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

[Bob Howland]

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).

If we took a picture using film with a 20 f/1.4 lens and, after development, we took scissors to the negative trimming it from 36m x 24 mm to 22.5mm x 15 mm, would "equivalence" change the lens to something other than a 20 f/1.4?

 

[neuroanatomist]

If we took a picture using film with a 20 f/1.4 lens and, after development, we took scissors to the negative trimming it from 36m x 24 mm to 22.5mm x 15 mm, would "equivalence" change the lens to something other than a 20 f/1.4?

If we did that, would we have a the same picture?



If we look at a wallet-size print, is that same thing as looking at an 11x14 print? If we took a picture using T-Max 100 film and a picture using T-Max 3200 film that we pushed a stop in development, would they look the same?

Note that I stated, “To those who understand equivalence…” I do. If you do not, I can provide some links that explain the concept. If you do, then you’re asking a rhetorical question, presumably to start an argument. Nice.

 

[Bob Howland]

If we did that, would we have a the same picture?

View attachment 224347

If we look at a wallet-size print, is that same thing as looking at an 11x14 print? If we took a picture using T-Max 100 film and a picture using T-Max 3200 film that we pushed a stop in development, would they look the same?

Note that I stated, “To those who understand equivalence…” I do. If you do not, I can provide some links that explain the concept. If you do, then you’re asking a rhetorical question, presumably to start an argument. Nice.

Your definition of equivalence holds the the field of view and depth of field constant but forces the exposure to change. My preference is to hold the field of view and exposure constant but allow the depth of field to change.

Update: My "rhetorical question" holds the depth of field and exposure constant but allows the field of view to change.

 

[neuroanatomist]

Your definition of equivalence holds the the field of view and depth of field constant but forces the exposure to change. My preference is to hold the field of view and exposure constant but allow the depth of field to change.

Perhaps you’re trapped within the circle of confusion. It’s not ‘my definition’, it’s an established concept in photography. Evidently you don’t understand that concept sufficiently. Applying it doesn’t require holding anything constant. Rather, it’s a concept that elaborates the proper way to compare different formats (e.g., different sensor sizes or cropping in post).

The key point is that you need to use absolute values to do so, not relative values. Your comment about exposure is exactly the misapprehension that an understanding of equivalence obviates. Exposure is a relative measure (light density, i.e., light per unit area), whereas total light captured is absolute. Similarly, the f/number is relative (it’s a ratio by definition), aperture (entrance pupil) diameter is absolute.

Try these articles, the first is simpler while the second is more technical and comprehensive.

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

Equivalence

www.josephjamesphotography.com

You can take whatever pictures you want. You can trim prints with scissors if you prefer. You can put wallet sized portraits in tiny frames, hang them on the wall and view them from across the room if you like. None of that changes the definition of equivalence as a photographic concept.

 

[Stig Nygaard]

Fujirumors has some specs for the zoom.
535g and internal zoom.
Sounds pretty good to me...

 

[InternalRevenue]

Fujirumors has some specs for the zoom.
535g and internal zoom.
Sounds pretty good to me...

For reference that's less than the weight of a EF-S 18-135 with the ef/rf adapter, or the EF-S 17-55 f/2.8 or 15-85 alone. Fantastic news for those looking to use it as a walkaround, though I wonder what kind of compromises they're making to get it that light. Heavy use of digital corrections perhaps? Are the other modern Art series lenses known to go that route?

 

[f2_productions]

So this new zooms will be an 535g internal zoom, declickable apertur ring, wheater sealed, optically very good and with low focus breathing? Nice work, Sigma!

By the time they release the follow up to the 50-100mm f1.8, which could be an 40-120mm f1.8, they could really make a great duo for filmmaking, and events!

All in all this sounds very appealing. Also the 12mm f1.4 sounds very interesting!

 

[EricN]

An APS-f f/1 will be close the same size as the equivalent FF f/1.4. If you slap a speed booster on a FF f/1.4, you get .7x FL f/1 lens. Given that 1.4 is less than 1.6, the speed booster is theoretically capable of a bit more illumination area than Canon APS-c, but not all that much. Bottom line, if you want to catch that many photons, it makes sense to go to FF.

Thanks for explaining

 

[Bob Howland]

An APS-f f/1 will be close the same size as the equivalent FF f/1.4. If you slap a speed booster on a FF f/1.4, you get .7x FL f/1 lens. Given that 1.4 is less than 1.6, the speed booster is theoretically capable of a bit more illumination area than Canon APS-c, but not all that much. Bottom line, if you want to catch that many photons, it makes sense to go to FF.

I'm not sure I understand what you're saying. I do know that a speed booster doesn't change the number of photons going through the lens. It just concentrates them onto a smaller area. "Exposure" is the number of photons per unit area for a given time. Likewise, a Teleconverter doesn't change the number of photons. It just spreads them out onto a larger area.

 

[AJ]

the advantages of APS-C remain lower cost and size/weight.

Yes indeed. However these new Sigma lenses try to compete with aperture/speed, which is not a natural advantage of APSC. IMO, those looking for speed/selective focus are better served with a FF system. As such I bet Sigma would do better with an inexpensive and light zoom such as a 15-85. Right now it seems the APSC choices are zooms with limited range (e.g. 14-30, 18-45) or superzooms (e.g. 18-150, 16-300). Sigma, how about a standard standard zoom?

 

[neuroanatomist]

Right now it seems the APSC choices are zooms with limited range (e.g. 14-30, 18-45) or superzooms (e.g. 18-150, 16-300). Sigma, how about a standard standard zoom?

Maybe not Sigma’s choice, if Canon can choose which lens designs to license for the RF mount.

 

[Walrus]

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

 

[neuroanatomist]

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

You might benefit from reading the articles on equivalence I linked above. You gain ~1.3 stops of light from a wider f/stop, you lose ~1.3 stops by throwing away 60% of the light the FF sensor can capture.

Or you can go ahead and buy a FF camera that you plan to use in crop mode…it’s your money to waste.

 

[Sharlin]

For reference that's less than the weight of a EF-S 18-135 with the ef/rf adapter, or the EF-S 17-55 f/2.8 or 15-85 alone.

Maybe more pertinently, it’s almost 300g(!!) less than the 18–35, which honestly makes me question the veracity of the rumor.

 

[neuroanatomist]

Maybe more pertinently, it’s almost 300g(!!) less than the 18–35, which honestly makes me question the veracity of the rumor.

This is the range in which a shorter flange distance makes a real difference. Compare the EF 11-24/4 with the RF 10-20/4, for example.

 

[AJ]

You might benefit from reading the articles on equivalence I linked above. You gain ~1.3 stops of light from a wider f/stop, you lose ~1.3 stops by throwing away 60% of the light the FF sensor can capture.

Or you can go ahead and buy a FF camera that you plan to use in crop mode…it’s your money to waste.

There is no throwing away of light. The 17-40/1.8 collects the same amount of light as the RF 28-70/2.8. The 17-40 just projects that light in a smaller image circle. Because the image is spatially compressed, it is brighter, as the lower f-stop reflects.

Now, pixels on APSC are typically smaller than those on full-frame, and thus noisier. To get true equivalence you'd shoot the 17-40 with an iso that's 2.5 stops faster, e.g. 500 iso with the 28-70 versus 100 iso with the 17-40. So now the shutterspeeds and noise characteristics are the same as well. So, @Walrus might as well buy a RF 28-70 and shoot it on a R5 with the iso bumped up a bit, to get speed.

We'll see how all of this stacks up in terms of weight and price. My guess we'll see "equivalence" in this department as well.

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.

 

[Skux]

If we took a picture using film with a 20 f/1.4 lens and, after development, we took scissors to the negative trimming it from 36m x 24 mm to 22.5mm x 15 mm, would "equivalence" change the lens to something other than a 20 f/1.4?

No, because we know the lens isn't actually changing, which is why we use the word equivalent.

The whole point is to understand the performance of lenses in different image sensor formats in comparison with a standard (usually 35mm film).

 

[Walrus]

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.

That's true for still subjects, or helps with video; with moving subjects IS is pretty irrelevant if you need to freeze motion

 

[neuroanatomist]

There is no throwing away of light. The 17-40/1.8 collects the same amount of light as the RF 28-70/2.8. The 17-40 just projects that light in a smaller image circle. Because the image is spatially compressed, it is brighter, as the lower f-stop reflects.

Now, pixels on APSC are typically smaller than those on full-frame, and thus noisier. To get true equivalence you'd shoot the 17-40 with an iso that's 2.5 stops faster, e.g. 500 iso with the 28-70 versus 100 iso with the 17-40. So now the shutterspeeds and noise characteristics are the same as well. So, @Walrus might as well buy a RF 28-70 and shoot it on a R5 with the iso bumped up a bit, to get speed.

We'll see how all of this stacks up in terms of weight and price. My guess we'll see "equivalence" in this department as well.

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.

So many misunderstandings. Please, please read the links provided above on equivalence. Please.

1) The light being ‘thrown away’ is because using a crop sensor (or the area of a FF sensor contributing to the image in crop mode) is <40% of the FF sensor area.

2) The light is not ‘spatially compressed’, the f/1.8 lens has a wider physical aperture at a given focal length so it passes more light (a lens with a smaller image circle isn’t the same as a speedbooster).

3) The primary determinant of image noise is sensor size (or area used), not pixel size. Same size sensor + smaller pixels = same noise floor = same DR (e.g., R6II vs R5II). Smaller sensor + same size pixels = higher noise floor = less DR (e.g., R5II in crop mode).

As @Walrus correctly points out, IS is of little help with moving subjects. 5-stops of IS would enable you to shoot at a shutter speed of 0.5 s instead of 1/60 s, but even people holding still for a picture will lose sharpness to motion blur.

You might be right on the weight and price comparison, we’ll see.

 

[EricN]

There is no throwing away of light. The 17-40/1.8 collects the same amount of light as the RF 28-70/2.8. The 17-40 just projects that light in a smaller image circle. Because the image is spatially compressed, it is brighter, as the lower f-stop reflects.

Now, pixels on APSC are typically smaller than those on full-frame, and thus noisier. To get true equivalence you'd shoot the 17-40 with an iso that's 2.5 stops faster, e.g. 500 iso with the 28-70 versus 100 iso with the 17-40. So now the shutterspeeds and noise characteristics are the same as well. So, @Walrus might as well buy a RF 28-70 and shoot it on a R5 with the iso bumped up a bit, to get speed.

We'll see how all of this stacks up in terms of weight and price. My guess we'll see "equivalence" in this department as well.

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.

Why would anyone sane buy an R5 to use it with a crop lens?