Friday, March 30, 2007

Split ND Filters vs Photoshop Correction

I have been asked why I use split ND filters instead of just combing highlight and shadow exposures in Photoshop. The response is that I use both techniques, however I have found that it can be very difficult to get a natural looking transition when a darker sky is combined with a light foreground in Photoshop. Split ND filters are used to hold back the exposure of the sky while allowing more light to reach the foreground. I use the Lee filter system, which fits on my medium format lenses. There are many brands made of split ND filters. Most common are the 1,2 and 3 stop split ND’s (sometimes designated as
        0.3, 0.6, and 0.9 respectively). I find that I use the 3 stop (.9) ND the most - when I need a split ND at sunset or sunrise I really need to darken the sky in order to get good light on the foreground. If I use a split ND filter I have to do much less post processing in photoshop. It can be difficult to combine a foreground exposure with a sky exposure in Photoshop and not end up with the tell tale pixel fringe between the 2 areas. Below is an example of an image that I used a split ND filter on. You can see that the trees are slightly darker in the areas that were behind the shaded part of the filter, but it is not too difficult to lighten this in Photoshop. It would have been much more difficult to insert a darker sky from a different exposure - the tree that extends into the sky would have been difficult to lighten up or to mask without fringing. If you have questions about the basics of split ND use a quick google search on the topic will find many helpful articles. I highly recommend  them for landscape photography, even with digital cameras. Be sure to experiment with them to become familiar with how to get the best results for your images. You don't want to have a great image ruined by improper use of a split ND filter.


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