Summary: manual focus, focus before you insert the filter, fix your focal length
A critical element in landscape photography is achieving the appropriate depth of field. For the most part, landscape photographers try to obtain as large a depth of field as possible to retain sharp focus from foreground to background. To effectively achieve this, the photographer needs to pin point areas of the image to focus upon; either the correct point of focus for a single image, or multiple points of focus for a focus stacked image. When photographing long exposures, it is much more common to attempt the former. My tips to achieve this are as follows:
- Turn off autofocus. If you put a dense ND filter on, your camera will not be able to focus properly and may often default to infinity. This would result in an unusable, out of focus image.
- Make sure you obtain the correct focal point before slotting in the ND filter. I prefer to do this using manual focus but you can use autofocus if you prefer, so long as you remember to turn off autofocus after the ND filter has been inserted.
- If your lens is zoom lens, try to use a focal length lock if this is a feature. This stops any shift in focal length if you accidentally move the lens excessively during placement of the ND filter. Remember, focal points change as your focal length changes.
Long Exposure Photography with a 15 Stop NiSi ND?
by Dylan Toh