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There are three things that control exposure. Shutter speed, aperture (size of the hole in the lens) and the sensitivity of the medium (ISO setting). If you change any one of these...without changing the other...you will change the exposure.
With an automatic (point & shoot) camera...the camera will decide these things for you. Even with a $10,000 DSLR...if you use auto mode...the camera will decide these things for you. The trouble is that the cameras don't know what they are shooting...or what you want it to look like.
So back to your question. If you just changed the shutter speed (to let in more light)...you would have to compensate by changing something else. The problem is that you don't want to set the shutter any slower...because that will cause blurriness from a) camera shake and/or b) subject movement.
So as an example...let say that we want to keep the shutter at 1/125. Any slower and we might get some blur...
If you set the camera to 'Tv' which is shutter priority...the camera will pick an aperture that will give you enough light for a normal exposure. Now if it's not very bright...the aperture will need to be big (low F number)...but there is a limit as to how big it can get. The maximum might be F3.5...and with continuous lights, indoors...the combination of F3.5 and 1/125 will probably not be enough to make your exposure. What about ISO you say?...well the next step would be to turn up your ISO...but the more you do that...the more digital noise you will get. A good DSLR is good but not great at ISO 800 (digi-cams are crap at ISO 400)...so you don't want to go any higher than that.
So in this case...we might be stuck. We don't want to go any slower than 1/125...the lens is at it's maximum F3.5 and the ISO is at 800...what do we do if we still can't get enough light for the exposure? One option is to use a 'faster' lens...that has a bigger maximum aperture...but a wider aperture will reduce our DOF (depth of field)...which we may not want...and even a bigger aperture still has a limit. The only other option would be to increase the power of the light....so that brings us back to why strobes are good...because they are so POWERFULL.
Sorry, was that too wordy? It's Friday and I want to go home :X
With an automatic (point & shoot) camera...the camera will decide these things for you. Even with a $10,000 DSLR...if you use auto mode...the camera will decide these things for you. The trouble is that the cameras don't know what they are shooting...or what you want it to look like.
So back to your question. If you just changed the shutter speed (to let in more light)...you would have to compensate by changing something else. The problem is that you don't want to set the shutter any slower...because that will cause blurriness from a) camera shake and/or b) subject movement.
So as an example...let say that we want to keep the shutter at 1/125. Any slower and we might get some blur...
If you set the camera to 'Tv' which is shutter priority...the camera will pick an aperture that will give you enough light for a normal exposure. Now if it's not very bright...the aperture will need to be big (low F number)...but there is a limit as to how big it can get. The maximum might be F3.5...and with continuous lights, indoors...the combination of F3.5 and 1/125 will probably not be enough to make your exposure. What about ISO you say?...well the next step would be to turn up your ISO...but the more you do that...the more digital noise you will get. A good DSLR is good but not great at ISO 800 (digi-cams are crap at ISO 400)...so you don't want to go any higher than that.
So in this case...we might be stuck. We don't want to go any slower than 1/125...the lens is at it's maximum F3.5 and the ISO is at 800...what do we do if we still can't get enough light for the exposure? One option is to use a 'faster' lens...that has a bigger maximum aperture...but a wider aperture will reduce our DOF (depth of field)...which we may not want...and even a bigger aperture still has a limit. The only other option would be to increase the power of the light....so that brings us back to why strobes are good...because they are so POWERFULL.
Sorry, was that too wordy? It's Friday and I want to go home :X