Originally posted by Eruditass When you want to use both
1/4000, ISO 100, and F1.4 is an EV 13 environment. EV 14 for the same at IS0 50. Add the CPL at ISO 50 an you are close to EV 16. Hard to imagine needing f1.4 in an EV 16 environment much, but OK.
Stacking a CPL on top of a ND filter is probably only going to be an issue on wide lenses. Let's hope there is a 10-16mm f2.8 at some point, so that we actually have a fast wide lens: 1/4000, f2.8, and ISO 100, is an EV 15 environment. With just a CPL you are a little above an EV 16 environment.
So for any f1.4 lens, stacking a CPL over a ND grad will work, and for any lens where stacking won't work, there isn't enough aperture to become a limit.
I guess the question then becomes, how much will a ND filter cost, over getting it "free" in the camera? Considering you can get a three stop ND filter for the same price as a one stop ND filter, the "free" one stop solution seems a little less likely to be as viable in the larger scheme of things, so maybe its cost is worth bearing.
If the new camera body has ISO 50, that's great, but if it doesn't, I don't see it as being an issue. The K-r already raised shutter speed to 1/6000, so that camera already is a half stop above the examples above. If the K-5 matches the K-r or raises the shutter speed to 1/8000, you've got your extra stop or close enough to it to take all the f1.4 shots you want in an EV 16 environment. Yeah, I know, you really want to take f1.2 photos. ;-)
Thank you
Russell