Sigma working on APS-C 50-140 f/2.8 and an external zoom full frame 70-200 f/2.8
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It is certainly not going to be released for the RF mount anyway, so who cares?
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Yes and no.
Even with what I said earlier in post #7, the fact is, the lens will still have a focal length range of 50-140 mm, and, to your point, a focal ratio of 2.8. Those are the optical properties of the lens, and they don't change based on what kind of sensor is behind it.
The "equivalent focal length" is generally understood to be based on field of view, relative to a "full frame" 35 mm sensor (24x36 mm). On a sensor with a 1.6x crop factor (22.5x15 mm), this lens will provide the same FOV range as an 80-220 mm zoom lens on a full-frame sensor.
Equivalent focal ratio isn't as cut and dry. The f-ratio affects many things, so what is "equivalent" depends on which f-ratio-dependent property you are interested in. In terms of exposure calculation ("sunny 16" rule, e.g.), optical flux density (light per unit area) at the sensor plane, diffraction calculations, etc., the focal ratio is 2.8. Again, that is an optical property of the lens that doesn't change based on the sensor that's behind it.
If shallow DOF is your main concern, then, yes, there's definitely a dependency (but if that's your overriding consideration, you're better off shooting FF or MF anyway). DOF is a qualitative property of the final image and viewing conditions, not an optical property of the lens. DOF calculations depend on lens focal length and focal ratio, as well as the subject distance, final image magnification (size of the image being viewed versus size of the sensor) and viewing distance, along with an assumed "typical" viewer's tolerable "minimum circle of confusion".
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If you talk DoF yes; if you talk just exposure then no. Depends on what you photograph; as an avid wedding photographer, for me (fast) exposure in low light is the biggest concern, so I honestly don't care about DoF, for me 2.8 is 2.8
Maybe in the studio I'll reason differently, but generally speaking I care much more about exposure then DoF.
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It was Canon's choice to design the lens that way, they didn't need to do it. It doesn't outperform the Sony GM II version of the same lens, which has internal zooming, allows TCs, and matches the weight of the RF lens. Canon just wanted their version to be ultra-compact and made design decisions to make that happen. (This is not to say you should switch to Sony, obviously.)
It will be interesting to see how the new Sigma lenses perform. I share your concerns with their performance, but at the same time they will come at a far lower price. There are plenty of people out there who want a 70-200/2.8 but don't need (or want to pay for) that last ~10% of performance that the best first party lenses give over the best 3rd party glass. Sigma has generally kept their new mirrorless lenses at the same price as the DSLR lenses they replaced, or sometimes reduced the price. If they do that here and sell their new 70-200/2.8 for $1499, I think they will sell a lot of them.
I guess the big question is, will Canon ever allow it to be sold on RF?
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No. Go back to study. Maybe learn how an exposure meter works, so you'll discover then there's no "camera sensor size" parameter in it.
A scene measured f2 1/200s 100iso will be captured (almost) exactly in the same way (same brightness) by any camera having manual exposure control, from a smartphone to a medium format camera, or even an optical bench fwiw, when you input those exact exposure parameters.
What changes, sensor size to sensor size, given the same exposure triangle, is the DoF (and noise, but that's a whole different story); brightness and freezing motion won't change between film/sensor sizes.
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What you're missing are things like noise and DR.
Generally for a given generation and resolution, you will lose one stop of both on APS-C vs FF. So if you shoot at ISO 400 in APS-C, you can expect roughly the same noise and DR from ISO 800 on FF. (Again, with sensors of the same resolution and of the same generation.)
Combined with the loss of DOF, it really does make an f2.8 on APS-C perform like an f4 on FF.
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And what you are missing is that my bride and my groom know nothing about DR, DoF, noise levels, etc; they just want a bright photo of them with a sufficient shutter time to freeze them avoiding motion blur.
And I can assure you that if you're on my side, second shooting with me, we're in front of the same scene with the same brightness; I'll have a medium format camera (anyone...Hassie, Phase One, pick one) and you'll have a 1" sensor compact camera like a G7XIII, but to obtain the same picture with the same correct exposure (in terms of brightness) and stopping power, we'll use the exact same exposure triangle parameters, and our pictures will look (almost) exactly the same in terms of brightness. f2.8 is f2.8 regardless of the sensor size and system brand.
THEN of course if the iso part of the exposure triangle is 12.800iso then yes, the picture is not going to look the same due to noise and sh*t, but that's a whole different story; my story is "a f2.8 lens sends to the sensor the same amount of light regardless of the sensor size, given that the circle of coverage will cover both sensor formats". Anything else is SOMETHING ELSE, but man, exposure triangle is exposure triangle, and an f2.8 lens is an f2.8 lens, and I didn't invented it, it's the laws of physics.
People needs to stop thinking about sh*t and reading forums and looking YT channels; just reason like you're on a film camera, so you just take care of THREE things in a picture: iso, aperture, shutter. And partially, the color of light (so WB, or choosing a film with the right °K, or gelling the lights if possible).
All the other cr*p like dynamic range, color depth, noise levels, etc, is totally useless and will cloud you brain. Photography is light. End of it. Marketing overcomplicates stuff, so they can sell you the new thing, the new function, the new superprocessor with super NR, etc. Stop reading marketing sh*t and just go outside and take pictures.
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To get the same amount of light to hit the sensor (and thus the same amount of noise and dynamic range) at f2.8 in your APS-C camera, you have to shoot at f2. It doesn't matter what it says in the camera, because while the ISOs may both say 100, those values are not equivalent in how much they degrade your pictures. There are no standardized gain-values for ISO. ISO is a made up number, and what that number shows makes no difference in the amount of light that is captured by the sensor. This is the crucial part you have to understand.
If you take your APS-C lens with f2.8 and attach it on a full frame camera, it can only capture as much light as an f4 lens, due to the crop factor.
Your APS-C lens can only capture half as much light as an equivalent-rated full frame lens. If this wasn't the case, these lenses wouldn't be smaller and lighter than their full frame equivalents.
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Yes I agree. The current RF 70-200mm f2.8 LIS is a mircale in small foot print packaging due to it's external zoom design. It's way lighter than the EF versions too. However, if Canon had chosen to make this lens about an inch longer...it could have allowed RF teleconverters.
The f4 version is often seen as the junior brother to the f2.8. It's not, it's actually an excellent lens in it's own right.
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Man, seriously, no.
Go in the studio. Take exposure with an incident light meter, it will say (example) 100iso f8 1/200s
Now take a medium format camera with a given lens (80mm, example), input those numbers and shoot. Then take that 80mm and adapt it on a fullframe, take 5 step back and shoot with same parameters. Then mount the lens on Aps-C, take 10 steps back and shoot.
SURPRISE, the picture is the same. Same BRIGHTNESS and EXPOSURE.
DoF is different? Yes? DR different? Yes. Noise different? Well, maybe not at 100iso but let's say yes. But in terms of exposure, you don't care about DoF, DR or noise.
Seriously, you have absolutely no idea of how light works, lens works, and camera sensor (or film) works. I take you never shot film across different formats, and/or never used an incident light meter to measure environment and/or flash exposure.
EV (exposure value) of a scene is constant, regardless of the apparatus you use to record that scene. If the apparatus changes, but if the standardize parameters are the same (lens is the same, shutter time is the same if the cameras are not defected, iso is almost the same, yes you have some variations on iso between manufacturers, but they're difference between systems, they have nothing to do with the EV of the scene in front of you, and yes two f2.8 lenses from different manufactures may have T stop difference, but hey that's gear tolerance, again we're not touching EV), then the picture you obtain is the same.
Aps, ff or mf sensor are hit exactly by the same amount of light if the exposure triangle doesn't change; and they're expected to react (aka produce comparable images in terms of BRIGHTNESS) the same way with those parameters, that are fullfilled by an external source (an incident light meter) that doesn't know if you're using film or digital, and what size is your film or you sensor.
Noise and dynamic range are concept baked in your head by marketing material, and they're real of course, and they have their place to be cosidered, but they have NOTHING to do with the EV of a scene. An exposure triangle produces an absolute brightness level, or EV as we said, who is (should be) interpreted in the same way by ANY camera you use, because those terms are absolute, and not relative to your apparatus.
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The Aps lens is smaller and lighter because IT COVERS A SMALLER SENSOR!!!! There's LESS AREA TO COVER!!!
But the light that passes from it IT'S THE SAME of any equivalent (in terms of f-stops) lens for ff! A Sigma 30mm DC f1.4 produces, at f1.4 exatly the same exposure of ANY f1.4 lens of ANY focal lenght, regardless of size and format of the lens! If you mount the 30 DC on Aps and a 35 art, a 50 art, an 85 art, a 105 art, all of them being f1.4 and you shoot the same subject with aps and ff, YOU GET THE SAME DAMN EXPOSURE, given that shutter and iso are also the same.
Man, your absolute ignorance is incredible. That's my LAST answer, this is becoming like talking astronomy with someone who just knows astrology but thinks he knows about astronomy. I've no more time to lose; people pay me to teach them photography, and you're not paying me, so no more free lessons. You believe what you want to believe, good for you
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I often used 24X36 and 6X6 for exactly the same subject in argentic days.The Aps lens is smaller and lighter because IT COVERS A SMALLER SENSOR!!!! There's LESS AREA TO COVER!!!
But the light that passes from it IT'S THE SAME of any equivalent (in terms of f-stops) lens for ff! A Sigma 30mm DC f1.4 produces, at f1.4 exatly the same exposure of ANY f1.4 lens of ANY focal lenght, regardless of size and format of the lens! If you mount the 30 DC on Aps and a 35 art, a 50 art, an 85 art, a 105 art, all of them being f1.4 and you shoot the same subject with aps and ff, YOU GET THE SAME DAMN EXPOSURE, given that shutter and iso are also the same.
Man, your absolute ignorance is incredible. That's my LAST answer, this is becoming like talking astronomy with someone who just knows astrology but thinks he knows about astronomy. I've no more time to lose. You believe what you want to believe, good for you
Same ASA, diaphragm and shutter speed.
Results: absolutely similar, apart from differences in contrast, dof and geometry. But the exposure was perfect for both. Same with digital, as you already stated!
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The key is "incident light meter"
if he would have know what the thing is and would have known how to use it, he would know.But he doesn't, and that's a shame.
In fim days I used same exposure for 24x36 too, and then for 6x6 first with Polaroid back and then with the film back (which technically are two different "sensors" for the same camera), of course adjusting for iso according to the film speed if needed, and the EV recorded of course was always (almost) the same.
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Right, shutter and diaphragm precision tolerances exist, yet their influence is rather limited...The key is "incident light meter"
But he doesn't, and that's a shame.
In fim days I used same exposure for 24x36 too, and then for 6x6 first with Polaroid back and then with the film back (which technically are two different "sensors" for the same camera), of course adjusting for iso according to the film speed if needed, and the EV recorded of course was always (almost) the same.
What I have found out, is that lenses with few elements ,Leica M W.A.s, for instance, need slightly shorter shutter speeds than my Canons. But definitely not in the EV range.
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No, its not the same.
And there's the kicker: The noise is not the same (even at 100 ISO).
To get an accurate equivalency/comparison, here's how you need to shoot:
APS-C: f2.8, 1/100th, 100 ISO
Full frame: f4, 1/100th, 200 ISO
Now they will have captured the same amount of light and the same amount of noise. Can you see now how f2.8 on APS-C is not equivalent to f2.8 on full frame?
Bumping up your ISO from 100 to 200 does not make your f1.8 lens into an f1.2.
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No it doesn't. ISO is digital amplification. It doesn't get more light onto the sensor. Turning up the gain on your 15w speaker amplifier to 200℅ doesn't mean that it is now a 30w amplifier.And yes, exposure wise, bumping iso from 100 to 200 actually do positively transform a f1.8 lens into a f1.2 lens
You embarrass yourself, go home kid
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