different results in NDVI

[Michèlevon_Kocemba]

Hello all, 

I am working with a Landsat 8 scene and realised that I achieve different results for the NDVI if I do it manually by using the raster calculator or via the option that can be found in the image analysis tool. Can someone tell me why that is so? I've only realised about the possibility to automatically calculate the NDVI via the image analysis window and would out of habit prefer the raster calculator mode, but if someone could tell me the difference, I would be very thankful. 

with kind regards
Michele 

[VinayViswambharan]

For rendering purposes, when using functions or the Image analysis window we scale the NDVI values to 8 bit. You have the option to return unscaled (scientific) values in the tool. 

Refer - scientific output in this link: Using the NDVI button on the Image Analysis window—Help | ArcGIS for Desktop 

[benjaminasuku]

I had the same issue crop up. using the raster calculator and the imagery indices function gives two different results in Arcgis Pro