Patent: Canon RF 70-200mm f/2.8L IS USM

Ale_F

6D - 7D
Nov 22, 2018
75
51
What are the potential advantages in using the RF 70-200 f/2.8 over the recently released EF 70-200 f/2.8 III? Would the AF be faster? I don't get why Canon releases the 70-200 III and then another almost similar version a year later (albeit for the RF system)
At 70mm the back focus is 14mm, so it's native for ML. What are the other advantages?
Firstly the zoom scheme is different from EF. This lens has a variable dimension and for a ML is a great advantage.
Secondly in the patent there also an example for f4 version....
 
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gmon750

CR Pro
Jan 30, 2015
137
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I thought the bigger RF lens mount allows the lens designer to move the heavier lens elements towards the side of the body. So Canon has not explored that design concept here.

The RF mount is the exact same size as the EF mount. Only the distance between the mount and sensor has been reduced. From what I've read, it does allow elements to be pushed towards the back of the lens, and less elements to be used overall so the lens would technically be lighter.

As to why Canon has not done that, given that they are the master of lenses, I will be more than happy to claim ignorance and simply accept that they most likely know what they're doing.
 
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Jul 21, 2010
31,088
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Pardon, but I still don't get why there are both SP & SSP.
SP is the standard aperture diaphragm. But consider – f/number is focal length divided by aperture diameter. So, a 200mm f/2.8 lens needs a max aperture of ~71mm (200/2.8). Zoom a 70-200mm lens to 70mm, that lens could be f/1.0 (although that's an oversimplification, and even so it would entail all sorts of other optical problems). Regardless, the intent is a constant zoom. A 70mm f/2.8 lens needs a 25mm diameter max aperture, and focal lengths between 200mm and 70mm need max apertures between 71mm and 25mm. The SSP aperture stop creates that effective max aperture to maintain a constant f/2.8 at all focal lengths.
 
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Nov 29, 2018
113
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I had the R and the 24-105/4 L on a two-week rental. Primarily, I used it for wildlife, with some landscape and running border collies thrown in.

Much of the wildlife was flying bald eagles, fishing for salmon, and most of the time the lens was the 500/4 Lii, sometimes with the 1.4x and sometimes not. This is a demanding subject, under adverse conditions of cold, wind and low light. The R performed very well, focusing very accurately whenever I did my part of the job well. Sure, a higher frame rate would have been nice, as it would for fast, unpredictable action in sports. But the camera was capable of doing the job. I imagine something will be coming along in the not too distant future which will be more capable for sports and high action.

Before sending the camera back, I took it out for a little torture test. I put the 2xiii on the 100-400 L ii and went to the local duck pond to try get some photos of ducks in flight. I had to bump the ISO up much higher than I would have liked to get a decent shutter speed for something moving as fast as a duck, but the camera was capable of picking up focus and locking on. It was not easy, but then this subject never is, and focus was noticeably slower. But if you prefocused to near the correct distance of the incoming ducks, the camera could pick them up and deliver an in focus photo.

Part of the torture test was the background of the duck pond. It is little aspens, pines and willows--a very dense and busy background. Sasquatch could be napping in there. I chose it because it would be a very difficult situation for the autofocus to work, and work it did. The EVF also worked well. I was surprised, actually. An OVF would still be better in this situation but the R still did the job and is a testament to how good its EVF is. That said, the EVF could still be better, more pixels and faster refresh. Maybe the next generation, a year or two down the road.

I will not be buying the R, but I am impressed. I wanted to see if mirrorless could meet my needs. My only real disappointment was not getting to use it in extreme cold, minus 20 to minus 40, to see if and when the touch interface failed, The coldest I worked with the camera was minus 11F. It worked fine at that temp. If the next RF camera more closely meets my needs, I will be buying.
 
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jolyonralph

Game Boy Camera
CR Pro
Aug 25, 2015
1,423
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This doesn't look like an L lens to me.

Compare it with the optical formula of the EF 70-300 IS II, it's not identical but it's similar in number and layout of elements.

This is a design for a (relatively) cheap lens - a budget RF 70-200 f/2.8 IS

I also don't think such a lens would come to market. I think far more likely would be a slower 70-300 type variant of the design. But who knows!
 
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Michael Clark

Now we see through a glass, darkly...
Apr 5, 2016
4,722
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SP is the standard aperture diaphragm. But consider – f/number is focal length divided by aperture diameter. So, a 200mm f/2.8 lens needs a max aperture of ~71mm (200/2.8). Zoom a 70-200mm lens to 70mm, that lens could be f/1.0 (although that's an oversimplification, and even so it would entail all sorts of other optical problems). Regardless, the intent is a constant zoom. A 70mm f/2.8 lens needs a 25mm diameter max aperture, and focal lengths between 200mm and 70mm need max apertures between 71mm and 25mm. The SSP aperture stop creates that effective max aperture to maintain a constant f/2.8 at all focal lengths.

F-number is focal length divided by entrance pupil (often mislabeled as the *effective aperture*), which is affected by magnification between the physical aperture diaphragm and the front of the lens. The SSP in Canon constant aperture zoom lenses only compensates for the slight difference in the ratio between changes in magnification and changes in entrance pupil diameter as the lens is zoomed in and out. There are also many variable aperture Canon EF lenses that us SSPs.

Including an SSP in a non-retrofocus lens, such as a 70-200mm f/2.8 lens for a 20mm registration distance, is new territory for Canon EOS lenses.

With 44mm registration distance EF lenses, all the zoom designs thus far that incorporate an SSP are also retrofocus designs, at least when zoomed at their widest focal lengths.

This is true of every lens with block diagrams included at the Canon Camera Museum site. Many very early EF lenses do not have block diagrams there, but most mid-grade and higher lenses introduced since about 1990 do.

Looking at the lists below, we can see some tendencies:

- Lenses with secondary apertures are "L" grade premium lenses or mid-to-upper tier consumer lenses. (The singular exception in terms of optics is listed next)

- The lower tier "kit" zoom lenses and other "entry level" zoom lenses produced during the same eras, even those that also use retrofocus designs, usually did not include a secondary aperture in their design. A pair of 28-80mm kit lenses from 1999, which share the same optical formula and only differ with regard to the type of focus motor each uses, are the only exceptions.

- Some lenses with secondary apertures are constant aperture while others are variable aperture lenses.

- All lenses with secondary apertures use retrofocus designs.

- The vast majority of retrofocus entry level lenses are not given a secondary aperture.

- There are no Canon EF zoom lenses of any grade which do not use a retrofocus design that include secondary apertures in their design.

In summary, the thing Canon lenses with secondary apertures have in common is they are retrofocus designs incorporated into zoom lenses well above entry level (with the noted exception of one lens design that was offered in USM/non-USM versions).

EF zoom lenses with an SSP shown in their block diagrams at The Canon Camera Museum:

- EF 28-70mm f/2.8L USM (November 1993) This is the oldest lens with a published block diagram at the Canon Camera Museum that includes a secondary aperture.
- EF 17-35mm f/2.8L USM (1996)
- EF 24-85mm f/3.5-4.5 USM (1996)
- EF 28-80mm f/3.5-5.6 II (1999)
- EF 28-80mm f/3.5-5.6 V USM (1999)
- EF 16-35mm f/2.8L USM (2001)
- EF 24-70mm f/2.8L USM (2002)
- EF 17-40mm f/4L USM (2003)
- EF-S 10-22mm f/3.5-4.5 USM (2004)
- EF 24-105mm f/4L IS USM (2005)
- EF-S 17-55mm f/2.8 IS USM (2006)
- EF 16-35mm f/2.8L II USM (2007)
- EF 8-15mm f/4L Fisheye USM (2011)
- EF 24-70mm f/2.8L II USM (2012)
- EF 24-70mm f/4L IS USM (2012)
- EF 16-35mm f/4L IS USM (2014)
- EF 24-105mm f/4L IS II USM (2016)
- EF 16-35mm f/2.8L III USM (2016) - shows *three* aperture positions in the block diagram

EF zoom lenses that do show the SP position but no SSP in their block diagrams at TCCM:

- EF 35-135mm f/4-5.6 USM (1990)
- EF 100-300mm f/4.5-5.6 USM (1990)
- EF 28-105mm f/3.5-4.5 USM (1992)
- EF 20-35mm f/3.5-45 USM (1993)
- EF 28-80mm f/3.5-5.6 II USM (1993)
- EF 35-80mm f/4-5.6 III (1995)
- EF 70-200mm f/2.8L USM (1995)
- EF 75-300mm f/4-5.6 IS USM (1995)
- EF 28-135mm f/3.5-5.6 IS USM (1998)
- EF 55-200mm f/4.5-5.6 USM (1998)
- EF 22-55mm f/4-5.6 USM (1998)
- EF 100-400mm f/45-5.6L IS USM (1998)
- EF 75-300mm f/4-5.6 III (1999)
- EF 75-300mm f/4-5.6 III USM (1999)
- EF 70-200mm f/4L USM (1999)
- EF 28-90mm f/4-5.6 (2000)
- EF 28-90mm f/4-5.6 USM (2000)
- EF 28-200mm f/3.5-5.6 (2000)
- EF 28-200mm f/3.5-5.6 USM (2000)
- EF 28-105mm f/3.5-4.5 II USM (2000)
- EF 70-200mm f/2.8L IS (2001)
- EF 28-105mm f/4-5.6 (2002)
- EF 28-105mm f/4-5.6 USM (2002)
- EF 28-90mm f/4-5.6 II USM (2002)
- EF 90-300mm f/4.5-5.6 USM (2002)
- EF 28-90mm f/4-5.6 II (2003)
- EF 55-200mm f/4.5-5.6 II USM (2003)
- EF 90-300mm f/4.5-5.6 (2003)
- EF 28-300mm f/3.5-5.6L IS USM (2004)
- EF 70-300mm f/4.5-5.6 DO IS USM (2004)
- EF-S 17-85mm f/4-5.6 IS USM (2004)
- EF-S 18-55mm f/3.5-5.6 (2004)
- EF-S 18-55mm f/3.5-5.6 USM (2004)
- EF 28-90mm f/4-5.6 III (2004)
- EF-S 18-55mm f/3.5-5.6 II (2005)
- EF-S 18-55mm f/3.5-5.6 II USM (2005)
- EF 70-300mm f/4-5.6 IS USM (2005)
- EF 70-200mm f/4L IS USM (2006)
- EF-S 18-55mm f/3.5-5.6 IS (2007)
- EF-S 55-250mm f/4-5.6 IS (2007)
- EF-S 18-200mm f/3.5-5.6 IS (2008)
- EF-S 15-85mm f/3.5-5.6 IS USM (2009)
- EF-S 18-135mm f/3.5-5.6 IS (2009)
- EF 70-200mm f/2.8L IS II USM (2010)
- EF 70-300mm f/4-5.6L IS USM (2010)
- EF-S 18-55mm f/3.5-5.6 III (2011)
- EF-S 18-55mm f/3.5-5.6 IS II (2011)
- EF-S 55-250mm f/4-5.6 IS II (2011)
- EF 200-400mm f/4L IS USM Extender 1.4x (2013)
- EF-S 55-250mm f/4-5.6 IS STM (2013)
- EF 24-105mm f/3.5-5.6 IS STM (2014)
- EF 100-400mm f/4.5-5.6L IS II USM (2014)
- EF 70-300mm f/4-5.6 IS II USM (2016)

EF lenses with block diagrams at TCCM that show no aperture positions:


- EF 35-350mm f/3.5-5.6 L USM (1993)
- EF-S 18-135mm f/3.5-5.6 IS STM (2012)
- EF-S 18-55mm f/3.5-5.6 IS STM (2013)
- EF-S 10-18mm f/4.5-5.6 IS STM (2014)
- EF 11-24mm f/4L USM (2015)
- EF-S 18-135mm f/3.5-5.6 IS USM (2016)

Every lens that includes a block diagram but does not show aperture position(s) is a retrofocus design.

I find the exclusion of aperture position(s) for the 11-24mm f/4's block diagram particularly curious. Other than the 1993 35-350mm, all the rest are relatively new EF-S variable aperture lenses.
 
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