Step 1: Gather Materials
- Zipper lock bag: 1 Gallon size is fine for a DSLR and a medium zoom lens.
- Filter to fit your lens: You probably want a transparent "Skylight" or "UV" filter. I got cheap ones for this project because I expect them to take some abuse.
- Sealing tape: I used electrical tape, but duct tape might provide a superior seal. The tape will only touch the bag and the outer ring of your filter, so if it leaves gunk behind, it's no big deal.
- Marking implement: Fine-tip sharpies write well on plastic bags.
- Cutting implement: A small pair of scissors works well.
Step 2: Trace Filter
For short lenses you can put the filter smack in the middle of the bag. This will help to keep the zipper away from the controls. For longer lenses, you may have to arrange the camera diagonally.
Step 3: Cut filter hole
Step 4: Put filter on lens
You can also do this using two filters and attach the lens later, but that means you're putting more layers of glass and air in front of your lens, so you risk more reflections and worse optical quality.