Distance to object (mm)

d = 6*12*25.4

Height of CCD (mm)

h = 6.8;

Angle between baseline and ray to object (rad)

theta[B_] := ArcTan[2*d/B]

Focal length (mm)

f = 6;

Angle of one pixel (rad)

theta1 = ArcTan[h/(f*484)]

Error in distance (mm)

sigD[B_] := 
      Sqrt[2*theta1^2*(B*Sin[theta[B]]^2/(Sin[2*theta[B]]^2))^2]

Plot[sigD[B], {B, 1, 300}]

Show[%,Frame -> True,FrameLabel->{"Baseline  mm",  "Depth  error  mm"}]

Table[{B, sigD[B]}, {B, 50, 300, 25}] // TableForm

sigD2[B_] := d*d/(B*f)*h/484;

Plot[sigD2[B], {B, 1, 300}]

Table[{B, sigD2[B]}, {B, 50, 300, 1}] // TableForm