Just following up on how to calculate NDVI through the Raster Calculator:
The basic formula is : (NIR-VisRed)/(NIR+VisRed), where NIR = near-infrared band (or raster) and VisRed = visible red band (or raster).
There are two tricky parts to using this formula in Raster Calculator:
1.) You will likely want to specify an individual raster band (or bands) within a multiband raster. You can only do this using the full file path in (10.1 at least), appending "\Band_1" (or other band number) to the end. For example, this would point to band 5 in a raster stored in "C:/rasters/raster.tiff": "C:/rasters/raster.tiff/Band_5"
2.) Your bands are likely integer rasters. An integer raster plus, minus, multiplied, or divided by another integer raster results in an integer raster. However, an integer raster operated by a floating point raster results in a floating point raster. We want a floating point NDVI layer in the end, so we must cast at least one of the integer rasters to floating point (the floating point will propagate through the formula). You can cast an integer to floating point using "Float(raster)" (note the capital "F").
In the example below, I have a one-band NIR raster loaded in ArcMap and an RGB colour raster, from which I pull the red band.
(Float("0015_nir.tiff") - "C:\rasters\0015_rgb.tiff\Band_1")/("0015_nir.tiff" + "C:\rasters\0015_rgb.tiff\Band_1")