close enough. Minolta, Sony, Canon, Fuji-X, Konica, and all other Leica lenses are shorter FFD.

Optical adapters are available for some of those mounts. These act as short teleconverters (TCs) and somewhat impact image quality. If you have a very special lens, it will no longer be as special.

MOUNT: Most SLRs of the last several decades use bayonet or breech-lock lens mounts; some use screwmounts, either the common M42 (including Pentax Takumars), the Russian M39, or the Leica LTM|L39. Screwmount lenses can mount on Pentax PK with simple adapters, but Leica LTM|L39 still won't reach infinity focus. Some bayonets (OM, C/Y some Nikon) are more-or-less easy to modify for PK mount; some, like C/Y and Leica R, have modification kits and services available. But AFAIK there are no simple mods for Canon, Sony, Minolta etc lenses.

I've written up mods for NI, OM, C/Y, Exakta, Petri, and Argus lenses. The Impossible Lens Club here describe other mods. Some people *have* modded Canon lenses. That skill level is beyond me.

CONTROL: The three main methods of automatic aperture control (for stop-down metering) are: 1) mechanical linkage; 2) electrical contacts; 3) none. Canon, Nikon, and Sony-Minolta AF lenses use electrical controls that just don't work with Pentax. Most MF non-Pentax and all screwmount auto lenses have mechanical links that won't connect with the PK linkage either, or no links, but they can be used with totally manual aperture control. Some of these have little quirks that are beyond the scope of this post. Ah, yet more stuff to discuss...
________________________________________________

That's my long way of saying,: Forget Canon lenses, and Sony-Minolta, and groovy old Leica glass. But you're not stranded. Third-party lensmaker do (or did) make new lenses for Pentax: Tamron, Sigma, Samyang (Tokina and Zeiss have stopped). Many other lensmakers churned out Pentax-compatible glasss in the past, with a thriving market in used lenses. But Canon glass is just not worth your while. Cheers!