There are already rumors that Ricoh is planning to revamp the current DA★ lenses with new motor drives and electronics and the first two lenses benefiting from this treatment will most likely be the current 16-50mm f/2.8 and 50-135mm f/2.8 models.
In the case of the DA★ 16-50mm f/2.8 the revamping could include some tweaks in the optical formula aimed at mitigating one of the main weaknesses of the current lens, its high level of chromatic aberrations.
A recently published Ricoh Imaging patent application (P2018-45172A) put emphasis on the minimisation of chromatic aberrations. There are 10 examples in the patent. All of them could be commercially designated as 16-50mm f/2.8 APS-C zoom lenses (more precisely: the shortest focal distance goes from 16.46mm to 16.52mm, the longest focal distance goes from 48.35mm to 48.83mm, maximum aperture is always f/2.9, the image circle’s radius is 14.24mm). Five examples include 16 elements in 13 groups, three examples include 17 elements in 13 groups, two examples include 15 elements in 12 groups.
The current smc Pentax-DA★ 16-50mm f/2.8 ED AL [IF] SDM lens includes 15 elements in 12 groups:
The two examples in the patent include 15 elements in 12 groups too (example #4 and example #7) and are pretty close to the current DA★.
Example #4:
Example #7:
Conclusion: this patent application (2018-45172) could be for the new DA★ 16-50mm f/2.8 lens that will be close to the current model but with some tweaks in its optical formula aimed at reducing the level of chromatic aberrations.
Thanks Mistral75!
