How fast of a 28mm are you looking for? Seems like about $80 for a good fast prime would be the budget. The 2.8's go for about $50 + shipping on ebay from Japan. ~75$ on Amazon https://www.amazon.com/Canon-Lens-FD-28mm-2-8/dp/B00AAZG5YA Just to add here the F2 is harder to find and a $1300 purchase, pretty expensive for a manual focus lens if you not buying it as a collector item.
Wecome to the forum, Fizz, I have a TX which is a bit similar, I use a 28mm F2.8 lens. I get excellet images from it. this lens is plentiful and cheap. If you want something farster t will cost more.
One thing worth saying is that there are a LOT of 3rd-party 28mm f2.8 lenses out there, all of the manufacturers made them and they generally got things right optically, and they'll often have good reviews - but usually it isn't for the FD version. FD mounts are mechanically complex compared to most other 35mm cameras, and there seem to be a LOT of poorly-designed 3rd party mounts that failed in use, usually they won't stop down at all, or have other iris-related issues. I deal in old cameras and lenses on eBay and see a lot of them, every so often I sell a job lot of faulty lenses and there are always a few with FD mount in the mix. The one I usually recommend is the Tamron Adaptall 2 28mm f2.5 - it's a very good lens and Adaptall 2 FD mounts are fairly common and reasonably cheap, and generally work well. In the UK they're usually cheaper than Canon lenses. There's also a good 24mm f2.5, but they're not nearly as common. Unfortunately it's months since I've had either of them, so I can't help with this.
I agree with you , Markus, I use my Tamron Adaptil2 28mm F2.5 on not only my canon, FD mount cameras, TX, AE1 Programe and my digital EOS cameras,this includes other cameras such as my Pentax, K1000, and several other film cameras as well. Having variety of adapters that suit the camera/len combo is a big help. I have never had any issues using the lens on the different cameras.
For my own use I've got Nikon, Pentax K and M42 mounts for Adaptall - no actual lenses at the moment, but I hope to pick up one of their macro lenses sooner or later, I'd probably keep that for my own use. Unfortunately there is no good EF mount, the only one I've seen is a bit of metal which is basically a spacer between the camera and lens. The best bet is probably using the M42 mount in a M42-EF adapter with an AF confirm chip. There's an album of pictures I took with the 28/2.5 on a Pentax K200D here https://www.flickr.com/photos/150868539@N02/albums/72157719061822833
I have only had one adaper with a AF confermation chip, A Nikon K mount to Canon EOS, it did not seem to work, it may have been me or the adapter but I did a work around by using my liveview screen and the magnifying button (+) a couple of times to achieve fine focus. The 200mm to 400mm push/pull style of lens works fine on my Nikon F90X and F601 cameras.
Markus, i may be way off base here but would the Pentacon 29mm ƒ2.8 fit the bill? its an M42 so fully manual but it performs pretty well via the M42 adapter on my M50
Nice detail in this shot, Caladina. To be honest I have never come acros this lens, It has similar results to the Tamron Adaptall two, 28mm f2.5 which I do have, along with the Canon 28mm f2.8 FL mount and the super Takimar 28mm f2.8 M42 mount. Of the three the Adaptall two seems the sharpest. Now for the fly in the ointment, I have a Nikon K mount 28mm f1.8 G, unlike the others this lens has autofocus but is the sharpst of them all. Since this is a canon forum and I have not tried it on any of my Canon cameras, I have a Adapter for it to the Canon but have no autofocus using the adapter.
I was wondering what a EOS mount 28mm f1.8 would cost so I looked it up on Ebay around 600 dollars secon hand and up to 10000 dollars for the latest ang greatest.