Patent: Canon RF 17-70mm f/4-5.6 BR

Fischer

EOS RP
Mar 17, 2020
319
230
BR elements are brilliant but it also makes this lens sound expensive if it comes to market. The difference between the already excellent 35mm f/1.4 L II and the 35mm f/1.4 L II was noticeable in many lighting situations. Its the one Canon lens I kept after going mirrorless. Software can do a lot but nothing beats a clean RAW file.
 

LogicExtremist

Lux pictor
Sep 26, 2021
190
117
BR elements are brilliant but it also makes this lens sound expensive if it comes to market. The difference between the already excellent 35mm f/1.4 L II and the 35mm f/1.4 L II was noticeable in many lighting situations. Its the one Canon lens I kept after going mirrorless. Software can do a lot but nothing beats a clean RAW file.
If the BR lens only fixes CA, and the design requires image stretching from 17mm to about 28mm, are we looking at another heavily distorted lens with an extended focal range, that requires heavy software correction, like the RF 24-240mm?

Welcome to Canon's brave new world! :oops:
 
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Joules

doom
CR Pro
Jul 16, 2017
1,762
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The second paragraph includes an interesting point "BR optics is based on a new organic optical material", which is a fancy way of saying that they're using an optical plastic lens element, that they've sandwiched between two glass elements.
I recall seeing the fantastic nickname 'the blue goo' being given to the BR material by a few forum members for that reason :LOL:
If the BR lens only fixes CA, and the design requires image stretching from 17mm to about 28mm, are we looking at another heavily distorted lens with an extended focal range, that requires heavy software correction, like the RF 24-240mm?

Welcome to Canon's brave new world! :oops:
It isn't necessarily a distorted image though. The wording is a bit confusing perhaps, but the remark about 28 mm isn't saying that the 17 mm setting requires stretching ro a 28 mm field of view.

As the patent shows, the image circle doesn't cover a FF sensor until the lens is zoomed to about 28 mm. So the image will have black corners at wider than 28 mm on a FF sensor. But we can't really know what that means in terms of distortion yet.
 
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AlanF

Stay at home
CR Pro
Aug 16, 2012
9,091
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Had to look up Canon's website for more info on BR lens elements.

It's worth taking a look at their web page, which shows how effectively the BR lens reduces CA in the EF 35mm f/1.4L II USM compared to the EF 35mm f/1.4L USM


"This color fringing – called chromatic aberration – has long been the Achilles heel of lens performance. As part of ongoing efforts to correct chromatic aberration, Canon successively developed and implemented fluorite, UD, and Super UD lenses. Now, aiming to achieve ideal correction of chromatic aberration, Canon has developed BR (Blue Spectrum Refractive) optics, delivering anomalous dispersion characteristics equal to or surpassing fluorite."

ef85a5a36b454f6eb2a259949bfa9653_BR001_EN.png


"BR optics is based on a new organic optical material, developed by reexamining lens material from its molecular structure. This new lens material features unique anomalous dispersion characteristics that are capable of greatly refracting blue light (short wavelengths spectrum), which has traditionally been difficult to focus on a single point."


The second paragraph includes an interesting point "BR optics is based on a new organic optical material", which is a fancy way of saying that they're using an optical plastic lens element, that they've sandwiched between two glass elements.
That write up by Canon's marketing is scientific nonsense. It claims that blue light is more difficult to refract than red, which is the wrong way round. Shorter wavelengths have higher refractive indexes than longer wavelengths.
 
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LogicExtremist

Lux pictor
Sep 26, 2021
190
117
That write up by Canon's marketing is scientific nonsense. It claims that blue light is more difficult to refract than red, which is the wrong way round. Shorter wavelengths have higher refractive indexes than longer wavelengths.
What they probably meant was that index of refraction varies with wavelength, and is usually higher for blue than red, so blue light bends more.

Conversely, when focussing light on a sensor, the diffraction limit, the smallest theoretical spot which can be created by a lens, is dependent on wavelength: Minimum Spot Size(Airy Disk Diameter)[μm]=2.44×λ[μm]×(f/#), which tells us it's easier to get a small circle of blue light than red light at the same aperture.

I don't understand enough about optics to determine which for of chromatic aberrations this is meant to correct, is it just lateral color shift, or is it chromatic focal shift as well? They really could explain thing better.
 

Fischer

EOS RP
Mar 17, 2020
319
230
If the BR lens only fixes CA, and the design requires image stretching from 17mm to about 28mm, are we looking at another heavily distorted lens with an extended focal range, that requires heavy software correction, like the RF 24-240mm?

Welcome to Canon's brave new world! :oops:
Maybe. But those are other issues. BR helps with CA which is a big thing - esspecially for wide lenses.
 
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LogicExtremist

Lux pictor
Sep 26, 2021
190
117
Maybe. But those are other issues. BR helps with CA which is a big thing - especially for wide lenses.
The difference that the BR lens makes on the 35mm f/1.4 L II is pretty amazing.

We'll have to wait and see what this lens have to offer, and what it reveals about Canon's future direction. I've seen a few mentions of this lens and the RF 16mm f/2 as decent APSC lenses if that ever happens.
 

Alam

EOS M50
Dec 24, 2019
34
19
Not faulting Canon for trying new directions with RF lenses. It is good to distinguish themselves from other manufacturers like Sony. Unfortunately that is often leaving out the excellent mid-priced lenses often with either very fast, very high quality, but overpriced lenses or cheaper, lower resolution lens. Canon knows the market and what they are doing, but that leaves me stuck in he middle and I would think, a lot of serious but not professional photographers also stuck in the middle. I mean hell, there is the cheap 50 1.8 or 50 1.2. Just gimme a goddam quality 50mm lens like Nikon's 50 1.8. Then there is the issue of the R6. Yes, it is excellent, but for $100 more I could get a Nikon Z6II with 24-70 f/4. Canon has better focus and overall is better, but as one interested in landscape and general nature photography (I don't do video) I could give a rats ass about the better autofocus. I cringe when I see these reviewers running at you and darting from side to side to test the autofocus. To quote John Shaw in his book...John Shaw's Focus on Nature: "Not Once have my lenses gone out and taken a photograph." I don't intend on switching from Canon. It has served me extremely well and I am sure should I go to mirrorless I would still have equipment capable of excellent photos even going with the cheaper lenses, but won't settle for any lens numerically higher than f4, unless something like a 500mm f/5.6, but I won't hold my breath on that one.
Nah. Imho go cheap and compact or go super expensive

Mid range leave the taste of "if only i spend more"

There's a reason to keep cheap compact and top of the line, grab the cheap for casual and grab the flagship for serious work

In the other hand, there's no reason to have both mid range with top of the line or cheap compact, the benefit is too low
 
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LogicExtremist

Lux pictor
Sep 26, 2021
190
117
Nah. Imho go cheap and compact or go super expensive

Mid range leave the taste of "if only i spend more"

There's a reason to keep cheap compact and top of the line, grab the cheap for casual and grab the flagship for serious work

In the other hand, there's no reason to have both mid range with top of the line or cheap compact, the benefit is too low
Perhaps Canon's biggest markets are beginners who buy lower-tier Rebel DSLRs and M50s, and retired old men who buy all the latest and greatest top-tier stuff often. It could be that the mid-tier enthusiast/prosumer market is not big enough to be a priority. Could this be how Canon is planning to rationalise their product lines? :unsure:

We do know while the RF L-series lenses are replacing their EF counterparts, no surprises there. If the budget RF lenses are replacing both the old APSC lenses, and the various tiers of regular EF lenses, this will result in a drastically rationalised two-tier system, where the choice is either go budget, or pay the big money and go pro. Pure speculation, but food for thought nevertheless.
 
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bbasiaga

Canon Shooter
Nov 15, 2011
483
582
USA
It's looks like Canon are using some more computational photography then the EF system (Vignetting, Distortion) with the entry level R lenses to keep lens sizes smaller and lighter.

Hopefully they will include a remote cable release port on an entry level APS-C R body unlike the M50, in my opinion the good old fashioned wired cable is just easier to use.
I'm wondering if this is the first in a series of lenses for APSc, but which also work on FF as entry level offerings? There has been much talk of RF-s lenses and how unlikely it is that Canon will go that route. And there have been a number of patents that have lenses that just don't quite make a FF image circle, but get close. While they would require stretching on a FF sensor, they'd be fine on a crop. So they could be sold to owners of both body types. And if you bought one as a kit with your APSc body, it would work with your R5 or R6 when you upgrade.

Brian
 

SteveC

R5
CR Pro
Sep 3, 2019
2,506
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Perhaps Canon's biggest markets are beginners who buy lower-tier Rebel DSLRs and M50s, and retired old men who buy all the latest and greatest top-tier stuff often. It could be that the mid-tier enthusiast/prosumer market is not big enough to be a priority. Could this be how Canon is planning to rationalise their product lines? :unsure:

We do know while the RF L-series lenses are replacing their EF counterparts, no surprises there. If the budget RF lenses are replacing both the old APSC lenses, and the various tiers of regular EF lenses, this will result in a drastically rationalised two-tier system, where the choice is either go budget, or pay the big money and go pro. Pure speculation, but food for thought nevertheless.

I think it's simpler and perhaps subtler than that.

Imagine you're trying to create a new (but backward compatible) system. The first thing you're going to want to do is show off its capabilities. So you'll produce high end lenses.

As you want to expand your line of lenses you're going to want lenses as different as can be from the ones already there; those will by their nature pull in more new people than ones similar to what's already there.

The maximum difference is the low end, since the high end is covered.

Only later do you fill in the wide gap between the two. We're not at this step yet.
 

Alam

EOS M50
Dec 24, 2019
34
19
Perhaps Canon's biggest markets are beginners who buy lower-tier Rebel DSLRs and M50s, and retired old men who buy all the latest and greatest top-tier stuff often. It could be that the mid-tier enthusiast/prosumer market is not big enough to be a priority. Could this be how Canon is planning to rationalise their product lines? :unsure:

We do know while the RF L-series lenses are replacing their EF counterparts, no surprises there. If the budget RF lenses are replacing both the old APSC lenses, and the various tiers of regular EF lenses, this will result in a drastically rationalised two-tier system, where the choice is either go budget, or pay the big money and go pro. Pure speculation, but food for thought nevertheless.
Well, IMHO prosumers aren't as big as we thought they are, but they are loud in the internet

Most photog i know make a living with rebels, nikon 3xxx sony a6000 and nifty fifty, especially with how good editing software now the difference between mid and low gear is tiny
 
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LogicExtremist

Lux pictor
Sep 26, 2021
190
117
Well, IMHO prosumers aren't as big as we thought they are, but they are loud in the internet

Most photog i know make a living with rebels, nikon 3xxx sony a6000 and nifty fifty, especially with how good editing software now the difference between mid and low gear is tiny
There may be an element of an uncomfortable truth in what you're saying, maybe mid-tier prosumers are a vocal minority! :(
Without seeing a breakdown of Canon's sales stats, can't say for sure, but someone here is probably resourceful enough to find that sort of data.
 

Alam

EOS M50
Dec 24, 2019
34
19
"WDemand drop as price rises, and demand rises as price drops"

That's already a Law in economy

"With X factor taken out, this law is unquestionable"

That's how the chinese rule the market nowadays
 

Kit.

EOS 5D Mark IV
Apr 25, 2011
2,217
1,531
"WDemand drop as price rises, and demand rises as price drops"

That's already a Law in economy

"With X factor taken out, this law is unquestionable"

That's how the chinese rule the market nowadays
Actually, when all the factors other than price are irrelevant, the good is a Veblen good and the law doesn't work.