RF adaptor

[BryanShaw1]

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.

[Tronhard]

HI Ernie et al.

I was asked to explain why, as a long-lens shooter, I prefer sensors of a reduced size, which common nomenclature calls crop.  I have done so, using the terminology (which I admit is poorly defined in the industry) as best I can, trying to make sense out of a hotly debated subject.   

Ernie suggests that considering the impact of smaller sensors is only valid for those using both FF and crop sensors and that is not my experience - I have seen it with students I have taught.  It comes into effect when people describe images they shoot with ("my 300mm lens is actually a 480mm lens"), or the examples I gave in my article where someone bought a wide-angle lens they had seen work on a FF camera and could not understand why it didn't give the same results on their smaller-sensor camera.  It also comes into play when one looks at pixel density when choosing a format for super long tele images.  These are real issues.

The term crop is not one I invented, it is in common use in the industry because it IS smaller compared to a 35mm sensor and as these different formats exist beside each other there will be times when that terminology is needed..  See THIS ARTICLE  If we don't like the term crop sensor, then we need to come up with one that allows us to describe the relationship between sensors of different sizes, we can't just say 'no it's wrong'.  If one is going to take exception to the term crop then we must also take exception to the term Full Frame, as they are both arbitrary terms, as are the terms Medium Format and Large Format. Those were developed in the film era, not in digital to descibe succincly the relationship between formats of different sizes.  If one is going to avoid them, then we need to use an absolute terminology such as the actual dimensions, but that would be rather long-winded and clumsy considering the number of dimensional variations.  Call it what you like, but the effect is the same.

I am simply trying to make sense of a poorly-defined subject; however, leaving the semantics aside, the physics speak for themselves.  My description of the optics is well-supported by other articles on the subject, which is why I included them.  If you want to explore a very technical approach I would encourage you to view the whole series of lectures by Prof Emitus Mark Levoy, of Standford University, a link to which I enclose HERE. 

From the diagram I included with the single lense model, the smaller sensor reduces what  the lens delivers - to me term crop in this context is not unreasonable, but translate to a term of your choice.  Essentially, being smaller than the FF sensor, it crops (reduces) the image area (compared to what a FF sensor would accept) at the point of recording the image.  The diagram expresses this elequently, I believe.

The fact is, that by doing so it has done the work of effectively reducing the FoV delived by the lens (so if one has an issue with that then call it an Equivalent FoV), but using the total amount of pixels in that sensor and this is what is significant for long lens users.  A 20MP APS-C sensor will record the image on all 20MP, whereas to get the same FoV the FF sensor of the same capacity would have the effective sensor area reduced by the square of the crop factor.  The image capture of the smaller sensor is thus quite different from using a FF sensor and cropping it afterwards, either in PP or by taking a print and a pair of scissors, although the latter would reduce the final print area, whereas cropping in PP would allow one to produce a print of the same dimensions as a fully-captured image, albeit in reduced resolution.

Let me be clear, the image collected by the smaller sensor is not magnified at the point of delivery to the sensor - that is determined completely by the lens and that never changes: that magnification factor is consistant to all sensors. 

When the image is magnified is when it is taken and delivered either to a screen or a print, in comparison to the image area captured by a FF sensor.  That was shown in the diagram with the two birds.  Thus, if one takes the image from a FF sensor and produces, say a 10x8 image, it will appear to have a wider FoV compared to that of a 10x8 print of the same subject  from a smaller sensor.

So, argue against the terminology if you will, but we need some kind of identifier to describe the relationship between the image areas captured by the different sensor sizes.  The physics are demonstrable and clear: the terminology should not block us from recognizing that.   That is why the term Equivalence has been invented and that is why it should not be ignored.

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@ebiggs1 wrote:

Trevor, 

That's a fine article but I will take exception with. a "crop" sensor camera it does not crop anything. It only appears to crop if you intend on comparing it to a 35mm sized camera.  Most people today do not even think that and have to be told they have a crop sensor camera. All cameras give exactly what you see in the view finder or LCD.  They are all essentially full frame cameras.

I know some manufacturers tend to keep this falsification going, too. If you never intend on owning or using a FF camera, it is totally confusing and useless.  If you are an advanced or even just a hobbyists and have several bodies I suppose you can make a case for comparing equivalent focal lengths. However, IMHO, totally unnecessary which is born out by the fact guys that use medium or large format gear don't do it. Although they certainly could but would have to use an "enlargement" factor.

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[Tronhard]

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@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.

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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!  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! 

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).

[Tronhard]

Crop mode in the R5 and R6 is used to achieve the same FoV as one would get using an APS-C sensor camera. It is necessary if someone like yourself is proposing to use an EF-S lens via an adaptor on the R-series FF bodies.

On EOS DLSRs this was not possible because the lens reaches far into the body and, on a FF camera, will impinge on the physical space used up by the mirror as it flips up. With the MILCs and an adaptor that distance is no longer an issue, but the lens optics are not designed to give full coverage to a FF sensor, so the images would have significant black vignetting if the image was not cropped by the camera software. This is done automatically in the later R-series camera bodies.

In your case, we come to a challenge that exactly ties to my whole issue of understanding FoV, cropping and pixel density!  You apparently have EF-S lenses designed specifically for APS-C bodies, and the R series cameras will allow those lenses to be used, but at a much reduced resolution.   So, if you really want the benefit of the 20MP of your camera, you need to get lenses designed for a FF unit.  You could get an EF-L unit and use it with an adaptor - there are a lot of bargains to be had in that space as a constituency of photographers turn over their EF lenses for the new RF ones.  Yet, a good lens is a good lens!  I have shot with the following EF lenses on my R6 bodies: Canon - EF 24-105L f/4 MkI, 70-200 f/2.8L IS USM MkII, 100-400L IS USM MkII, all three EF 70-300 units; Sigma - 150-600c and 60-600s lenses.  They have all worked flawlessly.

Depending upon your needs and the budget - I don't recall you saying exactly what focal ranges you want to work within, the RF 24-240 lens is a bargain: admittedly, it's not weather sealed, but it delivers stunning images for the type of unit it is, and again, depending upon what you produce, it might suit your purposes.  Your R6 will do a lot of image correction in-camera to the viewfinder, and with the JPG files; and bringing RAW images into PS or LR should apply auto correction for vignetting and chromatic aberration, both of which look horrific without those.  This lens is an extreme expression of a trend in lenses these days, a degree of optical performance, but combined with significant image correction in firmware (in camera) or software (in PP).  Basically, I think we are at last seeing the benefits of computational imaging, long used for cell phones, arriving in camera optics. 

I also use the RF 24-105L f/4 and 100-500L units and they are both brilliant lenses, yet the 24-105 is not significantly better than the 24-240 after processing, oddly enough - although it has a constant aperture and is weather-sealed.

If searched in my archives and found a couple of images taken with the RF 24-240 and RF 100-500 FWIW, but bear in mind that the quality has been much reduced to fit into the 5MP limit for posting to this site.

Details: Canon EOS R6, RF 24-240 IS USM, 230mm, f/6.3, 1/120sec, ISO-3600, hand-held

Canon EOS R6, RF 100-500L IS USM @500mm, f/7.1, 1/500sec, ISO-640, Hand-held

[Lotus7]

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@BryanShaw1 wrote:

What's a crop mode?

Assuming that you are asking specifically about the crop mode on an R6;

As Tronhard explained in detail:

"In your case we come to a challenge.  You apparently have APS-C lenses and the camera will allow those lenses to be used, but at a much reduced resolution.   So if you really want the benefit of the 20MP of your camera, you need to get lenses designed for a FF unit."

More specifically, in "FF Mode" the R6 sensor actually covers an optical area of 23.9 mm High X 35.9 mm Wide which is nearly the size of a full frame of 35 mm film (24 X 36 mm).  Given the pixel density of the R6 sensor, that equates to an usable digital image of 19.96 Mpix. (3648 X 5472  pixels).  To optically cover that sensor area requires a Canon EF or equivalent lens.

When an EFS lens (with its smaller circle of illumination) is mounted using an adapter, the camera is automatically switched to "Crop Mode".  That reduces the usable part of the sensor to the central 14.86 mm H X 22.36 mm W imaging area or 2272 X 3408 pixels. This sensor area is commonly called "APS-C"; the area the EFS lens was designed to cover.  You now have a 7.74 Mpix R6 Camera. Think slightly less than a EOS 30D.  Obviously, the reduced sampling resolution will limit the maximum usable final image size (probably to no larger than 11X14 inches without visable sampling artifacts) and will limit the amount of any post cropping possible. 

"Full-Frame" cameras need EF lenses.  Allowing the use of "APS-C" lenses is fine as long as you are well aware of the limitations it entails, and that you are aware that you are no longer using a "FF" imaging system.

[Tronhard]

Exactly!   And having invested a not insignificant amount for a FF MILC body, it seems a pity to cripple it by using APS-C lenses.

[Waddizzle]

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@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.

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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.

[ebiggs1]

"Ernie suggests that considering the impact of smaller sensors is only valid for those using both FF and crop sensors and that is not my experience ...I have seen it with students I have taught."

However it is my experience.  People have to be taught crop "theory". And, I am guilty because I have done it in my DSLR 101 classes myself. And, I have come to regret it as I mature, too. The biggest misconception is a crop sensor actually crops a picture. It does not crop anything. You can cite as many sources as you wish as I have already conceded that this, IMHO, nonsense is propagated by several sources.

Trevor we are going to have to agree on this subject we disagree. All the advantages, or disadvantages, you make are physical characteristics of the sensor. They do not and have no relationship to any other sensor unless you want to, or think you need to, compare them. It is more of a use the right tool for the job. I guess it is human nature to think they need to compare all things to other things. They seem to do it a lot.

[BryanShaw1]

OK so my main lens is an EF 100-400. I asked the question to see if I could also continue using a couple of walk about EF-S lenses which would save carrying around my 7D. You've both answered my question and given me lots more to think about for which I thank you! 

[ebiggs1]

Your best avenue is to just use what works and stop worrying about or tying to figure out how it would be on a different camera. It really doesn't matter. It makes photography much more fun that way.

[Lotus7]

I suspect you will ultimately find which way you go depending on the specific shooting situation you're going for.

With any given EFS lens plus adapter, the mirrorless R6 will provide better autofocus, low-light sensitivity and higher frame rates, but at a reduced total image digital resolution of less than 8 Mp, whle the 7D will always give you almost 18 Mp to better utilize the len's intrinsic optical resolution.  If you're shooting landscapes with a wide EFS lens that you're planning on printing at 16 X 20 the 7D would probably be the right choice, but for EFS tele wildlife shots or sports, the "cropped" R6 might be best.

As always, it's best to try your different possible combinations to find what fits your personal style.  Above all have fun and don't get bogged down in the technical flotsum.  Some of my most valued images were taken years ago using an Olympus C3040 with its 35-105 mm (eqv.) fixed zoom lens and only a 3.34 Mp sensor.