Sunday, October 2, 2011

Experimenting with Long Explosures

Over the last couple of weeks I've been experimenting with daylight long exposure photography, and thought I'd document my trials and tribulations to date and the "how too" that I've experienced.  By long exposure I mean multiple minute exposures during the day, of course that usually presents some challenges with exposure...

Here is the first picture I've taken that I'm happy with, I continue to stock other locations that I think might work out, but I'm waiting for the right weather...  So far just test pictures, nothing worth posting yet, but they'll come eventually if all goes well.  This is from my Alberta Plains gallery.



Filters

To start you're going to need some neutral density filters.  I'd suggest the screw on variety unless you want to punish yourself by manually holding something in front of your lens...  Not really my idea of fun, but it might be yours.  :)  You should consider buying filters at your largest filter size and then use step down rings for your other lenses.  That way your purchases will work across your lens lineup if you're lucky enough to have a number of lenses.

As for the number of stops that you need, in my own experience, you probably want filters that are able to "soak up" between 13-16 stops.  On bright days 16 stops seems to be a good fit, on low light days you might be able to get away with 13.  Since the more pieces of glass, the worse the image quality, you want to do this in as few filters as possible.  So, in a perfect world you'll probably want a 10 stop, and 3 or (and?) 6 stop filters so you'll be able to stack two together.  I don't think at this stage anyone appears to be selling single filters over 10 stops.

A world of caution - I've seen people use the "cheap" variable ND filters and they've given them very poor results.  (I don't believe the very expensive filter from a certain manufacturer has this problem.)  There were odd light leakage problems, and some of the images almost appeared to have zebra stripes - I'm staying away from the "cheapies".

Tripod

You need a sturdy tripod.  It's my own personal belief that it's worth while to invest in a tripod (and ball head) while it may not be as exciting as a new camera or lens, buying something for a few hundred dollars should last you for years - you'll be able to rely on it when you need it.  Years ago I bought my first inexpensive tripod off of E-Bay, and I initially thought it was a great deal - every time I used it however a new part broke/fell off of it.  Getting it to stay in one spot (like a tripod should) also proved to be too difficult for it.  Don't make the same mistake I did..

Other Incidentals

You'll also need a timer/cable release so you'll be able to put your camera in bulb mode too take the long exposures.  If you're taking pictures in direct sunlight, it's also a good idea to put on something to block the light from entering the viewfinder, otherwise light may leak into your images.  (It's possible for this to happen from other seams in your camera or even lenses as well, but hopefully that won't happen to you.)  Some straps have the little plastic piece to do this, or you can improvise with something else (clothes, filter holder, etc).

The Pictures
  1. Find perfect day, perfect composition, and of course perfect light.  (Or wing it - we all have to start somewhere!)  Compose your future image, with no filters.  Put your lens on manual focus, and take a test shot, and ensure you're happy with what you just took.  (In focus, correct exposure, and so on.)
  2. Determine how many stops of light you'd like to put on (more on this later) your lens, and assemble your filters.  Plug in your timer/cable release to your camera.
  3. Once your happy, without changing anything else screw your filters onto your lens, ensuring not to touch your focus, or focal length.  Once the filters are on you aren't going to be able to see anything through your viewfinder.
  4. Now set your camera in bulb mode, and adjust your exposure (based upon your test picture) the required amount of stops that you just put on your lens.  You can make yourself a cheat sheet, or there are also a whole host of "exposure calculator" apps for the various smart phones out there. (I haven't been able to find one for Android that goes above 10 stops, if someone knows of one that does please let me know!)  After practice, you might be able to do the calculation in your head.  Worst case you can also count the stop changes as you change your exposure.
  5. Cover your camera's viewfinder if it's in the sun, and take your picture with your cable release/timer ensuring you expose your image the correct amount of time.
  6. Show the world your fantastic new images (of course), sell them, Profit?  Credit me?
Other Tips

I'm of course no expert at this, if you google for "long exposure photographers" you'll find a ton, there is also a large community of people who are clearly experts at this type of art on Google+.  That said, these are a couple more things I've learnt thus far:
  • Generally speaking, clouds and water tends to be blurred out after a minute or so. 
  • For clouds, the direction of the wind clearly impacts the types of "streaks" that appear in the clouds.  Longer exposures of clouds tend to loose impact a bit the longer you go.  Experiment with this yourself - I still am.
  • You want your camera on the lowest (native) ISO your camera supports.  (E.g. Canon - ISO 100, Nikon - ISO 200).  This also helps reduce your shutter speed.
  • Of course people walking in and out of your image will become "ghosts" the longer the exposure is.  If they stand in front of you wearing a florescent jacket, you'll probably see them however..
  • You'll probably find there is often a strange color cast on the images as a result of using the filters.  It happens, but of course many folks are also converting the images to black and white anyway.
  • Turn off IS (Canon) or VR (Nikon) on your lenses if you have it.  Some lenses actually say not to tripod mount them with it on, but even if you do it will probably cause problems with long exposure shots anyway.
Have fun! I'll post more pictures using this technique in the future as well.

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