Digital bandwidth is a feature that has influence from the user. It is influenced by the sample frequency, sample rate, and memory size. A capture window is the length of signal time the scope can capture when the ADC is running at its maximum sampling rate and the scope fills the acquisition memory. If the user went into the horizontal menu and reduced the memory to one quarter of the original amount and the sampling rate stayed the same, the shaded area on the right side of the display on this slide would not be captured. The capture window is being lowered by three quarters because the acquisition memory was reduced by three quarters. If the user instead kept the time base the same and captured the same length of signal time but only used one fourth of the memory the scope would reduce the sampling rate by a factor of four, so that the time elapsed between each sample was four times as long. That way one fourth of the memory length can still cover the same amount of signal time. Beginning with a scope whose ADCs could sample at 1 GS/s, by reducing the memory they are only running at 250 MS/s. This has an effect on the bandwidth of the signals that can be captured. The digital bandwidth of the scope is determined by whether the ADC is running fast enough to digitize the shape of the signal accurately. Analog bandwidth and digital bandwidth are different. Typically when selecting an oscilloscope, the analog bandwidth should be considered first, but the sampling rate should be kept high so that the digital bandwidth is also good.