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Recently I witnessed an x ray imaging of an entire thorax, and I was pretty sure it was a film cassette with analogue film that was used, but was taught that it was a digital sensor. This sensor had an enormous size. Doing a bit research gave me some more information about this kind of sensors: The technology used to produce them is similar to display tft technology. The sensor itself senses visible light which is emitted by a scintillator material that is stimulated by the x rays. The typical resolution of such sensors is in the 10 megapixel range, and I am not sure about the dynamic range but e.g. here is such a panel that uses 14 or 16 bit a/d conversion which would not be required if the dynamic range is too poor.

While the resolution may or may not be enough for modern photography, resolution is not everything, and the technology would make a reasonable candidate for large format photographic image sensors. Why did that not happen so far?

Edit: What I forgot to mention is that the price tag of such sensors seems to start in the < $10k range. Not too expensive given the size …

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    what problem would that sensor solve? – aaaaaa Feb 22 '18 at 0:59
  • The external link in the question is dead. – Michael C Feb 22 '18 at 7:15
  • There is potential for an actually useful kickstarter project here - the first generation of that kind of equipment is probably starting to be retired, so buy up the sensors at scrap value and make large format cameras from them! – rackandboneman Nov 29 '18 at 13:36
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While the resolution may or may not be enough for modern photography, resolution is not everything, and the technology would make a reasonable candidate for large format photographic image sensors. Why did that not happen so far?

I think you're being too generous to your argument, when you say resolution is not everything in regards to large format photography. The whole point of large format is to capture a high degree of detail (resolution).

Let's say we're talking about an 8×10 large format camera. With good film, you're looking at an equivalent resolution in the range of 800 MP, probably even more.

Even thought the flat panel detector (FPD) you linked to is 17×17, let's assume a smaller, 8×10 detector is also 10 megapixels. That 10 MP FPD is giving up an 80:1 advantage to film, or a spatial resolution of 9:1. To what end? Why go through the hassle of carrying and setting up an ultra-low-resolution imaging system, that can only produce results about the same as the front (selfie) camera in the smartphone in your pocket?

Put another way, for 8×10 large format photographers who already have the camera(s), lenses, etc., what advantage does such a low resolution imaging system give them?

Thus, ignoring other potential considerations, if this technology is representative of the current state of the art (at least at the price point), then the reason it hasn't happened so far is simply because the resolution is far behind what comparable film sizes can produce.

  • "Why go through the hassle of carrying and setting up an ultra-low-resolution imaging system?" - light sensitivity 200x higher than full frame might be a reason :-] (unrealistically assuming equivalent sensor technology and lens...) – szulat Oct 30 '17 at 23:20
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    @Chris, conventional photographic sensor technology started with MUCH smaller sensors and for quite some time even that wasn't enough for many photographers. – walther Oct 31 '17 at 9:28
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    @Chris I agree, it's almost certainly not the entire story. I am speculating. But in general, a big part of answering any "why hasn't technology X happened?" question probably involves cost-benefit gains. But to your point, "large format is about the look", indeed, and part of the look is the incredible detail available. However, 10 MP / 80 in² is ludicrously low pixel density in today's photographic technology. – scottbb Oct 31 '17 at 12:12
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    OK, maybe the question was asked the wrong way. I should have asked “… What is missing technology-wise to adapt this technology for photography purposes? What is the current state of dynamic range and pixel density and what seems possible in the next 5 to 10 years? What are the show stoppers technologically?” – Chris Oct 31 '17 at 14:08
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    @MichaelClark could it have anything to do with that? Probably somewhere in the neighborhood of everything... =) – scottbb Feb 22 '18 at 0:38
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It is, and will be possible in the not too distant future for large and medium format sensors to be made at a cost factor that would make them accesssble to the average photographer. It is however, unlikely that any of the current DSLR camera manufacturers will develop and bring such sensors to market. This is because it would be possible to release a sensor system that would fit many existing medium format cameras from the past and most large format cameras. This might hurt the sales of DSLR’s and Mirrorless camera systems going forwards. If it happens at all, it will probably be an independent new comer into the electronic imaging world. It would be amazing to have a 500 mega pixel digital sensor that would have the profile of a 8x10 dark slide, including built in flash/card storage. The technology already exists to make this happen but the manufacturing cost/production/performance capabilities is not yet here.

It will eventually happen when someone decided to go out and do it.

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I'm guessing the colour gamut the sensor can reproduce is too small to have any application to normal colour photography.

  • Do you have some data about it? What is the difference to a “normal” CMOS sensor, assuming a Bayer CFA is applied onto the sensor? – Chris Oct 31 '17 at 6:31
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It couldn't possibly have anything to do with the need for x-rays, rather than visible light, to create an image could it?

I mean, what's wrong with suggesting we start lugging around 800 GWS "Alien X-Ray Bees" and start dosing everything we image with high intensity X-ray radiation?

Apart from the public health concerns and the fact that we don't see X-ray wavelengths (hint: any medical imaging using X-rays is false-color imaging), or that we usually don't want to see through many solid types of material such as clothing and skin, there's the additional cost of those sources of X-ray radiation in addition to the < $10K cost of the low resolution panel.

The TFT sensors in question are designed to respond to the light emitted by a scintillator bombarded by X-rays at virtually zero distance between the scintillator and the sensor panel. They might not (as in, they most likely do not) respond to more typical natural visible light (or artificial light created to be much like light natural light) at typical brightnesses at all.

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    no, the detector in question only reacts to visible light, it just happens to be placed next to a special scintillator layer, emitting light when hit by xrays – szulat Feb 22 '18 at 1:33
  • And what is the nature of that light emitted by the scintillator layer when bombarded with X-rays? How do we reproduce that type of light? Hmm, I don't know. Maybe by bombarding a scintillator with X-rays? – Michael C Feb 22 '18 at 1:50
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    according to modern science, all light in the universe has the same nature ;-) but why would anyone want to reproduce what scintillator emits and why would anyone care about xray? the question specifically asks for tft-based visible light sensors and their performance. – szulat Feb 22 '18 at 2:04
  • And the TFT sensors in question are designed to respond to the light emitted by a scintillator bombarded by X-rays at virtually zero distance between the scintillator and the sensor panel. They might not (as in, they most likely do not) respond to more typical natural visible light (or artificial light created to be much like natural light) at typical brightnesses at all. – Michael C Feb 22 '18 at 2:09
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    the scintillator produces visible light from x-rays, in the same way as the coating in a neon tube produces visible light from UV. – ths Feb 22 '18 at 14:21

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