# Studies: Price histograms and Volume histograms

Q:  When using the price histogram on a Constant volume bar chart, if you select either Volume or Price in the Formula box of the Price Histogram Properties window, shouldn't the POC and the inner and outer range levels stay the same.  They change quite a bit and I wanted to understand why so I could decide which made more sense for me.

A:  The histogram will change.

For example if the volume is  300, and the formula is Price and the bar spans 3 prices, then the 3 counters for the 3 price will increment by 1.   If the formula is Volume then the 3 counters share the volume and will increment by 100.

Now if a bar spans 6 prices, for Price selection the 6 counters still increment by 1.  But for Volume the 6 counters increment by 50.

In this example you see that rate of incrementing a counter, volume bar size, will be a constant 1 for the Price formula to reflect the price was visited by a bar.   But the rate of incrementing will be higher when fewer prices have to share the volume, ie 100 vs 50 in the example.  This variable rate leads to a different looking histogram.