The Fogra Measuring Bar (FMB) provides a reliable reference for determining tonal value on offset printing plates.
It consists of a 13 cm x 20 cm plate bearing 2 sets of halftone step wedges, one using a screen ruling of 60 L/cm and the other stochastic screening with dots in the size of 22 µm. The set consists of 2 series of 16 halftone patches ranging from 2 % to 98 % and the dot percentages are precisely measured at the Fogra Institute. The results are recorded in a set of reference measurements supplied with the Fogra-FMB.
The user can then measure the halftone patches with the plate measurement device at his disposal and compare these results with the Fogra reference measurements. If the results are virtually identical, this provides reassurance. If they differ, it provides a clear picture of the situation and a decision can be made about whether it is best to adjust the measurement device or whether the difference in the tonal values can be taken into account from now on in the daily usage.
The determination of the tonal transfer curves between data set and reproduction on the printing plate will now be more consistent and soundly based. For the record, Fogra bases its measurements on the reference measurements of the Bundesanstalt für Materialprüfung in Berlin (BAM) (Federal Materials Testing Institute in Berlin).
The development of the Fogra Measuring Bar was supported by:
- Agfa Gevaert AG, Graphic Systems
- GretagMacbeth AG
- Kodak Polychrome Graphics GmbH
- Lastra Plurimetal GmbH
- TECHKON GmbH
Important Remark
The exposure to light causes the contrast of the FMB to fade over time.
