ND Filters? Tell me all about em please. :-)

[RbrtPtikLeoSeny]

So I've been trying to find a way to do nifty affects with long exposures. The basics I guess, nice smooth water with water falls, moving lights, stuff like that. I rrreeeaaalllyyyyy wanna do some long exposures with cloud formations though, and that's just impossible. I can never get the shutters slow enough.

I stumbled across the ND filter things recently, and I'm very interested now! Basically they just reduce the amount of light that gets to the sensor, thus allowing for godly long exposure that would be otherwise impossible?

What would be a good one? I found a bunch of B+W brand 77mm ones that I could use on my 17-40L. Is that a good brand?

And there are so many different ones! Like, ND .3, ND .6, and the one that looks crazy sweet; ND 6.0. I was thinking ND 1.8 would be a good start. Cuts back 6 stops of light according to bhphoto, but which one would you guys recommend? I'm guessing for the rushing cloud affect I would need a rrrlllyyy long exposure and the ND 6.0ish would be better? Ehhh....

Alright, last question, is there any other equiptment needed to use these? Like, my cam can only go up to a 30 sec exposure... would I need one of those cabel releases that allows for up to 3-7 hours or something?

Thanks alot! I know that's a lot to read... sorry...:p

[jjonsalt]

You may wish to consider a polarizer instead. It can always be used as a ND filter and just may give you an effect with the clouds and sky you may not otherwise get. B&W would be an excelent choice for a filter.

[Ikinaa]

Here's an example of a lightning.
Taken with a ND1000 filter from B+W, also called ND3.0, gaining 10 stops that way.
B+W is good quality, and you won't find a lot of manufacturers for ND3.0 or ND6.0...

Its out of focus. I took it with the EFs18-55 on the 20D, unfortunately, there's no distance scale.
With a ND1000 you simply can't focus, the only thing you see is darkness, so you have to focus before putting the filter on it or use the distance scale.

I took it in Manual Mode, then pressed the button.
Looking at the exif, I could have set the ISO to 100 and the time to 60s, even more as it is slightly underexposed, and of course closed the aperture... but I would have had to take the remote in bulb mode, because otherwise it's limited to 30 secs.

I hope that helps a bit.

here (http://www.schneider-kreuznach.de/pdf/filter/bw_filter_programm_e.pdf)'s the B+W-Filter catalog, interesting reading too...

ExposureTime - 15 seconds
FNumber - 5.60
ISOSpeedRatings - 400
(more exif included with the picture)

[scr7b]

You should have a search for "Kodak Wratten" Gelatin filters... They're just 3" by 3" sheets which can be cut to size, and your 17-40 has a little slot on the back where you can slip them in. I'm sure they're cheaper than screw-on filters.

You should be aware though, that ND 6.0 is HUGE, and will almost certainly mean that you won't see anything through the viewfinder!

[DaveG]

So I've been trying to find a way to do nifty affects with long exposures. The basics I guess, nice smooth water with water falls, moving lights, stuff like that. I rrreeeaaalllyyyyy wanna do some long exposures with cloud formations though, and that's just impossible. I can never get the shutters slow enough.

I stumbled across the ND filter things recently, and I'm very interested now! Basically they just reduce the amount of light that gets to the sensor, thus allowing for godly long exposure that would be otherwise impossible?

What would be a good one? I found a bunch of B+W brand 77mm ones that I could use on my 17-40L. Is that a good brand?

And there are so many different ones! Like, ND .3, ND .6, and the one that looks crazy sweet; ND 6.0. I was thinking ND 1.8 would be a good start. Cuts back 6 stops of light according to bhphoto, but which one would you guys recommend? I'm guessing for the rushing cloud affect I would need a rrrlllyyy long exposure and the ND 6.0ish would be better? Ehhh....

Alright, last question, is there any other equiptment needed to use these? Like, my cam can only go up to a 30 sec exposure... would I need one of those cabel releases that allows for up to 3-7 hours or something?

Thanks alot! I know that's a lot to read... sorry...:p

I like to use ND filters for the same type of shots that you described. I found that the "silky water" waterfall shot took an eight second exposure and like you - I could never get a slow enough shutterspeed.

Be careful about how you read the ND's effect. There's ND in stops (which is the only way that makes sense to me) and then there's filter factor. A filter factor of 2 yields only a one STOP ND effect. A FF of 4 is two stops and a FF of 8 is three stops. So that ND 6 you describe might be six stops or it might just be a filter factor of 6 (2 & 2/3 stops).

Although a Polarizing filter will knock off two stops of light it isn't always the best ND filter to choose. Sometimes you WANT reflection & especially in moving water. I shot a stream once and used a P filter. It nicely took all of the reflection off of the surface of the stream yielding a nice muddy brown bottom! I think that a P can be used as a ND but they are two different golf clubs with two different functions when it come to club selection, if you follow my golphing metaphor. Besides two stops might not be enough and then you're stacking ND filters.

You might want to look into some good quality resin filters and if you aren't doing this all that much check out the cheaper Cokin filters. These filters are placed in holders in front of the lens and since they are less expensive you could buy a set. I used Kodak Wrattan filters with my large format camera and they worked very well, although they are extremely delicate.

If you do decide to get a screw in filter then get the biggest size for your biggest lens. The you can buy inexpensive step down rings that will let you use the filter with all of your lenses.

[Mycroft]

I can't take credit for this one, as it was devised by a friend of mine, but it's such a good idea I thought I would borrow it. You can make a variable ND filter quite easily. All you need is a linear polarizer (linear because it's cheap), and a circular polarizer (to repolarize the light correctly for autofocus to work). Put the the circular polarizer on the lens, then the linear polarizer on top of the circular one. Rotate them in relation to each other, and voila, variable ND filter. You can block a -lot- of light this way and don't have to spend so much money on expensive ND filters that only block a preset amount of light. The image through the viewfinder may have a very purple tinge to it, but long exposures tend to remove the purple. If it doesn't, you could always shoot raw and adjust whitebalance later, or even do custom white balance in-camera with the filter on and set to the density you wish.

[Neilyb]

Try the Cokin filters, they are cheaper than one or ever two polorising filters and will get you started. I paid about £24 for the Holder, the adaptor and an ND grad filter (which also can be used as an ND as the dark area covers my 58mm lens). The separate resin filters are about £11. You also then have the option of buying any number of coloured and FX filters!

[StevenHanna]

I use the Cokin Z-PRO ND Grad filters (x2, x4, x8) and a LEE filter holder on my 17 - 40.
Love them. Expensive, but worth it.

Steven

[Neilyb]

On second thoughts, ig you are using L glass then you might want to consider the more expensive glass filters...

[RbrtPtikLeoSeny]

Cool, thanks everyone for the responces, and sorry it's taken me a while to get back to this thread.

How could a circular polarizer work like a ND filter though? That'd be pretty awesome if it'd work affectively.

[Jon]

A polarizer has a "filter factor" (which means "you have to adjust your external light meter's reading by") of about 2 stops, so it's the same as a 0.6 ND/2 stop ND filter. Using 2 polarizers and rotating them, you'll cut still more light to get the effect of a stronger ND filter.

[RbrtPtikLeoSeny]

Woah! That rocks! And a polarizer would have a lot of other uses as well. Hm, well, thanks everyone! Looks like a polarizer may be finding it's way onto my christmas list this year. :-)