I tried 50mm 1,4 and I'm amazed how good it is in dark, BUT because of its DOF f1,4 becomes useless. At least to me. If you're taking a portrait photo with f1,4 on 50mm face will be half sharp half blurred and that is not good.


here is the example (thanks to Google)


if I'm right this is taken with f1,4 and tho photo look nice but the birdhouse is out of focus. only closer part is sharp.


if you can buy 1,4 buy it, you can always go to narrow aperture, but if you buy 2,8 you can never go to 1,4