Adapting EF lenses to an EOS R6 Mark II

[CarterS66]

Are there any EF lenses that don’t have a 1.6x crop when you adapt them to an RF mount? For example, I want to purchase a 24-70 to be able to take astrophotography pictures but also be able to do a wide range of shots. I don’t have the budget for an RF 24-70, but I’m worried that an EF 24-70 will have a 1.6x crop

[Waddizzle]

The EF 24-70mm is a full frame lens.  Avoid the EF-S lenses.

Lenses do not have crop factors, the camera bodies do.  The EOS R6 Mark II is a full frame sensor camera, which means it does not have a crop factor.  BUT…. (There is always a but)

But, EOS lenses have come in two different flavors.  There are EF lenses and EF-S lenses.  The EF series of lenses project a full size image circle on the sensor and are made for full frame cameras.  

The EF-S series of lenses are made for APS-C sensor cameras.  They project a smaller image circle that is just large enough to cover the smaller APS-C image sensors.  The EF-S lenses use a lens mount that prevents them from being mounted on a full frame camera body.

[CarterS66]

Okay, thanks for your clarification. Whenever I use my Sigma 30mm f/1.4 or Canon EF 50mm f/1.4, the camera won’t let me change the crop factor from 1.6x even though I believe neither of these lenses are EF-S lenses.

[deebatman316]

Do you have a different camera to test the mount adapter or lens on. It could be a faulty mount adapter or camera. Full Frame EF lenses won't cause a 1.6x crop. 3rd Party APS-C lenses may or may NOT cause the camera to crop. 3rd Party APS-C lenses use the EF Mount with an APS-C image circle.

[CarterS66]

Funny enough I just retested my Canon EF 50mm f/1.4 and it works full frame. I think it was just that the sigma 30mm f/1.4 lens I was using was causing the crop.

[deebatman316 · Accepted solution]

The Sigma is a crop only lens. Sigma use DG (Full Frame) and DC (APS-C). To differentiate between the 2 formats. But those lenses use the Full Frame EF Mount for both. Instead of Canon's approach of 2 different mounts for APS-C (EF-S) and Full Frame (EF).

[kvbarkley]

There is another but...

If you you use an EF-S lens on an RF full-frame body, it turns into a crop sensor camera, to avoid using the "bad" part of the image circle.

[krahe]

Using an EF-S (or RF-S) lens on an RF full-frame body actually goes beyond just turning it into a crop sensor camera. It turns it into a low-resolution crop sensor camera.

[deebatman316]

Yes that is true. Image sensor capacity is reduced by a factor of 2.5x. 

[ebiggs1]

" I want to purchase a 24-70 to be able to take astrophotography pictures ..." 

A better choice for that might be the Rokinon 14mm F2.8 Full Frame Ultra Wide Angle. Besides it is very much cheaper.