16-50mm f/2.8 patent application, potentially that of the revamped DA★

Started Mar 22, 2018 | Discussions thread
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Mistral75 Senior Member • Posts: 1,031
16-50mm f/2.8 patent application, potentially that of the revamped DA★

asahi man told us about the plans of Ricoh Imaging to revamp the current DA★ lenses with new motor drives and electronics, the first two lenses benefiting from this treatment most probably being the 16-50mm and 50-135mm f/2.8.

Today, I will go a step further: 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.

Indeed, a patent application filed by Ricoh Imaging (P2018-45172A) was published today. In the description of the benefits of the invention, emphasis is put 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 includes 15 elements in 12 groups:

The two examples of the patent which include 15 elements in 12 groups too (example #4 and example #7) are pretty close to the current DA★.

Example #4:

Example #7:

Hence my assumption: this patent could be that of a revamped DA★ 16-50mm f/2.8, close to the current lens but with some tweaks in its optical formula aimed at reducing the level of chromatic aberrations.

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