While you should be comparing pictures/scenes shot with both and then presented on comparable mediums (screen or paper).
Nope, comparing shutter speeds of 70/2.8 to shutter speeds of 35/1.8 is not helping at all.I didn't compare it specifically with 70mm, I compared it with a 24-70mm, because that was the comparison others made that started the debate.
Otherwise the comparison is meaningless.
Which of those FAQs are you challenging?
Everything that relates to shutter speed.
Because it's not like people do (or at least should
) pick their shutter speeds based on some fancy digits printed on their lenses. People should pick their shutter speeds based on the subject movements they need to freeze. If you cannot afford some part of the subject to move more than 5mm (in the subject plane) during the time of exposure, you will need to estimate the speed of this part (in mm/s) and divide it by 5 - then you will get (in 1/s) the lowest shutter speed you could afford to
use in your shot, and then you will need to live with whatever amount of shot noise you are getting from the object get at this speed.
Now let's look how much noise we are actually getting. On our final image (printed or displayed on the monitor) we choose the smallest scale we need to resolve. It's historically - from the film era - called "circle of confusion" when reduced to length units in sensor plane; by at the moment we don't need it in length units, we need the solid angle that comprises this circle, the solid angle of the feature we need to resolve, the solid angle we need to get our photons from. And then the number of photons caught by this circle is the number of photons coming to our lens from that solid angle during the time of exposure - and then passing through the entrance pupil of our lens.
Then the absolute shot noise will be the square root of that number.
And the relative shot noise will be (absolute shot noise)-1
See? No fancy digits printed on the lens. No sensor size. Even no sensor's pixel size. Only the subject (under the lighting), the desired end result and the absolute effective lens opening (in square millimeters or similar area units). Once you get this fixed, you know what noise you will get for your shutter speed, and you know what shutter speed corresponds to your noise.
Of course, you may want to boost your sensor's ISO to reduce the in-camera noise (and the right setting of ISO usually makes in-camera noise irrelevant when you need higher shutter speeds). But that's what you can
afford to control. What you cannot
afford to control is the amount of photons coming from your subject.
Actually, the same considerations also hold true for background blur, DoF and - in some sense - bokeh. All what you would ideally see on the final picture was already determined when the light coming from the subject crossed the (virtual) entrance pupil (the rendering of diaphragm visible through the front lens), then anything lying after the entrance pupil only added its distortions to it.
When you want to apply the same to bokeh, you will need to take into consideration the non-uniformity (and dependence on the distance) of the entrance pupil's transparency
for out-of-focus objects. It's uniform for lenses with well-corrected spherical aberrations, darker in center (and lighter at the blades) for nearer objects in under-corrected lenses and for farther objects in over-corrected lenses, and lighter in center (and darker at the blades) otherwise.
For example, an unobscured bright dot at infinity will be rendered on the final picture exactly like the entrance pupil moved (without change of its physical size) into the subject's plane of focus in the direction of that dot. It will be flatly lighted for lenses with well-corrected spherical aberrations, nicely round for lenses with under-corrected spherical aberrations and doughnut-shaped for lenses with over-corrected spherical aberrations. Other than that, nothing should happen behind the entrance pupil in a good lens (of course, there could be ghosts and stuff if the lens is not so good). So, if your shoot with EF 50/1.4 wide open, a bright dot on your (far enough) background will be rendered as a flat octagon of ~36 mm (in subject's plane of focus) diameter, no matter what subject you shoot, no matter what your magnification is (well, if it's true macro, there could be exceptions), no matter what sensor size your camera has.
This doesn't advance the debate at hand.
Just the opposite. The end result is about the same, because it is mostly limited by purely optical considerations. No matter what technical solutions are employed between the subject and the final image on paper or on monitor.
You seem to think that all that matters is the amount of light falling on a square micrometer of the sensor.If you read the thread, you'll understand that my objective was to dispel the notion that f/1.8 on APS-C is in effect the same as f/2.8 on full frame. That notion is actually an unhelpful
Well, I could not just go and say that most guides that teach photography by numbers do it in the wrong way
(not that their numbers are wrong, but they just focus your attention on secondary details, letting you fail to see what really happens with the picture). I needed some pretext for that.
Those guides pay too much attention to what happens in the camera
, although it's what happens outside the camera
is what forms your images. The camera just adds its own technical limitations. These technical limitations were big enough during the "35mm film rolls" era, big enough to limit your thinking about your subject and about your end result. Those limitations weren't as big for sheet film, those limitations aren't as big for current large photo sensors, you can focus now on what happens outside the camera, paying only secondary attention on what happens inside.
They aren't noisier "because of their typically smaller pixels". Given the same size of the lens' entrance pupil (i.e. the same amount of light captured by the lens from an area on the subject), the same angle of view and enough of pixel well depth, they all will provide about the same amount of noise on the final medium.
They are noisier because the entrance pupils of their smaller lenses are generally smaller than on the lenses that provide the same angle of view for larger sensor formats. There are physical limitations in making large entrance pupils for smaller focal lengths, as pupils bigger than f/0.5 are impossible even theoretically.
From my personal experience of 5D II vs 7D, that simply isn't the case.
Maybe you did it wrong then.