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

[Canon Rumors]

Most of us out there are convinced that Canon is going to announce the EOS R7 Mark II in the next couple of months. We're looking at announcement coming in May or June of this year, at least that's what all the signs point to. With the new “flagship” APS-C EOS R camera, we can […]

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[Tom R5R7]

Well, a 15-70 f/4 would be a great addition to the lineup. Kind of a jack of many trades type of lens, an APS-C version of something like the well-liked 24-105 f/4L. In fact, in terms of field of view equivalent, it would be a 24-113 mm lens. I'd buy the lens on its own merit for any APS-C R body really.

 

[BlueBomberTurbo]

F/6.3 equivalent is nice for a kit lens, but come on already, Canon.

 

[Xpenelas]

Sounds like a good replacement for the EF-S 15-85mm f/3.5-5.6 IS USM.

 

[Xpenelas]

Well, a 15-70 f/4 would be a great addition to the lineup. Kind of a jack of many trades type of lens, an APS-C version of something like the well-liked 24-105 f/4L. In fact, in terms of field of view equivalent, it would be a 24-113 mm lens. I'd buy the lens on its own merit for any APS-C R body really.

Should be a perfect kit lense for the R7 mkII if it's sharp enough.

 

[InternalRevenue]

Sounds like a good replacement for the EF-S 15-85mm f/3.5-5.6 IS USM.

If it comes with a nice weight and size reduction I wouldn’t be too miffed about the loss of focal length on the long end. The 15-85 had soft corners (and distortion at 15mm) which I would like to see dealt with too, though I imagine if so it’ll be entirely digital correction.

 

[Xpenelas]

Distortion and vignetting on the 15-85 it's well corrected by digital correction, an RF version should be a lot smaller, like all angular APS-C lenses are because of the flange distance reduction.

Should be a big upgrade over RF-S 14-30 or 18-150 as a kit lense.

 

[Bob Howland]

F/6.3 equivalent is nice for a kit lens, but come on already, Canon.

It's not f/6.3. It's a 15-70 f/4 lens with the DOF of a 15-70 f/4 lens, regardless of the size of sensor. The only reason the DOF changes is when people move forward or back or change the focal length to maintain the same FOV. I'm rather interested in this lens but I already own the 18-50 Sigma and I highly value small size and especially light weight.

 

[Uneternal]

f/4 ... meh. Not great, not terrible. Depending on the price.
But I guess I still keep my adapted Sigma 17-70mm f/2.8-4, which weighs just 575 grams (incl adapter).

 

[zapper]

It's not f/6.3. It's a 15-70 f/4 lens with the DOF of a 15-70 f/4 lens, regardless of the size of sensor. The only reason the DOF changes is when people move forward or back or change the focal length to maintain the same FOV. I'm rather interested in this lens but I already own the 18-50 Sigma and I highly value small size and especially light weight.

He said "f/6.3 equivalent", which is (approximately) correct. It will take similar photos to a hypothetical 24-112mm f/6.4 full frame (same position, same DOF, same FOV, same shutter speed, same image quality with the full frame aperture and ISO 1.6x higher than APS-C). However, the hypothetical 24-112mm f/6.4 will take photos with higher IQ if the exposure permits base ISO, compared to the 15-70 f/4.

I would not buy a f/6.4 FF mid zoom, nor I would not buy a f/4 APS-C mid zoom. I consider FF f/4 to be acceptable compromise of versatility, IQ, and size/weight for wide and mid zooms, and f/2.8 to be acceptable on APS-C (I have the Sigma 10-18 and 18-50 f/2.8 lenses). I would LOVE a 15-70 f/2.8 RF-S lens. But f/4 on APS-C is a stop slower than I want.

 

[Mr. Warbucks]

Weight is the key differentiator imo. It would line up nicely with the 70-200 F4.0L lens, which is low weight as well. Wondering whether we will see a birding rf-s lens upto say 200-400 or 500 at apenditure F4.0, a step up from the rf 100-400 which is at the long range F8.0 or so…..
And, indeed, why not vcm? Or is that only relevant for primes?
Hurry up with the R7ii, very keen to see what it will be!

 

[neuroanatomist]

Wondering whether we will see a birding rf-s lens upto say 200-400 or 500 at apenditure F4.0, a step up from the rf 100-400 which is at the long range F8.0 or so…..

No, we won't. Not ever. Because physics. A 400/4 or 500/4 would be the same size and weight for an APS-C image circle as for a FF image circle.

 

[Bob Howland]

He said "f/6.3 equivalent", which is (approximately) correct. It will take similar photos to a hypothetical 24-112mm f/6.4 full frame (same position, same DOF, same FOV, same shutter speed, same image quality with the full frame aperture and ISO 1.6x higher than APS-C). However, the hypothetical 24-112mm f/6.4 will take photos with higher IQ if the exposure permits base ISO, compared to the 15-70 f/4.

I would not buy a f/6.4 FF mid zoom, nor I would not buy a f/4 APS-C mid zoom. I consider FF f/4 to be acceptable compromise of versatility, IQ, and size/weight for wide and mid zooms, and f/2.8 to be acceptable on APS-C (I have the Sigma 10-18 and 18-50 f/2.8 lenses). I would LOVE a 15-70 f/2.8 RF-S lens. But f/4 on APS-C is a stop slower than I want.

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.

 

[Xpenelas]

He said "f/6.3 equivalent", which is (approximately) correct. It will take similar photos to a hypothetical 24-112mm f/6.4 full frame (same position, same DOF, same FOV, same shutter speed, same image quality with the full frame aperture and ISO 1.6x higher than APS-C). However, the hypothetical 24-112mm f/6.4 will take photos with higher IQ if the exposure permits base ISO, compared to the 15-70 f/4.

I would not buy a f/6.4 FF mid zoom, nor I would not buy a f/4 APS-C mid zoom. I consider FF f/4 to be acceptable compromise of versatility, IQ, and size/weight for wide and mid zooms, and f/2.8 to be acceptable on APS-C (I have the Sigma 10-18 and 18-50 f/2.8 lenses). I would LOVE a 15-70 f/2.8 RF-S lens. But f/4 on APS-C is a stop slower than I want.

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.

 

[neuroanatomist]

To maintain the same DOF for same FOV with differently sized sensors and the same subject distance, 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.

Must? No, you can change the ISO. Like all triangles, the exposure triangle has three sides.

It's been a few months since I posted a couple of good links that explain equivalence. I'm guessing you didn't read them, but I'll post them again in case someone other than you actually wants to try to properly understand the concept.

This link has a thorough explanation of the concept:

Equivalence

This link is a decent summary:

What is equivalence and why should I care?

Equivalence, at its most simple, is a way of comparing different formats (sensor sizes) on a common basis. Sounds straightforward enough, but the concept is still somewhat controversial and not always clearly understood. We thought it was about time we explained - and demonstrated - what...

www.dpreview.com

 

[Xpenelas]

No, we won't. Not ever. Because physics. A 400/4 or 500/4 would be the same size and weight for an APS-C image circle as for a FF image circle.

No we want cause market is not enought, but, not cause the lenses couldn't be less size and weight. The smaller the image circle the nearer the back lens could be an with DO you could remove all the unused diameter, almost 1/3 at 400mm, of the front lenses or get faster aperture.

 

[Bob Howland]

Must? No, you can change the ISO. Like all triangles, the exposure triangle has three sides.

It's been a few months since I posted a couple of good links that explain equivalence. I'm guessing you didn't read them, but I'll post them again in case someone other than you actually wants to try to properly understand the concept.

This link has a thorough explanation of the concept:

Equivalence

This link is a decent summary:

What is equivalence and why should I care?

Equivalence, at its most simple, is a way of comparing different formats (sensor sizes) on a common basis. Sounds straightforward enough, but the concept is still somewhat controversial and not always clearly understood. We thought it was about time we explained - and demonstrated - what...

www.dpreview.com

Are you serious? You're correct about the ISO and I modified my previous posing but I replied to your cited posting, three posts later. Can't you read?

 

[neuroanatomist]

No we want cause market is not enought, but, not cause the lenses couldn't be less size and weight. The smaller the image circle the nearer the back lens could be an with DO you could remove all the unused diameter, almost 1/3 at 400mm, of the front lenses or get faster aperture.

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).

 

[neuroanatomist]

Are you serious? You're correct about the ISO and I modified my previous posing but I replied to your cited posting, three posts later. Can't you read?

Yes, but I said properly understand. Clearly, you don't. Just because you prefer 'keeping the same FOV and exposure and letting the DOF fall where it may' doesn't mean that's a universal belief.

It's not f/6.3. It's a 15-70 f/4 lens with the DOF of a 15-70 f/4 lens, regardless of the size of sensor. The only reason the DOF changes is when people move forward or back or change the focal length to maintain the same FOV.

You should have stopped with the above. That was a correct statement.

 

[Xpenelas]

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).

Just get a lens and test.
You can put an inferior diameter filter without vignetting or open more the diafragm without softening the corners of the image , cause you don't see the part of the image it's losening sharpness .