A few questions RE: ND filters

[Compaq]

I've found myself in several locations where I'd like to smooth the water out - mid day. When driving across our country, we climb mountains and drive past many nice waterfalls, streams and all that stuff. I try to frame stuff in my mind. Anyway, without a ND filter that would prove problematic.

So, I'm aiming my camera out on green trees on an overcast day. On ISO 100 and f/22 (just to use the extremes, I'd probably like to be around f/5.6-8 on a aps-c sensor) I'm getting 0.3 seconds. Not slow enough.

1 stop: 0.6 seconds
2 stop: 1.2 seconds
3 stop: 2.4 seconds
4 stop: 4.8 seconds
5 stop: 9.6 seconds

ISO 100 at f/8 gives me 1/25th

1 stop: 1/15th
2 stop: 1/8th
3 stop: 1/4th
4 stop: 0.5 seconds
5 stop: 1 second

This was metered off of a tree, I'd imagine water reflects more light than a tree, so these numbers aren't all that exact. Anyway, what would you say is the most versatile ND filter powah out there? Should I have just one, which one? Round or squared/rectangular? I believe there are ways of making a too small round filter fit a bigger lens by some sort of thingamagees you put on the lens, correct?

-Compaq

 

[Robin Usagani]

Get the 3 stops one. As far as size and shape, are you planning on getting common L lenses? If you are then I would buy a round 77mm. You can buy a cheap step up ring 58 to 77mm. So you have to use the ring when you use your 50mm and kit lens. When you buy 24-70L or 70-200 2.8L IS you won't need a ring. When you buy 35L, 24L then you need 72mm to 77mm step up ring.

 

[tyler_h]

50 f/1.8 is only 52mm

24L is 77mm
16-35 is the only (unless you get off brand) >77 at 82mm

Circular vs Square; ever planning on GNDs... then may as well go square.

 

[Compaq]

With three stops less worth of light, I'd have to get back when the sun has set, at least if I want to shoot at f/8, and that isn't very convenient 1000 meters above sea level half way home. Based on my little experiment three stops wouldn't be sufficient.

GND? Perhaps one day. When I feel I need them, I might get some.

 

[Robin Usagani]

tyler, really? I didnt know. My 1.4 version is 58 and so is my kit lens.

 

[Robin Usagani]

It doesnt take that long to blur the stream. Thats what you want anyway when the sun is kinda down or your range is too high and you will have blown area.

 

[tyler_h]

tyler, really? I didnt know. My 1.4 version is 58 and so is my kit lens.

A few of the cheap primes (28 f/2.8 + 35 f/2 + 50 f/1.8) are 52mm, along with the 135 f/2.8 Softfocus, 50 f/2.5 Marco and a couple of old slow zoom too I think.

The 24L and 16-35L sizings I listed is most recent versions; older 16-35 is 77 and I think the first 24 was the 72 you mentioned.