Wednesday, 20 May 2015

exposure - When should I use graduated ND filters and when should I use HDR processing?


I'd really like to stop blowing out the sky and/or underexposing the ground in my pictures. The traditional solution would be to use graduated ND filters, but taking multiple exposures and applying HDR postprocessing would also work (and some point-and-shoot cameras can even do that in-camera).


When should I use graduated ND filters, and when would HDR be a better bet? Or is it just a matter of personal preference?




Answer



ND filters


Advantages



  • No extra post-processing required.

  • You can see the result in the viewfinder.


Disadvantages



  • Making the exposure is more complicated because you have to select a filter and place the transition appropriately for the scene.


  • You probably need several filters (of different density and transition abruptness) to cover a sufficiently wide variety of scenes.

  • The straight transition between dark and light needs to more or less match the needs of the scene (for example, a large mountain with sunlit clouds behind probably won't work).

  • ND filters are more fragile than other filters because they are placed in a frame so you can shift around the transition.

  • Good ND filters aren't cheap, and you may need multiple sets to fit different lenses.


HDR


Advantages



  • No mucking around at exposure time (just make the exposures).

  • Can deal with arbitrarily shaped transition between light and dark areas.


  • A variety of HDR software is available for free (though there are pay options as well).


Disadvantages



  • Lots of mucking around in post.

  • If your camera doesn't support bracketing with a sufficient number of frames, a tripod will be required and you'll have to adjust exposure manually.

  • Scenes with moving objects will lead to difficult or impossible editing in post.

  • Significant practice is required for good results, particularly if you don't want the "HDR look".


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