Some time ago I came across this thread in a forum and I recognized the style of photos. I always liked them but I assumed that most of them used $300 ND filters which I didn’t have intention to buy. But seeing good results from a cheap piece of welding glass got me interested. I got a smaller piece of glass first, but it was very prone to light leaks.
I then purchased a much larger one ( able to fit over my 10-22 wide angle) for $6 at the local hardware store and use a reverse fitted lens hood to attach it to my lens with rubber bands. I still get occasional light leaks, especially shooting in bright sunlight so at one point I will buy a cheap filter and glue it to one.
When shooting I use a tripod and a remote shutter release. Two issues to look out for when shooting with a piece of welding glass attached to your lens:
1) Manual Focus. Focus before you attach the piece of glass because it is so dark that once attached you will have a hard time focusing. After focusing I set it to manual focus so it stays in position
2) Manual White Balance. I only recently figured that one out. My welding glass gives me a very greenish tint ( the reason a real ND filter costs a couple of hundred dollars more). But if I set the white balance manually it removes most of the greenish cast and then shooting RAW gives me post processing control to to really take care of the issue.
As you see though in the end my images end up as black and white images because somehow the photos work better in that way for me.
These were the first two photos I took with the welding glass. They were exposed at about 30 seconds at F11. I got up to 2 minutes with F22 but having a camera on a slippery rock with a piece of welding glass attached with rubber bands makes me want to shoot a bit faster. Most images are shot at 45 secs in RAW at f11.
This was the second time I went out with the welding glass. I hadn’t figured out the manual white balance yet so the greenish tint was removed in Photoshop. In the first image you can see the light leak that forms the big circle. I have taped up the edges of the glass but I don’t know if it has really helped. These days I put my lens cleaning cloth on top of the lens and glass when shooting hoping to minimize the light coming through.
My third time experimenting. When shooting with such a high f stop I need to remember to clean my sensor and lens as you can see some of the dirt on my lenses.
And finally my latest experiments. Stationary objects with flowing water around them really makes this technique shine.