I want to take an image of a laser show projected in a wall. Indoors in low light I use longer exposure 1/8 or 1/25 second. Outdoors the images are completely washed out. I want to know if there is a standard setting I can use or if there is a filter I can use to limit but not stop the normal sunlight and still capture the laser images. They are created by rapid scanning and don’t show up with normal settings on a phone or standard 35mm DSLR. I seem to really need the longer exposure to get the full scan but then during the day I can’t see anything.
I am not sure if I understand, but this seems to be the problem:
- Need shutter speed of about 1/8 to 1/30 to capture the full laser scan, and
- Captured image is too bright when shooting at 1/8 to 1/30
If this is the case, then you'd like to keep the same shutter speed yet achieve a less bright or 'blown out' image. To fix that, you probably already:
- Shoot in manual mode, so that you can
- Set ISO as low as possible (100 or less),
- Stop down aperture to f/11-f/14 (don't go to a higher number otherwise image quality will degrade),
- Maintain same shutter speed of 1/8 to 1/25.
If this is not enough (which it likely isn't if you are in bright daylight), then you will need to purchase a neutral density (ND) filter. These reduce the rate at which light enters your camera thus allowing you to keep your intended shutter speed. Now, the tricky thing is determining which ND filter to buy as they come in different intensities. You can either purchase a variable filter (good for experimentation) or you can purchase a filter with a set darkness.
Most likely, you will need to darken your image by 5-6 stops of brightness which relates to a filter rating of ND 1.5-1.8 as shown in the image below.
Read more at B&H's article on ND filters.