tlitody
Well-known
It occurs to me that since the shutter is not opening as a circle getting bigger but rather as a wedge getting bigger, then the faster the shutter speed the greater the pecentage of the exposure will be with a partially opened shutter. Therefore bokeh will be variable with shutter speed. Slow shutter speed and smooth bokeh, fast shutter speed and less smooth bokeh. Unless the sensor is only switched on when the shutter is fully open and switched off before the shutter starts to close in which case you get smooth bokeh for everything if the literature is correct.
So all you experts, do digital camera sensors only get switched on and off when shutter is fully open?
And is that the real reason why digital camera leaf shutters have such fast shutter speeds. i.e. its the electronic switching of the sensor combined with the timing of the mechanical shutter which is the limiting factor of the effective shutter speed. The mechanical shutter really only there to protect the sensor from light when not being used. Just speculating.
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Alpacaman
keen bean
It depends, really. From my (limited) knowledge it would seem to be a combination of the precision allowed by modern manufacturing and electronics combined with the fact that most modern cameras do not have full frame sensors, so are easier to cover in a shorter amount of time.
Whether the sensor is turned on when the shutter trips, or whether it is always on is dependent on the type of sensor in there, but I don't think most modern sensors can switch on/off quickly enough to provide the faster speeds anyway, they still for the most part rely on the shutter.
That built in ND filter on the X100 looks damned cool (and handy). Has that been done before? I am curious.
tlitody
Well-known
Many fast long focal length lenses have had built in filter turrets. Contax 300 f2.8 had them I think. Three differnet filters, red, orange, yellow for B+W photography as filter size for front element would have been massive. So its nothing new except its ND.
Arjay
Time Traveller
Interesting question - but one we won't be able to answer unless we would know the specific architecture of the sensor Fuji will be using.
I recall that Nikon's D70 DSLR had what Nikon called a 'hybrid shutter' design: The focal plane shutter would define all longer shutter speeds down to 1/250s, and shorter shutter speeds were defined by electronically switching the sensor. This brought the advantage that this camera had a flash sync speed of at least 1/1000s (I don't recall the exact value, but the Strobist blog wrote an entire series of articles about it). So, for speeds faster than that 1/250s, the mechanical shutter would work at 1/250s, whereas the electronically defined shutter speed would be triggered inside the the time window defined by the mechanical shutter.
Unfortunately, not every sensor can be switched on and off at specifically defined times. The relevant factor is how the individual sensor pixels are read out after exposure: Some designs 'freeze' the electric charge acquired during exposure and do not accumulate additional charge during readout under continued exposure. Others remain light-sensitive, and read out the acquired charge in a sequential fashion, effectively mimicking the action of a travelling focal plane shutter window - such sensors obviously need a mechanical shutter for clearly defined high shutter speeds.
It's interesting to note that e.g. Nikon has abandoned the 'hybrid shutter' concept in its later models, which can be seen from the fact that they all feature slower flash sync times.
semilog
curmudgeonly optimist
^--- v. good post.
videogamemaker
Well-known
I'm sorry but this is just flat out false. The shutter speed will have no affect on the bokeh rendering. It (the bokeh) is a physical aspect of the glass, how fast a piece of plastic shoots across to expose the sensor will have no affect.
tlitody
Well-known
Think you need to read up on bokeh and the effect aperture shape has on it.
squirrel$$$bandit
Veteran
The shape of the shutter is not the same as the shape of the aperture. All the shutter will do is expose every part of the sensor for the same amount of time. It doesn't matter what pattern of exposure it uses to do so. The number of aperture blades has an effect on bokeh but that's not what we're talking about.
gavinlg
Veteran
This is interesting:
"Designing an F1.6 or F1.8 lens is not so difficult; however, in the case of a digital camera, even if an aperture larger than F2 is used, the light receiving elements on the sensor cannot effectively use the brighter portion of the incoming light because of low incident light gathering efficiency."
Are they saying that f2 was the fastest they could go without IQ declining due to SENSOR light collecting abilities?
"Designing an F1.6 or F1.8 lens is not so difficult; however, in the case of a digital camera, even if an aperture larger than F2 is used, the light receiving elements on the sensor cannot effectively use the brighter portion of the incoming light because of low incident light gathering efficiency."
Are they saying that f2 was the fastest they could go without IQ declining due to SENSOR light collecting abilities?
Matus
Well-known
That is exactly what they are saying.
tlitody
Well-known
I've no idea what you are talking about except you haven't understood what I'm talking about.
videogamemaker
Well-known
I did not say aperture, I'm very well aware aperture changes bokeh. You asserted the shutter would as well, which is incorrect.
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gavinlg
Veteran
This would then co-incide with the article on the luminous landscape which stated that digital sensors couldn't make full use of fast lenses so manufacturers are raising the gain of the sensor to falsely boost the speed in lenses < f2.
This is extremely interesting to me... I usually only use fast lenses on my DSLRs and would love to know more...
tlitody
Well-known
The wedge shape shutter passing over the circular aperture means the actual aperture shape at any point during the exposure is never circular. It is the shape of the shutter opening unless as I explained the shutter fires the sensor if and when it is fully open. So half waay through the exposure what shape is the aperture as the shutter passes across the aperture and explain to us all why the straight edge of the shutter doesn't have an effect on the bokeh?
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videogamemaker
Well-known
I agree completely. I find this blurb by Fujifilm and the open letter from LL to be dually interesting.
videogamemaker
Well-known
The shutter will not affect the bokeh, no matter the shape. If it's a moving object being used to control the amount of time the sensor is receiving light, it will not affect the bokeh. It has to be a stationary object for the duration of the exposure, such as the aperture, to affect bokeh. The shutter shape is irrelevant, and in a conversation I would brush it off, but other people with potential interest in the X100 could read and think is true, when it's not.
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Arjay
Time Traveller
That's correct , and at the same time it says something about the sensor technology the X100 will use:
It will be a conventional sensor design, in which the light-sensitive parts of the sensor are located in a pit with steep walls that consist of the supporting sync and readout circuitry. The steepness of these walls makes it difficult for these sensors to capture light that arrives at a rather flat incident angle.
Latest generation mobile phones/cameras already use a different sensor technology: backside-illuminated sensors.
These types of sensors are initially manufactured in a similar way: Photosites and supporting circuitry are built up on a substrate in several layers, in which the photositers come first, and consecutively, supporting circuitry is added in further layers on top of the sites, effectively forming a grid of ridges all across the sensor chip (with the potential problem of shading the photosites from light that arrives at low incident angles). But then comes the crucial trick:
Once the sensor is 'finished' in a conventional way, the chip receives a covering layer on top that is fastened on some type of carrier. Then, the old substrate (the lowest layer) is etched away, exposing the back side of the photosites! Now, the photosites aren't buried inside a grid of circuitry ridges, but they are the topmost layer of that new structure. Being on the top, the photosites aren't shaded by any ridges and thus can also take up light that arrives at lower incident angles.
These new sensors offer two advantages:
- Since the circuitry is located below the photosites, the sites can occupy a larger portion of the sensor's area. This translates into a higher photon efficiency, i.e. higher sensitivity at a given signal-to-noise ratio.
- Since there are no ridges throwing shadows on the photosites, the sites will exhibit a less directional sensitivity behavior and thus will be more forgiving to low light incident angles. Of course, there's a limit to this - surface reflection.
Matus
Well-known
I think that videomaker is trying to say that any possible effect of the shutter gets "averaged out" because of its motion. Think of all the focal plane shutters in SLR cameras. None of the leaf shutters in LF or MF lenses produces a circular opening either.
_________
In an extreme case (if the shutter slit would be very narrow - academic type of "gedanken experiment") the shutter could cause lower contrast of the image because of diffraction (on a narrow slit), but I guess that in reality it does not play any role - the focal plane shutters are very close to film plane - few millimeters at most - so to get some f/32 you would need a slit only about 0.1 mm narrow.
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videogamemaker
Well-known
My memory might be fuzzy, but I seem to recall an article by I believe Sony, explaining how the back illuminated sensors are most beneficial on the ultra small sensors like cell phones and point and shoots, and less on larger crop and FF sensors, I seem to recall it even saying it might be near irrelevant on FF sensors. Take that with a grain of salt, but maybe this jogs someone's memory with a link to the article?
Are there any large sensor cameras out yet with back illuminated sensors?
Arjay
Time Traveller
I presume making FF back-illuminated sensors is a lot harder than making cute breadcrumb-sized sensors. Of course, surface reflections could still be a problem.