Hello René,
If such kind of projects are typical for your work, you may consider the following masking approach:
- after building the model similar to the one you have on the screenshot (object + rulers and charts), duplicate it in the Workspace pane and remove all mesh components related to the rulers, charts and any other background elements,
- run File Menu -> Import Masks procedure and choose "From Model" option - it will create masks for all the aligned cameras, based on the existing mesh model,
- then manually review the images, where the charts and rulers are captured in sharp details and unmask them there,
- switch the default mesh model in the Workspace pane to the original model,
- rebuild the texture with the desired parameters.