If there is only a photographic light and no external flash, what kind of setting is better for Canon 550D SLR?

If you can use a photographic lamp, shoot according to normal conditions, with aperture priority, shutter priority or manual mode, and the sensitivity should not be too high; If you can't use the camera light and the ambient light is dim, you can only increase the aperture to improve the shooting sensitivity. The sensitivity of 550D should be no problem with 600, and the image quality can be 800.