Before we had light meters in cameras, we had Sunny 16: set the aperture to f/16 and the shutter speed to 1/ISO in mid-day sunlight. That method of exposure still works, but we have very sophisticated light meters in cameras these days, so many think we don’t have to worry about Sunny 16 any more.
So why do I say it’s still an important thing? Simple: it helps you evaluate systems and lenses and their potential usefulness from just specifications.
This came up recently with the Nikon 1 and the 70-300mm lens. At 300mm it’s really 810mm equivalent in a very small package. But it’s also f/5.6 on a small sensor. The first thing I do when I hear about a new lens/system like this is do the Sunny 16 calculation.
My measured ISO on the V3 is 100, not the 160 listed by the camera. So in sunlit subjects I’m expecting an exposure of f/16 at 1/100. Well, 1/100 isn’t nearly good enough for an 810mm equivalent lens, even one with VR. So let’s run that up to 1/800. Three stops (1/100->1/200->1/400->1/800). Okay, so we have to run the aperture down three stops: f/5.6 (f/16->f/11->f/8->f/5.6). Eek.
What the Sunny 16 calculation tells me is that the V3 and 70-300mm combination is right on the margin for sunlit subjects. If I’m going to use that lens in the shade or edge of day, I’ll be boosting ISO, stat. ISO 400 is as far as I usually want to go with the V3 for best results, and that’s really about ISO 250, and I’ll end up with just a little over a stop better off. Using my old Nikon Field Guide Sunny 16 rules, that means I’m wide open at a solid shutter speed in heavy haze to maybe thin, high cloud cover. In open shade and moderate overcast, I’m going to have to boost to ISO 1600, which is about as far as I want to push the V3’s sensor.
So just from using the Sunny 16 rule and my dynamic range tests on the camera, I can tell that the 70-300mm will probably work for me on safari in Africa during the day, but will start to push me into tough-to-process results or too-long shutter speeds at the edge of the day. Which is why Nikon really needs to make a 26-75mm or 25-100mm f/2.8 lens for the Nikon 1 series. At least then I could switch lenses, lose some focal length, but gain back ISO when shooting at the edge of day. Of course, with the FT1 I can just bring my 24-70mm f/2.8 FX lens and get the same thing, but it’s a big heavy lens and I lose all but the center AF sensor by using the FT1.
The 70-300mm has an odd ramp of aperture with focal length, by the way. It immediately jumps from f/4.5 to f/4.8 when you move from 70mm. Then it has a long slope until it hits f/5.6 at about 175mm, at which point it is f/5.6 for all longer focal lengths.
Sunny 16 is your friend. Try using it more often to calculate whether products will be appropriate for your use. In the case of the V3 and 70-300mm, I’m thinking the 70-200mm f/2.8 on the FT1 might be a better choice for shooting that’s not outside in the sun. Even the 70-200mm f/4 gives me more flexibility than the 70-300mm CX.
Don’t get me wrong, though. The 70-300mm is a welcome lens for CX. It’s mostly a friendly weather, mid-day lens, though. Knowing that before you head out the door to some exotic place might help you make the right lens choices.