I'm putting together a list with the most common abbreviations found on microscope objective barrels. I'll add this list to a flickr post I've made about the use of microscope objectives in photography. My intention is that this article should serve as a guide for "micro-curious" photographers. In other words, I want to keep it relatively simple and with a photographer's perspective.
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The rest of the article can be found here: http://www.flickr.com/photos/johnhallmen/5379235010/
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I'm sure there are a lot of things to add, correct and improve here. Any help in this regard is deeply appreciated!Achromat – Achromatic The objective is corrected against color aberrations. According to the definition an achromatic objective should be able to bring two wavelenghths into focus at the plane. See Apo.
Apo – Apochromatic The objective is highly corrected against color aberrations. According to the definition an achromatic objective should be able to bring three wavelenghths into focus at the plane. See PlanApo.
BD Brightfield / Darkfield. Sometimes called HD (German: Hell / Dunkel). Objectives designed to work with an illumination system where the subject is lit by light through the barrel of the objective. These objectives have a special hollow chamber surrounding the optical elements through which subject illumination can be provided using specialized illumination equipment. For regular use this hollow compartment needs to be covered/stuffed with something in order to prevent light from leaking in but otherwise they are just like their non-BD counterparts. Nikon's highly regarded series of objectives marked "M Plan" have optically identical BD versions marked "BD Plan" which work just as well for photography. At least provided that the outer barrel is unscrewed and removed (otherwise the working distance can be compromised), that no light is allowed to pass through the hollow chamber and that the (often larger than normal) mounting thread isn't a problem.
CF – Chromatic aberration Free. Nikon has used this abbreviation to describe their finest objectives. The CF-objectives make most necessary corrections in the objectives themselves which sets them apart from most other objectives that typically need to be used with designated eyepieces in order to deliver a well corrected image. Because of this feature the Nikon CF objectives has a well deserved reputation for being among the best objectives for photography. Note that only some CF objectives are marked as such which makes identification a task for the experienced users.
DIC – Differential Interference Contrast. An illumination technique for enhancing contrast in transparent specimens. Sometimes called NIC (Nomarski Interference Contrast). The glass elements of DIC objectives are made of "strain free" glass. For regular photography this does not matter and they behave just like their non-DIC counterparts. More info: en.wikipedia.org/wiki/Differential_interference_contrast_...
EPI – The objective is designed to work well with a certain type of lighting system where the subject is lit by light rays coming through the objective itself (via a special epi-illumination accessory containing prisms and/or half reflecting mirrors inserted into the optical path of the system). When an epi-illumination system is not used these objectives behave just like regular objectives. Also see BD.
ELWD – Extra Long Working Distance. Also see LWD and SLWD.
Flour – Flourescence. The objective is designed to work well in a flourescence imaging system. Flourescence is a technique where the electrons in the subject are excited using high intensity illumination. When they relax back into their normal state they send out a photon and this light is captured by the Flourescence imaging system. By separating the excitation light from the light transmitted from the subject the result is an image where the light is coming from the subject itself rather than from a separate source of light. Flour objectives are highly corrected against aberrations (almost on par with Plan Apo). Alternative meaning: Flourite The objective has elements made from flourite glass – more expensive than regular glass but with some desirable properties in terms of aberration resistance. objectives with flourite elements often have shorter than usual working distance.
HD Hell/Dunkel. See BD. In some cases it stands for High Definition but I've only seen this in optics other than microscope objectives.
HMC – Hoffman Modulation Contrast A microscopy technique intended to increase contrast in low contrast areas using modulation filters inserted at the rear end of the objective. I'm not sure how HMC objectives behave when for regular photography when the HMC modulation filter is removed but I'm guessing they then become very similar to a non-HMC objective (please correct me if I'm wrong!). More info: www.olympusmicro.com/primer/techniques/hoffman.html
LWD – Long working distance. The objective is constructed in a way that allows more room between the front element and the subject. Also see ELWD and SLWD.
NA – Numerical Aperture. The number following this states the brightness of the objective (much in the same way as the F-number of a camera lens). The higher the NA, the higher the potential resolution which the objective can deliver is. The equivalent F-number on a standard camera lens (the widest aperture) is approximately F=1/(2*NA)*M/(M+1) where F is the widest aperture (for instance 1.8 for a "50mm f/1.8" lens), NA is the numerical aperture on the objective (for instance 0.25 for a "10x NA=0.25" objective) and M is the rated magnification of the objective.
NIC – Nomarski Interference Contrast. See DIC.
M – Metallurgical. The objective is intended for use in metallurgical applications. This generally means that it's corrected for use without a cover glass.
Oil - Oil immersion, sometimes Oel (german). Objectives intended to be used with a drop of immersion oil between the front element and the cover slip. These objectives usually have higher NA than usual and often very high magnification. They don't work well without the oil and their working distance is very short so they are not very useful for regular photography.
Plan – The objective offers a flatter field than a semiplan or non-plan objective.
Planachromat – A chromatically corrected objecitive with a flat field. Also see Plan and Achromat.
Planapo – Sometimes Plan Apo. A highly color corrected objective with a flat field. Generally an indication of a high end objective. Also see Plan and Apo.
Ph – Phase contrast. A microscopy technique used to reveal certain structures/details. This abbreviation is i often followed by a number (i.e. Ph 5.) indicating the size of the contrast ring to make it easier to match with the appropriate condenser. Looking through one of these objectives you can clearly make out what looks like a darker ring shaped area somewhere in the light path. For regular use this Phase Contrast feature is not desirable. Phase contrast objectives are far from useless but given a choice it's probably better to avoid them for regular use. Charles Krebs has made a nice comparison revealing the effect of phase contrast objectives in regular use.
Semiplan – Indicates flatter field than regular objectives but less flat than Plan. See also Plan.
SLWD – Super Long Working Distance Used by Nikon to identify objectives designed to give maximum working distance. More often than not, the extra working distance comes at the cost of a somewhat lower NA. Also see LWD, ELWD, ULWD
ULWD – Ultra Long Working Distance Used by Olympus to identify objectives designed to give maximum working distance. More often than not, the extra working distance comes at the cost of a somewhat lower NA. Also see LWD, ELWD, SLWD
WI – Water Immersion The objective is designed to be partially immersed in water. Since water have different optical properties than air it's likely that they perform better when used with water between the front element and the subject. However, in at least some WI objectives the front cone-shaped piece can be screwed off, leaving an objective well suited for regular photography (as shown by David Millard here).
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A similar list of abbreviations is available on Nikon's site here: www.microscopyu.com/articles/optics/objectivespecs.html or at Olympus' site: http://www.olympusmicro.com/primer/anat ... tions.html
One confusing thing is "Flour". Looking at Nikon's own list of abbreviations it's supposed to mean "Fluorite aberration correction". However reading about their "Plan Flour" series it doesn't say a word about flourite: http://www.nikoninstruments.eu/Products ... uor-Series and instead I get the strong sense that it refers to the flourescense technique.
Again – any help and input appreciated!
