The emf adaptors are kinda expensive, but allows you to set the focal length and do micro adjust and the AI focus tracking works.
I use the normal af chips on lens adaptors which just allows me to get a focus assist light when it is in focus while the exif will always say "50mm 1.4". With some lenses the AF is spot on , others I need to focus it on the border between light on/light off.
I found no reviews of generations, but I have spent many hours browsing for thees and came across all types of them - here's my impression of the nomenclature:
No chip on the adaptor: your camera will say act as if no lens is attached. some cmaeras force you to enable shooting without lens. Focus confirm doesnt work. EXIF data may be difficult to handle.
1st generation: Requires MF mode. fixed exif 50mm F2 (or whatever other number they chose for you), focus assist works. Auto focus tracking modes do not work. ETTL cant negotiate the correct numbers.
2nd generation/3rd generation - no EMF: like 1st gen but better built (3rd gen better built than 2nd gen), fixed exif 50mm F1.4.
2nd generation/3rd generation - with EMF : you can now program the f and F numbers yourself through the aperture dial (not user friendly interface), which helps you with EXIf data and ETTL metering. AF microadjust allows you to calibrate back/front focus.
4th generation: Advanced EMF, AF simulation allows AF modes to be used which means old cameras that require a lens with AF to give focus "beeps" or "lights" will work, and AI focus will work, too. Focus locking works as well. These cost quite a lot.
PPA adapter is an adapter with any of the EMF capable chips on it. You can by adapters without chips and buy the chip yourself. Then it is not PPA before you create it yourself by attaching the chip. a 1-3 gen without EMF does not make it a PPA (Personalized programming Adapter).
Sellers do seem confused about which gen they are selling, so I think that the only real options are:
- Chip with no EMF fixed 50mm F1.4 ( I use this on my Pentax M 50mm F1.4 )
- Chip with EMF
- 4th gen AF simulation chip. (was going to get this for my Helios 58mm F2, and Orestegor 200mm F4, but the seller wanted 30E for each and didnt budge, so I got no. 1 for these , too , hehe).
Expect to pay 30E on ebay for an adapter with one of the advanced babies pre-attached. 10E for those without EMF and 15-20 for normal EMF. 1st gen seems out of the market, or at least not interesting.