OH CROP!
EOS R series cameras fitted with the EF-EOS R mount adapter can be used with lenses for crop sensor cameras, such as Canon’s EF-S line. If you use independent lenses you’ll need to set the crop factor by yourself.
I’ve used Canon EF-S lenses on my EOS R without any concern, the camera automatically detects it is an EF-S lens and switches to 1.6x crop mode. This makes your RAW files only 11.6MP on the EOS R and 10.1MP on the EOS RP. I have received a question about independent lenses. So I started thinking how about independent models such as Sigma DC and Tamron Di series lenses for crop sensor cameras fare.
Sigma DC series lenses
For many years Sigma has manufactured lenses for crop sensor cameras, using the DC letters in the name to identify them. If you put a DC lens on the EOS R or RP, then there’s a good chance you’ll get images with vignetting, even circular images depending on the lens and where you zoom to.
I asked a few friends if they had a Sigma DC lens. One was kind enough to let me try their Sigma 17-70mm F2.8-4 DC Macro OS HSM lens on my EOS R. As soon as it was fitted you could see vignetting on the LCD and in the EVF at almost any focal length. 17mm was particularly bad with an almost complete black circle around the image.
I have also had a question sent in about the Sigma 18-300mm F3.5-6.3 DC MACRO OS HSM producing similar images.
Sigma 17-70mm at 17mm
Sigma 17-70mm at 70mm
Tamron Di series lenses
As luck would have it, another person had a Tamron Di lens, a pretty old and tired 55-200mm f/4-5.6 Di II LD Macro AF. This also failed to make the EOS R to switch to crop mode, but the vignetting was not as extreme as the Sigma. Though it is easier to make a longer lens cover more of the sensor, than a wide one.
The image below taken with the Tamron lens zoomed to 64mm, shows not so much corner shading. This particular lens had no AF drive – it was pretty tired – and so the EOS R focus guide proved rather helpful.
Tamron 55-200mm Di at 64mm
The solution – cropping / aspect ratio
The solution to using these lenses is to manually do what the Canon EF-S lenses automatically do, select 1.6x crop mode. Fortunately it’s easy, and the setting is on the first of the red tabbed menus. EOS R menus shown below.
You can also choose the crop by pressing the Q button and changing it from the onscreen options.
Don’t forget that in crop mode you have a lot less pixels in the image.
- EOS R – crop mode is just 4176 x 2784 – 11.6MP
- EOS RP – crop mode is just 3888 x 2592 – 10.1MP
What is vital to remember is that you’ll need to reset the crop, when you switch to a full-frame lens. You could simplify the approach and use one of the custom shooting modes with the crop factor applied.
I’d love to hear your experience with Tokina and any other independent lenses for crop sensor cameras.
Thank you for this article. I just replaced my t3i Rebel with an RP, and was horrified by the vingetting I got with the mount adapter using my old Sigma CD 18-250 and Rokinon 14mm. Now I’m back in business. Also got the Meke RF mount 50mm, which is a miracle for the price.
Hello Brian, very helpful article. I’ve just ordered a RP with 24-240 as a first move into FF. Could I ask if the crop mode can be engaged while using a FF lens such as the above. I know I could crop in post to get a longer effective focal length but doing so while shooting might help with framing.
Thanks, John.
Hi John,
Yes you can enable crop mode with the RF24-240mm lens. Just remember that cropped images are much lower resolution than full-frame images, around 10MP.
Brian / p4pictures
Thanks Brian, yes I understand the reduced resolution but when out walking and cycling it’s an acceptable trade-off to avoid changing lenses. For other times, I expect to add other lenses at some stage but I really did want a travel kit at this moment. Thanks again.
Hi Brian
Thank you for this article. Reassuring!
I just purchased the R6 with the Canon lens adapter to use with my current EF lenses – I was pretty shocked at the degree of vignetting – I wasn’t expecting it to be quite that extreme – exactly as in your images above.
As you say, cropping in to remove the vignetting must have quite an effect on the resolution.
Should I continue working with my EF lenses – which I’ve built up a collection of over the years – or resign myself to the financial outlay of buying full-frame R lenses?
I guess my question is: just how much of an effect is that drop in resolution going to have on the quality of my work?
Thanks
Chris
Thanks for this: very helpful. I have a CANON R camera my first full frame and useing 24 240 lens. Early days but delighted so far: much better results than many or the reviews I read…I did test it before purchasing though.
I have a FF Fish eye lens but when I go on holiday I will be taking my SIGMA 10-20 4 -5.6 lens with me and the 1.6 crop trick had been perfect. Will let you know how the landscapes go comparing panoramas as well with both lenses if anyone is interested.
I’ve recently purchased the canon R6 (September 2022). When mounting the Sigma 18 – 300 (purchased march 2021) the R6 automatically sets to the 1.6 crop. No vignetting even at max zoom. all functions seem to work ok.