How to Capture the Perfect Exposure
Laying the gradation along the skyline works well, but where using grad filters falls down is if there are features cutting that skyline (eg. snowdonia_30I5576 below), like a mountain, tree or supermodel. The grad will darken those areas too resulting in a “grad head” look, not good.
In these situations with the camera on a tripod you can shoot two frames, one exposed for the sky and one for the landscape and merge them in Photoshop.
It works well, and is a very handy technique to master. In fact doing a number of exposures to cope with extremes of contrast in an image and merging them is a really useful option.
The perfect registration between the images makes the merging easy. I'm not going to get sidetracked into Photoshop Speak now but believe me, it's not rocket science.
So if that's the case, why bother with filters at all?
Rolling farmland on the edge of Snowdonia National Park, nr Ysbyty Ifan, County Conway, North Wales. Canon 1Ds mkIII, 70-200mm lens, ISO 125, 1/10sec @ f11. The trees breaking the skyline made using a grad filter inadvisable if I was to retain detail in the autumn colours of the leaves in the top branches so two exposures were merged here.
Movement. Trees swaying in the breeze, waves breaking, cloud scudding across the sky. These are effects we love to maximise in our landscapes, aren't they? But that movement will make making a perfect join of multiple exposures very difficult. And obviously when shooting hand held a perfect registration between multiple frames isn't possible. (eg. umbria030I3208 below) Clearly there's a time and a place for both techniques. In fact in a really high contrast situation such as when shooting straight into the light I often use both; merging exposures made with a filter attached.
An olive grove near Montefalco, Umbria, Italy. Canon 1Ds mkIII, 16-35mm lens, ISO 100, 1/30 sec @ f11. The branch swaying in the breeze meant that merging exposures would have been difficult so a 0.6 ND grad was used to hold detail in the sky.
So to recap where possible I'll always try and make the RAW image as perfect as possible exposing just one frame and using a filter if necessary. If there's a complex composition that makes using a grad impossible I'll resort to merging multiple exposures. Also when using extreme wide angle lenses such as my 15mm fish eye or 14mm fully corrected optic on a full frame sensored camera filters are out due to vignetting, so merging is the only alternative. (eg. goldencap8086 below) And whilst we're talking about merging exposures I have to mention that notorious three lettered acronym; HDR.
Sunset over the Jurassic Coast from the Golden Cap, Dorset, England. Canon 1Ds mkII, 15mm lens, ISO 100, 0.3 sec @ f16. Merging two exposures was the only option due to the curvature of the front element and vignetting.