> There is no depth of field, even at moderate magnification. The > difference between 'in-focus' and 'out-of-focus' at 1000X is less > than 1,5 um. For example when the binocular tube is in good focus > the camera tube is so far out of focus that almost no detail can > be seen and the difference in height is only 2,5 um. At 100X its > slightly better and the range may be as much at 40 um or a bit > more -- I'll check.
> An RBC is a couple of um thick as it lies on the slide. A > neutrophile might be twice, or a little more in thickness. Focus > on the neutrophile and the RBC is no longer sharp (at 1000X). > However, you can't see this on the pictures I put up because they > are so magnified that everything is a bit fuzzy. However, there is > a still lot of fine detail to be seen in the white cell nuclei. > However, since there is no camera lens involved and no diaphragm > to close the DOF is not useful. Yes, Don, I understand. I am not sure that my attempt at humor was detected, however, when I referred to "that 'huge' DOF at 1570X - <VBG>". ;-) Nonetheless, I am aware of the lack of DOF. I have seen what you described - that focusing on the nucleus of a WBC may cause the RBC's to fade a bit into the background, and that's at 1000X. Also, you mentioned the apparent crenation in cells due to desiccation in slide preparation. I have seen this often also, and I have always thought that there had to be a better way of preparing blood for examination than the ol' tried and (sort of) true "smear" across a slide... Fred
