1/2 F stop

[dannat]

Has anyone done any tests between lens with 1/2 a stop difference, I am considering 2 lens, one is f1.6, the other is f2... Is it going to be subtle over 30 sec exp or wil there be a bigger diff meaning I should get the f1.6 (the 1.6 lens is MF only, the f2 is AF)

[Terry B]

What do you plan on using the lens for?

[space oddity]

22 second exposure instead of 30 second is the difference. Could be something to be said for stopping the lens down to f/2 to get a bit better quality of image. Quite often, those super fast lenses are awful in performance wide open.

[dannat]

Terry used for nightscape, wide fields, either as single exp or stacked or stitched to video

[Terry B]

For that use then as stated above you can get away with a bit shorter exposures with the faster lens. For stars it would make little difference as they would probably be extremely undersampled anyway. Assuming a very short focal length, a star would be smaller than an individual pixel. The faster lens has to be a bit bigger in diameter so in theory has slightly better resolution but optical aberation may null that effect anyway.
If you can afford the faster lens go for it as you can always stop it down and probably achieve a better image than the slower lens wide open.

[troypiggo]

Can you tell us more about the lenses? What brands? What focal lengths? Aside from one lens being slightly faster than the other in terms of f-stops, could be over-riding factors that would tip you the other way such as optical quality.

Most lenses wide open, ie at those maximum apertures, are not the sharpest and/or have more noticeable chromatic aberrations. They improve drastically when stopped down a little. Varies from lens to lens, but each does have a sweet spot. So after stopping each of those down a touch to some sweet spot, might be f/2.8, might be f/4, if it were me I'd be considering the overall quality difference of the lenses over the 1/2 stop maximum available aperture since it may not even be used at that.

[dannat]

They are Mu4/3 lens OLY 12mm f2 & slr magic 12mm f1.6...on raw files the OLY has much more distortion wide open, I think I'll get the slr magic

[troypiggo]

I'm not as familiar with Oly gear, but what I said above still stands.

Googling some reviews:
Not a good one for the Oly: http://theonlinephotographer.typepad.com/the_online_photographer/2011/11/olympus-12mm-review.html
Not bad for the SLR Magic, but he also speaks better than the above about the Oly: http://www.stevehuffphoto.com/2011/10/20/the-slr-magic-12mm-f1-6-hyperprime-lens-review-for-micro-43-by-steve-huff/
Scroll down for bunch of reviews on the SLR Magic: http://www.43rumors.com/slrmagic-hyperprime-12mm-f1-6-lens-officially-announced-bye-bye-noktor/

[Wavytone]

Only lens I would consider using wide open - let alone on stars - is a Leica. The rest - 2 stops down.

[Max Vondel]

Go for the faster lens Daniel
Even if stoppered down while imaging
:D