NullMind wrote in post #17346421
When you are in S mode, what tells you what shutter speed to be at ?
I use shutter speed allot on long exposures, but for quick shots my experience is limited
The shutter speed I want to be at is decided by the requirements for the shot, and how I want it to look. I use my experience to choose an appropriate speed to get that result.
You need to first decide if you want to freeze all motion, or use some degree of blur in part(s) of the image for effect. If you want to freeze all motion you need to decide how fast a shutter speed will do that. You have to allow for avoiding camera shake (i.e. movement of the camera) and freezing the motion of the subject itself. To avoid camera shake the old rule of thumb is to shoot at a minimum speed of the reciprocal of the focal length of the lens. So, that would involve shooting at 1/50th or faster with a 50mm lens, 1/200th or faster with a 200mm lens etc. That is based on using a FF sensor (or 35mm film) when using a crop sensor you need to multiply by the crop factor as well (so 1/80th and 1/320th for the two examples above). It also doesn't take into account IS systems which allow you to go slower by between 2 and 4 stops. A 4 stop IS mechanism would allow the 1/200th to be reduced to maybe 1/12th. This is a general guideline though, a lot depends on your ability to hold a camera steady and brace it correctly. On a good quality tripod of course, you should be able to use any shutter speed without fear of camera shake.
The subject motion is another matter, there is no easy general rule of thumb. The faster the subject is moving, as well as the greater the angle relative to the camera, the faster the shutter speed needs to be to freeze the motion. IS will have no affect on subject speed so cannot help you here.
Now, if you want to introduce some blur, you need to slow the shutter speed down enough to give you the blur that you want, where you want it, whilst still being fast enough to keep the crucial parts of the subject sharp. This is very much an experience thing, you need to learn what works for you. Personally, I like to shoot helicopters at 1/80th to get reasonable blur in the rotors, and will go slower at times (especially with a hovering helicopter). Propeller driven aircraft I will shoot at around 1/160th, sometimes a bit slower, in order to get enough prop blur but keep the fuselage sharp, too fast a shutter speed and the propeller looks as if it isn't moving and the plane looks as if the engine has stopped. Similarly, I will use a slow shutter speed for motor racing shots and pan with the subject to keep them sharp but create significant blur in the background and wheels, to give an impression of speed. Again, too fast a shutter speed and a fast moving car can look as if it is parked and not moving, I often shoot at 1/60th with a 600mm lens for instance.
The best thing to do, when you are uncertain about what speed to use, is to use different speeds and see which get you the results you want. If shooting a motor race for instance, you can start off with a moderately high shutter speed, then drop it a notch after each lap or two. So you may shoot the first lap at 1/400th, then the next at 1/320th, the next at 1/250th etc. This will ensure that you end up with some shots that are sharp enough, with the faster speeds, but also give you a variety of degrees of motion blur and you should get some with nice blur but still with a sharp subject. Then you can study the results later and see which shutter speeds are most effective. Any speed at which you were getting no usable shots is best left unused for a while, until you have improved your panning technique. Personally, I try and use a speed which may give me quite a high percentage of unusable shots, but where there are sufficient number of shots with a sharp subject to get me results, and those results will show the most motion blur that I can get. I prefer to have fewer keepers at the end of the day, but for those keepers to be as dramatic as possible, so I push the envelope. Obviously, when you have to get a shot, then get a couple in the bag with a "safe" speed before playing around seeing how slow you can go.
With some experience you will quickly gain an instinct for what shutter speed will give you the results you want, in a specific image. However, you really do need to get a feel for it yourself, as it depends so much on your own requirements and ability.