kiwiengr said:
amorse said:
kiwiengr said:
Are these continued rumours of of various EF lenses a ruse by Canon to have the punters believe that FF mirrorless is not going elsewhere in terms of mount?
Do we know for sure that these are EF lenses (honest question)? The article here and on Canon news don't mention EF specifically so unless the patent itself says they are EF mount lenses, I'm not sure it's indicative of mirrorless applications either way. I am not familiar enough with the patent application process to verify in the patent itself to be fair.
This patent covers the following:
EF 200mm f/2
EF 400mm f/2.8
EF 800mm f/5.6
Hi amorse!
I' am trying to deliver a more specific and scientific answer to your question, if those formulae are EF or other lens types.
Short answer:
You'll have to look into the patents in detail so see the values of the optical formulae.
The people at Canon Rumors, Canon News, Northlight, etc. normally do that before they post an article or rumor.
So normally you can believe them, if they write EF or EF-whatever mount.
Long answer:
To get the answer it is necessary to understand the patent and look at the calculated optical formulae in detail:
First you can find there the value of the "
image height" which is half the radius of the image circle on the image plane.
Here for all 5 examples this is 21.6 mm, which is typical for a FF sensor. So none of the calculated formulae is just for APS-C sensors like EF-S and EF-M mount.
The second interesting value is the "
back focus BF". This is the distance between the last optical element and the image plane. For a normal EF mount/FF this must be more than about 44 mm. Otherwise the optical elements would protrude over the lens mount into the mirror box and therefore the mirror would collide with the lens. For EF-S or EF-M this can be shorter, but I don't have memorised the values.
For all these 5 examples (tele lenses) the BF is somewhere between 54.0 and 77.6 mm, so longer than 44 mm.
This also indicates that these are EF/FF lenses.
If there was a new EF x mirrorless mount for FF sensors, these optical formulae would also work for that mount but the lens barrel would be longer to compensate the shorter flange distance between camera mount and image plane /sensor.
Edit: Normally nowhere in the patent the lens type or lens mount is mentioned. The patent just covers the optical formula and other specific information like the use of special optical glass or DO elements.