We present a revised TRGB calibration , accurate to 2.7 % of distance .
A modified TRGB magnitude corrected for the color dependence of the TRGB , the QT magnitude , is introduced for better measurement of the TRGB .
We determine the color-magnitude relation of the TRGB from photometry of deep images of HST/ACS fields around eight nearby galaxies .
The zero-point of the TRGB at the fiducial metallicity ( [ Fe/H ] = -1.6 ( ( V - I ) _ { 0 ,TRGB } = 1.5 ) ) is obtained from photometry of two distance anchors , NGC 4258 ( M106 ) and the LMC , to which precise geometric distances are known : M _ { QT,TRGB } = -4.023 \pm 0.073 mag from NGC 4258 and M _ { QT,TRGB } = -4.004 \pm 0.096 mag from the LMC .
A weighted mean of the two zero-points is M _ { QT,TRGB } = -4.016 \pm 0.058 mag .
Quoted uncertainty is \sim 2 times smaller than those of the previous calibrations .
We compare the empirical TRGB calibration derived in this study with theoretical stellar models , finding that there are significant discrepancies , especially for red color ( ( F 606 W - F 814 W ) _ { 0 } \gtrsim 2.5 ) .
We provide the revised TRGB calibration in several magnitude systems for future studies .