Canon APS-C Shooters Rejoice: Sigma to Launch the RF 17-40mm f/1.8 and RF 12mm f/1.4

You didn’t mention depth of field equivalent in the post I replied to. You simply refered to f-stop. Everyone knows that depth of field increases as the lens objective diameter decreases. As I said you didnt mention depth of field.
 
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Thanks. I am actually comparing two lenses and assume that the one that collects more light and direct it to the image circle would then require a lower ISO setting, hence 'better' in ISO performance. This all assumes the same aperture, and f-stop can certainly change depending on focal length (ie 50mm at f5 for apsc would have the same aperture diameter as 80mm at f8 for FF).
Your last statement is correct, but I still have the feeling that you are thinking the larger aperture on a FF lens is going to net you better performance on an aps-c camera and that is not typically the case because the FF lens is going to illuminate an area beyond the aps-c sensor and that light will be wasted. OTOH, using a FF lens on an aps-c camera does have the benefit that you are using the middle of the image circle and that results in less vignetting, so to that degree, you will typically get a bit more light on the aps-c sensor with a ff lens than with an aps-c lens with the same f number.
 
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For example, the main camera in the iPhone 16 has a focal length of 6.9mm, meaning its f/1.78 lens requires a maximum physical aperture diameter of 3.9 mm. The reason the focal length can be short and the aperture can be small is because the sensor is small.

the 6.9mm lens of the iPhone 16 (~3.5x crop sensor), a 15mm lens on a Canon APS-C camera (1.6x crop sensor) and a 24mm lens on a FF camera all give the same field of view. That's equivalence in terms of field of view, or if you prefer equivalence in terms of focal length.
Yes. In terms of fstop equivalence, the iphone 16 is f/1.8. This equates to f/4 for APSC and to f/6.3 for full-frame. So the iphone's 6.9 mm f/1.8 lens can be thought of as 24 mm f/6.3, in full-frame terms.
 
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You didn’t mention depth of field equivalent in the post I replied to. You simply refered to f-stop. Everyone knows that depth of field increases as the lens objective diameter decreases. As I said you didnt mention depth of field.
I stated, “The FFeq [full frame equivalent] of 17-40/1.8 is 27-64/2.9,” which is accurate. If I’d meant only focal length, I’d have stated that 17mm on APS-C delivers an equivalent field of view to 27mm on FF.

Equivalence doesn’t apply to just focal length…it applies to DoF and also image noise. For the example here at the wide end, 17/1.8 on APS-C would give the same DoF and image noise as 27/2.8 on FF. If you had a 27/1.8 lens on FF to match the FoV of 17mm on APS-C, either the DoF would be thinner and the image noise would be lower, or you could stop that 27/1.8 lens down to f/2.8 and the DoF and noise would be the same.

The bottom line is that the crop factor applies to FoV as well as DoF and noise.

Incidentally, despite what ‘everyone knows’ (= you believe) the DoF does not necessarily increase as the objective diameter decreases, but rather as the lens aperture / iris diaphragm diameter decreases. For long telephoto designs, the front element diameter approximates the lens aperture but for shorter lenses it doesn’t. Example: the RF 28/2.8 has a front element that’s ~11 mm in diameter so by your logic it should have a much deeper DoF than a lens with a 44 mm diameter front element…such as the EF 28/2.8. My money would be on two 28/2.8 lenses having pretty much the same DoF despite the 4-fold difference in front element diameter.
 
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Your last statement is correct, but I still have the feeling that you are thinking the larger aperture on a FF lens is going to net you better performance on an aps-c camera and that is not typically the case because the FF lens is going to illuminate an area beyond the aps-c sensor and that light will be wasted. OTOH, using a FF lens on an aps-c camera does have the benefit that you are using the middle of the image circle and that results in less vignetting, so to that degree, you will typically get a bit more light on the aps-c sensor with a ff lens than with an aps-c lens with the same f number.
Thanks again. It is probably the way I express the idea that was not clear. No, I was not thinking that a larger aperture on a FF will have better performance. I was simply trying to figure out if a FF lens with larger lens (front) elements would provide more light when compared to an (equivalent) APSC lens with smaller (front) lens element when the aperture (not f-stop) is kept the same. I realise that it is not easy to compare in reality, but as you said, it is probably valid at least for the central region of the image.
 
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Thanks again. It is probably the way I express the idea that was not clear. No, I was not thinking that a larger aperture on a FF will have better performance. I was simply trying to figure out if a FF lens with larger lens (front) elements would provide more light when compared to an (equivalent) APSC lens with smaller (front) lens element when the aperture (not f-stop) is kept the same. I realise that it is not easy to compare in reality, but as you said, it is probably valid at least for the central region of the image.
For telephoto designs, the size of the front element is typically a reasonable rule-of-thumb measure of how much light the lens can capture, but for shorter designs, that is not necessarily the case. Retrofocus designs that were typical of short lenses used on DSLR cameras that required a long back throw to clear the mirror usually had large front elements, whereas designs for mirrorless cameras with a short flange distance can avoid a retrofocus design and thus will typically have a smaller front element and a larger rear element. Here is a comparison to make the point. https://www.the-digital-picture.com/Reviews/Lens-Specifications.aspx?Lens=824&LensComp=1224 . The RF lens is actually a slightly faster lens with a much smaller front element. Otherwise, the two lenses are very similar at f/4 and f.5.6 with the RF version being a bit sharper and wide apertures. https://www.the-digital-picture.com...LensComp=824&CameraComp=0&FLIComp=0&APIComp=0
Internally, the two lenses are radically different, with the element sizes virtually inverted https://global.canon/en/c-museum/product/rf473.html and https://global.canon/en/c-museum/product/ef426.html Click on the "block diagram" link to see the structure of the lens. The RF version has a relatively tiny front element, but it is faster, so it lets in a bit more light.
Note that my previous comment about vignetting only affects the periphery of the image. The center will typically be same between an aps-c lens and a ff lens of the same f number.
If you are truly concerned about how much light you are really going to get, then you need to study t-stop as f-stop does not guarantee a particular light level, but rather defines the iris size and thus the theoretical light level. The quality of the elements and the coatings on those elements determines how much light will be lost as an image makes its way through the lens. the t-stop number refers to the actual light level that arrives at the imager and was historically used by cinematographers concerned with the actual exposure of film and cinematography lenses are still defined in this way. The t-stop will always by a higher number than the f-stop, sometimes by only a bit and sometimes by a substantial amount. They haven't kept up with reviewing modern lenses all that well, but DXOmark has transmission information on a lot of lenses. https://www.dxomark.com/camera-lenses/ . Notably, the EF 35mm f/2 in the above example measures at t/2, which is extremely good. The RF version has not been tested by DXOmark, so no data.
 
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As "Internal Revenue" said: lets see what 12 years of progress will bring. I used the old Sigma EF 18-35mm for about 8 years and finally made it a gift to the girlfriend of my oldest son, just to have this little temptation out of the lens vitrine.



Neuro shot me (and my love for crop lenses) down now three time with his equivalence calculations, still the EF 18-35 was a lens which made me leave the full frame stuff at home and go out with EOS 80D and that lens. However this lens had some issues. When real estate in the camera bag is limited I got headaches about choosing between the stabilized 17-50 from Canon and the Sigma. And like always when I decided for IS I later did not need it, when I went for the 1.8 I discovered later how nice 20mm more reach can be.



The real problem with this lens (at least for me was is all metal build+ heavy glass which made this lens fog up at any inconvenient moment. Traveling in Asia or South America: out of the cruise ship into the sun.... lens completly fogged up from inside and not usable for several minutes, Out of the heavy air conditioned subway into the daylight another 5 minutes with fog. A stroll through that 26 degree Celsius Guangzhou rain and into a museum... fog again. No other lens I owned showed that behavior in such a bad way.



By the way the other Sigma zoom darling, the 50-100 1.8 (which I suppose will follow in Sigmas lens line up someday) is aging in the lens vitrine now for several years with not more than 50 shots taken with it. It is such a heavy lens, that there is always a more logical lens combination to pack in you bag.



So my hope, much more high tech plastic in the new lens to reduce weight and fogging. The other battle IS or no IS is at the moment no question as neither Tamron nor Sigma offer stabilization in their 2.8 competitors
 
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I'm starting thinking about going R5 with the 17-40, that could be an interesting solution, 17mpx crop is not far from the 20mpx of my R6, and I get a stop (and a third) better then the 28-70 STM; if the performance is good on R7, then it's probably killing on the R5, let's see when test will show online, and which price they'll ask for it
I think you would be better off with the RF 28-70 f/2.8 IS on your R6.
We will have to see.
 
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One further thing to keep in mind is that the 28-70 has IS while the Sigma supposedly does not. This allows one to shoot with higher fstops.
This lens is within the focal range where lens stabilization does not provide much benefit over IBIS.
Lens IS a big deal for APS-C, since most Canon APS-C cameras do not have IBIS.
There are still tons of us who have an RP, R8. R5 C, C80, or C400, which are full-frame with no IBIS.
 
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The DSLR era 18-35 f/1.8 that this lens would be replacing is an APS-C Art lens, and a popular one at that. No surprise that they would eventually create a mirrorless successor.
I do not think it will sell as well.
Super 35 video was far more popular when the Sigma 18-35 came out.
On the other hand, the R50 V, C70, ZV-E10, and FX30 are all pretty popular for video right now.
 
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There are a lot of factors that go into ISO performance.
The pixel size the most obvious and gets talked about the most.
I think the 24 MP R6 II aoutperforms the 20 MP R6 in low light, so it is not always so simple.
The effect of pixel size on ISO performance is most obvious to and gets talked about the most by people who don't have a clue about the underlying principles. Those of us who do understand those principles know that pixel size has a minimal impact on the ISO performance of a sensor.
 
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...it looks like it would be a bit awkward on a camera like the EOS R50 V

It looks awkward even on that a6700.


sigma12leak.jpg
 
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I don’t care about APS-C lenses. I want third party full frame lenses. I kid you not, I’m closer now than ever to switching!
Then do it. Every person should choose the brand that gives them products that best suit their needs. This seems obvious to most people when it comes to buying a washer or drier or vacuum cleaner, but for whatever reason, people on photography forums think that brand loyalty is somehow important. What is even stranger is the threats of switching (why would anyone else care?) or the announcement of switching (again, why would anyone else care?).
 
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Then do it. Every person should choose the brand that gives them products that best suit their needs. This seems obvious to most people when it comes to buying a washer or drier or vacuum cleaner, but for whatever reason, people on photography forums think that brand loyalty is somehow important. What is even stranger is the threats of switching (why would anyone else care?) or the announcement of switching (again, why would anyone else care?).
Maybe he thinks posting a threat on a forum will alter Canon's business plan ;).
 
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The lenses look very interesting, but not sufficiently so to tempt me to buy an APS-C R body to use them.

To those who understand equivalence, the advantages of APS-C remain lower cost and size/weight. The FFeq of 17-40/1.8 is 27-64/2.9, so my RF 24-105/2.8 is ‘better’. Likewise, 12/1.4 is equivalent to 19/2.2 and the extra 1-1/3 stops of my 20/1.4 is worth more than the 0.5 mm difference (to me, based on DxO correction of barrel distortion).
Sorry my ignorance, but I am still not quite sure about the equivalence.
Are we talking amount of light, amount of noise, depth of field, dynamic range, sharpness or what else?
I remember when I used the crop mode on my R5 video, I didn't change the exposure, I switched to crop mode to get more reach and I continued shootng. The crop yes, the noise in the raw files yes, but I would like to know more about it.
Thanks for additional explanation.
I need to know where I am wrong in my reasoning below.
I have a 12mm F1.4, I don't put my camera on a crop mode, I have very strong vignette, but in video mode I put IS on, and digital IS enhanced, vignette is gone, or reduced to minimum. My VCM doesn't have IS either so regardless I need to put on the same settings. In one word, whether it is the rumored Sigma or my own VCM, I have to put both on full frame and activate same IBIS.
There is no 20mm IS at F1.4 that allows me to rely only on lens IS so I am stuck.
Currently, I am using a Laowa 15mm F2, but for what I am shooting, F2 is still too dark and no auto-focus, I need F1.4. What am I loosing here?
Obviously, on a photography side of things, I loose 100% going 17MP on a crop mode.
I do not intend to buy any Sigma lens at least for now, I hated what happened when moving from DSLR to mirrorless, I don't want that any longer.
I just want to know how it works.
Thanks.
 
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Sorry my ignorance, but I am still not quite sure about the equivalence.
Are we talking amount of light, amount of noise, depth of field, dynamic range, sharpness or what else?
I remember when I used the crop mode on my R5 video, I didn't change the exposure, I switched to crop mode to get more reach and I continued shootng. The crop yes, the noise in the raw files yes, but I would like to know more about it.
Thanks for additional explanation.
I need to know where I am wrong in my reasoning below.
I have a 12mm F1.4, I don't put my camera on a crop mode, I have very strong vignette, but in video mode I put IS on, and digital IS enhanced, vignette is gone, or reduced to minimum. My VCM doesn't have IS either so regardless I need to put on the same settings. In one word, whether it is the rumored Sigma or my own VCM, I have to put both on full frame and activate same IBIS.
There is no 20mm IS at F1.4 that allows me to rely only on lens IS so I am stuck.
Currently, I am using a Laowa 15mm F2, but for what I am shooting, F2 is still too dark and no auto-focus, I need F1.4. What am I loosing here?
Obviously, on a photography side of things, I loose 100% going 17MP on a crop mode.
I do not intend to buy any Sigma lens at least for now, I hated what happened when moving from DSLR to mirrorless, I don't want that any longer.
I just want to know how it works.
Thanks.
Equivalence applies to most of those, but not sharpness (at least, not directly though of course image noise affects resolution).

The simple version is that image (and video) noise is inversely proportional to the size of the sensor, or the area of the sensor used for capture. So...smaller sensor, more noise. The difference between FF and APS-C is ~1.3-stops, so for example ISO 800 on a crop sensor gives the same image noise as ISO 2000 on a FF sensor. The exposure settings are the same, so if you're at f/1.4 the metered exposure (e.g. 1/60 s, ISO 800) will be the same on both crop and FF cameras. But the image noise at that setting will be lower with FF. Or, you could choose to set the FF camera to 1/180s, ISO 2000 (same exposure, 1.3 stops faster shutter, 1.3 stops higher ISO) and the noise will be the same but you'll be able to stop faster motion.

I don't shoot video on my ILCs, but I know that some video modes are cropped and that cropping affects the noise as described above (in proportion, e.g. if the crop isn't 1.6x but rather 1.2x, then the increase in image noise will be less).
 
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