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neuroanatomist · Apr 6, 2026

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.

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.

neuroanatomist · Apr 6, 2026

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.

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).

zapper · Apr 6, 2026

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.)

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.

zapper · Apr 6, 2026

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).

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.

AJ · Apr 6, 2026

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 · Apr 6, 2026

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.)

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.

zapper · Apr 6, 2026

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.

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.

“Equivalence” in a Nutshell | Sans Mirror | Thom Hogan

Equivalence in camera systems

www.sansmirror.com

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.

neuroanatomist · Apr 6, 2026

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.

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.)

zapper · Apr 6, 2026

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.

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.

neuroanatomist · Apr 6, 2026

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.

neuroanatomist · Apr 6, 2026

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).

Xpenelas · Apr 6, 2026

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.

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.

neuroanatomist · Apr 6, 2026

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.

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.

becceric · Apr 6, 2026

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

AlanF · Apr 6, 2026

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.

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.

danfaz · Apr 6, 2026

fox40phil said:
But Canon better release something for Wildlife along the R7ii!

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

Tom R5R7 · Apr 6, 2026

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...

F-Stop Calculator: Focal Length, Aperture Diameter, and F-Stop & Formula Online Calculator Ultra

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.

fox40phil · Apr 6, 2026

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!

Del Paso · Apr 6, 2026

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.

Xpenelas · Apr 6, 2026

Bob Howland said:
What do you mean by "reducing the image circle"? That is what a Metabone or Meike speed booster does. That is why you have to use a FF EF lens with APS-C RF body. I have one from each manufacturer and use them regularly with my 150-600 f/5-6.3 Sigma Sport lens. That lens effectively becomes a 106-426 f/3.5-4.5. Then the 1.6X APS-C crop gets applied by my R7.

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.

Xpenelas · Apr 6, 2026

AlanF said:
What lighter and smaller telephotos does Nikon make for their crop cameras? They have done their best to make lighter weight ones for full frame, but they haven't made any of them as smaller and lighter versions for crop because not even they can get around the laws of optics.

Nikon is getting lighter and smaller telephotos reducing image circle and correcting vignetting on processing. Just go further and you have more.

Bob Howland · Apr 6, 2026

Xpenelas said:
No manufacturer makes them cause there's no profitable market to do that, but integrated teleconverters are showing that you can squeeze aperture and size to get the same reach when reducing the image circle.

What do you mean by "reducing the image circle"? That is what a Metabone or Meike speed booster does. That is why you have to use a FF EF lens with APS-C RF body. I have one from each manufacturer and use them regularly with my 150-600 f/5-6.3 Sigma Sport lens. That lens effectively becomes a 106-426 f/3.5-4.5 but only covers an APS-C sensor..

AlanF · Apr 6, 2026

Xpenelas said:
So, you know more than Nikon's lens engineering. Go ****** yourself.

What lighter and smaller telephotos does Nikon make for their crop cameras? They have done their best to make lighter weight ones for full frame, but they haven't made any of them as smaller and lighter versions for crop because not even they can get around the laws of optics.

danfaz · Apr 6, 2026

Xpenelas said:
No manufacturer makes them cause there's no profitable market to do that, but integrated teleconverters are showing that you can squeeze aperture and size to get the same reach when reducing the image circle.

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