topic Re: EOS RF Lens Compatibility with EOS R7 in EF & RF Lenses

EOS RF Lens Compatibility with EOS R7

stevety — Sat, 23 Jul 2022 19:07:44 GMT

Canon RF 100-400mm F5.6-8 IS USM will these work on the canon eos r7 or do i need adapter

Re: EOS RF Lens Compatibility with EOS R7

Tronhard — Sat, 23 Jul 2022 20:29:23 GMT

The RF 100-400 will work on the R7, but its Field of Capture: essentially the area it records will be significantly less because the sensor is smaller. What this means in effect is that you are then shooting with something equivalent to a 160-640mm lens on a full-frame camera, and the effective depth of field will be equivalent to an aperture of f/7.2-11.3. If you want a full explanation of this phenomenon see the following: What is Equivalence and Why Should I care, an article from DPReview.

Re: EOS RF Lens Compatibility with EOS R7

Waddizzle — Sat, 23 Jul 2022 19:19:17 GMT

I do not subscribe to the idea that crop factor should be applied to aperture. I think that is an interesting thought experiment from the days when the transition was being made from film to digital.

The digital cameras were capturing a different field of view because the first digital image sensors were not full frame in size. Someone figured out that you can capture the same field of view as a 35mm film camera if you applied a crop factor to the focal length. You could also recreate the same amount of background blur by adjusting your aperture using the same crop factor, PROVIDED that you wanted to capture the same field of view AND background blur.

I do not know of anyone who shoots like that, applying crop factor to exposure settings in order to reproduce what a full frame digital sensor would capture. Do you?

People just pick up the camera shoot photographs. An APS-C sensor will capture the same amount of background blur as a full frame sensor with any lens. The caveat is that the image from the APS-C sensor will have a narrower angle of view.

Re: EOS RF Lens Compatibility with EOS R7

kvbarkley — Sat, 23 Jul 2022 19:57:29 GMT

Crop factor has no influence on aperture. The light falls on the whole sensor equally, whether it is a FF or crop frame. (Except for any vignetting, of course)

Re: EOS RF Lens Compatibility with EOS R7

Tronhard — Sat, 23 Jul 2022 20:10:17 GMT

I agree that the physical aperture of the lens does not change, just like the physical FL does not, but it's about the outcome to the image when the smaller sensor is taken into account - and to me the result is what counts.
Essentially, if one accepts that using a smaller sensor with an ASP-C camera with a given lens has an effect equivalent to using a lens on a FF body with a 1.6x that focal length, then considering that the f/stop is calculated by defined as:
f (focal length)/ aperture. If once considers the equivalent focal length = f x1.6 then the f/stop is increased by that factor too.

I ran this pass several photographers and a physics professor (who also happens to be an photography enthusiast) and he agrees with me, it is also referred to in one of Prof Marc Levoy's lectures on photography. I already quoted one article, but am happy to add more to support my case.
The article that follows bridges these two points of view:
"This really shouldn’t be controversial
You do not need to consider equivalence for a moment when choosing an exposure. You do not have to multiply the f-number by the crop factor, unless you want to understand its behavior, relative to another system. However, it is completely legitimate to do so. The logic behind it is mathematically sound, it holds up in real-world testing, and it can be informative, if you’re interested. It’s an effective tool, whether you have need for it or not." from DPREVIEW 2nd article on Equivalence

Photography Life on Equivalence

There are a couple of videos that demonstrate this phenomenon, the most obvious one is Tony Northrop's one.
HERE Even if you are not a fan of the man himself, he clearly demonstrates the effects and they are undeniable.

I do disagree with his terminology: the lens doesn't "become" a longer focal length lens, nor does the physical aperture aperture change, but the resultant FoV and DoF do because of the reduced capture area of the sensor.

Re: EOS RF Lens Compatibility with EOS R7

Tronhard — Sat, 23 Jul 2022 20:19:50 GMT

I agree that the sensor has no impact on the physical aperture of the camera, what I actually say is that the result of the recorded image, because of the cropping effect of the smaller sensor with that same lens has an effect on the Depth of field, which is expressed as an equivalent focal length.

Actually, while the light falls equally on each unit area of the sensor, the sensor is smaller and that has a clear impact on the field of capture. You are considering the lens on its own, or the light per unit area and in that context I agree with you, however that is not the issue - it is about comparing the overall image from one system to another. People don't look at an image per sq.mm, they look at a photo as a unit. Watch the Northrop video to which I posted a reference (without bias) and it is clearly demonstrated).

The question was originally if one can fit a RF 100-400 on a crop R7 body. Yes, we likely all agree that it does - so let's put that part aside. I have clearly demonstrated by references the case I am making. Where are yours?

Re: EOS RF Lens Compatibility with EOS R7

kvbarkley — Sat, 23 Jul 2022 20:28:12 GMT

Yes, but the main effect of aperture is exposure, not depth of field, and crop factor has no effect on that, so it is very misleading to say that crop factor changes the aperture of the lens.

Re: EOS RF Lens Compatibility with EOS R7

Tronhard — Sat, 23 Jul 2022 20:42:32 GMT

I am not saying the crop factor changes the physical aperture of the lens, and I am not saying it has an impact on the light per unit area of the projected image. I have gone back to amend my post to make sure this is even more clear, if that caused a misinterpretation. You are arguing something completely different from my point.
Let me try to make my point crystal clear.

The physics of a lens do not change - both the focal length and aperture are physically defined by the lens
The image one gets is not purely based on the lens FL and aperture though, it is based also on what the sensor captures
So one has to consider the impact on the image - which is what is the outcome that one wants
When the lens projects onto the sensor the intensity of light / unit area remains the same, but the overall light is reduced because of the smaller area of the sensor. But that is not the real issue and is a bit of a red herring. What is at stake is the curvature of the lens system that focuses the image onto the sensor. Because the sensor accepts a much small area that curvature is reduced, it accepts that from the centre of the lens which has the same effect of using a longer FL lens.

The rules for DoF are:
the closer the object the smaller the DoF
the wider the aperture the smaller the DoF
the longer the FL the smaller the DoF.
because the outcome of the combination of lens and smaller sensor is (as we seem to agree) equivalent to the FoV of a longer FL lens on a FF body, so the physics dictate that the sampled area will also have a different DoF.
Again, I ask you to review the video I linked to from Northrop and tell me where the video is not demonstrating that.

Re: EOS RF Lens Compatibility with EOS R7

Waddizzle — Sat, 23 Jul 2022 20:44:24 GMT

I’m not a fan of Northrup’s controversial series of videos on this topic. He comes across as if this is something that mandatory to do.

Like I said, it was an interesting thought experiment over 20 years ago. No one shoots like that, anymore. Last I checked, light meters do not have crop factors.

Re: EOS RF Lens Compatibility with EOS R7

Tronhard — Sat, 23 Jul 2022 20:56:34 GMT

You are showing bias toward Northrop without apparently looking at the results - I would urge you to get past that and LOOK.
Furthermore I have provided material from multiple respected sources to back up my statements but you seem to ignore all of that.

The issue of crop factor has come back with a vengeance with the ability to attach RF-S and EF-S (via an adapter) onto a FF R body. The issue is clearly addressed by Canon in its own documentation within the manuals. It has a real effect on the resolution of the resultant image and it does in terms of Field of Capture and DoF.
I fail to see why you are determined to stick with your own statements when you cannot provide documentary evidence to support them, but I can for mine.

Re: EOS RF Lens Compatibility with EOS R7

ebiggs1 — Sun, 24 Jul 2022 15:12:37 GMT

"I do not subscribe to the idea that crop factor should be applied to aperture."

Neither do I. Sometimes even smart people come up with dumb theories.

"Yes, but the main effect of aperture is exposure, not depth of field, and crop factor has no effect on that, so it is very misleading to say that crop factor changes the aperture of the lens."

Correct! The whole crop factor concept has been misleading ever since it was. Lenses are lenses are lenses are lenses and there is no good reason to compare them to other cameras you may not have or even if you do have.

In my DSLR 101 classes I never had a single person that even knew about crop factor until some smartie brought it up. Mostly soccer moms and dads for sure but happily ignorant of crop factor and loving their Rebels.

Re: EOS RF Lens Compatibility with EOS R7

Waddizzle — Sun, 24 Jul 2022 15:38:23 GMT

@Tronhard wrote:
You are showing bias toward Northrop without apparently looking at the results - I would urge you to get past that and LOOK.
Furthermore I have provided material from multiple respected sources to back up my statements but you seem to ignore all of that..

I am not ignoring it. I think it is now a novel thought experiment without any practical use in the real world, anymore.

I’ve debated with Northrup on his YouTube channel on this topic. I might one of the reasons he has made multiple videos on the topic defending the idea. I pointed out that he’s wrong to promote the idea that applying crop factor your aperture to recreate what FF sensor would capture is compulsory. He has walked that back without removing the previous misleading videos.

Again, no one uses a camera like that, anymore. Northrup is chocked full of dinosaur ideas that have been obsolete for years. The best thing that has happened to him has been mirrorless cameras, which seem to have made him rethink how cameras can be used. It has been amusing watching him enlighten himself.

Re: EOS RF Lens Compatibility with EOS R7

Tronhard — Sun, 24 Jul 2022 16:52:29 GMT

Dear Bill and Ernie:

With total respect to you both, I fear that this is one issue that we will have to agree to disagree on. {:-)

Re: EOS RF Lens Compatibility with EOS R7

ebiggs1 — Sun, 24 Jul 2022 17:58:31 GMT

This statement sums it up entirely.

"... it is now a novel thought experiment without any practical use in the real world, anymore."

Although I never thought it had any practical use except for intellectuals. And most of them are not and do not make a living with their cameras. There is a big difference there.

Re: EOS RF Lens Compatibility with EOS R7

Tronhard — Sun, 24 Jul 2022 18:05:47 GMT

Refer my previous post.

Re: EOS RF Lens Compatibility with EOS R7

ebiggs1 — Sun, 24 Jul 2022 18:05:57 GMT

"I’m not a fan of Northrup’s controversial series of videos on this topic. He comes across as if this is something that mandatory to do."

Me neither, never was. His thinking is flawed and he is hesitant to change or correct it even though he has mostly been proved wrong in his theory.

"The light falls on the whole sensor equally, ..."

This is the big thing Tony didn't or doesn't understand. It is also a stumbling block for lots of folks. The entire issue can be summed up by AOV, Angle of View.

Re: EOS RF Lens Compatibility with EOS R7

Waddizzle — Sun, 24 Jul 2022 18:27:25 GMT

“I’ll agree that the sensor has no impact on the physical aperture of the camera, what I actually say is that the result of the recorded image, because of the cropping effect of the smaller sensor with that same lens has an effect on the Depth of field, which is expressed as an equivalent focal length. “.

They key phrase here is same lens. This is what I told Northrup. The depth of field changes because of the lens swap, not because of the sensor size.

We will just to have to agree to disagree on the usefulness of taking photos this way. I have never seen anyone do it since the transition from film to digital. A product photographer wanted to know why his images looked different. With a white background DOF was irrelevant. He just wanted the same field of view.

Have you ever used this approach in the real world? I haven’t.

Re: EOS RF Lens Compatibility with EOS R7

Tronhard — Sun, 24 Jul 2022 22:30:33 GMT

Bill, when I look at the Northrop video I see that the lens is a constant and the variable is the type of sensor of each camera attached to that lens - which appears to be the exact opposite of what I understand you are seeing. If the lens was varied then the experiment would be totally invalid, but it wasn't.

Part of this, as I have commented in other materials, is one of nomenclature. I look at the image that a lens projects onto a sensor, which is essentially a cone of light, and see that as delivering an Angle of View. Angles are measured in units of arc, not mm of x by y. What the sensor captures from that projected cone of light is what is actually recorded - which is what counts in considering the end result, so the sensor must be considered - and is measured in mm x mm. All consumer cameras use some kind of rectangular image within that projected cone. Given that convention has identified a sensor of 24mm x 36mm as 'Full Frame' (and I agree with others that this is a rather ad hoc thing, but it is generally accepted).

As to lenses... I think we all agree that any lens of a given focal length and aperture range has those characteristics within its physical makeup no matter what camera body or sensor it is associated with. Where I think we differ is that I consider that the resultant image is the result of the angle of projection of the lens together with what is captured by the sensor. This, to me is not an angle of view, it is a Field of View or Field of Capture. It is the terminology and lack of differentiation between lens output and sensor capture that starts to undermine the discussion. It soon progresses into talking 'chalk and cheese'.

I won't go back over the ground that Norton, who by the way is only ONE reference I provided, including some seriously respected publications and authorities in optics. So far, from what I see the contrary argument is based on personal belief or experience.

I will suggest as regards looking at the impact of the combination of lens + sensor to simply go through the various Depth of Field calculators available on the market. For ONE example, I will give a shot and link to that explained and used on the website Cambridgeincolour - a well-respected website: the link is HERE . One can see how to get the same effect for perspective and DoF one must use different values for different sensors. Here a FF camera with 50mm at f/8 is compared to an APS-C camera and to get the same result it requires substantially different characteristics for a lens.

The phenomena of reduced FoV and DoF exist, and there is lots of documentary and practical proof to that effect. The question is, is that of any practical impact on a photographer? I see that Ernie does not see that it does, and is rather dismissive of those who may have ventured into this territory in his classes. I don't dismiss it or those that ask, I engage with them. In the majority of my classes - especially those for non-technical novices, I don't bring it up unless asked - but it DOES come up where people are engaging with gear between sensor platforms.

In one case I had a chap in a class who was getting into real estate photography. He had a friend who was already doing this, using a FF Canon camera and an EF 17-40L lens. He tried that lens out on his friend's camera and based on its performance, he bought the same unit. He was upset that he didn't get anything like the coverage on his own camera. Why? Because he was using an APS-C camera and the Field of Capture was significantly reduced to an effective 27-64mm FoV. The lens he should have bought would have been in the region of 10-20mm - like the EF-S lens of that range that would have rendered a FoV of 16-32mm. The issue was he was ignorant of the phenomenon and worked off the numbers on the lens alone, without considering the differences in sensor.

As to DoF. I agree that this is an issue to a much smaller constituency: I would suggest predominantly those engaged in portrait photography where DoF and the ability to limit that with wide apertures is of significance. That is what I saw demonstrated by Northrop. The phenomenon of DoF variance when trying to maintain a level of perspective and depth of field is measured in the calculators of which the one I liked to is an example.

Finally, as to the relevance of considering how sensor and lens designs will interact is demonstrated by posts here and in the documentation for the R-series FF bodies. I have seen people wanting to use EF-S and RF-S lenses on their FF R-series bodies. Now, it can be done for the former via the EF-RF adapter, or directly for the RF-S lenses. It should be noted that the 15-45mm and 18-135 lenses now available are meant to be used on the R7 and R10 bodies but CAN be physically connected to the FF bodies - this was not possible on the DSLR platform, so was not an issue. Because those EF-S and RF-S lenses are designed for a smaller crop sensor, they do not project onto the whole area of a FF sensor, and this results in the effective resolution being reduced dramatically - by a factor of 2.56 in fact. This is not obvious to those not aware of the context within which these two platforms engage, but is it buried in the manuals, for example this one for the R6 body that documents how the resolution is reduced from 20MP to 7.7MP:

My point is that these are traps for the unwary and they are of practical significance, not just theory. So consideration of these issues is not unreasonable.

Re: EOS RF Lens Compatibility with EOS R7

CaliforniaDream — Fri, 29 Jul 2022 00:04:22 GMT

Wow, again and again, This topic has been talked to death!! I have an opinion as to who is "More Correct" but I will not share.

Re: EOS RF Lens Compatibility with EOS R7

ebiggs1 — Fri, 29 Jul 2022 14:20:32 GMT

The problem with this and a lot of topics is "over thinking". Trying to see a problem when none exists.