FA 50mm f1.7 vs FA 50mm f1.4?

After waiting for a good deal on an f1.4 I have compromised and ordered an f1.7 from ffordes, for use on my DS and MX

I could probably got an A or M f1.4 easier but I wanted to have autofocus.

How many stops difference between 1.7 and 1.4?
ALso any views between quality of these lenses?

Thanks

Kevin

Well, the 1.4 is heavier - 7.8oz as opposed to 6oz because it has 7 elements in 6 groups where the 1.7 has 6 in 5 groups and the front element is larger.
Optically, I expect that there's very little in it between the two and the 1.4 is, as the figures show, less than half a stop faster and this difference would rarely be significant unless you regularly shoot in very low light.
Faster lenses are more expensive because they are harder to produce and contain more of the costly optical glass and lenses faster than 1.4 are incredibly expensive and the image quality is often not quite as good.
Really fast lenses are designed for professionals who 'absolutely must get that shot' and can afford to buy them in the first place.

I'm sure you'll be more than happy with your 1.7, it is a very fine lens indeed!

Hi,
Generally speaking, the differences between the 1.7 and 1.4 lenses is similiar across the board. The 1.7s tend to have a better flat field performance and because of this Pentax always used to recommend that they should be used for macro work, in particular if using bellows. The 1.4s have always been optimised for "3D" and as such to tend to give better modelling. In reality these differences are very minor and both perform extremly well and certainly much better than the zooms.

Enjoy!

Kim