Conditional likelihoods |$\mathcal {L}(\Omega _{\rm m})$| (solid blue line) and |$\mathcal {L}(w)$| (solid red line), along with their Gaussian approximations derived with the Fisher formalism (⁠|$\sigma _\mu = 1/\sqrt{F_{\mu \mu }}$|⁠, dashed green line), for an observation of ellipticity spectrum |$C_E^\epsilon (\ell )$| with the Euclid survey characteristics with all other parameters fixed to their fiducial values. The multipole range was set to 10 ≤ ℓ ≤ 100 and the spectrum |$C^\epsilon _E(\ell )$| entering the likelihood calculation resulted from the CNPT model.