Delapool
Member
Yes thats it, the one with the strips and app. Its really easy to use and gives you numbers, logs it for you etc so I'm a big fan of it and wish there was other like it. As you've mentioned you can get off readings so you test again and get a more realistic number, so I make sure there is no shadows on the cards and take the picture in the same place to avoid lighting discrepancies. After a while I decided it may be time to try something else I'm leaning towards API Master Test Kit.
This is following on but I dug out JBL Proscan as the API gh test kit had expired.
First strip had colours run a little and results didn’t match too well. Second strip I took more care and the readings matched the api test, ph probes, etc much better.
So it seemed to me that don’t want any colour run or partial shade as well as posted above.