I'll second this request, more bins, better labeling of the bins, and the capability to move limits out without removing the filter entirely would be helpful. The example @tomacorp links to is indeed much more usable than the current implementation, although it does lack the ability to fine-tune that is provided by the current zooming application. Once manual entry is implemented it should be much easier to recover from mistakenly cropping too much. If you are set on using the zoom, perhaps you can zoom in but leave a couple of bins on both sides of the slider to allow the selection to be easily expanded. It may also be useful to put a little number on each side showing how many results are cropped in both directions, to provide context on where the user is on the continuum of values. Labeling could also be improved, giving a single value for each histogram bin makes the cutoffs between each bin somewhat ambiguous, but this becomes less important as you use more bins.