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RF adaptor


I'm looking at purchasing an R6 with an adaptor so I can continue to use my existing lenses. I am told that the Canon adaptor is only good for EF lenses, but I see on Amazon that the Viltrox adaptor is good for both EF and EF-S lenses. Any information gratefully received.


@ebiggs1 wrote:

Maybe my point isn't coming across. I am not disputing the information or its accuracy, I am claiming it isn't necessary. The only people that care about this stuff are like you. Me too, at one time but as I watched most people's eyes gloss over when you try to bring it up. Folks like us, a long time ago in my case, delve into the inner workings and have several cameras but most folks don't. They just want nice photos and don't care how it might look or work or be transformed on a different format camera.

Ernie, I think you and I actually both agree that for the vast majority of people this is a non-issue.  I have never disputed that.  I have simply maintained that the phenomenon IS actually true - which you seem to concur with - and that for some people it is an issue.  While I am responding to you, I am aware that others are reading this, so I am not trying to insult you by stating what you may consider is obvious.


I think here, it is apropos to comment on the inadequacy of terminology in discussing the results of the behaviour of lens+sensor combinations. For a start, let's get rid of the nomenclature issue:  like it or not, way back when digital came in the term Full-Frame was associated with standard 35mm film-sized sensors.   My research indicates that this was because of the dominance of that format in the stills film industry, within which most consumers and a significant number of professionals did their activities.  The terms 'medium format' and 'large format' had been well-established for quite some time before that.  The rise of the APS film format heralded a new subset of the film industry, but it was essentially killed off by the fast development of digital.  Nevertheless, it gave a name to the 1.5-1.6 crop sensor format, considering the similarity of their respective sizes and has been extended to all smaller sensor formats.


The term "crop" referred to a sensor's reduced ability, in comparison to the FF format, to capture an image from a constant AoV.  What I call the Field of View (FoV), is the area recorded by the sensor.  An APS-C sensor, being relatively smaller than that of the FF sensor, reduces the FoV captured, so in that context the term 'crop' as relating the output of the two formats was not unreasonable. Cropping on the captured image goes way back to the earliest large-format cameras, where there were full plates, half and quarter plates and then the multiples of exposures on one plate for cartes de visite, popular in the latter part of the 1860's - so this has history.


In the early digital cameras for example, Canon's first home-grown DSLR was the D30, had an APS-C CMOS sensor, and used only EF lenses which resulted in a smaller FoV compared to the same lens on 35mm film camera.  Like it or not, it became well established as a colloqual term, if not a genre. So, for simplicity's sake, I shall use the terms rather than search for something else.


For me, based on the questions and discussions to which I have been a party, the issue  appears under the following condition:  where outputs crop sensor and lens combinations are compared to the behaviour of FF sensor and lens combinations, and where people are considering the focal lengths of lenses as their only criteria.   As we all agree, a lens has a given focal length and aperture and they don't change.  But the lens is not the only element in deciding what is captured as an image - which is what a photographer wants in the end, after all. 


To tidy up the delivery path terminology as I understand it: the resultant image is initially defined by the focal length, producing a given AoV - measured in degrees or radians, but then the sensor size comes into play and it takes that potential and captures a specific area of that cone of delivery, determined by the sensor's dimensions - so to me it could be measured as either an angle (as we see in binocular design, or by dimensions, which seems more logical considering we are looking at producing some kind of image on a medium: ie. either a screen or a print - that I define as the Field of View, and for a 'crop' sensor it is considerably smaller that that of a 'FF' sensor.  Measuring the output performance of a sensor+lens combination should not be based soley on lens focal length, but it has become a general misnomer to do so, and FoV (or any other appropriate term someone could invent) rarely comes up in the documentation or discussions.  What is controversially called and Equivalent FL needs an agreed term and that used to quantify the performance of the image capture.  Equivalence is used somewhat inconsistenly in documentation and artlicles in an effort to reconcile this.


As you very correctly point out, a huge mass of people using cameras will look through the viewfinder and consider what they choose to include in their FoV, based on what they see rather than the numbers.  No argument there, but for a certain constituency there are issues, and it is in that context that I have responded to the OP.


In my experience, the cases where this rears its head, in practical terms, include:

1. Someone with a crop-sensor camera was starting up in real-estate photography.  They were looking for a super wide-angle lens for interiors and they looked at a lens that was recommended by someone who had a FF camera.  Based on their viewing of the images they saw looking through the viewfinder of the FF camera, that person purchased the same lens, but was very disappointed to discover that the width of coverage was much less, because they were using a camera with a smaller sensor.  Apparently neither of the two parties had any idea that the FoV changed with sensor size, and this resulted in the one the APS-C camera not getting the return on the investment they wanted.


2.  At the other end of the scale.  I do most of my shooting at the super telephoto end.  I have a Canon EOS 5DMkIII camera but I prefer to use the 7DMkII to shoot wildlife because of the fact that the reduced FoV of the 7D crops the image before it is recorded.  Sure, I could crop the image of the 5DIII afterwards, but since they both have about the same number of photo receptors they produce images of about 21MP.   The 7DII gives me the full 21MP on the resultant image, whereas the 5DIII would have effectively had its image cropped in PP to the same FoV reduced that to around 8MP.  In other words, I have greater pixel density for the same image outpuit which gives me more potential to crop the image further or produce larger prints.  A lot of photographers like me prefer crop sensors for that specific reason.


3.  In this particular thread, the OP was specifically inquiring about using AF-S lenses designed for crop-sensor bodies on his FF R6. It was that that brought to the fore the question of how those lenses would behave on the R6 body, which is not just a case of putting one on the adaptor and getting a 20MP image - which is what the unwary might expect when they bought the body.  Previously, that combination of APS-C lens and FF body would not have been possible with native Canon glass, although some other 3rd pary lenses would have permitted that.  Essentially, the new mirrorless design, coupled with the adaptor, has made possible the merging of the two lens technologies into the same body. 


Now with this new arrangement, one can put a Canon lens designed for a crop sensor body, onto a FF body, but because of the distance of the rear element being closer to the sensor, the FoV captured will remain smaller.  If Canon did not have software to compensate for that the resultant image would have massive vignetting, but they do have such a fix to tidy up the image. Essentially, sofware is now manipulating the image delivered by the EF-S lens and resulting in a tidy cropped image.  That is a new phenomenon on Canon cameras, but not on Nikon for example.  One could put DX lenses designed for their APS bodies on a FX (FF) body, but Nikon clearly stated that the resultant image would have major vignetting - i.e. cropped.  So, now we are not talking about someone simply playing with the numbers, we are looking at practical issues.  If someone had a body with a 20MP APS-C sensor, they are going to get considerably less resolution out of the R6, which is likely not what they were expecting...


For example I have a EF-S 60mm macro lens and an EF 100mm macro lens.  If I simply had a Rebel or other APS-C body, they would have rendered FoV's Equivalent to 96mm and 160mm respectivley - giving me different results.   If I had a FF DSLR body only, I could only have used the EF100mm lens and got 100mm out of it.  However, now both lenses can go on the same body, but if I put them on my R6 body they will render FoV's of 96 and 100mm respectively, which are almost the same!


Not only that, but the quality of the image will be different.  The image from the EF-S 60mm will be around 8MP, while that of the 100mm EF lens will be 20MP.   Depending upon what the user does with the image that could be significant.  This is not just an academic numbers game, I expect that there will be a constituency of people moving up from APS-C to R FF bodies with APS-C lenses that know they can use an adaptor but don't twig on the implactions to their FoV and image resolution.  Sure, if they just limit themselves to looking through the viewfinder they will see a corrected FoV, but the image size will be nowhere near the advertised 20MP - I expect at least some will notice that.

cheers, TREVOR

Before you ask us, have you looked in the manual or on the Canon Support Site?
"All the beauty of life is made up of light and shadow", Leo Tolstoy;
"Skill in photography is acquired by practice and not by purchase" Percy W. Harris

You may remember I initiated this thread at the start of the year.

I finally purchased a mirrorless camera and decided on the R as, unfortunately, I could not afford the R6 whoich I would have preferred. However, I can confirm that the adaptor works well with my 100 - 400 as does the 2 x converter with the camera's autofocus - so all in all very pleased.


One thing though. With the 2 x fitted, the IS on the 100-400 lens appears not to be working. Should it be compatible?

Have you used that lens + extender on another camera? I don't have a 2x converter but have used the 1.4x converter with the 100-400 mark II on my R, and IMO, the longer the zoom, the less I can tell the IS has kicked in or it takes longer for me to notice it. Also, is your camera firmware up to date?

It would help to know what version of the 100-400 you are using: the Mk I is quite old - released in 1998, while the MkII was release in 2014.  The version of teleconverter is even more critical.  There are big differences on how AF and AE work with different combinations of camera body, lens and teleconverter, so your description of components needs to be very precise. 


I have the 100-400MkII, and the 1.4 and 2.0 MkIII teleconverters.  I shot with a Canon EOS R6 (I don't have an R) - hand-held.  I have used the 2.0 teleconverter (extender) and had no issue with focus.  The minimum f/stop is f/9 FWTW - I actually shot at f/10.


At 100mm (now 200mm)

_62_2067 copy.jpg


At 200mm (400mm)

_62_2066 copy.jpg


At 400mm (800mm)

_62_2064 copy.jpg

cheers, TREVOR

Before you ask us, have you looked in the manual or on the Canon Support Site?
"All the beauty of life is made up of light and shadow", Leo Tolstoy;
"Skill in photography is acquired by practice and not by purchase" Percy W. Harris

Thanks for the replies.

the lens is he older mark 1. It works fine on my 7D so I was wondering what effect the rf adaptor has on the IS.

It may be working, but it doesn't have the same immediate 'lurch' as I am used to. I've only just got the camera so lots more shots to take before I can give a better review of what's happening.

I agree that unfortunately it's probably the older electronics. I have an EF 300mm f/4 L (released 1997), and when paired with my R and my R5 I found it disappointing in a number of ways. On the other hand, my "newer" EF 100-400 mk 2 gives excellent results. I don't think the adaptor is to blame but the improved technology and resulting different electronics from when those lenses were designed. I'm currently on preorder for the RF 100-400, which isn't an L lens but I'm buying it because it weighs 1.4# vs 4# for the L and will be much easier for me to take on long walks.


You'll enjoy your R--it's a terrific camera. Two of the many things I love about Canon's mirrorless are the FV mode and that I can move the focus point around with my thumb while looking through the VF. And of course quality of images!

Once again Trevor, great shots. Beautiful!

EOS 1DX and 1D Mk IV and several lenses!

A very interesting article - thank you.

As I understand it, the FoV is determined by the FL (using equivalency or not).

If commited to a FF camera due to the other benefits of the R6, then the answer would be to use a longer lens or even a converter to negate the reduction in pixels. Also with a FF, a 2 x extender means 2x, rather than the 1.? something with a crop sensor.

@BryanShaw1 wrote:

A very interesting article - thank you.

As I understand it, the FoV is determined by the FL (using equivalency or not).

If commited to a FF camera due to the other benefits of the R6, then the answer would be to use a longer lens or even a converter to negate the reduction in pixels. Also with a FF, a 2 x extender means 2x, rather than the 1.? something with a crop sensor.

As I explained in my response to your inquiry and Ernies objections, the terminology in this area is poorly defined, but if one wants to get down to the nitty gritty of it, technically, what the lens delivers is the Angle of View: the Field of View is a combination of both the Angle of View delivered by the lens, and the area of that coverage accepted by the sensor.  For most discussions the terms are used somewhat interchangeably, but your point is well made and I believe using these two terms to differentiate between the two stages of light delivery and capture is the best we can hope for.  Something has to be used to describe the result of the lens and sensor combination on image capture...


If you are committed to using a FF sensor, which is absolutely fine as you will get benefits at the wide angle, then using an extender is one solution.  However, any extender comes with a cost in the reduction of light delivered. Given that the f-value is the focal length/aperture diameter, increasing the effective focal lenght increases the f-value too. So a 1.4 extender increased the focal length by a factor of 1.4, but it reduces the aperture effective efficiency by the same factor.  Thus, if you are using a 100-500 f4.5-7.1 at its full zoom and widest aperture, and add a 1.4x extender, then the effective focal length will increase to 700mm, but the f/value of 7.1 will be changed to f/9.9, making the lens much less efficient - here is another terminology issue: we would call a lens "faster" or "slower", but those terms refer to speed, which is a function of the shutter!  By the same token, using a 2x extender will increase the effective focal length to 1000mm, but reduce the max aperture to f/14.  Then, one must consider the impact of all the extra glass there is on image quality and the cost/benefit of the added expense - extenders are not cheap.  I think Ernie would agree with me that we see this question come up a lot, and generally the advice we give is to get a longer lens for the job.


I shoot with a lot of gear - check out my profile to see the list! Smiley Tongue I use crop-sensor bodies for long tele work (as I have explained and it works for me), and I use a lot of super tele zooms because I move around a lot and have to change relative positions often.  I don't change lenses in the field so I don't want to carry multiple primes. Your experience may be different, so my advice would be to invest in a lens for the job. 


As I always say, a lot depends on the quality of the image you intend to produce.  The investment required for large-format, finely-detailed Art (with a capital A) prints, is much different from creating images for social media, digital display or modest sized prints that will not going to be pixel-peeped.  What gear is best for the outcome one wants is really an issue only the user can determine, although everyone else will be tempted to tell you what you should do! Smiley Happy


There is a lot of speculation right now as to where Canon will go as regards sensors - Canon Rumors website claims that an R7 APS-C prototype has been out field-testing for some time, but an announcement may be some way off because of manufacturing capacity issues. Yet, perhaps we will see Canon abandon the crop sensor market completely? It's all speculation...


Personally, I have two conflicting desires: to be able to get the greatest pixel density I can for very long tele shots, and to have a large pixel count at the other end for landscape imagery - something that my EOS 5DsR addresses.    To add to that is the question, if Canon makes a R7 APS-C sensor camera of, say 40MP (which would have the same pixel density of 104MP FF sensor image cropped to the same FoV), will they then make lenses for that format? Do they NEED to make lenses for that format??


Another possible approach combines both divergent philosophies.  Make a camera with a FF sensor of significantly larger pixel capacity - in excess of 100MP and use the built-in crop features to reduce the FoV, with a resultant capacity of say  40MP.  The larger sensor capacity, reduced to APS-C format would still yield a decent pixel density, but then there is the cost of cramming all those photosites onto a sensor...  


However, this is another issue here common to all sensors.  Cramming more pixels onto the same area reduces the size of the photosites.  This is demonstrated in the relationship between the R5 and R6.  The R6 may have only 20MP as compared to the R5's 45MP in the same area, but reports indicate it has up to 1EV better light performance as a result, in general FF sensors compared to their crop sensor cousins of the same pixel count are brighter.  So, one could speculate that a potential APS-C sensor might be in the 30-34MP range (as was the Canon EOS 90D).




cheers, TREVOR

Before you ask us, have you looked in the manual or on the Canon Support Site?
"All the beauty of life is made up of light and shadow", Leo Tolstoy;
"Skill in photography is acquired by practice and not by purchase" Percy W. Harris

@Tronhard wrote:

Since you asked, I have the R6 and a Canon EF adapter.  I attached an EF-S 18-135 IS STM unit to the R6 via the adaptor, without any changes to the menu system and it worked ok, applying the crop function to reduce the FoV and image size accordingly.


I stand corrected.  All of the R series bodies are able to automatically crop the image when you use an EF-S lens with the Canon mount adapter.  The RP provides a really good upgrade path for Rebel shooters to transition to a FF body.  The RP even shares the same battery with the latest Rebel releases.

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