All lenses — even the really expensive ones — have their flaws; Lensfun helps compensate for these flaws using a generous and ever-growing collection of project-approved LCPs (lens-correction profiles).
Due to their general obscurity, many of my older lenses aren’t included in the Lensfun database (at least, not at the time of writing). Some of these lenses get used a lot, so creating LCPs for them was obviously a good investment.
As for the more popular lenses I own, all of them are duely catered for; however, the ‘accuracy’ of the stock LCPs seem somewhat hit and miss to me (in particular, results from the XC 35mm ƒ/2 LCP just don’t look quite right 🤔).
Most of my custom LCPs either contain geometric distortion data only, or the remaining data has been copied from existing samples (I tend to lean on the built-in tools of RawTherapee and GIMP to correct for other abberations). Submitting incomplete LCPs, though acceptable, would be somewhat less than ideal.¹
Furthermore, it’s never been my intention to submit replacement LCPs; ‘beauty is in the eye of the beholder,’ and to promote my humble efforts as being ‘better’ in any way would be very naive and extremely rude (and while it’s often nice to have a choice, submitting them as alternatives would only lead to confusion).²
I’m very pleased with them, personally, but why not judge for yourself?
Fujifilm XC 35mm ƒ/2 custom LCP
¹ ² Having said this, my custom LCPs are completely free and open-source; if you’re a Lensfun maintainer and you’d like to include anything, please feel free — just be sure to leave me out of the politics! 😉