15-70 f/4 would be a great video lens for me - especially when it is equipped with motorized zoom (PZ). Could "replace" the cinema lens with 18-80 range for simple applications.
I always wanted a 15-60 f/4 with high correction - if this lens has it, might be a replacement for my RF-S 24-105.

neuroanatomist said:

Indeed, there is a size/weight advantage when designing lenses for a smaller sensor for focal lengths in the ultrawide, wide, normal and short/mid telephoto ranges. But at longer focal lengths, there is no advantage to designing lenses for a smaller sensor.

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Right, if D = f/N, (D=entrance pupil, f=focal length, N=f number) and f and N both are scaled by the same crop factor for an equivalent focal length and aperture, then D is the same for a FF and equivalent APS-C lens. And the diameter of the lenses is the biggest factor in weight. However, since f does scale down for APS-C, that equivalent lens will be shorter, which should yield some saving in the length dimension and weight too.

neuroanatomist said:

The main advantages of crop over FF are that the former can yield a system that is smaller, lighter and cheaper. Those are definitely tangible and significant benefits. Higher pixel density can be another one, for some use cases. But FF systems generally offer better image quality in many settings, and more control over DoF when wanted (try finding an APS-C lens to match the framing and DoF of an 85mm f/1.2 lens on FF).

Click to expand...

I agree. I have a FF Nikon (Z7), which is what I use when I want top image quality. Especially when I can use a tripod and use the base ISO of 80, the IQ is top notch. I don't have any f/1.2 lenses though - I'm not really into super short DOF. The R7 makes a great birding camera, due to high pixels density, as you mention, and a great lightweight travel camera with limited financial exposure should some low life steal it.

If this turns out to be true, this would be an instant purchase for me. I've been using the old EF 180mm for years.

zapper said:

My Sigma RF-S 10-18 f2.8 and 18-50 f2.8, when mounted on my R7, show "Not available with the attached lens" for distortion correction, and "Cannot correct - no data" for Digital Lens Optimizer, in the Lens aberration correction menu. This doesn't bother me much, as I shoot raw and process in Lightroom, which does apply the corrections.

Click to expand...

I did quite a bit of research on this when I bought the Sigma 17-40mm f/1.8 and while it's difficult to find solid answers, what I found seemed to indicate:

• "Not available with the attached lens" for distortion correction is actually because it's force to be ON, similar to many Canon recent lenses. It's a very confusing message because it seems like it's off, but from what I read (and have experienced), it's actually on.
• "Cannot correct - no data" for Digital Lens Optimizer is actually OFF because Canon does not provide the physics mapping provided for these more advanced corrections (which include diffraction, low-pass filter blur, and more specific optical aberrations).
• Peripheral illumination and Chromatic Aberration corrections are ON for the Sigma lenses (not sure which menu this option this is covered under, but it seems to work).

My experience with the Sigma 17-40mm f/1.8 has reflected those findings, the JPEGs seem to be very well-corrected. Why Canon has made the menu so confusing, I'm not sure. I can't speak to Contemporary Sigma lenses that may need more advanced corrections and could benefit from the DLO mapping, but the 17-40 is beautifully corrected with the available correction profiles.

FINALLY!!! Why has it taken so long for Canon to realize that there is a real need for an all around 24mm equivalent zoom for apc-c, after all there are 3 FF lenses that has this 24mm starting point. This will by my travel and walk around combo, small light hopefully F4 through out.

zapper said:

Another FF vs APS-C comparison, between lenses I own:

Nikon Z 24-70 f/4 S: ø: 77.5 x L: 88.5 mm; 500g
Sigma RF-S 18-50 f/2.8: ø: 69.2 x L: 74.5 mm; 300 g

Nikon Z 14-30mm f/4 S: ø: 89 x L: 85 mm; 485g
Sigma RF-S 10-18m f/2.8: ø: 71.1 x L: 61 mm; 270g

Not a strict apples to apples comparison, but two pairs of approximately equivalent lenses in terms of focal range and aperture. There is a significant reduction in size and weight for the APS-C lenses. That is partly due to differences in construction and materials (the Nikon S lenses are a higher grade of lens than the Sigma Contemporary), but the reduction in lens size due to the smaller sensor is a major factor.

The R7 and the Sigma f/2.8 lenses will accompany me to Spain this week, and the Z7 and the Nikon f/4 lenses will stay home, because I'm packing light.

Click to expand...

The crucial point in these discussions is as follows. Above a certain focal length, 50-100mm or so, the natural image diameter of a simple lens is larger, or as the focal length increases, many times larger than the diameter of the circle required to cover a full frame sensor. So, a lens for sensors smaller than full frame will also cover full frame, and the lens cannot be made smaller just to have a smaller diameter for crop, M4/3 etc. Conversely, for shorter focal length lenses, the natural image circle of a simple lens becomes smaller than required to cover the full frame and so clever optics with complex elements is required to expand effectively the image circle. The smaller the sensor, the easier it is to make a lens to cover its image circle. The comparison is not a "Not a strict apple to apples..." but is a quite different situation.

zapper said:

These examples definitely show the advantage of a larger sensor, but they aren't taken under the conditions of equivalency, where the R10 would have an ISO of 25600 / 1.6 = 16,000. Under those conditions the two images should look similar. But in real world low light conditions, you would likely shoot the two cameras at equal exposure (maximum aperture, as low a shutter speed as possible, and as high an ISO as you can tolerate). Then the images won't be equivalent. The R3 will have lower noise, and the R10 greater depth of field.

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My point was not about equivalence nor to show that, but merely to show the reason that I would never set an APS-C camera to ISO 25,600 while I routinely use that setting on modern FF cameras.

zapper said:

Another FF vs APS-C comparison, between lenses I own...

Not a strict apples to apples comparison, but two pairs of approximately equivalent lenses in terms of focal range and aperture. There is a significant reduction in size and weight for the APS-C lenses. That is partly due to differences in construction and materials (the Nikon S lenses are a higher grade of lens than the Sigma Contemporary), but the reduction in lens size due to the smaller sensor is a major factor.

The R7 and the Sigma f/2.8 lenses will accompany me to Spain this week, and the Z7 and the Nikon f/4 lenses will stay home, because I'm packing light.

Click to expand...

Indeed, there is a size/weight advantage when designing lenses for a smaller sensor for focal lengths in the ultrawide, wide, normal and short/mid telephoto ranges. But at longer focal lengths, there is no advantage to designing lenses for a smaller sensor.

The main advantages of crop over FF are that the former can yield a system that is smaller, lighter and cheaper. Those are definitely tangible and significant benefits. Higher pixel density can be another one, for some use cases. But FF systems generally offer better image quality in many settings, and more control over DoF when wanted (try finding an APS-C lens to match the framing and DoF of an 85mm f/1.2 lens on FF).

neuroanatomist said:

Benefits of collecting more total light, and not just at base ISO. At lower ISOs, the DR advantage is what is most noticeable - presumably what you mean by 'advantage in IQ'. At the other end of the ISO scale, the ~1.3 stops more light collected by the FF camera benefits not only DR but also image noise directly. I routinely use my R1 at ISO 25,600, a setting I wouldn't even consider with an APS-C camera.

View attachment 228774
(Showing the R3 because DPR's comparator doesn't have the R1, but I also routinely used the R3 at ISO 25,600.)

Click to expand...

These examples definitely show the advantage of a larger sensor, but they aren't taken under the conditions of equivalency, where the R10 would have an ISO of 25600 / 1.6 = 16,000. Under those conditions the two images should look similar. But in real world low light conditions, you would likely shoot the two cameras at equal exposure (maximum aperture, as low a shutter speed as possible, and as high an ISO as you can tolerate). Then the images won't be equivalent. The R3 will have lower noise, and the R10 greater depth of field.

neuroanatomist said:

Sorry, but no. You can argue with physics, but you will lose. Every. Single. Time.

There is no 'unused diameter' to remove. With telephoto lens designs, the limiting factor is the entrance pupil diameter and that is coincident with the front element. A 400mm f/4 lens will need a 100mm front element (slightly less, because really a lens called a 400/4 would be something like a 392mm f/4.13 and thus could have a 95mm front element). A smaller sensor won't change that.

DO will make the lens shorter, not lighter or smaller in diameter.

Try an empirical comparison. The OM 150-400mm f/4.5 is 115mm in diameter and weighs 1.9 kg. The Canon EF 400mm f/4 DO is 128mm in diameter and weighs 2.1 kg. The OM lens is for m4/3 sensors with a 2x crop factor, yet it's pretty much the same diameter and weight as the FF lens from Canon (the differences are because the OM lens is 1/3-stop slower).

Click to expand...

Another FF vs APS-C comparison, between lenses I own:

Nikon Z 24-70 f/4 S: ø: 77.5 x L: 88.5 mm; 500g
Sigma RF-S 18-50 f/2.8: ø: 69.2 x L: 74.5 mm; 300 g

Nikon Z 14-30mm f/4 S: ø: 89 x L: 85 mm; 485g
Sigma RF-S 10-18m f/2.8: ø: 71.1 x L: 61 mm; 270g

Not a strict apples to apples comparison, but two pairs of approximately equivalent lenses in terms of focal range and aperture. There is a significant reduction in size and weight for the APS-C lenses. That is partly due to differences in construction and materials (the Nikon S lenses are a higher grade of lens than the Sigma Contemporary), but the reduction in lens size due to the smaller sensor is a major factor.

The R7 and the Sigma f/2.8 lenses will accompany me to Spain this week, and the Z7 and the Nikon f/4 lenses will stay home, because I'm packing light.

15-70/4 looks like a handy range. Nice to see RF-S support from Canon. Yes, f/4 is not sexy but selective focus is not the point of this lens.

neuroanatomist said:

Also, at the other end of the ISO scale the FF camera achieves better noise performance by ~1.3 stops. I routinely use my R1 at ISO 25,600, a setting I wouldn't even consider with an APS-C camera.

View attachment 228774
(Showing the R3 because DPR's comparator doesn't have the R1, but I also routinely used the R3 at ISO 25,600.)

Click to expand...

Very true. Equivalency only holds over the range where FF ISO = crop ISO * scale factor. Breaks down at both ends of the ISO scale - I forgot about the upper end.

Xpenelas said:

None of that equivalencies are true.

APS-C F4 needs just the same exposure for the same image. Just the DOF change affirmation are something near reality, and just cause you are nearer to the subject on FF, not even 1/2 stop equivalent nearer, but you need M43 just that stop DOF lose, not APS-C.

Click to expand...

Yes, APS-C needs the same exposure as FF. But to get an equivalent image (same exposure, FOV, DOF, motion blur, and image quality (photon noise)), different apertures and ISOs are needed. This is the formula for equivalence:

1) FF focal length = APS-C focal length * 1.6 (same FOV)
2) FF f number = APS-C f number * 1.6 (same DOF)
3) FF shutter = APS-C shutter (same motion blur)
4) FF ISO = APS-C ISO * 1.6 (this compensates for higher FF f number to get the same exposure)

IQ is the same because it is determined by the total amount of light hitting the sensor, which is determined by the entrance pupil size and the shutter speed.. The entrance pupil is the same for FF and APS-C, because entrance pupil = focal length / f number. For the FF case, both focal length and f number are multiplied by 1.6 compared to the APS-C numbers. The factor of 1.6 is in both the numerator and denominator, so it cancels out, leaving the same entrance pupil as the APS-C lens. The shutter speed is the same for both, so the amount of light is the same for both.

Here is an article written by an expert, if you don't follow my explanation.

The bottom line is that this 15-70mm f/4 lens will produce similar photos as a hypothetical 24-112mm f/6.4 full frame lens in most conditions, except where base ISO can be used in the FF camera, giving it ~ 1 stop better IQ. Therefore a FF camera will win for landscape photography most every time.

zapper said:

The bottom line: For many shooting situations, one can obtain similar results with an APS-C camera as a FF camera if the APS-C lens is one stop faster. However, if one can shoot base ISO in both cases, then the FF camera achieves ~ 1 stop advantage in IQ.

Click to expand...

Benefits of collecting more total light, and not just at base ISO. At lower ISOs, the DR advantage is what is most noticeable - presumably what you mean by 'advantage in IQ'. At the other end of the ISO scale, the ~1.3 stops more light collected by the FF camera benefits not only DR but also image noise directly. I routinely use my R1 at ISO 25,600, a setting I wouldn't even consider with an APS-C camera.


(Showing the R3 because DPR's comparator doesn't have the R1, but I also routinely used the R3 at ISO 25,600.)

Bob Howland said:

To maintain the same DOF for same FOV with differently sized sensors and the same subject distance (update: and the same ISO), the 15-70 and 24-112 lenses must have different apertures, which means they must have different shutter speeds, which may or may not be important, depending the situation and the photographer's intent. I prefer keeping the same FOV and exposure and letting the DOF fall where it may.

Click to expand...

That is partially correct.
- Yes, the apertures must be different, by the crop factor of 1.6 (the FF is bigger by 1.6). Notice that I multiplied the apertures for the hypothetical FF lens by this factor, but I forgot to state it explicitly.
- No, for equivalence, the shutter speeds must be the same.
- Since the aperture is smaller by 1.6, and the shutter speed is the same, the ISO must be higher by a factor of 1.6 on the FF camera.
- The total amount of light hitting the sensor is the same for both the APS-C and the FF camera is the same for both cases, since the entrance pupil is the same in both cases. The dominant factor in image quality (IQ) for modern sensors is the total number of photons hitting the sensor, therefore both sensors have the same IQ.

The bottom line: For many shooting situations, one can obtain similar results with an APS-C camera as a FF camera if the APS-C lens is one stop faster. However, if one can shoot base ISO in both cases, then the FF camera achieves ~ 1 stop advantage in IQ.

Much like the adage that you can lead a horse to water, but you can't make him drink, @Xpenelas shows us that you can lead a fool to correct information, but you can't make him think.

Yeah, but that lens only has an 86x zoom ratio, 9.3-800mm (18.6-1600mm with extender). A better 'deal' is the UHD DIGISUPER 122x 4K box lens that is 8.2-1000mm (16.4-2000mm with extender). That one sells for $213K (and @becceric it's 400 g lighter, weighing in at only 26.6 kg).

AlanF said:

You are 100% wrong. A speed booster reduces the size of the image circle, as stated by @Bob Howland . If it increased the size, it would spread the light over a larger area and be a speed reducer. A speed booster works by reducing the focal length of a lens.

Click to expand...

A speed booster get a bigger image circle (all the lens needs to be wider to fulfill the sped booster) of the lens and puts it on the little sensor. Getting then more light with the same image than an full frame.

Just doing that, you see why with the same size lens a cropped sensor camera could get one stop more light or get an lighter and smaller lens with the same.

Tom R5R7 said:

Incidentally, in terms of the exposure calculation the f/stop is what it is. In terms of depth-of-field (or the shallowness thereof), the sensor size/format plays a role. That is why some people say that an f/4 lens on an APS-C camera is the equivalent of f/6.3 or 6.4 on a full frame camera. The exposure isn't different, but the apparent depth of field is.

Click to expand...

Yes, it plays a role. But the major way in which is plays that role is when the photographer chooses a distance further from the subject to 'match the framing'. That means moving farther away with a smaller sensor, and it's that increased distance that results in the deeper DoF. In fact, if you keep the subject distance the same then with a smaller sensor, the framing will be tighter and the DoF will actually be shallower than with a larger sensor. The underlying concept there is the circle of confusion, and that is a source of confusion for some people.

I've always been a stills guy, but that deal may just turn me into a videographer.
Or a weight lifter

Xpenelas said:

No, a speed booster does the opposite, got a bigger image circle of the lens and concentrate it on the little sensor. Crop sensor gets the direction of a teleconverter, ditching the exterior part of the image circle and expand that on the bigger sensor.

With the modern sharper glass and camera vignetting corrections we are getting lighter and smaller lenses doing just that, reducing the image circle that goes trough the diafragm.

Click to expand...

You are 100% wrong. A speed booster reduces the size of the image circle, as stated by @Bob Howland . If it increased the size, it would spread the light over a larger area and be a speed reducer. A speed booster works by reducing the focal length of a lens.

fox40phil said:

But Canon better release something for Wildlife along the R7ii!

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I intend to pair the R7II with my 100-500. Don't think much else would be needed for me.

Show me a 400 mm f/4 lens that has a front element less than 100 mm in diameter and I'll show you a 400 mm lens that is smaller than f/4. If the entrance pupil is only 75 mm, assuming you still have a 400 mm lens, you have a 400 lens of approximately f/5.3. The f/stop is basically the focal length divided by the pupil. That is the mathematical definition of f/stop.

Here's a handy calculator...


Incidentally, in terms of the exposure calculation the f/stop is what it is. In terms of depth-of-field (or the shallowness thereof), the sensor size/format plays a role. That is why some people say that an f/4 lens on an APS-C camera is the equivalent of f/6.3 or 6.4 on a full frame camera. The exposure isn't different, but the apparent depth of field is.

4.0 is really sad…. Back in the days I wanted this EF 17-55 2.8 soo Hard…
This plus IS would be a premium Apsc lens! They could do it!

But Canon better release something for Wildlife along the R7ii!

I know from my own experience that even a "slight" modification of a product, in, my case, replacing a belt-drive with a chain -drive can take lots of time and even a huge amount of money, spent in modifying machinery, tooling, training staff, calculating cost, testing, informing, etc... etc...
For Sigma, it is not simply about paying licensing fees, adapting software and replacing the bayonet.
And, the article on (hugely biased and Sony friendly !) PhotoTrend was, in my opinion, more than vague...Nothing concrete!
I may add that I am more than happy with Canon's RF lens range, hoping for a few missing ones like TS and 24-70 II and 35mm f/1,2.
Sure, I wouldn't mind having more 3rd party choices and understand why some reasonably criticise Canon. Not speaking of the aggressive Sony trolls with their redundant and silly Canon-doom statements...
Yet, even in EF times, I've never bought Sigma or Tamron lenses. Only Zeiss (20mm f/2,8), since Canon's UWA were for a long time underwhelming.
I just expressed my personal and very subjective opinion.