 [Raster]-[Band Maths]
What is the band calculation doing?

example) band1 + band2

So what do you add to Band 1 and Band 2?

Brightness value?
Reflectance?

Or can we choose?

that depends on what data you are using. The band maths itself does not care about the input data, it simply adds the values of the rasters.

If you are working with Sentinel-2 L2A data, you are using reflectance.

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Reflectance of band1 is 0.2
Reflectance of band2 is 0.3

Reflectance of New band = band1 + band2 = 0.5

Does that mean it’s like above?

yes, that’s how map algebra works.

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Sorry.

An error occurs if you try to calculate the following band.

B1 + B2
(B1,B2: band name)
Error statement:
referanced rasters must all be of the same size

Is it not possible to calculate between bands?

I want to finally calculate this formula.
5.94 * B3 - 4.37 * B5 +3.76

It is possible to calculate only part [5.94 * B3]

Sentinel-2 products consist of bands with 10, 20 and 60 meter resolution. You have to run the S2 Resampling operator first.

Understood.
I’ll give it a try.

I could calculate the band, but I get an error when displaying the image.

The error statement is as follows.
java.lang.NullPointerException

Is this a problem with the program?

This error message does not tell much about the error. Please exactly describe the data you were working with and what expression you applied.

The data used for the work is the data of sentinel-2_MSI_Level2A obtained from the following site.
https://scihub.copernicus.eu/dhus/#/home

It is a zip file of jpeg2000.

The formula is like the attached image.

did you open the S2 product with File > Import > Optical Sensors > Sentinel-2?

If I try to open the resampled data for that item, the importable one will not be displayed.

It is not in the vectors folder, but one directory above

There was nothing up to the vectors.

you have to save the product after resampling first.

Please also have a look at this post: Resample processing time

It is solved.