Renko charts are traditionally plotted on the fixed price brick which is an absolute number. Below is the chart of Bhel plotted with 5 brick size Renko.
Bhel was trading around 300 during Feb 2015 and it traded below 100 during March 2016. Chart looks good but difficult to trade in the later stage because of brick size issue. In simple words, 5 brick size when it was trading at 300 becomes 1.66% of price, and when it is trading at 100 becomes 5% of the price. So the same brick size cannot be followed and it needs to be altered with the changes in price which is very difficult task. Moreover, a longer term chart is difficult to analyse with absolute brick size.
Log bricks are of great advantage. Below is the Renko chart of Bhel plotted with 5% brick size for the same period.
Brick size changes as per the price level due to the log scale which is accurate and practically possible to be followed. Notice the chart shown above where bricks are large because price level was high and they become smaller as price fell to lower levels.
This allows user to plot consistent chart and most importantly, make them practically trade-able. Below is the Bhel chart plotted with 1.5% brick size for the same period. Compare it with the figure 1 and notice the difference in the latter part when stock started falling.
Great advantage of Log Brick charts is the scanning that they allow across the group of stocks. 5 brick size for a stock trading at 1000 and for the one trading at 100 is different hence scanning is impossible with absolute brick size. But 1% across the chart remain 1% of the price irrespective of the price level it is trading at.