Low magnification, high numeric aperture (NA) microscope objectives are popular choices for multiphoton imaging. They offer excellent light collection properties, a wide field of view, and still permit high resolution imaging. However, they are challenging to design optically. Different manufactures have settled on different engineering compromises.

For example, Leica’s 20x/1.0NA objective is optically magnificent. I’ve been impressed with Leica’s coatings in the past, particularly for IR transmission, and they still outperform the competition. However, the thing is simply massive. It weighs 411 grams, and is 38 mm in diameter. It has a respectable 38 degree access angle, for getting pipettes underneath, but with only 2 mm of working distance, there isn’t much room for movement.

In contrast, Nikon’s 16x/0.8 NA objective is clearly inferior to the Leica optically, despite offering a wider field of view. However, it has some great ergonomics to offer. The working distance is 3 mm, the access angle is a comfortable 45 degrees, and it weighs a comparatively light 221 grams. Furthermore, the lower magnification of the Nikon partially compensates for the lower NA when it comes to image brightness.

For patching, the Nikon wins hands down. For pure imaging, the Leica wins hands down. But they’re not the only games in town. Olympus was the first manufacturer to really push this style of objective for multiphoton imaging, and they have a 25x/1.05 NA objective with a 2 mm working distance and 35 degree access angle. And Zeiss has a 20x/1.0 NA objective with a 38 degree access angle and a 2 mm working distance. This market has seen some really nice innovation in the past 5 years, and there are new designs coming out all the time. So be sure to check with several manufacturers before settling on a particular objective. They are very specialized, so the best objective for one experiment may be quite poor for another application.