Is this a good ND Filter?
 

Here's an ND filter (Light Craft Workshop - Fader ND filter (ND2~400) recommended from a wildlife photography forum. Will I need an ND filter for the Sigma 100-300 f4? The 82mm size costs $190. You can adjust it by turning it for more or less ND, from 2 stops to 8 stops to be exact.

Thanks in advance,

Caleb

Yes you will need a ND filter, perhaps 2, a #4 and a #8. Thier value will be evident if you shoot white birds. I use Hoya glass (a good deal cheaper than what you mentioned), and am not happy with it. I think it degrades the image slightly, but you get what you pay for.

This interesting type of filter is not a true Neutral Density filter but a modified polarization filter. As it was explained to me (I don’t claim to be an expert), it’s a linear polarizer with a circular polarizer mounted behind. The two halves of the linear polarizer allow you to adjust the darkness while the circular one restores the phase of the light that gets through so that your metering system works. If you pan in daylight or change to another camera angle the amount of “ND effect” will change as the plane of the filter changes with respect to the polarization plane of the light source. It will get lighter or darker. With that in mind, it still seems like it might be useful. Here’s another example:

Singh-Ray Filters: Vari-ND Variable Neutral Density Filter

One reason to go for the larger "professional" lenses is that you have rear filter slots that take little 42mm or so filters. Easier to insert and not an issue for flare either. That's the big thing I worry about with putting filters up front, they catch the light and are generally nowhere near so well coated as the lens itself.
Steve

A factor of all super telephoto pro lenses such as the 300mm f/2.8, 400mm f2/8, 500mm f/4, 600mm f/4, 800mm f/5.6 is that the front filter thread is normally very large - 122mm for example - and so to avoid the expense and weight of carrying a selection of huge front filters, a rear filter slot is built-in.

Some of the mid-aperture pro Nikkor ED-IF lenses such as the 300mm f/4 also have a rear filter slot.

The rear filter normally allows the insertion of 39mm (or 42mm etc) circular gelatine filters, or glass filter inside a seperate locking mount.

Special 39mm Polarizer filters with an external thumb wheel are also available.

I do own a few ultra-expensive 122mm Nikon filters for my 600mm lens.

The Sigma 100-300mm f/4 EX-DG does not have a rear filter slot, so you will need to use front mounted 82mm filters.

I do own a selection of ND filters, but rarely use them as much as polarizing filters.

Even on Canon XL lenses I use a front mounted 72mm or 82mm circular PL filter most of the time and only include the built-in ND filters during extra bright light conditions. Of note is that built-in filters on Canon XL lenses are not made of glass.

Hoya offer a complete range of glass filters at different prices, each offering varied layers of multi-coating and both wide or thin metal mounts (to avoid vignetting with wide angle lenses). I've never found them to degrade photos, and especially not if used for video. In fact none of the top brand filters such as Hoya, Nikon, Pentax, Sigma, Tiffen, B+W, etc.,will affect your picture quality (as long as you use only one at a time) and even cheaper filters such as Kood and Jessops are of good quality glass.

It can be argued that even multi-coated flat surface filters can sometimes cause problems with reflections in certain circumstances, and that the original curved multi-coated surface of a camera lens is better on its own. However, the huge advantages of using filters, especially PL filters, far outweigh not using one at all. Not only do they help control light levels, cut-out reflection, and enhance or deepen colours, but they also help protect that expensive front glass lens element.

Canon makes two types of rear filters on the supertele:

A specialized polarizer that can be adjusted with a wheel while shooting
A 52mm holder that takes regular screw on filters
I have both, and a couple screw-on solid ND to go with the second type.

I use the fader with smaller lenses. Even with a full mattebox setup, the fader makes sense to allow control when just shooting the camera and small lens.

This question really belongs in the 5DII/7D section, as regular video cams already have interal ND. It's also been discusses several times in the 5DII section.

While we're on the subject of filters, does anyone have a solution to this problem? Cokin P graduated neutral density filters are the only ones I have found that are affordable and fit the Canon XL series. The filters sit at a distance from the lens such that ANY dirt or scratch, even if it is totally invisible to close inspection creates a spot that is seen when panning against blue sky. The same dirt on the lens itself would be totally invisible. It all has to do with the distance between the lens and the filter. I have many worthless scenery pans to prove it. Any thoughts?

The Cokin P size glass filters are easier to keep clean than the cheaper resin ones. I use both and don't have much problem with spots or marks on skylines as long as I keep the filters clean. (I always carry sections of soft chamois leather and large make-up brushes to clean all my lenses and filters).

I also own the larger Cokin-X PRO filter holder and filters range designed for large format cameras and broadcast cameras shown here:

Cokin

I do actually prefer to use round filters and also have some ROUND GRAD ND filters in 72mm, 77mm and 82mm. These of course only twist round for adjustment so do not provide the up & down adjustments that a square filter provides. The advantages are that they don't need the extra weight, bulk and inconvenience of adding Cokin frames, bellows filter grooves or a matte box filter holder.