# How to separate raster bands in model builder?

I have a simple model that iterates through folders to collect imagery, mosaics them and clips the mosaic to a study area boundary. I need to produce an NDVI from the clipped 4-band mosaic "sa11_4band.tif" by incorporating the raster calculator into the model. The problem I am encountering is that the individual bands do not appear in the raster calculator when I incorporate the raster calculator tool. How should I separate the raster bands from "sa11_4band.tif" in order to perform the necessary calculation in the raster calculator?:

Float("sa11_4band.tif - Band_4"-"sa11_4band.tif - Band_3")/Float("sa11_4band.tif - Band_4" + "sa11_4band.tif - Band_3")


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For example: c:\path\to\my\raster.tif\band1