Originally posted by prinze18 So, I was out and about on sunday and wanted to attempt to take images of a water fall.
The sun was harsh and was not really suitable for taking but I tried anyway. As I tried to allow a longer exposure(Tv mode), I either over exposed the image or I "froze" the water. I was wanting to capture a "cotton candy" effect. I read in the shutterbug that a ND filter would be useful. True?
Take a look at the Ultimate Exposure Computer
Relationship Chart. A bright sunny day is going to be an EV 16 environment as seen in the
Exposure Value Chart. As the lowest ISO value we have on the digital cameras is ISO 100, follow the
ISO100 column down until you hit 16. Now to the right in the shutter speed portion, you'll see the lowest shutter speed possible at f32 is 1/60 of a second. Probably not slow enough to blur water and depending on the lens, f32 might not even be available.
There are a few ways around this, one is to allow less light into the lens via a filter or filters. ND filters simply lower the amount of light being let into the lens. A polarizer does the same but has other useful properties. A polarizer provides about two stops of light loss. This is equivalent to a ND4 / 0.6 ND filter. A ND8 / 0.9 ND filter will provide three stops of light loss.
Going back to the
Relationship Chart, and saying we will be using f22 instead of f32, follow the f22 column up for three stops and you'll have a shutter speed of 1/15 of a second. Nice thing about filters is that as long as you don't induce vignetting, they can be stacked, a ND8 with a polarizer would be five stops of light loss. That gets us down into 1/4 of a second shutter speed at f22 or 1/8 of a second at f16.
You can get a single ND filter with higher light loss:
- ND.3 (exposure adjustment = 1 stop)
- ND.6 (exposure adjustment = 2 stop)
- ND.9 (exposure adjustment = 3 stops)
- ND 1.2 (exposure adjustment = 4 stops)
- ND 1.8 (exposure adjustment = approx. 6 stops)
- ND 3.0 (exposure adjustment = 10 stops)
- ND 4.0 (exposure adjustment = 13-2/3 stops)
- ND 6.0 = (exposure adjustment = approx. 20 stops)
- Vari-ND = (exposure adjustment = 2-8 stops
Another way to achieve the effect of slow shutter on moving water without having filfters is to use multi-exposure. The K10D and K20D offers a way to do this. You can take up to nine exposures that are combined into one exposure. The end exposure of the final photo is correct for what was metered and because the movement of the water is not static, the effect is to blur the flow in the same way that a slow shutter would.
I think it is also possible to accomplish this with multiple digital photos of the same scene in post processing programs, but I don't have any experience with this.
Thank you
Russell