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#1
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39 megapixels vs. 4x5
On Sat, 21 Jan 2006 00:03:57 GMT, Mike wrote:
http://www.luminous-landscape.com/essays/Cramer.shtml Doesn't rattle my world because I don't have $40,000 to dish out for a P45 digital back and I enjoy traditional B&W work with my view camera Doesn't rattle it yet... but give it a few years. I'm not sure if large chunks of processed silicon will ever be "cheap" but maybe some day they'll be "affordable." Meanwhile, there are maybe one or two outfits on the planet still making drum scanners, and they're not cheap either. An Epson 4990 is a lame substitute. (Speaking from personal experience.) rafe b www.terrapinphoto.com |
#2
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39 megapixels vs. 4x5
rafe b wrote: I'm not sure if large chunks of processed silicon I'm alwasy so impressed with your grasp of technical photographic and engineering concepts... |
#3
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39 megapixels vs. 4x5
On Fri, 20 Jan 2006 18:11:26 -0700, Tom Phillips wrote:
rafe b wrote: I'm not sure if large chunks of processed silicon I'm alwasy so impressed with your grasp of technical photographic and engineering concepts... * Silicon yield plummits as the die size increases. This has not changed in 30+ years of silicon manufacturing. The largest microprocessor dies are no greater than around 400mm^2. * Current bayer sensors have inherent noise limits that will require a huge technological breakthrough. * Small sensors are diffraction limited Given these three points, I believe that there will not be a cheap 4x5 film replacement anytime soon. |
#4
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39 megapixels vs. 4x5
On Sat, 21 Jan 2006 01:24:26 GMT, Mike wrote:
* Silicon yield plummits as the die size increases. This has not changed in 30+ years of silicon manufacturing. The largest microprocessor dies are no greater than around 400mm^2. Here's the great paradox. Semiconductor technology has been pushing relentlessly toward smaller feature sizes in order to get ever-more active devices on "reasonably" sized chunks of silicon. (400 mm^2 being a very large chip, as you know) But for photosensors, the need is for huge areas of silicon -- and relatively huge features. An "optimal" photosite with current CMOS technology is around 5-7 microns on a side. Compare this with current process feature size limits, now at around 0.08 microns or less. (0.13 um being fairly routine.) So: a defect that kills a DRAM cell may have little or no effect on a sensel that covers 25 square microns. So it seems to me, the "classical" equations for yield vs. die area may need some modification for this particular technology. * Current bayer sensors have inherent noise limits that will require a huge technological breakthrough. These alleged noise limits haven't prevented DSLRs from utterly destroying the 35mm film and camera market. Odd, that. In fact, it's generally acknowledged tha DSLRs are far *less* noisy than film, particularly at high ISO values. And no, I am not expecting cheap MF-sized sensors any time soon, but that's more due to economies of scale (or lack thereof) than to technological limitations. The mass market is already well served with image sensors of 5x7mm. For a grand, you get 15x22mm, which easily beats 35mm. For three grand, you get 24x36mm, which begins to encroach on 645 film territory Those of us wanting MF or LF-quality digital capture are left holding the bag. But it won't take 6cm x 6cm of silicon to achieve that. Even if you figure, say, $3000 for a processed 12 inch wafer, it's still hard to figure how these MF backs command price tags of $40K. rafe b www.terrapinphoto.com |
#5
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39 megapixels vs. 4x5
So: a defect that kills a DRAM cell may have
little or no effect on a sensel that covers 25 square microns. But you are forgetting all of the logic and SRAM buffering that I imagine is integrated with each sensel. I haven't studied the current CMOS sensors, but I imagine there is a lot going on besides the capture of light. So it seems to me, the "classical" equations for yield vs. die area may need some modification for this particular technology. Sure. I agree. * Current bayer sensors have inherent noise limits that will require a huge technological breakthrough. These alleged noise limits haven't prevented DSLRs from utterly destroying the 35mm film and camera market. Odd, that. Right. I think the low-hanging fruit has been claimed. But I'm skeptical if we will see 15x22mm deliver 16-20 megapixels. Those of us wanting MF or LF-quality digital capture are left holding the bag. But it won't take 6cm x 6cm of silicon to achieve that. Right...I would guess 6x4.5cm of silicon will deliver 4x5" film quality within 5 years. Even if you figure, say, $3000 for a processed 12 inch wafer, it's still hard to figure how these MF backs command price tags of $40K. After you invest the $5 billion in the fab. Of course the niche players will contract out the fab. I wonder who is manufacturing the PhaseOne silicon? Even if you find a fab, creating those masks is not cheap and existing manufacturing processes are geared towards economies of scale (which you correctly pointed out will not exist for MF/LF sensors). Do you think a $3000 digital capture solution will be available in 5-8 years that can deliver 4x5 quality? I don't think so...but would value your thoughts. |
#6
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39 megapixels vs. 4x5
So: a defect that kills a DRAM cell may have little or no effect on a sensel that covers 25 square microns. So it seems to me, the "classical" equations for yield vs. die area may need some modification for this particular technology. My other thought is that even when feature sizes where _huge_ (say 2-5 microns), they still couldn't get away with making large dies. Processes have improved, but until wafers are manufactured in outer space, defects happen. |
#7
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39 megapixels vs. 4x5
rafe b wrote: These alleged noise limits haven't prevented DSLRs from utterly destroying the 35mm film and camera market. Odd, that. Mediocrity reigns... |
#8
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39 megapixels vs. 4x5
On Sat, 21 Jan 2006 03:43:07 GMT, Mike wrote:
So: a defect that kills a DRAM cell may have little or no effect on a sensel that covers 25 square microns. But you are forgetting all of the logic and SRAM buffering that I imagine is integrated with each sensel. I haven't studied the current CMOS sensors, but I imagine there is a lot going on besides the capture of light. There's no SRAM, as far as I now. A linear CCD is actually a pretty simple device -- an analog shift register, really. The only "digital" components in a linear CCD are the clocks and transfer gates. The sensing elements are simply capacitors. I have experience and some expertise in linear CCDs, but no experience in area arrays. I'm guessing an area CCD would be treated as an array of linear CCDs. I'm guessing there would be analog multiplexers at the ends of the arrays, if only to reduce the pin count and the number of analog channels to some manageable level. So it seems to me, the "classical" equations for yield vs. die area may need some modification for this particular technology. Sure. I agree. * Current bayer sensors have inherent noise limits that will require a huge technological breakthrough. These alleged noise limits haven't prevented DSLRs from utterly destroying the 35mm film and camera market. Odd, that. Right. I think the low-hanging fruit has been claimed. But I'm skeptical if we will see 15x22mm deliver 16-20 megapixels. I'm skeptical also, unless the basic underlying technology advances in some significant way. Currently, the sensor in the D200 seems to represent the state of the art for a 23.6 x 15.8 mm CCD. With any given technology, you need to go to a larger die to get more pixels of equivalent quality. If you reduce the area of the sensing elements, you get a more noise at any given ISO rating. Those of us wanting MF or LF-quality digital capture are left holding the bag. But it won't take 6cm x 6cm of silicon to achieve that. Right...I would guess 6x4.5cm of silicon will deliver 4x5" film quality within 5 years. That would be nice. We can dream, can't we. Even if you figure, say, $3000 for a processed 12 inch wafer, it's still hard to figure how these MF backs command price tags of $40K. After you invest the $5 billion in the fab. Of course the niche players will contract out the fab. I wonder who is manufacturing the PhaseOne silicon? 5 billion? Is it that high now? I've heard 1.5 billion, but that figure is a few years old. Even if you find a fab, creating those masks is not cheap and existing manufacturing processes are geared towards economies of scale (which you correctly pointed out will not exist for MF/LF sensors). Well, there are hundreds if not thousands of so-called "fabless" semiconductor companies -- and I work for one of them. It's not too big a deal nowadays. We've been averaging one major new chip per year, and we started doing that about ten years ago, with a team of only five engineers, and a fairly small capital base. I'm guessing a mask set and pilot run is on the order of $250K to $750K, but that doesn't include the initial engineering or layout, of course. Standard Verilog or VHDL don't apply to things like CCDs, so that's a diferent game from the one I know. Do you think a $3000 digital capture solution will be available in 5-8 years that can deliver 4x5 quality? I don't think so...but would value your thoughts. Your guess is as good as mine, Mike. The market is a fickle thing. It's been a wild ride so far, hasn't it? rafe b www.terrapinphoto.com |
#9
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39 megapixels vs. 4x5
rafe b wrote:
On Sat, 21 Jan 2006 03:43:07 GMT, Mike wrote: But you are forgetting all of the logic and SRAM buffering that I imagine is integrated with each sensel. I haven't studied the current CMOS sensors, but I imagine there is a lot going on besides the capture of light. There's no SRAM, as far as I now. A linear CCD is actually a pretty simple device -- an analog shift register, really. The only "digital" components in a linear CCD are the clocks and transfer gates. The sensing elements are simply capacitors. Mike mentioned CMOS, which is somewhat different. But you're right. Although the word "digital" is often used, the imaging part of a CCD is an analog device, as is the readout amplifier. That's why there's an A/D converter on board. I have experience and some expertise in linear CCDs, but no experience in area arrays. I'm guessing an area CCD would be treated as an array of linear CCDs. I'm guessing there would be analog multiplexers at the ends of the arrays, if only to reduce the pin count and the number of analog channels to some manageable level. There's a readout register. You shift a row into the readout register, shift charge down the readout register to the amplifier until you've finished the row, repeat. There are one or a few amplifiers, not one per row. Here are some pretty good pictures of how it works, including a little animation of the readout process (skip down to section 5): http://www.astro.virginia.edu/class/...lec11-f03.html One issue with really high pixel count detectors is that the readout time through the small number of amplifiers can become a bottleneck. Also, of course, you do get cosmetic defects. Bad single pixels could be interpolated over in software, since their location is known, but a defect in the wrong place can cause a bad column, which is pretty irritating but common in research grade device (i.e. large, expensive, but not NASA-level we'll pay through the nose for one without defects expensive). Bad readout amplifiers ... now that's bad news. I'm skeptical also, unless the basic underlying technology advances in some significant way. Currently, the sensor in the D200 seems to represent the state of the art for a 23.6 x 15.8 mm CCD. With any given technology, you need to go to a larger die to get more pixels of equivalent quality. If you reduce the area of the sensing elements, you get a more noise at any given ISO rating. Thermoelectric coolers, baby. Talk about your battery hogs! Even if you figure, say, $3000 for a processed 12 inch wafer, it's still hard to figure how these MF backs command price tags of $40K. My guess is that $3000 is an underestimate for a CCD of that size and pixel count. (I'm talking about the cost of just the CCD, not including the electronics that control it.) |
#10
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39 megapixels vs. 4x5
Mike wrote:
Do you think a $3000 digital capture solution will be available in 5-8 years that can deliver 4x5 quality? I don't think so...but would value your thoughts. If you are talking about an area sensor I see this as pretty unlikely, mostly because the market is so small for such a camera. If you are talking about a mechanically scanned linear sensor a $3000 camera is very doable cost wise but not nearly as useful as a camera based on an area CCD. Scott |
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