Two f/4 Telephotos Coming
I’m told we can expect two new f/4 telephotos to be announced in January, 2013.
The first will be an EF 300 f/4L IS II, you can obviously expect better coatings, IS and a slightly lighter weight.
The second is said to be an EF 400 f/4L IS, no mention of it being a DO lens. With the price of the coming EF 200-400 f/4L IS 1.4x, mixed with the also expensive 400 f/4 DO IS, there is probably a big market for a 400 f/4 prime that is “affordable”.
Canon has filed a patent for the optical formula of a new EF 300 f/4L IS II.
Patent Publication No. 2012-159726
- 2012.8.23 Release Date
- 2011.2.1 filing date
- F = 300mm focal length
- Fno. 4.0
- Tele ratio 0.68
- Inner Focus
- φr = 68.8mm
- φg1 = 67.8mm
- φg2 = 70.2mm
- When the miniaturization of the optical system, longitudinal chromatic aberration, chromatic aberration of magnification is remarkable
- As the focal length becomes longer, the telephoto lens system, chromatic aberration is noticeable
- There is a method of correcting the aberrations of a material having an anomalous dispersion resin, the resin is difficult to produce high-precision thick
- There is a method of sandwiching a thin glass resin material, the bonding peeling distortion problem bonding at high temperature
- Joining three or more optical elements
- The outer diameter of the resin is increased to reduce the distortion at the time of bonding
- Not adhere to each other resin outer glass element
- Between the optical element of the outside is gone, adhesive, the thickness of the adhesive distribution occurs
- Using a sealing agent to prevent change in shape of the resin and the refractive index change due to moisture absorption
- Do the black outer peripheral portion of the glass element
- Prevent flare and ghosting resin at the outer periphery
- Surface resin glue is not good