Pentax K mount or Canon FD?
 

I am getting ready to go on a shoot to Africa. I am taking a 50mm 1.8 and a 90mm 2.8 along with the kit lens. I would love to get a Sigma 30mm 1.4 before I go, but I don't think my pocket book will allow that before I leave. I have been looking at both Canon FD lens and Pentax K mount lens with adapters as a low cost option to get something a bit wider before I leave. I was hoping someone with some experience could let me know if they like one option over the other, or if I am wasting my time with both of them. Any help would be appreciated.

Re: Pentax K mount or Canon FD?
 

I would go with Pentax K mount lenses over Canon FD lenses for one simple reason - there is no focal length multiplier. That is, a 50mm K mount lens is still 50mm when adapted to the EF mount, but there is a 1.25x multiplier when dealing with FD lenses. This may not be a bad thing at longer focal lengths, but is a problem if you're looking for a wide-angle lens.

Re: Pentax K mount or Canon FD?
 

Thanks for the reply. I am leaning towards the K mount as well. The only thing that was scaring me was that I have read of people removing a tab on the Pentax K mount lenses. Depending on what you read, the tab may or may not interfere with the mirror on the camera body. Do you know anything about this?

Re: Pentax K mount or Canon FD?
 

I have a number of Pentax Takumar M42 (screw mount) lenses that I use on my 7D with an adaptor. One of the lenses had a similar tab. I took the lens to a local camera repair shot and he removed the offending appendage.

Re: Pentax K mount or Canon FD?
 

I'd definitely try to aviod FD, as they will require an adaptor with an additional glass element. This will give you more crop as well as a much softer image.

I'm using a Pentax 50mm f/1.7 on my 550D at the moment without any problems. I believe some lenses are worse that others, and the problem is also less of an issue on APS-C cameras than of the 5Dmkii - the bigger mirror on that is more easily obstructed.

Re: Pentax K mount or Canon FD?
 

Thanks for the replies/advice all. I read a few things in various places, but it is nice to hear from people with real world experience. I am definitely going the K mount route. From what I have gathered, the tabs on the lens are an issue on full frame mirrors and not on crop sensor bodies. I may still remove the offending tab as it seems like a pretty easy modification to make. Thanks again, as always this forum has proven invaluable.

Re: Pentax K mount or Canon FD?
 

If you're hoping for someone faster and wider with Pentax K or Canon FD, then I would say you're wasting your time with both of them.

You're much more likely to find a Pentax M42, Nikon or OM mount 35/2, 28/2 or 24/2. An OEM lens will likely cost the same as a Sigma 30/1.4, so you're looking for a 3rd party like a Vivitar or Kiron.

Realistically, your best economical choice is probably the kit 18-55IS lens.

Re: Pentax K mount or Canon FD?
 

I have both a Canon 5d and a T2i. My first was the 5D, and I adapted several Nikon and and Pentax lenses. I did do some minor surgery to flanges on the back of a lens or two, to avoid the mirror interference. In one case I recall just pealing of a "flance on the back of a Nikon lens. On a Pentax lens, I had to shorten a tab. Probably not a clean a job as a shop would do, but it was over and done without issue quickly.