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I am trying to achieve the type of photo where the people/moving parts of the photograph are virtually invisible, but the static background is perfectly sharp.
For example, I am taking a photo inside of Saint Peter's Basilica, and I want the photo to be of the beautiful architecture and decoration, not the other tourists. To achieve the effect where the people are like ghosts, I set the shutter speed to 4 seconds and let the camera figure the rest out itself.
Because of the limited lighting in the basilica, the 4 seconds are permissible and the photo comes out as desired. Here it is:
(Sorry about the image quality. It is a photo of a photo.)
How I can achieve this effect in an area with more light, like outdoors? Lowering the shutter speed alone will not help, for it will either give me a photo without the effect, or a white photo. I thought that maybe I could put a polarized filter over the lens to limit the amount of light that can enter. I also thought that maybe I can put a light gray filter on the lens to limit the amount of light but that might just make it grayer and not really help at all.
How can I achieve this effect in lighter conditions?