I assume you life-death stain has 2 different markers for a reason. So I would go with the manufacturers recommendation by calculating the integral within the wave length range specified. Including all wavelengths is not going to help you get better data, although you could use a little wider range than specified, but the specified rang is going to give most of the specific signal available just by the nature of the distribution of the emission spectra of the dyes/fluorophores used.

Calculation of the integral is pretty straight forward: sum fluorescence signals within the emission range of interest (eg 530 +/-12.5 and 620 +/- 20).

Thanks Gerco for your reply,

the problem is they say 530 nm +/- 12.5, but they do not say how accurate the reading shoul be. In other words, i can assume that they calculate accuracy of 0.5 nm or 1 or 10 nm.....this mean that i can have more or less fluorescent signal to integrate. So if i use 1 nm accuracy, i will have about 25 wavelength to integrate, while if i use a 12.5 nm accuracy i will have only 2 and result very different.

I think i will send an email to the manufacture company and see if they can help on this.

Thanks