Has anyone besides me noticed how little information there is available on some of the specialty coatings used by Pentax? The SMC coating is also limited and apparently had undergone numerous revisions since the early 70s. Some rumors say it was originally designed at the request of Japanese police for traffic cameras.

The Ghostless Coating was announced in 1992 and is considered a milestone for Pentax. It was apparently 1st used in 1997 on the the FA 43mm ltd and all subsequent limited lenses as well as certain * lenses. However, besides the LTD lenses, the other lens it was used on is unclear.

SP Coating The front surface of the optics is treated with the Pentax-original Super Protect (SP) coating. Applying a special fluorine compound to the lens surface through a vapor deposition process, this coating effectively repels dust, water and grease, making it easy to wipe off annoying stains such as fingerprints and cosmetic marks.

The Aero Bright Coating enhances image-description performance by effectively reducing reflections over a wider wavelength range. Compared to conventional multi-coatings, this new coating greatly improves light transmittance in the lens, while drastically reducing flare and ghost images that deteriorate image quality. It is an original lens coating using a silica aerogel with uniform porous structure as a base material to produce clear high-quality images by assuring and outstanding anti-reflection performance over a broad range of wavelengths. It is currently used on internal elements of the DA* 55mm for improved light transmission and reduced flaring and ghosting. Apparently the DA* 60-250mm also has the A.B. It is used on the new 645D lenses as well.

Update as of 2012:

Pentax released a new coating called the HD coating, which offers better reflectance (i.e. less ghosting/flare) compared to SMC, and it is more durable than Aero Bright and thus suitable for use on the front element as well as other elements.

	SMC	HD	Aero Bright
Reflectance	-	+	++
Durability	+	+	-
Cost	++	+	-

That is all I've turned up on these. However, Pentax has been close to the vest on Coatings all the way back to the 50s. This info is from Pentax Imaging, Dimitrov and Pentax press releases.

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HD CoatingHD CoatingAbout HD Coating

Typically, multicoatings are formed by using vacuum deposition to apply a thin layer to the lens surface. However, this fabrication process also presents problems because of the difficulty in increasing the density of the coating film and the variation in refraction rates and film thicknesses. PENTAX's solution to these problems was our HD Coating, which is fabricated using PENTAX's exclusive special fabrication process, where high-density film is applied with high precision at the nanometer level. This enables the reliable formation of the designed film thickness for a dramatic reduction of the reflection rate (up to 50% compared to conventional coatings) over the entire visible light range. It is also effective in reducing ghosting and flare. Moreover, the film coating has an extremely high hardness for providing superior durability.

From: PENTAX Lens Technology / Lenses / Products | RICOH IMAGING

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Super Protect (SP) CoatingSP Coating

SP coating is a PENTAX-original special coating that provides superior performance in repelling water and oils. It is used on the front surface of the first high-performance lens for effective protection of the lens surface. This coating not only prevents adhesion of dust, water drops, oils, and other substances, but it also makes it easy to wipe off objects that adhere to the lens.

Info from Ricoh: PENTAX Lens Technology / Lenses / Products | RICOH IMAGING

[angerdan]

Seems like Aerobright II is even better. And maybe perfect for IR ?

Product Overview | HD PENTAX-D FA?50mm F1.4 SDM AW | PENTAX STAR LENS | RICOH IMAGING