[voltraizer]

Is there a difference between coatings done for newer lens and lens made for films (say those bought or made in early 2000)? & what about ghosting and flares?-- someone told me-- ghosting inside digital sensors are caused not by front elements but inside reflection due to incompatibilty between films lens and dgital sensors? is this true?

[monochrome]

Is there a difference between coatings done for newer lens and lens made for films (say those bought or made in early 2000)? & what about ghosting and flares?-- someone told me-- ghosting inside digital sensors are caused not by front elements but inside reflection due to incompatibilty between films lens and dgital sensors? is this true?

Digital sensors have a glossy finish - film is more of a matte finish. Under certain conditions light reflects off the glossy sensor onto the rear lens element of some lenses causing a green ghost image. Film didn't cause that reflection.

Modern "digital optimized" lenses are supposed to have a coating on the rear element to reduce/eliminate this effect.

[Canada_Rockies]

As monochrome says, Yes, sort of.

Many of us use older lenses quite happily. I'm not running the oldest lenses in this forum by a long shot, but my M 400/5.6 and M 100/4 macro are about 30 years old. Others use 50 year old M42 lenses (with single or even no coating), who are also happy with the results.

[Adam]

The SMC coating found on all K-mount lenses is great - far better than that of many competitors.

However, although this isn't really advertised, many new lenses have a ghostless coating, which reduces flare even further. This coating is found on FA* and higher-end DA lenses.
Weather-resistant lenses also feature a special coating which protects them from dust.

M42 lenses without SMC in their names have older coatings that aren't quite as effective as SMC, or even no coating, as canada rockies said.
In the past, pentax also produced budget lenses without coating.