Jim Gollan @ OCA Landscape: Using a grad filter (34)

Requirement

x images

Purpose

To understand the role of the neutral graduated filter

Technical learning

ND filters reduce light across the whole of the image: they serve to introduce motion blur beyond the camera's unfiltered range. This is a specialist effect that is often used to give water a mist like appearance (see own image below) or to convey motion in trees.

Waterfall at Virginia Water Lake
Overcast conditions, ISO 100, f 22, ND filter 4 stop

Graduated ND filters reduce light progressively over the range of the image: they serve to change the contrast between parts of the scene. Specifically they are designed to address one of the key challenges of landscape photography. Rarely can any camera cope as well 'straight' photography (see what the eye sees) between the relative brightness of the sky and the land. Expose for the sky and the land is usually too dark. Expose for the land and the sky is washed out.

Exercise instructions

Set-up

Pick 3 scenes (a) a completely overcast day with a featureless sky, (b) an overcast sky with visible tonal differences and (c) a sunrise or sunset (shooting directly into the sun)
Use a tripod
Compose so that the horizon line is between 1/3rd and 2/3rds from the bottom of the frame

Images for all 3 scenes

Bracket 3 images without filter with a wide aperture
Bracket 3 images with the ND filter (edge at the horizon line) with a wide aperture
Bracket 3 images with the ND filter with a small aperture

For one of the scenes

Review

Examine how the filter balances the contrast between sky and land
Identify the differences in transition at the horizon between small and wide aperture
Consider the impact of changing from a wide angle to a telephoto lens

Images and review

Field on the road between Pitminster and Corfe, Somerset

Images without filter - Bracketed +1/-1 EV