Neutral Density filter
http://en.wikipedia.org/wiki/Neutral_density_filter
It takes light away (read the article for the precise thing it does)
Basically, if you want to catch a waterfall with the mist effect, what you want is to take the photo with a long exposition. So you will capture the movement of the water.
To do this, you need to get the speed up (or down, depending how you look at it) a lot, but that brings more light in. So you need to compensate with ISO and aperture. USe the lower ISO and use the max f number.
The problem is that in very bright light it wont be enough:
Using sunny 16 rule (
http://www.photomigrations.com/articles/0403200.htm ):
f16 at ISO100 speed:1/100 would be the exposition. YOu can have a bit more, a bit less, but we are assuming a bright day, so lets use sunny 16.
You need to use a very slow speed. That means that you need to have a speed of 1 sec, or 1/2 or 1/4. OR even 2 or 4 seconds to get that creamy effect.
See this post for the effect of shutter speed with a waterfall:
http://hankinslawrenceimages.wordpress.com/2008/07/22/shutter-speed-and-waterfall-photography/
You want a very low speed to get the effect. 1s looks good 6s also!
But you already are at ISO100 and f16. You cant dim the light any more. In my case its worst, because I have a Nex5, so it goes to ISO200, Im at 1/200 speed.
So to go to for instance 1 sec, you need to get
1s 1/2s 1/4s 1/8s 1/15s 1/30s 1/60s 1/125s
6 2/3s points of light less. (7 2/3s in the nex5 because of lower ISO being 200)
One way is to get an ND filter, and remove those points of light from the exposition.
It will still be hard in a very sunny day. The best thing would be to go at the late afternoon, but still it will be handy to have a ND Filter. For instance, for a late afternoon or shade you could consider f4 or f5.6 as the aperture.
YOu still have ISO100 and S=1/100. YOu need 6 2/3 stops less of light.
4 , 5.6, 8, 11, 16, 22, 30
That means almost 30. Your lens doesn't have it. It goes to 16, 22 top. So you still need LESS light! And in a NEx5 even one stop less.
Also, the sweet spot of many lenses is at 8, and some 11, so you dont want to go to 16. You want it at 8. That means that you can get only 3, 4 steps of light. So you need to substract between 2 and 4 steps of light. To get a 1s exposition. You cant get a 4s exposition still!!!! A ND filter will help you, you will be able to use f8, and get a very low shutter speed.
Another reason for a ND Filter in bright light is to be able to use your nice fast lens in bright light, and get shallow deft of field.
Agains, you are in a park, with very bright day, and want to take a subject with the background blurred. You want a very small aperture for that. YOu have a nice f1.4 manual focus like the 58mm minolta I have right now.
So, sunny 16:
f16, ISO 100, speed 100 (I will use 125 to make calculations of stops easier, but it is 1/3 less). In my case, again, NEX%, with ISO 200 is still worst.
So, you want less aperture, you want f1.4!!!! or f2!!!! to get nice out of focus background in very bright light. you need to go from f16, to f2, and not touch the ISO (cause you are already at the lower), you can only get the speed higher.
f/16, f/11, f/8, f/5.6, f/4, f/2.8, f/2, f/1.4
7 stops for f/1.4, 6 stops for f/2
you get those steps (actually you loose those steps) with a lower shutter speed (Less time, I get confused by this, because the number goes up, but actually the time is less, sorry if I did this wrong in my post).
1/125 1/250 1/500 1/1000 1/2000 1/4000
6 stops for the NEx5N, 5 stops for the Nex5.
So you see that you cant go very far in a sunny day. Of course the solution is, come back in the late afternoon, or go to a shaded place, or wait for a cloud to block the sun a bit. But sometimes thats not possible. An ND Filter will help you in those extreme sunny situations, and when you want a very big shutter speed (1s or more).
Remember that for the waterfall you will also need a tripod to stabilize the shot.
Ti@go
I havent seen fireflies in more than 20 years. Im jealous.
The waterfall / river is easy to do. But you need to be prepared. I almost did it last april in a vacation I made, but I needed an ND filter to achieve more slowness. A pity I didn't have with me.
enlighten me, I'm new to this, what's an ND filter, and why is it needed to get that smooth water effect?
And yes I'm sorry, I've actually gotten so used to fireflies that when they come in the summer I just say "Cool" and move on. I stopped just deeply staring years ago. It's a shame how you get acclimated to even the most amazing things. I wonder if that's how marriages fail...
Of course, I'll hopefully also have the camera!
