Excel 2013 2D/3D Surface charts-editing band size?

Hello

I am actually using Excel to visualise 3D pointcloud data (x,y,z) of a surface by using Excel 2D/3D Surface charts.
Creating the charts is quite easy, but I am having trouble trying to customise the way the chart looks.

It is interesting to point out that visualising the 3D pointcloud data can be done without even using a chart in Excel. You simply dump your (x,y,z) data in to a table (x running horizontally, y running vertically and the z values filling the interior of the table), select all the z values and apply a Conditional Formatting Colour Scale to it. (I have discrete values of x and y which makes doing this possible).

This is what my data looks like when I zoom out, essentially it is like a "heat map":

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Now taking this same data and creating a 2D Surface chart, the chart looks like this, which has a 3D shading type of effect which if good for visualising the troughs and valleys:

vqo0t0.jpg

The shaded 3D effect of the chart is very effective but the colour bands/bin sizes are quite coarse being 10 in size. I want to edit these to be 5 in size which will make visualisation of the data even more accurate. I can't work out how to change this. If I right click on the legend bands on the chart I get these options which don't help.

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If I right click the chart and change the chart type to a 3D Surface plot, the chart now looks like this, and as you can see it defaults the colour band/bin size to 5.

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If I right click on the vertical Z-axis on the chart I can edit the Axis options/Major Tick Size which in turn affects the colour band/bin size.

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How do I get the same colour band control when using a 2D surface plot? Why would this functionality NOT be a feature of 2D Surface plots which in theory you think are "easier" to process?

PS: I have tried rotating the 3D Surface plot to try to "look straight down" on it but after around 60 degrees of rotation the chart automatically changes to the 2D Surface chart I originally started with.