I find long exposures to be great fun, especially once you start really stopping down the light and extending that shutter to ridiculous lengths. The costs of getting started, however, can add up very quickly.
In Mathieu Stern’s latest video, which features long exposure photographer Thibault Roland, we are shown how we can get started very inexpensively using welding glass as a filter over our lens to cut down the amount of light hitting our sensor, and lengthening those shutter speeds.
I started off with a couple of inexpensive Cokin resin filters when I first wanted to have a go at long exposures. I didn’t know much about them at the time, and they were on the shelf at my local camera shop. So, I got a 2 stop ND grad, and a 3 stop ND. On a dull day, they worked out pretty good for letting me get exposures of 2-3 seconds.
Then I read of this tip with the welding glass on a photography forum about ten years ago and decided to give it a go. Again, I didn’t really know much about what I was doing with them then, but I was rather pleased with my results.
I’ve since upgraded my neutral density kit into Schneider 4×5.65″ and B+W 77mm threaded filters, but the welding glass really isn’t a bad way started getting into it. In fact, I just ordered a couple of pieces of it from eBay so that I can test a few theories on how to correct the colour shifts effectively (and if any of those theories pan out, I’ll definitely be posting a tutorial for you guys).
At the very least, the welding glass is going to give you a good idea on whether or not you even like the process of creating long exposures, and will give you some practical insight before you spend a couple of hundred $ on something a little higher end.
One thing to note with welding glass is that they don’t come in “stops” like neutral density. Instead they come with measurements called “Shades”, but the number can be converted.
According to The Astronomy Nexus, the formula breaks down a little something like this.
OD = -log T
SN = 1 + (7/3) OD
Where T is the amount of visible light that passes through the glass and SN is the “shade number” of the welding glass. If you want to read more about the maths, go ahead and read the page at The Astronomy Nexus or the comments on this post at Stack Exchange. For the rest of you, here’s a quick list of approximate equivalences.
- Shade 1.7 = 1 stop
- Shade 2.5 = 2 stops
- Shade 3 = 3 stops
- Shade 4 = 4 stops
- Shade 5 = 5 stops
- Shade 6 = 6 2/3 stops
- Shade 7 = 9 stops
- Shade 8 = 10 stops
- Shade 9 = 12 stops
- Shade 10 = 13 stops
- Shade 11 = 15 stops
- Shade 13 = 16 stops
- Shade 14 = 18 stops
Remember, these numbers only apply to visible light. Infrared and ultraviolet are treated a little differently, by both ND filters (especially the IR corrected ones) and welding glass, so some experimentation will be required.
Do you use welding glass for your long exposures? Have you tried it and loved it? Or hated it? Let us know your thoughts and experiences in the comments, and show off some of your long exposure images.