Table 2. Summary of a variety of methods used to measure relative focal shift.
Values are reported for our highest NA objectives, NA 1.49, imaging into an aqueous environment, n 2 = 1.33.
| Method | Apparent focal shift | Ease | Accuracy | Caveats |
|---|---|---|---|---|
| n 2/n 1 | 0.88 | +++ | - - | |
| Theory from [2] | 0.73 | ++ | ++/- | Accuracy limited for TIR objectives |
| Polynomial extrapolation | 0.59 | + | + | Ignores objective specific aberrations |
| Multiple bead sizes | 0.60 ± 0.03 | + | ++ | |
| Cross sections: ring-stain beads | 0.59 ± 0.02 | - | ++ | |
| Cross sections: single rod-like cells | 0.52 ± 0.04 | - - | ++ |