What happens when you use Shutter priority?

Chris, yes I understand that aspect, but for landscapes where the focus is on infinity it wouldnt have that problem surely?

Angie - I must experiment and see.

but for landscapes where the focus is on infinity it wouldnt have that problem surely?

The depth of field would still change if the aperture became wider, even if set on infinity; as the aperture becomes wider the amount of the image in sharp focus toward the front of the frame would change. The camera is presuming you have chosen the aperture you wish to work with and therefore changes the shutter speed. If you were to do the same in shutter priority, and selected a shutter speed, then the aperture would change accordingly.

Viv

AEB = Auto Exposure Bracketing. It's purpose is to bracket different exposures only. Even focused to infinity, the DOF of foreground objects, would still change, if the aperture is changed. By changing aperture, it controls the volume of light coming in, rather than the actual exposure to the light coming in.

Only ISO and shutter speed can alter exposure only. Aperture, although it can be used to control the light that is needed for an exposure, it also alters the way in which the light hits the sensor/film, as well as the DOF within a given image. It also has an effect on lens effects such as CA, which will also effect the image as a whole. So to have an AAB (Auto Aperture Bracketing) system would be near on useless

Conversely, in Shutter priority, the shutter speed remains as you set it and the camera varies the aperture.

You sure about that? Not known an AEB mode, that changes aperture, on any camera I've ever had. All do the same, which is adjust exposure via shuter speed, no matter what pre-set mode you use

Those are the standard warnings for under and over exposed "single" shots in Shutter Priority mode (I believe). AEB works like a separate shooting mode, no matter what pre-set mode you are using. It adjusts the exposure time of 3 separate shots, in order to increase dynamic range, when the 3 or more shots are blended together It does this by increasing or decreasing the shutter speed, to give a +/- exposure, either side of the correct exposure. If it did this in any way other than shutter speed (or in some cases ISO) adjustments, it would fundamentally alter each image, meaning blending them would be near on impossible, or with very poor results.

 For birds in flght i use shutter priority with auto ISO, which i set the min and max say 100 and 800, say i set the shutter at 1/1000 if it is bright the camera may select F8 so when the light level drops, the camera will then select the next wider aperture say F6.3  and shoot at this until the light level dropped again, if i had had no more wider apertures, ( say the lens was 500mm-F6.3) then the camera would raise the ISO to say 200 to achieve the correct exposure for the parameters set and would continue to do so as the light changed up or down. This would be regardless of the exposure compensation you were using. This is only my opinion and it works for me and my Nikon, also the OP may be using a bridge camera with auto ISO enabled.

The S9600 does +/- 1 stop at most when bracketing. Coupled with its tiny sensor which gives enormous depth of field, it's probably not quite as useless as the same thing on your Canon.