(Above: Optical design of a new Pentax 18-55mm F3.5-6.7 lens)
See this new Pentax patent, via Mirrorless Rumors.
The most mysterious thing is that 3.0mm back focus distance (of which the Pentax Q's is 9.2mm), especially consider that it is an APS-C lens, which at the first glance I believe that it is just a typo, but which is actually NOT! :-o
After all, could it be still using the K-mount with such short back focus distance?
Logging you in...
Rob · 665 weeks ago
dave9t5 · 665 weeks ago
Mistral75 · 665 weeks ago
Yes, they could. 3mm is the back focus of the lens, not that of the lens mount. It means that the last lens is very close to the sensor. You can achieve this with a K mount, the flange focal distance of which is 45.46mm, and a lens deeply recessing into the mount.
This is coherent with other data from the patent, e.g. a lens's total length of 6cm at f=18mm but with only 1.5cm protruding from the mount: it means that around 4.5cm of the lens are inside the mount.
Thus implying lenses of quite small a diameter, thus coherent with the f/6.7 max. aperture at f=55mm.
dave9t5 · 665 weeks ago
f./6.7 sounds pretty slow, but μ4/3 lens of similar focal lengths (i.e. 14-42mm) are f/5.6 at the long end which is equivalent (in terms of depth-of-field) to f/8.4 on APS-C.
A bigger concern is that they seem to say that distortion at 18mm is 20% ?!?!? On the other hand, they say that "the spherical aberration performance-0.1mm, the chromatic aberration of magnification is-0.01mm,-0.1mm astigmatism"...better than a prime lens.
Anyways, interesting stuff !
frank · 665 weeks ago