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Can I update the Adapter EF-EOS R 0.71x with a R5 C?


Can I update the Canon Mount Adapter EF-EOS R 0.71x with an R5 C camera or do I need a C70 for the update? I don't have a Canon Mount Adapter EF-EOS R 0.71x yet but I want to purchase one for my R5 C. I wanted to know if I can update the firmware before I purchase the adapter. The image attached was taken from a youtube video demonstrating updating the adapter's firmware with a C70.

Screenshot 2023-08-06 at 22.59.35.png




Greetings ,

The 0.71x adapter is supported under firmware  the features and improvements offered in this firmware are vast and many.  I recommend upgrading.  


Bay Area - CA

~R5 C ( ~RF Trinity, ~RF 100 Macro, ~RF 100~400, ~RF 100~500, +RF 1.4x TC, +Canon Control Ring, BG-R10, 430EX III-RT ~DxO PhotoLab Elite ~DaVinci Resolve ~Windows11 Pro ~ImageClass MF644Cdw/MF656Cdw ~Pixel 8
~CarePaks Are Worth It


The 0.71x adapter was designed for the EOS C70.  I don't see any literature about it being supported on the EOS R5 C.

From the adapter's version 1.3.0 Firmware notes, it states "It is also necessary to update the firmware of the camera body of the EOS C70."

Maybe the R5 C will be supported in the future? If so, I would assume that it would need to be set up to use a Super35 crop of the sensor.


Camera: EOS 5D IV, EF 50mm f/1.2L, EF 135mm f/2L
Lighting: Profoto Lights & Modifiers



Here is the info guys 🙂  I have not tested  as I do not have the adapter and do not shoot in Super35 or 16.  I took this to mean it's now supported.  Note, to upgrade the adapter's FW, you will need to be in Photo mode on the camera.  To upgrade the R5 C's FW you will be in Cinema mode.  **Use an SD card for both.

Installation Instructions
Firmware Version incorporates the following enhancements:
1. The following features are enabled when the following lenses are attached: CN-E14-35mm T1.7 L S, CN-E20-50mm T2.4 L F, CN-E45-135mm T2.4 L F, CN8x15 IAS S/E1,:
- Displaying metadata, such as the model name and the focal distance of the lens attached.
- Displaying T number.
- Support for Peripheral Illumination Correction and Chromatic Lens Aberration Correction.
- Support for Dual Pixel CMOS AF autofocus(CN8x15 IAS S/E1 only)
- Support for [Dual Pixel Focus Guide].
2. The following features are enabled when the following lenses are attached: RF-S18-45mm F4.5-6.3 IS STM, RF-S18-150mm F3.5-6.3 IS STM:
- Adds a menu to switch lens functions. (Focus Ring, Control Ring, Lens Optical Image Stabilization)
3. Adds EF lenses compatible with EF-EOS R 0.71x Mount Adapter.
CN-E14mm T3.1 L F
CN-E20mm T1.5 L F
CN-E24mm T1.5 L F
CN-E35mm T1.5 L F
CN-E50mm T1.3 L F
CN-E85mm T1.3 L F
CN-E135mm T2.2 L F
EF14mm f/2.8L II USM
EF24mm f/1.4L II USM
EF35mm f/1.4L II USM
EF50mm f/1.2L USM
EF85mm f/1.2L II USM
EF135mm f/2L USM
4. Enables left/right switching with one touch when using Magnify. (When recording 8K RAW with VR lens attached.)
5. Enables magnify during 8K MP4 recording. (Not available when HDMI 4K is output.)
6. Improves switching time between Video/Photo mode.
7. Adds Power Saving Mode.
8. Enhances Clear Scan resolution.
9. Adds Digital-Teleconverter function. (1.5x /2x /2.5x /3x)
10. Enables to change WFM size.
11. Enables to change Vector scope gain by touch.
12. Enables to change WFM/Vector scope opacity.
13. Improves AF performance.
- Enables tracking frame to change variably depending on subject.
- Enables to detect heads facing sideways or backwards, or in situations such as when wearing a helmet.
- Enables to select Face via control ring/dial.
14. Adds [Subject Selection] assignable function via control ring/dial.
15. Adds [Canon 709 / BT.709] to the Gamma/Color Space in Custom Picture setting.
16. Adds [CMT 709] in Proxy Rec Color Conversion.
17. Adds [CMT 709] in View Assist.
18. Adds [G Gain] in White Balance in Custom Picture settings.
19. Adds support for 4CH display in audio meter.
20. Fixes an issue in which the camera is unable to shoot properly under certain conditions in still image mode after having updated the camera firmware to Version

* 1-19 are the changes in Version, and 20 is the addition in Version

Bay Area - CA

~R5 C ( ~RF Trinity, ~RF 100 Macro, ~RF 100~400, ~RF 100~500, +RF 1.4x TC, +Canon Control Ring, BG-R10, 430EX III-RT ~DxO PhotoLab Elite ~DaVinci Resolve ~Windows11 Pro ~ImageClass MF644Cdw/MF656Cdw ~Pixel 8
~CarePaks Are Worth It


Yes the advantages of speed boosting the cropped sensor on the R5 C is a reduced rolling shutter effect, 1 extra stop of light, and the ability to shoot RAW 12bit in 5.9k with a near full frame sensor. Guess I'll have to get an adapter to confirm it. I always update my cameras to the latest FW I'm on now. Thank you for your replies, I was hoping someone had already done this that wanted to answer.

Hi Robetus, did you ever use the r5c with the reducer? did it work?

The speed reducer will for sure work but I never got it to try and update the firmware with the r5c.

OK, if you're happy with the very drastic loss of resolution, then I guess this could make sense.

Resolutions don't matter, the worlds most advance digital video/cinema camera the ARRI ALEXA 35 shoots in 4.6k.


The 0.71x adapter (like Speedboosters etc.) shrinks the image from a full-frame lens down to an APS-C sensor.  Since the R5C has a full frame sensor, this combination seems like a really bad idea.  Best case the R5C goes into crop mode, and the 45 megapixel camera you paid for is now a 17 megapixel camera.  Worst case, it just doesn't work.