I have to disagree with all responses.

NDVI = (N-R)/(N+R)

N=0, R=1 => NDVI = -1

N=1, R=0 => NDVI = 1

=> valid range of NDVI is (-1, 1)

EVI2 = 2.5x(N-R)/(N+2.4R+1)

N=0, R=1 => EVI2 = -1

N=1, R=0 => EVI2 = 1.25

=> valid range of EVI2 is (-1, 1.25)

Correct, in theory NDVI ranges between -1 and +.

On mid-resolution satellite imagery, NDVI seems not go below -0.2 or above 0.8 (Gils et al. 2012).

Article Development of a two-band enhanced vegetation index without ...

go through the link and read the article for more detail

thank you very much for your kind help really appreciate

Good responses... However, please note that the values extracted may not often times get to the extreem (-1 or +1).

Cheers.

Hi,

The extreme limits should be between +1 and -1. However, theses are just the extremes. Your values could be in between.

Yes, spectral signatures is expected between -1 and +1

I have to disagree with all responses.

NDVI = (N-R)/(N+R)

N=0, R=1 => NDVI = -1

N=1, R=0 => NDVI = 1

=> valid range of NDVI is (-1, 1)

EVI2 = 2.5x(N-R)/(N+2.4R+1)

N=0, R=1 => EVI2 = -1

N=1, R=0 => EVI2 = 1.25

=> valid range of EVI2 is (-1, 1.25)

Lan Nguyen your reasoning is good but I think you have to replace the 1s with 255 (Maximum values of a digital number in a pixel) so that the maximum and minimum values of NDVI remain unaffected i.e. -1 to 1, while those of EVI2 will range between -1.04 and 2.488. To me this makes EVI2 less reliable compared to NDVI since it is not normalized.