How to get silky smooth water and clouds with long exposure photography

There’s something absolutely magical about long exposure photography.  Rough water and waves turn to smooth patterns, cars vanish, and choppy clouds turn into smooth streams in the sky.  I love using these types of shots for architecture – all the distracting details disappear and you can feel a sense of motion.  But setting the right exposure can be tricky for several reasons.  First, if you need to use a neutral density (ND) filter to get a long shutter, your camera’s meter probably isn’t up to the task and you get exposures that are far from perfect.  Second, trial and error is extremely painful when each exposure takes several minutes.  You don’t want to be doing that over and over!

I use a very simple trick to find the right exposure:  I find the best exposure using a test shot at high ISO, and shoot my final image at the right ISO.  It’s dead simple.  If you need 4 seconds at ISO 6400, then you need 4 minutes at ISO 100.  My basic process is:

  • Compose the image and focus on a tripod before putting an ND filter on the camera (so you can see what you’re doing).
  • Once you’ve added the ND filter, set the ISO to 6400 and use the meter to get a starting shutter speed.
  • Take a test shot, evaluate the histogram, and try a new shutter speed as needed.
  • Once the histogram looks right, switch from ISO 6400 to 100, and use convert whatever shutter speed you had in seconds to minutes

You can make small variations on this as needed.  For example, if I want to go even longer on my D810, I’ll click my ISO down to 64 and bump up my exposure by 2/3rds of a stop from there.  In the video below, I show the whole process, but first I’ll add a few more general tips:

  • Get high quality neutral density filters.  Even if you can get the exposure at f/22, you’re losing image sharpness and bringing out a lot of dust spots with such small apertures.  I like to shoot at f/8-f/11 as much as possible.  See my gear page for a list of the filters I recommend.
  • I strongly recommend getting a digital bulb timer, such as the Nikon MC-36 Remote Shutter Release.  Manual shutter releases are cheaper, but I’ve had to redo many shots when I didn’t stop the exposure in time – plus it’s more relaxing to not have to watch the clock so carefully.
  • Hi Greg. thanks for the tip! I have a difficult image to capture! What I would like to do is have a long exposure of a river, however the main subject is a row of boats! I’d like the river to be soft (silky smooth with clouds) but the boats (moving up and down) to remain sharp! Are you able to point me in the right direction for this shot and is there a video with something similar using Lumenzia?

  • Greg Benz

    Hi Tony- I would suggest taking a look at various blur options in Photoshop. You can apply the blur on a duplicate layer and mask the effect into the target areas. Lumenzia can be used to help apply the mask if the boats/water differ in tone or color, but hand painting the mask with a low flow brush is probably what’s needed here. However, keep in mind that if you push the effect beyond a certain point, it will look “Photoshopped” as the viewer will perceive still boats in smooth water as looking unnatural. In Lightroom, you might also play with clarity, contrast, and exposure to reduce detail in the water and darken it slightly, which will similarly help take attention away from the water and put it back on the boats (though your cloud reflections may be tricky with this approach).

  • Thanks Greg. The water is a murky brown and I’m just trying to remove the ripples. I remember your video “How to remove Tourists in Photoshop’ and there is a part where you masked/blended some moving lights in the center of the building entrance! I’d like to try this and revert back to you. 😉

  • Greg Benz

    If you have multiple exposures to stack, you can do this. However, you’ll want to tweak the approach I used in the video because you aren’t trying to reveal a fixed object, “median” stack mode will give variable/unpredictable results. A better option is “mean” which will average the images to give you a blurred result, which is a rough approximation of a long shutter. As you’re blending fixed moments, you would need many images to blend or a blend of already relatively blurred images to get a smooth result, so you may still need to add some additional blur, but this may give you a better starting point than a single image.


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