technique - Should I prefer raising ISO or lowering the shutter speed in a low light condition?

Example:
1. A "still" object/scene.
2. Night time.
3. The only light source you have is: a tubelight on a wall.

Provided, you want sharpness all around so you won't maximize the aperture.
Flash produces unreal colours (in my case), so I don't use that.

So,
One choice would be to keep the camera on a tripod and lower the shutter speed to allow more light in.
Other choice is raising the ISO (assuming a high ISO does NOT produce noise).

1. Which one should be preferred for what technical reasons?


2. Does either of the choices create a flat light?


3. Do both the choices result in the "same" output?

Answer

There is no one answer that applies to every case.

1. 
   

   Depends on the shake profile and sensor performance (and post processing NR). At some point, ISO noise will decrease sharpness more than camera/subject(irrelevant in this case). And at some point, opening up the aperture will have less degradation than the aforementioned. This of course depends on lens performance as well as shake profile/sensor performance and is probably earlier than you think.

   
   

   Guidelines: Tripod? Shutter speed, lowest ISO. Hand-held? start at 1/(35mm equivalent focal length) but take into account IS, how steady you can hold it, if you can lean against a wall, etc.

   
   


2. 
   

   Neither has any effect on light, given that the lights are on for the entire exposure (exceptions being flash, a flashlight, etc.). Long shutter speeds (on a still surface like a tripod) may give the impression of more even lighting because the shadows are not lost in the ISO noise.

   
   


3. 
   

   No, unless your definition of same is different than mine.

   
   
   

Why does flash use unreal colors? You can gel the flash to match the ambient lighting. You can take the flash off the camera to get a more pleasing non-direct-flash look due to placement of specular reflections, highlights and shadows.