I've had a few discussions on here about Neutral Density Filters with people who were confused about them - so here are a few tips if anyone is interested. For what it's worth, this shot was taken with a Hoya ND400 filter (as well as a Hoya Circular Polarizing Filter) and a 30 second shutter speed:
Firstly, an ND filter is supposed to darken the light entering the lens evenly (thus "neutral density") - it shouldn't create a colour tint, although they will always cause at least a slight colour cast and inferior filters will potentially cause severe colour issues. The Circular Polarizing Filter (CPL), on the other hand, cuts down reflected light in certain situations - in the case of this photo, allowing the water to become see-through so we can see the submerged rocks.
To understand which ND filter to buy, you can work out the number of "stops" that you want to reduce the light by. Each "stop" or "EV" is half/double the light, so to reduce the light by 3 stops you need to reduce it to 1/2 x 1/2 x 1/2, i.e. reduce the incoming light to 1/8th of the original. So an ND8 filter generally means it reduces the light by 3 stops. 10 stops would be 1/1024, so an ND1000 is a 10 stop filter. And 9 stops would be 512 - an ND400 is close to 9 stops.
You can also work out what shutter speed you are after. If you're shooting in bright light at 1/2000th of a second and you add an ND8, your shutter speed will now be 1/250th - not enough at all to slow down a waterfall to get the cotton-wool look, or to smooth out the ocean, or whatever - but probably enough to sync a flash.
But if it's sunrise, your shutter speed is 1/50th, and you add an ND1000, you will now go to a shutter speed of 20 seconds for the same exposure - and things will get interesting as far as moving water, clouds, etc. Add the ND400 instead and the shutter speed will be more around 8 to 10 seconds - just close the aperture down 1 stop (e.g. from f/8 to f/11) and you're back to the 20 seconds.
So, if you want the really long exposure effects, go for a quality ND filter (made by B+W, Lee, Hoya, etc.) of around 9 or 10 stops - an ND400 or ND1000. If you just want a few stops to enable flash sync in bright light, the ND8 might be useful.
As an aside, you can stack filters - an ND8 and an ND400 will give you 3 + 9 = 12 stops of light reduction. Also, the CPL filter will reduce the light by about 2 stops, so ND400 + CPL = around 11 stops.
Finally, there have been questions in the past about how to focus when using these things - they will likely be way too dark to auto-focus and too hard to see through to manually focus at the aperture/ISO you are shooting with. The answer depends a bit on the camera you are using, but one or more of the following options should be possible:
- Remove the ND filter, set up the manual focus and composition, then carefully add the ND filter again without disturbing the camera on the tripod.
- Change the mode of the LiveView display so it is always bright.
- Open the aperture right up, compose and manually focus, then stop down again.
- Turn the ISO up high, compose and manually focus with LiveView, then bring the ISO back down.
You are a star! I have been looking into this for a while. I recently got an Hoya ND8 and am planning to get a Hoya ND64 or ND128. This will allow me to have more flexibility than getting just a ND400. Think this is a good route to go?
Thanks for the explanation! I get it more now... The lady at the shop I went to buy one for offered me one of 2 I looked at her blankly and sAid I didn't know what I wanted or needed and she said ok and put them away!! These shops bitch abut ppl buying online! With service like that.... Gah! /rant anyhow so http://cameraparadise.com/Hoya-Variable-Density-ND-Filter-72mm-1406.html could be an ok option for sea scapes during the day??
Thanks so much for all this info. I purchased a graduated ND filter. I have used it once or twice but I see to get a blue tint to my images.
I'm planning on getting over to the lake later this week to see what I can do to improve. It may have been my white balance with that shot or it may have been that it was taken middle of the day rather than early or late in the day.
@k1w1 If you shoot to RAW files you can more readily fix the white balance after the fact - either way, you should be able to reduce the blue tint. The idea of the graduated ND is to reduce the brightness in the sky to balance with the land; I find it easier to do this while processing the RAW files.
@pizzaboy i should have been more specific - its a 9 stop variable filter so I've got plenty to play with...well we'll see how it goes when I get out with it!
Thanks for the tuturial Mick. I was looking them up on Amazon this morning trying to decide which one to use for my Nikon and now I saw this. You helped me make up my mind :)
This is great, thanks for writing this. The only problem is that I came here just now because I'm completely bogged down in a very complex mathematical computation involving a reliability study I'm doing for work and now the one working brain cell I had firing is shot. I shall be back, but I think I'll go look at pretty pictures until my brain can reboot.
I just had a "aha moment" reading the last paragraph!! I have the Hoya ND400 filter and definitely love it! My problem has been the focus issue due to, of course the darkness when the filter is attached, so I have been focusing and composing the shot and then putting the filter on. This is a hassle, so I am excited to try using my live view and changing the ISO or f-stop to focus!! Thank you!
Mick, Thank you for this informative tutorial. You have made it so simple for the lay person. These filters are not cheap. The threaded filters are specific for a lens and I have heard about Lee, Cokin , hytec & others with their large rectangle/square ND filters with holders/adapters. For, those planning to get into it, try it with welding glass with rubber bands which is under 10$ and see if, long exposure is for u.
I think I will cut ans paste this info... And breath through the read. Thank you for going into this Mick, I am looking at using some filters, but do not know where to start.
@sparkle Sorry, I think I meant to reply to @brav - so Richard, " I think you'll use an nd400 more - you really want to slow things down to at least 30 seconds or even a couple of minutes." - I really wouldn't bother with ND64 or ND128.
Thanks so much that was really helpful. I have bought a B&W 10 stop filter and then was told I wouldn't ever use it and should have bought a graduated one!! At least now I know it will come in handy as I originally thought!
I almost bought a variable ND filter but something about the reviewer comments scared me off. I think there was talk of a purple cast or something so I went with a kit instead.
@andrina The B+W 10 stop filter is awesome. I actually have one but it is too small for most of my lenses so I picked up the Hoya 9 stop in a larger size. I took this one of a shipwreck at a surf beach back in July with the B+W 10 stop:
I've been wanting to delve into the world of ND filters for daytime long exposures for the longest time but always felt so intimidated by them! This thread is a huge help. Thanks Mick! I'll definitely bookmark this for later :D
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I'm planning on getting over to the lake later this week to see what I can do to improve. It may have been my white balance with that shot or it may have been that it was taken middle of the day rather than early or late in the day.