  We present deep VLT spectra of early type galaxies at z~1 in the Chandra Deep
Field South, from which we derive velocity dispersions. Together with
structural parameters from Hubble Space Telescope imaging, we can study the
Fundamental Plane for field early type galaxies at that epoch. We determine
accurate mass-to-light ratios and colors for four field early type galaxies in
the redshift range 0.96<z<1.14, and two with 0.65<z<0.70.
  The galaxies were selected by color and morphology, and have generally red
colors. Their velocity dispersions show, however, that they have a considerable
spread in mass-to-light ratios (factor of 3). We find that the colors and
directly measured mass-to-light ratios correlate well, demonstrating that the
spread in mass-to-light ratios is real and reflects variations in stellar
populations.
  The most massive galaxies have mass-to-light ratios comparable to massive
cluster galaxies at similar redshift, and therefore have stellar populations
which formed at high redshift (z>2). The lower mass galaxies at z~1 have a
lower average mass-to-light ratio, and one is a genuine 'E+A' galaxy. The
mass-to-light ratios indicate that their luminosity weighted ages are a factor
of three younger at the epoch of observation, due to either a late formation
redshift, or due to late bursts of star formation contributing 20-30% of the
mass.
