Collar corrected water immersion objectives are widely misunderstood and under used. For those interested in fresh and living materials they should be your standard high power. The collar allows you to work the lens at optimum adjustment for spherical correction under a wide variety of conditions, not just those which the lens designer anticipated.In addition to this, the low viscosity of water immersion allows you to move the slide about under the lens. With oil immersion the high viscosity tends to make the cover glass stick to the lens so that it doesn't move when the slide moves, thus wrecking your preparation. These are general advantages which apply to all high power W.I. objectives. A particular advantage of this lens is its very high optical index (O.I.= 1000X NA/magnification) which means it gives a very crisp, sharp image, allowing the use of high power eyepieces or magnification changers.Also it is of good quality and very, very cheap: most of the few high power W.I. objectives made now cost thousands of dollars. It is not a plan lens, but for visual use this is of little significance and anyone doing photography at high powers these days should be using Helicon Focus or some such image stacking software.
Overall a remarkable lens which I strongly recommend to anyone interested in the microscopy of aqueous mounted material.
Pros: Gives the best obtainable image quality for examining aqueous mounted specimens (fresh and living) at high power.
Cons: None really, alt...
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