Fergus Ferguson
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Does anyone know the effective focal length of an EF-S lens on the EOS R when using the adaptor.
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EF-S Focal length
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Bob Janes
Veteran Member
It will be interesting to see if you get an automatic crop when mounting the EF-s lens and whether there will be an option for not cropping - sometimes the image circles give more than APS-C coverage.
Steve Balcombe
Forum Pro
An EOS R with an adapter acts just like an APS-C body when you attach an EF-S lens. The crop factor is the same and any equivalence calculations are the same.
It will be interesting to see the contents of the RAW files. My Panasonic LX100 uses a different crop for the different aspect ratios, but it has been shown that the RAW files contain the full sensor image. You do need to use specialized RAW software, as the panasonic converters only show the orginal crop.
Steve Balcombe
Forum Pro
And there is also the question of what happens when you use a Sigma DC lens (for example) which has an EF mount and won't be automatically detected as a crop lens. But I wanted to give a straightforward response to the question as put.
Le Kilt
Senior Member
AS has been said, you'll get a 1.6 crop just like on APS-C, so :
Crop : 1.6x
MPixels : 30/(1.6x1.6) = 11.7
Crop is automatic for EF-S lenses
RAW file saves the cropped image only
N.B. EF-S will cover the 4K video area (approx 1.8 crop), so could be useful for that, notably the UWAs, 10-18mm and 11-22mm.
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Bob Janes
Veteran Member
Do we know that the crop is definitely only automatic?
Sony had an automatic crop on A mount SLR cameras, but later on, when they were doing full-frame e-mount they gave an option for not cropping, cropping everything and automatically cropping APS-C - although you do get a larger RAW file, the ability to get the whole image and just crop out the bits you want (10x8 or 4x3) is useful.
Le Kilt
Senior Member
Yes, check pages 80-82 of the manual, and it was confirmed by a Canon guy, but I can't recall which one.
I can understand Canon choosing this, but it would be fun to play with some uncropped EF-S!
Steve Balcombe
Forum Pro
Page 80 in the manual: "With EF-S lenses, [1.6x (crop)] is set automatically, and no other option is available."
But for other lenses there is a choice of cropping/aspect ratios which include 1.6x crop.
So it's automatic only for EF-S lenses, optional for all others.
Bob Janes
Veteran Member
I wonder if there is something on the adapter that senses the EF-S mount, or whether it relies on the lens ID?
Sony did it for the a99 with lens ID (they had to as there is no physical difference between the full-frame and APS-C Sony lenses as far as mounts are concerned) - I seem to remember that with A-mount, some of the third-party lenses were not automatically detected, and would shoot uncropped - which might be a kind of 'easter egg' for those lenses.
There is a way of forcing the a99 not to crop APS-C - you push in the lens release button - unfortunately you also lose aperture and AF, so you are limited to shooting wide open at whetever the lens is set to, but it does allow you to shoot; the same thing might work with the R...
Shouldn't it be ~19 Mpixels? ( edit: no)
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