LFingar Loc: Claverack, NY

It is a common misunderstanding that EF and EFs lenses use different mounts. Except for the white and red dots the mounts are identical. You could remove the mount ring from either an EF or EFs lens and it will mate perfectly with either a full frame or crop sensor Canon EOS body. The difference is in the construction of the lens body. In almost all cases the rear structure of the lens protrudes into the camera body and prevents the mount halves from even touching, much less mounting. I have heard that there is an EFs lens or two that will mount due to their construction but never heard which ones that would be.
If you check Canon's lens spec's you will see that the EFs lenses show as having the EF mount. There is no EFs mount, only EFs lenses.

Picture Taker Loc: Michigan Thumb

I also have an R5 and bought the non Canon adaptor and all my old Canon lenses work fine. I had a Tamron lens (older model) that did not I have since bought another non Canon adaptor for another older lens and keep them mounted so the 2 older Canon lenses that I use a lot can just be switched.

robertjerl Loc: Corona, California

The EF-s lenses made by Canon have an extra tab that prevents them from mounting on an EF FF body and even some of the older crop sensor bodies. Every single one of my family owned EF-s lenses from Canon have that tab. If you have one without the tab then someone had modified the mount.

If the FF body mount does not have the cutout for the tab than the mounts are ALMOST the same but not exactly the same.

PHRubin Loc: Nashville TN USA

I misspoke. I should have said "while an EF-S lens will protrude into..."

PHRubin Loc: Nashville TN USA

But as I said, crop the 45MP by 1.6 and get only 17.6 MP, rather low by today's standards. If you need the "reach" of the crop factor the crop body is the way to go. And they make crop lenses that are wider than full frame lenses to get the wider angle of view when needed. It all depends on what you shoot.

LFingar Loc: Claverack, NY

I'm not going to argue. This has been around for a long time. Back when I had both EF and EFs lenses, out of curiosity, I did thorough exam of both. The mounts are identical. I stated that you should check the lens specs on the Canon site. I haven't looked at them in years but a quick look now shows that for the EFs lenses anyway Canon has cut back the spec sheet to the bare minimum. It doesn't specify the mount. However, Canon does still list six APSc bodies on its site. Such as the 90D. If you look you will see that the lens mount for them is listed as an EF, not an EFs. There is no EFs mount, only EFs lenses.

Edit: I see that you have several EFs lenses. Perhaps you could post a photo of the tab you mention.

User ID

If I crop my 45MP FF to APSC I get waaaay more than 17MP. Ive still got 27MP. Thaz the benefit of not limiting my options. But if 17MP is really somehow the result with your set up, that is a rather unfortunately heavy loss. The math doesnt hold up, but maybe your FW is doing that ?

PHRubin Loc: Nashville TN USA

The math is as follows: BOTH length and width are reduced by 1.6. So, start with 45 then 45/1.6/1.6=17.57. Now that is reducing the 45MP by a 1.6 crop per side. If you got more you reduced it less.

User ID

Okaaay. Ive found the discrepency. Its partly me and partly that old devil, Nikon vs Canon.

Firstly, I get 22.7MP, not 27.2MP. The rest of the difference is, as I described earlier, that I am cropping the image myself so starting out with FF I cut it right in half, to 18x24mm. My 45MP body is a Nikon so, even if I were to let the camera engage the APSC format, Id still retain more than 17MP cuz 17 is peculiar to Canons reduced version of the APSC format.

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I had figured from my Nikon cuz my Canon is 50MP and so acoarst my cropping that image myself to 18x24 would leave 25MP. If I were to let that camera internally engage Canons own version of APSC, that would leave 20MP. So, bottom line, I was using Nikon specs.

PHRubin Loc: Nashville TN USA

Actually, you were cropping yourself and ignoring the APS-C level of crop which for Nikon is 1.5. Using the Nikon crop factor 45/1.5/1.5=20

robertjerl Loc: Corona, California

I have one or two of the old EF-s lenses around, I will have to dig and check in my camera storage cabinet. In the meantime -
From the Canon USA site - support Q&A:


"deebatman316
Authority deebatman316 (Where it says Authority, it means a Canon certified expert/authority.)
Authority
‎10-01-2023 11:45 AM

The EF-S Mount was released in 2003 alongside the first Digital Rebel series camera. From there the mount would be found on ALL APS-C DSLRs. ALL of Canon's APS-C DSLRs are FULLY COMPATIBLE with EF lenses. EF-S lenses ARE COMPLETELY INCOMPATIBLE with Full Frame & APS-H DSLRs and EOS AF SLRs. The EF-S Mount is MECHANICALLY INCOMPATIBLE but ELECTRICALLY COMPATIBLE with the original EF Mount. EF-S Mount lenses sit further into the camera than EF lens would. The mirror would hit the rear lens element and cause serious damage on a Full Frame DSLR. ALL EOS Film SLRs Full Frame DSLRs ARE INCOMPATIBLE with EF-S lenses and won't mount. So even though EF-S came later on you can't accidentally mount the lens. The lens was designed NOT to be mounted to those cameras. Canon's APS-C DSLRs have 2 mounting indexes one at the 12 o'clock position and one at the 1 o'clock. EF lenses use the one at the 12 o'clock position and is a red circle. EF-S lenses use one on at the 1 o'clock position and is a white square."


I see Canon uses the term "indexes" I am used to seeing and using the term "tab". I will have to try and remember to use Canon's term in the future.

LFingar Loc: Claverack, NY

I suggest you take a real close look at the EFs lens mounts you have.

User ID

Yes ! By cropping intentionally from FF I dont hafta discard that 2mm along the 24mm side. Thaz what I had said earlier about "keeping my options open" by cropping on my own vs using a crop format camera. That 3:4 aspect ratio is a bit roomier than a 2:3 (plus, its a good looking rectangle).

The attached pic is about half a Canon ASPC frame, camera vertical, cropped for a "rising front" shift. Detail and texture are OK, but I really wish I had cropped from a FF camera.

Jose Malones Mexican Irish restaurant.

(Download)

joecichjr Loc: Chicago S. Suburbs, Illinois, USA

What a beautiful eye catcher

robertjerl Loc: Corona, California

Why? They work on my crop sensor bodies and the ones I own by Canon do have a protuberance, tab whatever you want to call it that prevents mounting it on a full frame. On the other hand, the Sigma and Tamron crop sensor lenses just use the EF mounting ring and will mount on a FF body. Of course, they are made without the protruding lens element that can damage the mirror. I get anything from a circular image in the middle of the frame to vignetted corners. I have done it just for fun with an ultrawide angle to fairly long zoom lens from Tamron. When I put a 1.4x extender on it there was barely any vignette at all and with a 2x towards the long end of the zoom range no vignette at all.

Now that knowledge and $20 will get you a "Big Mac Bundle" at my local McDonald's