Thank you all for your thoughts on this technique.
As previously mentioned I am trying to determine the time required to develop some technical pan. I have previously used times taken from the massive development chart with mixed results generally the film has been under developed, typically the film leader extremely light in colour.
I have been thinking about how I could use this technique for a little while and at least one flaw with it is that you have to develop for a fixed time and for me this is a problem. I have no idea where best to start. 10, 20, 30 or XX minutes.
So I decided to modify this suggested technique a little.
I developed several small strips of film as recommended, but at various intervals removed a strip and fixed it. Creating a sort of test strip.
I then used these to visually decide when increased development seemed to given no further benefit to density. Very subjective I know but the best I can do without having the means to measure density.
The starting time I chose was taken from the massive development chart.
Rodinal dilute 1+150 for 7 minutes. (This is for film rated at 25asa, my next problem to solve.) (My stand development dilution as 1+100 for 60 minutes so the 1+150 seemed a reasonable compromise.)
The intervals chosen were: 3.5, 7, 10.5, 14, 17.5, 21, 24.5.
Having compared them side by side, I determinate that 17.5 mins seemed to be the point were there was little increase in density for the extra time.
I have quickly run a short roll (three frames) through the camera nominally rated at 25 asa, developed using 17.5 minutes and got reasonable negatives.
Still room for improvement but I have a better starting point than I have had previously.
Thanks once again.
Mike