How To Improve The Accuracy Of Water Test Kits

Dear All,
I don't know if it bothers others but from my experience the quality of the colour charts that come with water test kits really lets them down. Add to that different lighting conditions and people that are colour blind they seem almost useless to me.
So one day I set about try to find a better way and I think I did and this is what the post is about.

During the process I had an Email conversation with Nathan Hill at PFK magazine who asked if I could write it up as a review, so like a sucker I did. I didn't actually get a rejection letter but well ..... trust me you haven't missed it in the magazine.... but anyhoo, I not offended or bitter (much). I have a quirky writing style that probably killed it and it kept me amused for an afternoon.
So this is a draft of the (unpublished [sniff, wipe tear from eye] article)

What I now have is a water test using a standard kit that can take a reading with resolution below 1ppm, tell me how much water to change and then after a substantial water change be within a couple of ppm of the predicted value and can indicate when main external filter medium needs attention.

Have a read, if its interesting I can post the excel spread sheets that do the maths.
Regards
Andy the minion

@Andys101 I know, the colourimeter is easy to use - and somebody will have to drag it from my cold dead hands before I give it up, but it is also overkill. As an intermediate step try replacing the colour chart with a good image of it on a tablet or phone, zoom in and then hold the sample in front of a white area of screen so that it is backlit You may find this to be a bit more consistent than ambient lighting.