I have downloaded landsat image from this site and now Im wondering if i can get NDVI index from it.
In raster calculator I have only 3 ranges, shouldnt be four?
Or am I doing something wrong?
If it helps its Landsat 8 sensor: OLI
You will not be able to generate the NDVI from Landsat Look images. These are generated from the visible bands to "simulate natural color"
In order to get the image with all bands, including red and near infrared, download it from another source - for example the USGS EarthExplorer
For Landsat 8 the NDVI is calculated as
(band5 - band4) / (band5 + band4).
edit: No per answer above (I must have overlooked the image type)
Yes you can. I have no idea what's going on in that screencap, but you only need to use two of the bands in the calculation:
NDVI = (NIR - R) / (NIR + R)
That's as specific as I can be without knowing which Landsat you are using.