I suppose the answer depends on resolution and imaging area, but can you provide some ball park measures of imaging times with an SEM?
It's been a decade since I last used an SEM, but back then you would start using a fast scan that was real time i.e. you could move the sample around, change focus, etc and see the effect in real time. However the realtime image is noisy because the numbers of electrons being captured is small. Once you had the picture you wanted you would record them image using a much slower scan to reduce the signal to noise. From memory this took a couple of minutes.