I recently puchased a T-ring for my D50 on ebay, should be here in a week or so. now i just realized today that an old film SLR i have here ,a Praktica MTL5, (pretty old cause it says made in the German democratic republic on it).. well it uses a 42mm screw mount for the lenses, same as the T-ring has. The camera has a 135mm f2.8 prime lens. Will this lens work on the D50 via the T-ring? will be fully manual and metering probably wont work right?