f-stop conversion factor for mount adapter?

Started Feb 18, 2013 | Questions thread
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f-stop conversion factor for mount adapter?
Feb 18, 2013

for K-30 camera body:

I've got a Minolta Rokkor-X MD f1.4 50mm lens, and I'm trying to decide if it's redundant to my Pentax-DA 35mm F2.4 AL. I can buy an MD --> K mount adapter, but what I don't know is whether the result will still effectively be an f1.4 lens, or I'l lose enough light that I might as well use the Pentax f2.4 and forget the older lens.

It's about a $70 swing, because the adapter (Fotodiox) costs about $40, or I could try to just sell the lens on ebay and maybe if I'm lucky clear $30 to put toward a new lens.

Any advice/information I should consider? Anyone using MD lenses on their K-5 or K-30?


 bob5050's gear list:bob5050's gear list
Olympus C-5050 Zoom Pentax K-30 Pentax K-3 Pentax smc DA 18-135mm F3.5-5.6ED AL [IF] DC WR Pentax smc DA 18-55mm F3.5-5.6 AL WR +2 more
Pentax K-30 Pentax K-5
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