There’s an interesting series of videos appeared that were produced by Lee Filters with conversation between the revered landscape photographers, Joe Cornish and David Noton. Epsiode 2 sees them discussing the changes digital photography has made in capturing the moment, and why they still use graduated filters. It’s not like the usual manufacturer produced media as there’s no mention of Lee filters, and well worth a view.

Here’s a list of current used graduated filters for sale on PhotographyAttic:

B+W 77mm 502 Grey Grad 25%
Cokin A 120 Gradual Grey 1
Cokin A 122 Gradual Blue 1
Cokin A 123 Gradual Blue 2
Cokin A 124 Gradual Tobacco T1
Cokin A 151 Fog 2
Cokin A 198 Gradual Sunset 2
Cokin P 120 Gradual Grey 1
Cokin P 121 Gradual Grey 2
Cokin P 122 Gradual Blue 1
Cokin P 123 Gradual Blue 2
Cokin P 124 Gradual Tobacco 1
Cokin P 125 Gradual Tobacco 2
Cokin P 198 Gradual Sunset 2
Cokin P 665 Gradual Fluo R2 red
Cromatek G210 Dark Green Graduated Filter
Cromatek G211 Light Yellow Graduated Filter
Cromatek G212 Dark Yellow Graduated Filter
Cromatek G215 Light Sepia Graduated Filter
Hitech Yellow 3 Grad 100 System 94mm
Hoyarex 527 Gradual Y2
Hoyarex 521 Gradual G2
Hoyarex 522 Gradual B2
Hoyarex 523 Gradual T2
Hoyarex 524 Gradual M2
Hoyarex 525 Gradual P2
Hoyarex 526 Gradual E2
Lee 100×150 Pop Red Grad Hard
Tiffen 77mm sunrise grad
Tiffen 77mm blue grad
Unbranded 84mm ND Grad 0.3
Unbranded 84mm Cool Blue Grad 0.3
Unbranded 75mm Square red grad
Unbranded 75mm Square Green Grad
Unbranded 75mm Square blue grad

The Neutral Density (ND) filter is one of the more useful filters you could include in your collection. Digital image processing can do many things but it can’t reduce the light reaching the film or CCD. That’s the job of the camera’s exposure system and an ND filter throws in a helping hand.

The name explains its purpose. It’s neutral (in colour) and it has a density (level of opaqueness).

Neutral Density filters come in a range of densities. The basic ND2 has a 2x exposure factor (or one f/stop) and an ND4 has 4x (two f/stops). There’s also an ND8 (8x or three f/stops) and a less common ND64 (64x or six stops).  You can go even further with specialist ND filters such as the Big Stopper from Lee Filters. This one has ten stops light reduction. So a shutter speed of 1/30sec would need to be increased to 30 seconds!

The filter goes over the lens and reduces the light reaching the film by the exposure factor of the filter.

If, for example, you had an exposure of  1/125sec at f/11 and you added an ND8, the shutter speed would reduce to 1/15sec or the aperture would need to be opened to f/4.

The reason to use an ND filter suddenly become obvious. If you want to force a slow shutter speed, for motion blur, or you want the lens at the widest aperture, for shallow depth-of-field, the ND filter can help.

It can also be used in combination with a flash to effectively reduce the guide number for close range photography.

The ND2 is hardly worth bothering with so we’d suggest you’re first ND filter be a ND4.

And another interesting type is the variable ND, like the one illustrated above. These are variable in strength, but, as reviewers have found, tend to cause criss-cross patterned illumination at stronger settings.