Canon Patents

Patent: Canon continues to work on focal length reducers

Canon Rumors
Posted onJan 11, 2019 at 8:18 AM

Canon continues to work on focal length reducers.

What’s a focal length reducer you ask?

It’s an adapter that reduces the focal length of a lens and at the same time increases the maximum aperture, basically the opposite of teleconverters.

Canon has yet to release such a product, but we suspect this type of converter could benefit the EOS M system as well as an upcoming APS-C EOS R body.

Below are a bunch of focal length reduced optical formulas from Japan patent JP-A-2019-003074

Specification and lens arrangement of master lens 1 (18-55mm, F2.8)

  • Zoom ratio: 3.05
  • Focal length: 17.50 – 53.3 mm
  • F number: 2.80 – 2.80
  • Half angle of view: 36.65 – 13.71
  • Image height: 13.02 – 13.02mm
  • Lens length: 148.81 – 172.70mm
  • Back focus: 35.51 – 40.31mm

Specification and lens arrangement of master lens 1 with reducer 1

  • Focal length: 11.36mm
  • F number: 1.82
  • Half angle of view: 36.67
  • Image height: 8.46mm
  • Lens length: 142.26mm
  • Back focus: 2.00mm

Specification and lens arrangement of master lens 2 (34mm, F1.4)

  • Focal length: 34.20mm
  • F number: 1.45
  • Half angle of view: 32.32
  • Image height: 21.64mm
  • Lens length: 129.16mm
  • Back focus: 39.35mm

Specification and lens arrangement of master lens 2 with reducer 5

  • Focal length: 23.92mm
  • F number: 1.02
  • Half angle of view: 32.33
  • Image height: 15.14mm
  • Lens length: 125.59mm
  • Back focus: 2.00mm
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C

criscokkat

EOS M50
#2
Sep 26, 2017
99
55
Madison, WI
#2
I'm not sure how this would affect an APS-C R camera - both of these seem to change it to a back focus 2 mm behind the reducer, which would work with a EF-M. I wonder if both of these are R adapters or if one of them are a new EF to EF-M adapter and the other is an R to EF-M?

Not that they couldn't do this with an APS-C R with a R to R focal length adapter, but I don't think these specific patents apply.
 
Don Haines

Don Haines

posting cat pictures on the internet since 1986
#3
Jun 4, 2012
7,535
648
Canada
#3
criscokkat said:
I'm not sure how this would affect an APS-C R camera - both of these seem to change it to a back focus 2 mm behind the reducer, which would work with a EF-M. I wonder if both of these are R adapters or if one of them are a new EF to EF-M adapter and the other is an R to EF-M?

Not that they couldn't do this with an APS-C R with a R to R focal length adapter, but I don't think these specific patents apply.
Click to expand...
R to M seems to make the most sense to me.....
 
K

Kit.

EOS T7i
#4
Apr 25, 2011
533
154
#4
With 2mm back focus, it needs to be a fixed lens, otherwise the user risks damaging the sensor while mounting.
 
Berowne

Berowne

EOS M5
#5
Jun 7, 2014
225
73
#5
Is this the "concept lens", which was mentioned by Mr. Mizoguchi in the interview with Dave Etchells at Imaging Resource?
 
J

Joules

EOS M50
#6
Jul 16, 2017
96
25
Hamburg, Germany
#6
Exciting stuff. If my calculations are correct, reducer 1 turns an APS-C sensor Camera into an actual FF equaivalent with an effectivw crop of 1 (11.36/17.5*1.6) and reducer 5 yields an effective crop factoe of 1.2 (23.92/34.2*1.6) which is still really nice.

Probably won't be cheap adapters, if they come to market. And they really blur the lines between APS-C and FullFrame.
 
B

Bob Howland

EOS T7i
#9
Mar 25, 2012
391
10
#9
Joules said:
Exciting stuff. If my calculations are correct, reducer 1 turns an APS-C sensor Camera into an actual FF equaivalent with an effectivw crop of 1 (11.36/17.5*1.6) and reducer 5 yields an effective crop factoe of 1.2 (23.92/34.2*1.6) which is still really nice.

Probably won't be cheap adapters, if they come to market. And they really blur the lines between APS-C and FullFrame.
Click to expand...
Your ratios are correct, but the larger sensor being assumed for reducer 1 is actually APS-C, not FF, and the smaller sensor being assumed is even smaller than APS-C. A linear reduction of 1.58 would change the aperture by 4/3 stop and is awfully close to the 1.60 (or more typically 1.62) crop factor for Canon APS-C sensors. As much as I would like to see such a reducer for FF lenses and Canon APS-C sensors, I have to think that a good one would be extremely difficult to design and very expensive.
 
J

Joules

EOS M50
#10
Jul 16, 2017
96
25
Hamburg, Germany
#10
Bob Howland said:
Your ratios are correct, but the larger sensor being assumed for reducer 1 is actually APS-C, not FF, and the smaller sensor being assumed is even smaller than APS-C. A linear reduction of 1.58 would change the aperture by 4/3 stop and is awfully close to the 1.60 (or more typically 1.62) crop factor for Canon APS-C sensors. As much as I would like to see such a reducer for FF lenses and Canon APS-C sensors, I have to think that a good one would be extremely difficult to design and very expensive.
Click to expand...
You are right, the first adapter is shown to be used with an APS-C lens. I didn't pay attention to that. It does not necessarily mean that it could not be used with full frame lenses on an APS-C sensor. Maybe the example actually references a use case flip314 mentioned?

Anyway, these adapters look really strange. Why does the lens length decrease when used with the reducer? And does the reducer sit inside the camera mount to enable this 2mm back focus distance or am I missing something there.

I would have thought that producing such adapters wouldn't be too hard for Canon, seeing that the Metabones ones seem to be quite good and Canon has great Teleconverters, which are similar in principle in my mind. Honestly I'm surprised this generates so little interest on this forum.
 
TommyLee

TommyLee

EOS T7i
#11
Sep 29, 2012
295
1
#11
I have always wanted to be a little taller..
...and slimmer...can I have both?

Also ..Can I combine this with the Fountain of Youth?
 
Last edited:
J

johnhenry

EOS M50
#12
Apr 24, 2013
75
0
#12
Nice of Canon to think about us. Reducers have been around for the telescope people for nearly 50 YEARS now.

For my 8" f/10 Maksutov Cassegrain, I have a choice of a 0.63X, 0.50X , 0.40X, 0.33x and a 0.25X.

For my refractor, a 0.8X reducer/field flattener has been available 30 years.

I guess Cannon could see the writing in the magazines and figured "We should do something to make it look like we know what we are doing."
 
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