ND Filter Questions.

<p>I am thinking about purchasing a 5 stop ND filter, It is the screw on type. I have been using a Cokin P with Hitech Filters. I have been happy with that system up to a 1.2 ND. Anything above 1.2 seems to leave a cast that is hard to remove. On a cloudy day at f/16 I can get 3 second exposures with what I have. I would like to get over 10 second exposures at f/11.</p>

<p>I will be using it on a Nikon 12-24mm lens. Occasionally I will use a slim Nikon Polorizer with the ND filter, this will surely cause vignetting. If I use an 82mm ND with a 77mm step down ring, will that take care of any vignetting problem? Also, can anyone reccomend the best ND for the buck?</p>

<p>Thank You,<br>

Derek</p>

<p>I've had colour cast problems with dense Hitechs - one thing that sometimes works is to take a pic without the filter, and use that as a reference to colour-correct for the ND in post. I've also had fewer problems combining two ND filters than using one dense one - so you could try a Hitech 0.9 or 1.2 combined with a 0.6. The dogma says, don't combine filters if you needn't, but this has worked for me. It's also cheaper and avoids vignetting if you stay with your current holder.</p>

<p>John, I use a slim Nikon Polorizer with a P holder that has only 1 slot and it still vignetts from 12-14mm. With 2 slots used, I lose 12-17mm. I have 3 P holders that have been altered in different ways. Funny thing is they finally have Lee 4x4 systems in stock and I am considering the round filter.</p>

<p>I used to use Cokins and gave 'em up because of the very obvious magenta/purple cast. I switched to Hitech and find them to be essentially neutral.</p>

<p>I've been using B+W ND filters for years and am pleased. No color-cast to mention. You'll need a step-<strong>UP</strong> ring to go from the 77mm filter ring on your lens to an 82mm ND filter.</p>

<p>For the <em>occasional</em> use of adding a polarizer to the ND re: vignettting concern, I'd be inclined to live with it and very modestly crop when needed. Vignetting, if any, will likely disappear by 14mm setting on the zoom ring. If time permits this afternoon I'll mount my 12-24/f4 with a 77mm ND and Nikon Slim Pol, shoot some frames in the 12-15 zoom range and let you know what I see.</p>

<p>I have a 6-stop screw-in B+W; it has no colour cast worth mentioning. Instead the Cokin graduated NDs I have are magenta-ish. The B+W ND isn't exactly cheap, but it's good - so i cannot really answer best for the buck, since I learnt with some cheap filters that cheap isn't cheerful.<br /> I doubt whether a step-up ring will solve that much; it does not "immediately become 82mm", so a good part of it is still 77mm and can still cause vignetting. Next to that, there is a huge price difference between 77mm and 82mm filters already.<br>

[edit] now see the CP goes ina Cokin P - if a single P-filter holder vignettes up to 14mm (it did for me), adding a filter below it will also add vignetting, you'd probably end up around 15mm.</p>

<p>As Lily said, I would just live with the vignetting and zoom to ~14/15mm to be rid of it; maybe you'd gain a fraction with a 77mm screw-in ND and stack a 77mm screw-in CP slimline directly into that.</p>

<p>Singh Ray makes some good solid ND filters to fit lenses or holders. The one I have fits a Cokin P holder.<br>

I believe they have a 5 stop one too. Go here to get started looking:<br>

<a href="http://www.singh-ray.com/SolidND.html">http://www.singh-ray.com/SolidND.html</a></p>

<p>Joe Smith</p>

<p>Derek, what camera are you using? Some are more sensitive to IR light when you get to denser ND filters. Tiffen has a line that has IR blocking built in. I would reccomend looking into those if your cast is only in areas like the highlights.</p>

<p>Also, have you thought about shooting something like a color checker passport? Might help zero it out.</p>

<p>I just learned that Hitech has a whole new lineup of IR blocking ND filters. And, Hitech offers them in a cokin P size. May go that direction?</p>

<p>I would see if your camera needs the IR blocking or not. Coming from the Nikon world, the D200 really showed IR, but the D7000 less so. Go do some research on IR in long exposures to see if your tint issues match what IR looks like.</p>

<p>It is not as much camera related as it is density of the filter. ND filters with out a hot mirror filter built in do not even slow down IR. And that is the biggest reason other then just poor filters to get a color cast.</p>

<p>Most all of the variable ND filters have IR blocking built into them.</p>

<p>Filter color cast is something you have to live with, specially the ones with higher density or when you use more than one filter.<br>

You can reduce it quite a lot changing brands but you'll never eliminate completely the problem as you are fixing a piece of tinted material on the front of your lens and the path of the light that reaches your sensor.<br>

Hitech filters were marketed as producing no cast as opposed to Cokin performance, the same way as Lee Filters saying the same. At the end, Hitech also shows a magenta cast and Lee a blue one, even if it is very much lighter.<br>

Lee filters are very good and quite neutral as are Singh-Ray ones, but you also have to pay a considerable price premium to get them.<br>

At the end of the day it is important to get as less cat as possible and in a way that doesn't disturb your color preferences, adapting also your white balance adjustments during capture and RAW conversion and/or correcting the cast in Photoshop (or your editor of choice, if it offers the tools).<br>

I had your lens and as it was said by other members at the short end of the focal range you need to be careful to avoid vignetting, besides it produces an image circle that allows to use it with FX camera above 20 mm. So to use more than one filter the safest way is to use larger ones, either the 82 mm you referred or moving to Hitech (or Lee) 100 mm, instead of the 85 mm of P size.</p>

<p>I luckily picked up a 77mm B+W Hot Mirror, about a year ago, for £10 ($15!) and when added to my slim Haida (Chinese) ND 3.0 (10 stop), get neutral results after doing a Custon WB on a grey card under the lighting of the day.</p>

<p>I don't have a 'with' and 'without' on file, but remember they were different.....magenta without, <em>I think. </em>It was one of those, 'busy' places with no people 90 second exposures. Auto WB in CS4 fixed it instantly.</p>

<p>No IR leakage and no obvious colour shifts.......I suspect there would be on film though. An ND3.0 can lead into reciprocity regions.</p>

<p>Nobody seems to have addressed the first part of the OP's question yet, so here goes.<br>

Derek, a 5 stop ND won't be enough to get you the exposure times you're looking for. A 1.2D filter is already equivalent to 4 stops ND. Increasing the density by another stop only gets you in the range of 6 seconds at f/16. If you want to be working at 10+ seconds at f/11, then you'll need at least a 7 stop filter (2.1D or 128x).</p>

<p>I was lucky enough to come across a stockist that had some ND filters in an assortment of densities and sizes up to 12 stops and 82mm diameter. Even with this almost visually opaque density I haven't noticed any IR problem on a D700 or D800 - maybe these cameras have particularly good IR filtering built in? I have, however noticed that the colour is a bit shifted from neutral. I always shoot RAW, so this really isn't an issue, but if I only shot JPEGs then the easy solution would be to take a custom WB through the filter. This only needs a sheet of white paper handy to accomplish.</p>

<p>FWIW, the filters I came across were round aluminium mounted uncoated glass filters. The lack of coating doesn't appear to be much of a problem, after all you're losing most of the light transmission anyway. The filters were also incorrectly marked, with one marked 32ND actually being -12 stops! For this reason they were dirt cheap. I seem to remember I paid around £6 (~ $10 US) each for a number of them in various densities and sizes.</p>

<blockquote>

<p>It is not as much camera related as it is density of the filter. ND filters with out a hot mirror filter built in do not even slow down IR. And that is the biggest reason other then just poor filters to get a color cast.<br>

Most all of the variable ND filters have IR blocking built into them.</p>

</blockquote>

<p>Some cameras have IR blocking filters built into their sensor stack, and the degree that filter works varies by camera. So yes, camera does play a role.</p>

<p>As for the OP, one other thought is to buy a range of filters and stack. Get a 5-stop, 7-stop and 3-stop and combine as needed. Just beware flares and vignette.</p>

<p>I've got the same 6 stop ND from B+W as Wouter, no noticeable color cast.</p>