Sat 08-Dec-12 02:24 AM | edited Sat 08-Dec-12 02:33 AM by klrbee25
Using AutoISO in Manual mode is really flexible and convenient. You choose your shutter speed and f/stop. Let AutoISO choose any ISO from the minimum up to your chosen maximum. You won't set shutter speeds in AutoISO (or they won't be utilized) while in Manual mode. The camera will shoot at your selected speed and f/stop while varying the ISO to get proper exposure. As long as your exposure (shutter speed and f/stop for a given ambient light and subject illumination level) falls within the limits attainable by the AutoISO range you selected, you can shoot at your settings without thinking about anything other than capturing your subject. An AutoISO range of 100 to 6400 is 6EV...a huge range!
You can use this to your advantage if you start at one end of the AutoISO range and expect that any variations in your exposure will be in the opposite direction. For example, imagine you're a bright sunny outdoor sporting event. Say you find you can use a shutter speed of 1/500 at f/4 and ISO 100 which gives proper exposure in the direct sun. So you set up your manual mode to 1/500 at f/4 and turn on Auto ISO with a base of 100 and a limit of 1600. You now have 4 stops of additional sensitivity if clouds, shadows or anything else makes for a darker scene requiring longer exposure (or higher ISO)...while all the while you're shooting away without worrying about camera settings.