The slow look, as I call it, or were either the whole image or parts of the image such as water or moving people are blurred can be achieved in a number of ways. I use two. Results vary and yours will too.
First by panning during a faster shutter speed – although the shutter speed needs to be such that you have time to pan. 1/8,000 second won’t work.
Second by using a slow(er) shutter speed – usually through the use of a neutral density (ND) filter or just low light.
You can also combine the two as in the last photo in this post – panning the tripod head slowly for half the exposure.
Photo stacking 50 or so shots in Photoshop using the statistics function with either median or average as the blending option is another method but is a topic for another post.
This is a relatively simple technique but requires lots of trial and error to get a satisfactory result. And if you do it say at the beach in the middle of the day you might look a little silly! You don’t need any particular camera or lens but you do need to be able to change the shutter, aperture and/or ISO combinations.
First set your exposure to what you think is right for a ‘normal’ hand held photo, any way you like but pay attention to the histogram to get the optimal exposure. The link gives a good explanation of how. because you are panning across the scene you’ll need to use some sort of average exposure if there are large areas of light and dark in the scene as you pan. Trial and error will help. Try the method first and worry about the exposure on your next attempt or the next 100 attempts!
Change the aperture value and / or ISO so the shutter speed is around 1/30 to 1 second but the exposure is still optimal as per your histogram or what you have determined is the optimal exposure. Perhaps try it in the middle of the day first so there are no exposure challenges. Depending on the day you may need to fit an ND filter to get to that shutter value. or wait till it’s dull or cloudy. There are no issues with depth of field or diffraction as the whole image is going to be blurry anyway but experiment with wide and narrow apertures – it does give a different result. This technique lends itself to trying anything once you have the idea behind it.
Holding your camera in front of and against your body at your waist or chest – wherever it’s comfortable – you don’t need to look through the viewfinder or at the LCD screen, twist the top half of your body one way (to the right is natural for me, but left or right, doesn’t matter). A moment BEFORE you press the shutter start turning your body back the other way, ‘untwist’, don’t stop till after the shutter closes. If you either start turning after you press the shutter or stop before it closes you’ll get a part of the scene sharper than the rest. Try it anyway you may get a result you like. Try and keep the camera on a horizontal plane, unless you want the blur to go up or down hill. If you do it at the beach you might get a result like the following examples. Or maybe you prefer the privacy of your own backyard.
Neutral Density Filters /Low Light
Neutral density (ND) filters are used to reduce the amount of light coming through the lens and reaching the sensor.
That enables several things to be achieved.
1. A slower shutter speed, with the other settings staying constant (aperture and ISO). For example with an exposure having settings of say:
1/15 second, f8.0, ISO 200
adding a 3 stop neutral density filter to reduce the amount of light by 3 stops will allow settings of
1/2 second, f8.0, ISO 200
to give the same exposure.
You might do this to blur movement in the image or if the shutter speed is slow enough relative to what’s moving the moving object won’t show in the image at all. or may appear as a ghostly apparition like in the following example.
2. A wider aperture, with shutter speed and ISO staying constant. In the same example as about this would mean:
1/15 second, f8.0, ISO 200
would be the same as
1/15 second, f2.8, ISO 200
You might do this to use a wide aperture to throw the background out of focus. Like this:
Of course I could have increased the shutter speed to get the same result with no filter but I had the filter on already and I needed an example!
You could also hold shutter speed and aperture constant and change ISO but I’m not sure that’s relevant for a discussion of neutral density filters and this post is about getting to a slow shutter speed with filters.
Types of filters
There are either square (or rectangular) filters that sip into a holder that screws onto the lens such as the Lee or Cokin Systems or screw in filters from the likes of B+W or Hoya. I recommend the holder type of system from Lee or Cokin. If the filter is dense (more about that below) you cant see through it so have to focus before putting it on. If it’s the screw on type you tend to move the lens barrel a bit. There are magnetic rings you can attach to screw in filters by Xume but I have not tried them – they look interesting – once et up the filter just clicks on and off.
There are also variable ND filters available where you rotate the filter much like a polarizing filter to change the filter’s density from about 2 stops to about 8 stops. I use a Tiffen variable (2-8 stops) ND filter. Which is useful to reduce the shutter speed to give a slight blur to for example moving people.
Why can’t things be standardised? ND filters are used in Astronomy and Microscopy and I guess each discipline developed their own terms. Here some of the common photographic ND filters:
1 – Stop 0.3 ND2 ND0.3 ND101 1x
3 – Stop 0.9 ND8 ND0.9 ND103 3x
6 – Stop 1.8 ND64 ND1.8 ND106 6x
10-Stop 3.0 ND1024 ND3.0 ND110 10x
In the Lee system the 6 stop is referred to as the little stoper and the 10 stop as the big stopper.
If the ND filter is denser than around 6 stops (and maybe less than that depending on the camera) the camera won’t be able to ‘see through’ the filter to focus and measure exposure. You have to determine the exposure and focus before putting the filter on and than manually set shutter speed (or aperture) after allowing for the reduction in light from the filter. For example if the exposure is 1/60 second at f11, ISO200 and you want to slow the shutter speed to 1 second you would add a 6-stop filter.
1/60 no filter f11 ISO200
1/30 1 – stop f11 ISO200
1/15 2 – stops f11 ISO200
1/8 3 – stops f11 ISO200
1/4 4 – Stops f11 ISO200
1/2 5 – Stops f11 ISO200
1s 6 – Stops f11 ISO200
Of course the aperture could have been reduced to f22 in which case you would need a 4 stop filter. Most lenses though don’t perform optimally at their smallest aperture with diffraction introduced at f16 or f22 that softens the image. Also the ISO on some cameras can be reduced to 100 or 50 i.e. a value below their base ISO or the base ISO for camera is 100 (like the D800, the Fuji X-T1’s base ISO is 200). Cameras perform best at their base ISO. So long as aperture and ISO are not changed from the ‘no-filter’ values first determined they can be ignored from the calculation.
Of course there are apps to do all this! Some examples are ‘NDExposure’, ‘LE Calculator’, ‘Photopills’. There are versions for IPhone and Android.
Here are some examples of using ND filters
Combining panning and slow shutter!
I’ve used a few terms in this post that might not be familiar or perhaps I’ve not explained something in a way you understand. The following are links to some information that might help. Or you can use your favourite search engine. Or ask me – see the contact page or reply on facebook.