Lens quality marking from best to worse ?

[Kalleboy]

Hello
Zeiss lenses and other
How to arrange lens qualities form worse to best ?
[*] Plan
[*] Semiplan
[*] -No marking- just xxxx xxxx serial code or so
[*] Apocromatic
[*] Achromatic
[*] Infinity
[*] Neofluar
[*] A-Plan
[*] Ultrafluar
[*] Fluar
[*] EPI Plan
[*] POL
[*] PH2

Or Zeiss Eyepieces (Weird marking also)
[*] KP, KH ,or so
[*] K
[*] A
[*] -None-

[hkv]

You are mixing apples and pears here. And perhaps also some bananas.

Divide them into different buckets.

Bucket 1 - Quality related

*] Plan - Planar, meaning the image will be flat. Not blurry at the edges. Everything in focus at the same time.
[*] Semiplan - Less quality than above
[*] Apochromatic - Excellent colors. It compensates for color aberration at the highest level (these are almost always the best)
[*] Achromatic - Good colors. It compensates for color aberration at a decent level
[*] Neofluar - Better than Achromatics, but worse than APOs.
[*] A-Plan - Do not know what the "A" stands for, but otherwise planar.
[*] Ultrafluar -
[*] Fluar - Fluorite. See NeoFluar above.
[*] EPI Plan - For EPI illumination, meaning light from the top down through the backside of the objective. Then reflected back towards the eyepieces. So, it is an objective with plan-characteristics that is supposed to be used with EPI-illumination. Most likely to be used without a cover glass.

Bucket 2 - Lightning technique related

[*] POL - For polarized illumination. Meaning less strain in the glass and will not give strange colors when viewing
[*] PH2 - Phase objective and has a small phase ring inside. Need a special phase condenser to give a phase image.

[zzffnn]

To add to hkv's comments, regarding eyepiece, those marking does not indicate optical quality, but rather features:

K usually means compensating
Pl usually means plan (flat view field)
Some P means projecting or projection eyepiece

[75RR]

Each manufacturer has their own designations for similarly corrected eyepieces and objectives.

This link to the Zeiss Optical Systems brochure (see page 23) clarifies some of the ones Zeiss uses.

viewtopic.php?f=15&t=4323

Zeiss also has some semi-plan finite objectives which were made after the brochure was published.

viewtopic.php?f=5&t=464

[PeteM]

Just to add to HKV's notes on quality, a further subdivision might include:

- Color correction - from achro to apo being best with most fluorite lenses in between)
- Field flatness - with plan (flat across the entire field) best and semi-plan next
- Field width - often ranging from narrow in older apochromats to wide in many modern scopes)

Really depends on what you want and can afford.

[apochronaut]

This is all so complicated and has historically been very manufacturer specific. Even, over time , individual manufacturers adopted differing or altered usages for certain designations.
p on an eyepiece could mean plan( also pl), or plan compensating( also pk) or projection or photo or periplan, which is also known as hyperplane. compensation for plan performance is not the same as compensation for colour correction, yet both are called compensating. Additionally, different manufacturers use the same word covering differing degrees of a specification.
As time has marched on, some degree of harmonization has taken place and there is a sense of standardization, for objective coding at least.

In order to cover this topic adequately, an entire page would have to be devoted to each of about 11 of the original higher grade manufacturers, that still existed, perhaps. after the second w.w. or so.