RF24-70 & RF15-35 Reviews

[SecureGSM]

Well that is true, though a few people, notably Dustin Abbott, have praised its rendering you're quite right it falls short in measurable terms. Which again I feel re-inforces that the EF 24-70 2.8L II was just one of those lenses that set a new standard and somehow found something special previously missed. I don't say it as a Canon fanboy either. Probably the best example from recent years of such a lens was Nikon's 14-24. I wasn't alone in using it adapted to a Canon SLR back when Canon offered very little with high quality in the wide angle arena. All these years later and Sigma brings out a 14-24 2.8 Art that isn't really that much different. Canon never did bring one out a 14-24 2.8 and Tamron only got to 15mm.

Every now and then you get those kind of lenses that it takes years for others to catch up and I think the EF 24-70 2.8L II was just such a lens.

the Sigma 14-24/2.8 --is a great lens wide open. the issue: it suffers from a substantial focus shift once stopped down to F4 and beyond. yes, one can notice that even with such a deep DoF at super wide focal lengths. I was going to obtain one for my low light crowd shots.. 14mm sounds tempting.. but.. why, SIgma, why...

 

[wockawocka]

I can't see myself moving to these RF zooms in a hurry when the EF versions are just as sharp, lighter, cheaper and aren't focus by wire.

 

[AlP]

TDP now also published vignetting measurements for the 15-35.

At 15 mm and f/2.8 it looks a bit better than the EF 16-35 at 16 mm and f/2.8 (https://www.the-digital-picture.com...sComp=1073&CameraComp=979&FLIComp=0&APIComp=3)

At the other focal lengths the RF lens has more vignetting than the EF lens. And, the situation doesn't improve that much when stopping down.

Looks like low vignetting wasn't the top priority for this design.

 

[LesC]

These customers seem very happy with the RF15-35 ...

Canon RF 15-35mm f/2.8L IS USM Lens

Buy Canon RF 15-35mm f/2.8L IS USM Lens featuring RF-Mount Lens/Full-Frame Format, Aperture Range: f/2.8 to f/22, Three Aspherical Elements, Two Ultra-Low Dispersion Elements, Air-Sphere and Fluorine Coatings, Nano USM AF System, Optical Image Stabilizer, Customizable Control Ring, Rounded...

www.bhphotovideo.com

 

[Del Paso]

These customers seem very happy with the RF15-35 ...

Canon RF 15-35mm f/2.8L IS USM Lens

Buy Canon RF 15-35mm f/2.8L IS USM Lens featuring RF-Mount Lens/Full-Frame Format, Aperture Range: f/2.8 to f/22, Three Aspherical Elements, Two Ultra-Low Dispersion Elements, Air-Sphere and Fluorine Coatings, Nano USM AF System, Optical Image Stabilizer, Customizable Control Ring, Rounded...

www.bhphotovideo.com

Could there be a discrepancy between real world pictures and sterile MTF/chart pictures?
Leica M lenses almost always disappoint in "objective" tests, but convince when taking photographs...
Quote from Leica Camera: "Lenses are made for taking pictures, not to photograph charts..."

 

[Michael Clark]

Do engineering changes needed to accommodate IS affect image quality?

Lens based IS works by causing an intentional (slight) misalignment of the IS element/group. So yeah, it does affect optical image quality.

In a different way, IBIS moves the center of the imaging sensor away from the center of the lens's optical axis, so edge performance on one side will improve, but on the other side it will degrade.

Alas, TANSTAAFL.

 

[Michael Clark]

So both new RF zoom’s have average edge sharpness? Coming from the 50 and 85 and all the noise around those releases I’m disappointed the zooms aren’t as mind blowing (compared to their EF counterpart, not the primes.)

Truely somewhat disappointing. Esp. as they match the results of TDP.
Not bad - but not as good as the RF primes seemed to have promised.
(And the EF zoom counterparts, although IS is included now).

Well that is true, though a few people, notably Dustin Abbott, have praised its rendering you're quite right it falls short in measurable terms. Which again I feel re-inforces that the EF 24-70 2.8L II was just one of those lenses that set a new standard and somehow found something special previously missed. I don't say it as a Canon fanboy either. Probably the best example from recent years of such a lens was Nikon's 14-24. I wasn't alone in using it adapted to a Canon SLR back when Canon offered very little with high quality in the wide angle arena. All these years later and Sigma brings out a 14-24 2.8 Art that isn't really that much different. Canon never did bring one out a 14-24 2.8 and Tamron only got to 15mm.

Every now and then you get those kind of lenses that it takes years for others to catch up and I think the EF 24-70 2.8L II was just such a lens.

Could there be a discrepancy between real world pictures and sterile MTF/chart pictures?
Leica M lenses almost always disappoint in "objective" tests, but convince when taking photographs...
Quote from Leica Camera: "Lenses are made for taking pictures, not to photograph charts..."

Lens design is always a compromise.

Do you want a lens that can do better on the edges shooting flat test charts at the expense of pleasing out of focus areas when taking photos of a 3D world?

Or would you rather leave a little of the field curvature and spherochromatism uncorrected/undercorrected so that the bokeh is smooth and creamy?

 

[Viggo]

Lens design is always a compromise.

Do you want a lens that can do better on the edges shooting flat test charts at the expense of pleasing out of focus areas when taking photos of a 3D world?

Or would you rather leave a little of the field curvature and spherochromatism uncorrected/undercorrected so that the bokeh is smooth and creamy?

I’ll take both please, both my RF’s does both really, really well. And one of the reasons I really disliked the 50 L is field curvature, calibrated center focusing point was way frontfocused at the edges. And sharpness in the corners is a lot more important than bokeh for uwa imo Another argument for the excellent corner sharpness of for example the RF85 is that combined with the AF-point spread of the R, makes for an incredible freedom when composing.

 

[Maximilian]

Truely somewhat disappointing. Esp. as they match the results of TDP.
Not bad - but not as good as the RF primes seemed to have promised.
(And the EF zoom counterparts, although IS is included now).

Lens design is always a compromise.

Do you want ...

As I stated in my post you've quoted I compare a new lens design to its predecessor or similar lenses (EF vs. RF).
And I want a NEW one to be BETTER or at least AS GOOD as those. (or to be cheaper)
And the IQ improvement of the RF primes (compared to the EF counterparts) made me (and other people) hope that the zooms would continue that.
So somewhat disappointing - but still not bad.

 

[Michael Clark]

I’ll take both please, both my RF’s does both really, really well. And one of the reasons I really disliked the 50 L is field curvature, calibrated center focusing point was way frontfocused at the edges. And sharpness in the corners is a lot more important than bokeh for uwa imo Another argument for the excellent corner sharpness of for example the RF85 is that combined with the AF-point spread of the R, makes for an incredible freedom when composing.

Sometime you can't have both, at least not in the same measure as one can have either one or the other with different designs.

That's why Zeiss makes several series of prime lenses in some of the same focal lengths and maximum apertures. Otus? Planar? Batis? Milvus?

They all have different characteristics for different purposes.

50mm isn't UWA unless you're shooting LF, in which case you need an image circle between 3.75X and 8X larger than that cast by the EF 50mm f/1.2L.

If you use the center AF point, it will focus the center of the lens' FoV at the center. Even with field curvature, if you use the far left AF point, it will focus the portion of the lens' FoV under the far left AF point on whatever is visible at that point in the lens' FoV and the lens will be focused slightly further than that at the center of the FoV.

 

[Michael Clark]

As I stated in my post you've quoted I compare a new lens design to its predecessor or similar lenses (EF vs. RF).
And I want a NEW one to be BETTER or at least AS GOOD as those. (or to be cheaper)
And the IQ improvement of the RF primes (compared to the EF counterparts) made me (and other people) hope that the zooms would continue that.
So somewhat disappointing - but still not bad.

You compared them only in terms of how well they image a flat test chart. Not everyone wants to make their mark by being the best flat test chart photographer around.


Some lenses that are "soft" in the corners are actually "sharp" in the corners when the focus is adjusted to account for field curvature.

This actually comes in handy in a few applications, particularly portrait photography when fabrics have a strong weave pattern.

There's nothing like using a flat field macro lens for a head + half torso shot of a model in a "shoulder forward pose" with her face perfectly in focus and the spot on her shoulder down in the corner of the frame that is the exact same distance from the camera as her left eye screaming "LOOK AT ME!" because the weave of the fabric at that spot is sharper than the fabric on the other parts of her garment that are further away than the focus point. Use a lens like the EF 50mm f/1.2L and the field curvature pulls the field of focus just enough in front of that forward shoulder near the edge of the frame that it doesn't distract from her face.

 

[SteveC]

Well, let's say you are taking a picture of something flat, e.g., artwork in a museum. I would think then you'd want to (after assuring you're perpendicular with the subject) focus halfway to the side, halfway between the center and the edge. That way the center is slightly out of focus and so are the edges, but nothing is more than slightly out of focus (hopefully less so than you'd need pixel peeping to see). (Obviously you'll benefit greatly from a telephoto at higher distance.) If you were to instead focus on the center, it will be sharp, but the edges will be at least twice as much out of focus as they were in the first case. Likewise focusing on an edge will make the edge clear, but the center will be well out of focus. If your camera is centered on the picture however, at least the opposite edge should be in focus again. (I assume as I write this that the focus "plane" is actually part of a sphere.)

 

[LesC]

RF15-35 Review from Brendan van Son:

 

[Maximilian]

You compared them only in terms of how well they image a flat test chart.

You're right I didn't think about vigneting ot flare or anything else - not. It's the summary.

Not everyone wants to make their mark by being the best flat test chart photographer around.
...

You're right
Everyone wants to put subject into the center and then reframe in post by croping.
Nobody want's to use corner sharpness to compose according to the golden rule or else.
Everything has to be centralized

/sarc mode

 

[Michael Clark]

You're right I didn't think about vigneting ot flare or anything else - not. It's the summary.


You're right
Everyone wants to put subject into the center and then reframe in post by croping.
Nobody want's to use corner sharpness to compose according to the golden rule or else.
Everything has to be centralized

/sarc mode

You still fail to understand. Many of those lenses *are* sharper in the corners and on the edges than an ignorant perusal of the image of a flat test chart made when the lens is focused at the center of the test chart would lead an uninformed viewer to believe.

If one is concerned with focusing a subject on the edge of the field of view, why would one focus the center of the lens? Focus the lens so that the subject at the edge of the FoV is in sharpest focus. See how easy that was?

Further, if one is forced to use focus and recompose, a lens with field curvature will introduce *less* error than a lens highly corrected for flat field will.

 

[Maximilian]

You still fail to understand. Many of those lenses *are* sharper in the corners and on the edges ...

Now I understand your argumentation! Thank you. I hope that you are not only good in explaining but also right when it comes to your assumption on how the lens could be optimized.

...
If one is concerned with focusing a subject on the edge of the field of view, why would one focus the center of the lens?

Further, if one is forced to use focus and recompose...

Right on the first one but
I was never talking about "focus and recompose".


But that leads to one question:
If you are right here (R&D on field curvature), why do the RF primes look so well on flat field?
I would assume that Canon R&D would take the same primary IQ goals (field curvature sharpness) for lens design, even though primes and zooms are designed differently.

 

[SteveC]

Now I understand your argumentation! Thank you. I hope that you are not only good in explaining but also right when it comes to your assumption on how the lens could be optimized.

Right on the first one but
I was never talking about "focus and recompose".


But that leads to one question:
If you are right here (R&D on field curvature), why do the RF primes look so well on flat field?
I would assume that Canon R&D would take the same primary IQ goals (field curvature sharpness) for lens design, even though primes and zooms are designed differently.

As I understand it--and someone correct me if I am wrong--a lot of high end lenses actually play games with the optics to make the focal plane wavy rather than spherical. It reduces the error towards the edges but is in no way flat.

 

[Michael Clark]

Well, let's say you are taking a picture of something flat, e.g., artwork in a museum. I would think then you'd want to (after assuring you're perpendicular with the subject) focus halfway to the side, halfway between the center and the edge. That way the center is slightly out of focus and so are the edges, but nothing is more than slightly out of focus (hopefully less so than you'd need pixel peeping to see). (Obviously you'll benefit greatly from a telephoto at higher distance.) If you were to instead focus on the center, it will be sharp, but the edges will be at least twice as much out of focus as they were in the first case. Likewise focusing on an edge will make the edge clear, but the center will be well out of focus. If your camera is centered on the picture however, at least the opposite edge should be in focus again. (I assume as I write this that the focus "plane" is actually part of a sphere.)

That's why you use a macro lens highly corrected for field curvature and optimized for close focus distances to do 2D repro work. Or a T/S lens with a much larger image circle (so the "edges" are well out of the frame) as well as having a high degree of flat field correction and the ability to correct for shooting position when perfectly centered/perfectly perpendicular with respect to the target is not an option. As a 2D repro lens, the EF 85mm f/1.8 wipes the floor with the EF 85mm f/1.2L because the latter is not designed to do that job. But that does not mean the latter can't be sharp near the edge of the frame when properly focused to make a subject near the edge of the frame sharp.

The idea that a lens "sharper" on the edges and in the corners when imaging flat test charts is always "sharper" on the edges and in the corners than other lenses that do not have as flat a field of focus is often an incorrect assumption many make.

Here, for instance, is why you sometimes don't want to use a macro lens for 3D, wide aperture portrait work:

Different tools for different jobs.

 

[Michael Clark]

Now I understand your argumentation! Thank you. I hope that you are not only good in explaining but also right when it comes to your assumption on how the lens could be optimized.

Right on the first one but
I was never talking about "focus and recompose".


But that leads to one question:
If you are right here (R&D on field curvature), why do the RF primes look so well on flat field?
I would assume that Canon R&D would take the same primary IQ goals (field curvature sharpness) for lens design, even though primes and zooms are designed differently.

Every lens is not intended to be used to do 2D reproduction work. Sometimes the way out of focus areas are rendered is considered more important than flat field performance. Highly correcting for field curvature creates a field of focus that looks more like a lasagna noodle than a flat baking sheet. It also has an effect on the other optical characteristics of a lens (such as the way out of focus areas are blurred).

 

[Michael Clark]

As I understand it--and someone correct me if I am wrong--a lot of high end lenses actually play games with the optics to make the focal plane wavy rather than spherical. It reduces the error towards the edges but is in no way flat.

Yep. That's what Uncle roger discusses here and here (and more than a few other places).