SUNNY 16 rule = ISO = shutter speed @ f/16. Just changing the shutter speed to 1/250th and leaving the aperture at f/16 would underexpose the sky by 1 and 1/3 f/stops.
Yes but that will not allow for a shallow Depth of Field.
Maybe you missed the preamble. Here is it again:
My objective, not necessarily the OP's: Shoot a foreground subject in the shade with portable strobes and with a bright background in the distance (sunlit hills for example) at the normal exposure appearance (not washed out). And I wanted a somewhat shallow DOF.
Using the Sunny 16 rule, at ISO 200, one would need 1/200s at f/16 for the sunlit background. But f/16 IS NOT what I what. To achieve shallow DOF using f/5.6, one would need to go to a shutter speed of 1/1600. That’s fine for the background, but there is still the strobe to deal with. The
high shutter speed syncing is not a problem with an electronic shutter camera like a Canon G10 but impossible with a modern DSLR since the sync speed is closer to 1/200.
The next tool to use would be to lower the ISO. Let’s say the camera can only go down to ISO100. This means that we could reset the shutter to 1/800s which helps but is still two stops faster than sync speed. And that is as far as we can go without lightening the background or affecting the DOF which is not per our artistic vision.
One could next go for the aperture adjustment, but we’ve already noted that it would alter the character of the image. A small aperture would also increase diffraction effects, making in focus objects lose contrast and resolution. Once again we do not want to change the aperture! That will make the background sharper which is against my intent. We already used up the range for the ISO, so the next tool we have to bring the shutter speed down is to put the 2 stop ND filter on the lens.
Now finally the shutter can be lowered to 1/200 so that the camera can fully sync with the flash. But the flash power was also reduced by 2 stops from the ND filter and 1 stop from ISO reduction, I know. I also know that my 400ws strobe usually ends up set around 1/10 power from 8 feet away so there is reserve capacity available by simply raising the power setting three stops. The effect of the flash through the ND filter and ISO reduction is restored while the distant background is unaffected by the flash.
Obviously the method requires reserve capacity in the flash. At least three stops worth and more if you wish to darken the sky further. If you don’t have it, then it won’t work. But one should not just make a blanket statement that you can’t or shouldn't do this with a ND filter. Sure there are other methods, as you proposed, but the other thing I said is that unless you’re doing documentary work, photography is about the
art . Techniques are used to achieve the artistic objective. If your vision of the image calls for a blurry but properly exposed background, you’re not going to want to use f/32! You’re going to want to use a different method. Others such as UK Photographers use different methods like HSS. That’s fine when their equipment allows it.
The method I outlined above works for me. In the example below, the subject was facing away from the sun standing with the sun coming over her right shoulder. A diffused 400ws Elinchrom was the main light aimed at her left shoulder (coming from the right of the picture). A Nikon SB900 speedlight was the fill source through a mini softbox near the camera about 8 feet away. The lights were triggered by a hot shoe mounted Pocket Wizard. A 1 stop ND filter + about a 1.5 stop polarizer were over the lens. The EXIF data says the exposure was 1/160s, f3.5, ISO 100 at about 2PM on a sunny day. Foreground and background were both exposed the way I planned in terms of brightness and appearance.
just adjust to fine tune :