# Canon R with EF-S lens?



## Slyham (Sep 21, 2018)

Excuse my ignorance, but I feel like I am missing something. The new adapters for the RF mount state that it can take EF-S lenses. However, I thought EF-S lenses were only for crop sensors. How can a full frame sensor use a EF-S lens?


----------



## privatebydesign (Sep 21, 2018)

It can't. But it will cover the area of the sensor used when you shoot the cropped 4k so you can use EF-s lenses for 4k video.


----------



## jolyonralph (Sep 21, 2018)

Yes, the current crop 4K implementation on the R actually makes sense if you want to use low-cost low weight EF-S lenses for video. Videographers have been using EF-S lenses with canon Cine cameras for ages.

The EF-S 10-18 for example is a very cheap and compact lens, of high quality, for 4K ultrawide-wide video with the R.

In fact, it makes so much sense that I hope that Canon will keep at least an option for APS-X crop 4K on future bodies when they finally figure out how to do full-width 4K on sensors of this class.

(I actually had my EF-S 10-18 put aside ready to sell along with an infra-red converted EOS 1100D that I'm trying to get rid of, but now I'm going to keep the 10-18!)


----------



## Slyham (Sep 21, 2018)

Interesting. Is it only for 4k video? It is capable to take a cropped picture with EF-S?
Thanks


----------



## Macoose (Sep 21, 2018)

I saw in the manual that the R has a crop mode. Does that mean it would match an EF-S lens?
Or does the camera just use the area in the center of the sensor?


----------



## bhf3737 (Sep 21, 2018)

Slyham said:


> Excuse my ignorance, but I feel like I am missing something. The new adapters for the RF mount state that it can take EF-S lenses. However, I thought EF-S lenses were only for crop sensors. How can a full frame sensor use a EF-S lens?


I remember Rudy Winston in one of the introductory videos of EOS R system said: "When attaching an EF-S lens via any of Canon’s new R-series mount adapters, the EOS R automatically switches to APS-C crop mode". If correct, it should be around 18Mpixel still picture. Can it be done using 3rd party lenses such as Sigma 18-35mm f/1.8 DC? Not sure. Perhaps the new communication protocol and connection pins play a role in this.


----------



## Sharlin (Sep 21, 2018)

bhf3737 said:


> I remember Rudy Winston in one of the introductory videos of EOS R system said: "When attaching an EF-S lens via any of Canon’s new R-series mount adapters, the EOS R automatically switches to APS-C crop mode". If correct, it should be around 18Mpixel still picture.



Yes, except that the pictures will be about 11.8Mpix. Remember, you have to square the crop factor.


----------



## bhf3737 (Sep 21, 2018)

Sharlin said:


> Yes, except that the pictures will be about 11.8Mpix. Remember, you have to square the crop factor.


Yes, you are absolutely right.  
Crop mode on 5DSR is about 20Mpix and on EOS R is close to 12Mpix.


----------



## Don Haines (Sep 23, 2018)

Slyham said:


> Interesting. Is it only for 4k video? It is capable to take a cropped picture with EF-S?
> Thanks


From what I understand, it will use the center 40% of the sensor and take still images when an EF-S lens is mounted.... It will be interesting to see if this function can be modified in the menus, as (for example) I can use a Tokina 11-66 F2.8 crop lens on a 6D2, and at 16mm it covers the full sensor...


----------



## Mt Spokane Photography (Sep 24, 2018)

Don Haines said:


> From what I understand, it will use the center 40% of the sensor and take still images when an EF-S lens is mounted.... It will be interesting to see if this function can be modified in the menus, as (for example) I can use a Tokina 11-66 F2.8 crop lens on a 6D2, and at 16mm it covers the full sensor...


Check page 82 of the manual. When a EF-s lens is mounted, it uses a 1.6 crop and options to use other crops are disabled. So if your 3rd party lens tells the camera that it is a EF-s lens, it should set the crop and you cannot override it.


----------



## jolyonralph (Sep 24, 2018)

Mt Spokane Photography said:


> Check page 82 of the manual. When a EF-s lens is mounted, it uses a 1.6 crop and options to use other crops are disabled. So if your 3rd party lens tells the camera that it is a EF-s lens, it should set the crop and you cannot override it.



I don't think that the lens actually tells the camera it is crop, this wouldn't have been built into the original EF protocol because there was no EF-S at the time. What's more likely is that the camera checks for 'EF-S' in the lens name, which would make it likely that third party lenses wouldn't automatically crop.


----------



## bbb34 (Sep 24, 2018)

The EF lens interface is a bidirectional serial bus. The definition of data content is in the realm of software and may very well have evolved over the time.

Nevertheless, it appears that EF lenses send their identifier to the body, and the body firmware has a lookup table with the details of all genuine EF lenses.


----------



## Don Haines (Sep 24, 2018)

bbb34 said:


> The EF lens interface is a bidirectional serial bus. The definition of data content is in the realm of software and may very well have evolved over the time.
> 
> Nevertheless, it appears that EF lenses send their identifier to the body, and the body firmware has a lookup table with the details of all genuine EF lenses.



This is how I understand it. It will be interesting to see what happens with third party crop lenses......


----------



## Mt Spokane Photography (Sep 24, 2018)

jolyonralph said:


> I don't think that the lens actually tells the camera it is crop, this wouldn't have been built into the original EF protocol because there was no EF-S at the time. What's more likely is that the camera checks for 'EF-S' in the lens name, which would make it likely that third party lenses wouldn't automatically crop.



Each lens sends a code to the camera identifying it. The camera then knows exactly which lens is mounted. This has been true for all EF lenses. There is a lookup table in the camera with lens codes that may be used to control the way the camera works with a lens. This was well thought out when EF came along, not perfect, but it is what there is. Obviously, older cameras have a out of date lookup table.

there is a little more detailed info as to how this works here:

Lens ID Codes


Here are some typical lens ID codes. If there is no matching code in the camera, it will not know which lens is mounted. For example, tag 183 is for a Canon 100-400mm L. Several 3rd party lenses also send tag 183 to the camera. I don't know if they add the suffix (183.1, 183.2, etc)

EXIF Lens Tags for Canon


----------



## jolyonralph (Sep 25, 2018)

Mt Spokane Photography said:


> Here are some typical lens ID codes. If there is no matching code in the camera, it will not know which lens is mounted. For example, tag 183 is for a Canon 100-400mm L. Several 3rd party lenses also send tag 183 to the camera. I don't know if they add the suffix (183.1, 183.2, etc)
> 
> EXIF Lens Tags for Canon



Ok, interesting reading - the suffix isn't sent between the camera and the lens, only the code as an integer value. Also it's interesting to see variation between the metadata saved by different camera models. Some (eg the 500D) save the lens name within the metadata, others (eg the 80D) don't only saving the lens code.

It must be quite a difficult task for Lightroom etc to accurately identify which lens was being used (Canon or Sigma) if both share the same code ID. This is a big deal when it comes to ensuring the right automatic lens corrections are applied.


----------

