A New Constant f/4 Aperture RF-S Zoom Coming

[AJ]

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.

 

[zapper]

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).

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.

 

[zapper]

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.)

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]

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.

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]

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.

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.

 

[AlanF]

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.

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.

 

[Andreasb]

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]

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.

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.

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).

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.

 

[mb66energy]

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.

 

[zapper]

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.

But no commercial lens is a simple lens. In a complex lens, the size of the rear and intermediate elements can scale with sensor size, as these elements determine the image circle, not the front elements that set the entrance pupil.

 

[phree_ed]

How I would have liked a replacement to the 15-85 for my R7 but sorry Canon - too late. I got tired of waiting and just three days ago picked up a Sigma 17-40 f1.8.

Yeah I know it's only 40mm at the long end but I've got it and I won't be stuffing around selling it and purchasing another lens.

But never say never I guess

 

[neuroanatomist]

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.

It doesn’t scale like that, as @AlanF stated. For example, my RF 100-400mm f/8 has a front element of ~50 mm in diameter. 400 mm / 8 = 50 mm. So far so good.

If that relationship scaled across all focal lengths, my RF 10-20mm f/4 would have a front element of ~5 mm in diameter. In fact, its front element is ~60 mm in diameter, larger than that of the 100-400/8.

Lens design matters. The takeaway is that the entrance pupil is at the front element for long telephoto designs, so that becomes the limiting factor in lens diameter. At shorter focal lengths, other factors are limiting.

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.

For equivalent framing. Focal length is an intrinsic property of a lens, independent of the sensor behind it.

 

[Aldherrian]

This supposed RF-s 15-70 F4 is a lens I would have gladly bought to upgrade from the EF-s 18-135 and update the EF-s 15-85.

Both are variable apertures of 3.5 - 5.6 so a constant aperture at 4 is nice.
I don't find realistic to expect such a wide range of focal length to offer F2.8 unless it's a L lens and totally not the same package of size and price (and ultimately audience)

The lack of such a lens made me upgrade to FF format but I'm glad some stuff is finally happening to the APSC side

 

[Tom R5R7]

How I would have liked a replacement to the 15-85 for my R7 but sorry Canon - too late. I got tired of waiting and just three days ago picked up a Sigma 17-40 f1.8.

Yeah I know it's only 40mm at the long end but I've got it and I won't be stuffing around selling it and purchasing another lens.

But never say never I guess

I used the Canon 17-40 f/4L on my 10D and 30D cameras back in the day. At the time, it was about the sharpest ultra-wide Canon had, with some very rich colors and great contrast. 40 is a little bit short, but that Sigma f/1.8 has the potential to be a real gem.

 

[InternalRevenue]

How I would have liked a replacement to the 15-85 for my R7 but sorry Canon - too late. I got tired of waiting and just three days ago picked up a Sigma 17-40 f1.8.

Yeah I know it's only 40mm at the long end but I've got it and I won't be stuffing around selling it and purchasing another lens.

But never say never I guess

I somewhat feel the same but 17mm ends up just a little too tight often enough for my video projects that I still kept and use the 15-85 after buying the 17-40, despite the EF-S's many, many quirks and deficiencies for video use. The closeup IQ and MFD isn't that great on the Sigma either, and if Canon manages to get as good a MFD/magnification ratio on this thing like they did with the RF-S 18-150, I might just spring for this 15-70 (or buy it bundled with the R7ii if offered).