Processing behind makehdr and tone mapping algorithm?

When using makehdr of jpeg colored images(5 no.s), we get an hdr image and after tone mapping we calculate the RGB values using impixel command. Luminance is calculated using equation L= K*(.2127*R)+0.7151*G+0.0722*B), where calibration factor K=1, reference. When comparing the luminance value given by photomatix software, the value given by matlab is about 2-3 times greater than the luminance given by photomatix. For example, at a point Lphotomatix is 67 and Lmatlab is 208. Why is this happening?

Answer 1

[Image Analyst]

I guess they use different equations.

[Nithya]

Photomatix software gives the pixel values and luminance values.With the pixel values L was calculated manually using this same equation with k=1 which gave the same luminance value of photomatix.So it was proved correct which made me use the same equation in matlab. The RGB pixel values itself is not matching properly. Is it that when tonemapped some hdr information is lost?