I've got a black and white unit and I only used it to establish film speeds and development time when I got into sheet film (TriX and HC110 per St. Ansel) some years ago. I didn't use it again until I started doing unsharp and sharp masking. I didn't use it at all to determine my rating of Bergger BPF 200 or the use of ABC pyro. I spend my time making photographs today. Testing can be a all consuming affair.