Digitizing a logarithmic graph

Greetings,
I've been tasked with digitizing the following graph:

Original Graph.png

There are quite a few tools which allow one to calibrate axes and then get a series of points.
I have done this, and I have a data series for each curve. I've put them together on a scatter graph, yielding the following result:

Untitled.png

However, the issue is that the y-axis scale is different on the original image. Some measuring has shown that the distance between 1 and 2 is roughly equal to the distance between 2 and 4 so it's base 2 of some sort, but I have no idea how to replicate the original scaling.
If I set the y-axis as being logarithmic on Excel, I get a bunch of negative values as the original points I got go below one.
To top it off, technically the original points were already logarithmized (I'm assuming that's a word) - so technically I don't need to perform any mathematical operations on it, just have the scale not be linear.

Any suggestions?

Oh God. I thought it had made a bunch of negative values because it shoved the x-axis up to y = 1. I can't have the x-axis go to 0 but I can have it at 0.0000000001 Thanks!

Originally Posted by Richard Buttrey

Hi,

I suppose the first thing to do is establish why you've got negative points since the original doesn't show any - least not on the chart.

Are you sure you're not confusing the position of the x axis and the implication that points below this are negative. The x axis probably by default is showing alongside point 1 on the y axis. Set the x axis labels to 'Low' so that the x axis is at the foot of the chart.

Upload the actual workbook if you need more specific help.

Right, so I've kind of sorted it out; here's the result:
Result.png

I wanted to use polynomial trendlines (I mean the originals are almost perfect parabolas so...) to tidy it up.
Now before changing the scale to logarithmic, the trendlines look really great.
However once I logarithmize (I'm making this a word.) the scale, they become...not so good.
Trendlines.png
Is that just the nature of my data?

Never mind guys! I'm reacquiring the data sets and getting much smoother curves - thanks for all your help, truly appreciated.