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Author Topic: Open Source CMOS Medium Format Camera/Back - An initial exploration  (Read 11559 times)
torger
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« Reply #80 on: March 06, 2014, 08:32:57 AM »
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These Dicomed Bigshot backs from back in 1996 was made with those standard 16 megapixel 61x61mm aerial/satellite CCD sensors:

http://www.epi-centre.com/reports/9610ecs.html
http://www.epi-centre.com/reports/9604cs.html

as far as I understand Dicomed was not a particularly big company at the time, but as one of the article states they did get $27 million in funding for making these type backs, and the monocrome back was $35k and the color $55k.

I wonder what these type of sensors cost today. I would suspect that there could be very high pricing still even if yield is good, due to very low sales volumes. Sensors of this type is sold in different quality levels though, depending on how many pixels that are broken, so you can get a cheaper sensor with lower quality.
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byarvin
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« Reply #81 on: March 06, 2014, 11:56:25 AM »
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Those Big Shot backs were nothing but trouble and that trouble had nothing to do with the sensors. I suspect that the Phillips sensor combined with a modern image processing engine and card reader instead of the 1996 JackHammer scsi add-in card would do the trick.

Frankly, they were around so long ago that I've forgotten what their image quality was like. All I can recall was somebody emailing me a TIFF file and thinking "this is better than my Canon 10d."

« Last Edit: March 06, 2014, 11:58:31 AM by byarvin » Logged
eronald
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« Reply #82 on: March 06, 2014, 12:57:21 PM »
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Update - I've edited this post to tune it down Smiley

Eric,

If you insist on CCD, go ahead and do the analog electronics yourself. There's a reason MF backs used to be expensive: CCD backs are hard to make in a way that is noise-immune.
If you want a large CMOS sensor, as minimum (!) larger than the IQ250,  please name the supplier.
If you have the chip, I can make the electronics, no problem, and can find someone to the mechanical engineering.
Let us start with an existing chip, and learn to walk before we run!
When a larger nice chip comes along we will then be ready to do a useful new version.

Edmund.

We should all agree on some minimum set of key specifications for a first iteration, I think.

For me:
the sensor ideally would be bigger than the leica/pentax/IQ250 size
CMOS or CCD ok with me, but I still favor CCD.
Needs to have a universal design with possible adapter plates for different camera platforms(ie. If I can't get it to fit my camera(s) its not working for me, and probably others feel the same)
Pixel count not as important as sensitivity and ability to handle shifted lenses or wide angle lenses close to sensor.  




« Last Edit: March 07, 2014, 02:19:19 AM by eronald » Logged
eronald
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« Reply #83 on: March 07, 2014, 01:41:06 AM »
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Project Update.

I've looked a bit at the issues involved.

Starting from a CMOS sensor, a tethered open source still camera solution looks feasible.

The unit costs are probably around $1.5K plus the unit price of whatever sensor is employed, although the first few prototypes will probably cost more. These costs are exactly the same whether one uses a large sensor or a small one. I guess the time to have a usable object would be about a year.

An evolution towards a standalone unit might be possible, but it would be a much longer term project - about 3 years probably.

Maybe it is time to start a discussion list for potential participants in such a project. The technology is probably useful for anyone involved in imaging as most of the interface work will be done using an off the shelf FPGA board. Preliminary testing might involve a small cheap and commonly available sensor.

Edmund
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torger
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« Reply #84 on: March 07, 2014, 02:51:47 AM »
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Maybe you should change the heading to say "Open Source CMOS Medium Format Camera/Back", as what many really really want is larger sensor than 44x33 and will then get drawn into CCD. Apart from price I think the other main drawback that people reacted on with the IQ250 was the small size.

However, starting with this type of project now means that when ready there could already be larger CMOS sensors with better angular response out on the market, probably Sony-made, which then will be easy to integrate.
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eronald
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« Reply #85 on: March 07, 2014, 10:15:07 AM »
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You are right on both counts.

- Yes, I have changed the title.

- Yes, the interface specs tend to be the same in a sensor family, so if we have a proto, then moving to another chip from the same maker should be easy.

Thank you for your constructive remarks.

Edmund

Maybe you should change the heading to say "Open Source CMOS Medium Format Camera/Back", as what many really really want is larger sensor than 44x33 and will then get drawn into CCD. Apart from price I think the other main drawback that people reacted on with the IQ250 was the small size.

However, starting with this type of project now means that when ready there could already be larger CMOS sensors with better angular response out on the market, probably Sony-made, which then will be easy to integrate.
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eronald
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« Reply #86 on: March 07, 2014, 10:15:50 AM »
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You are right on both counts.

- Yes, I have changed the title.

- Yes, the interface specs tend to be the same in a sensor family, so if we have even a 35mm proto, then moving to another chip from the same maker should be easy.

Thank you for your constructive remarks.

Edmund

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EricWHiss
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« Reply #87 on: March 07, 2014, 10:16:28 PM »
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Edmund,
For me what's the point of coming up with something that has a smaller format than what we can buy now?  I mean if only wanted 48x36 then I could buy a used Leaf, Phase, Sinar or Hasselblad/Imacon back for like 5k and be happy.   What I'm interested in is coming up with something bigger than what is offered currently.

I'm not saying it has to be CCD but I don't know of any available CMOS sensors besides the one Sony just made that is even bigger than 24x35.  The Sony sensor isn't doing well with technical cameras so not sure its such a great option anyhow.   I'm not an electronics guy so if you are saying that its much harder to do CCD then that leaves us with some decisions.   I don't see the value in developing an open source 24x35 back - actually there are a number of units for astronomy that already can be worked with that include pixel binning and other cool things in that size and under. 

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« Reply #88 on: March 07, 2014, 10:42:22 PM »
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Hi,

The main reason Edmund wants to use a CMOS design with on sensor AD-s is that all the hard work is done on the sensor. So the output from the sensor is not a brittle analogue signal but an undestructable digital one. Building a support circuitry CCD cameras is very difficult as it must be designed to have very low electronic noise and excellent shielding. Also, analog readout is in all probability far more complex.

Sony's sensor has on sensor converters and so has the Leica M (240) sensor designed by CMOSIS, but Nikon D4 and all Canons use CMOS sensors with off chip ADCs. So all CMOS is not alike. With the Sony type design, the hard work has been done by the sensor vendor.

Best regards
Erik

Edmund,
For me what's the point of coming up with something that has a smaller format than what we can buy now?  I mean if only wanted 48x36 then I could buy a used Leaf, Phase, Sinar or Hasselblad/Imacon back for like 5k and be happy.   What I'm interested in is coming up with something bigger than what is offered currently.

I'm not saying it has to be CCD but I don't know of any available CMOS sensors besides the one Sony just made that is even bigger than 24x35.  The Sony sensor isn't doing well with technical cameras so not sure its such a great option anyhow.   I'm not an electronics guy so if you are saying that its much harder to do CCD then that leaves us with some decisions.   I don't see the value in developing an open source 24x35 back - actually there are a number of units for astronomy that already can be worked with that include pixel binning and other cool things in that size and under. 


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eronald
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« Reply #89 on: March 07, 2014, 11:07:58 PM »
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Erik,

 Thank you for explaining things much more clearly, as I should have.

 There is something I should add: Sensors come in families, often using the same cell structure and the same basic interface circuitry, and CFAs. So a design and software conceived to deal with one sensor will be easily converted to deal with another from that family.

 If we manage to start now with even a very small sensor, then I would expect that we will have gained a jump-start on the day a big sensor we like is freely released - we will know how to read in images, remove pattern noise and color shading, demosaic them, get live previews and add overlays, do edge detection for focus, calibrate for color, process shift and tilt etc.

  In fact I have been looking at the CMOSIS/Zedboard combo being employed by the Apertus project for their cine camera. The CMOSIS chip reads into the Zedboard which is built around a Xilinx Zynq chip that combines an ARM9 core set with an FPGA for IO. This means Linux code can be written fairly easily to control the chip, read the data out a speed, even do pattern noise reduction, and then ship previews or full files across to the host computer via a network connection which could be wifi.  

Engineering becomes much easier once you have a working prototype of a thing you want to perfect.

Edmund

Hi,

The main reason Edmund wants to use a CMOS design with on sensor AD-s is that all the hard work is done on the sensor. So the output from the sensor is not a brittle analogue signal but an undestructable digital one. Building a support circuitry CCD cameras is very difficult as it must be designed to have very low electronic noise and excellent shielding. Also, analog readout is in all probability far more complex.

Sony's sensor has on sensor converters and so has the Leica M (240) sensor designed by CMOSIS, but Nikon D4 and all Canons use CMOS sensors with off chip ADCs. So all CMOS is not alike. With the Sony type design, the hard work has been done by the sensor vendor.

Best regards
Erik

« Last Edit: March 07, 2014, 11:18:21 PM by eronald » Logged
MichaelEzra
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« Reply #90 on: March 07, 2014, 11:36:53 PM »
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How about a 3 CCD 36MP D800E sensor for true RGB color capture?
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ErikKaffehr
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« Reply #91 on: March 07, 2014, 11:57:38 PM »
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Hi,

A three sensor design is needs a beam splitter and very precise adjustments. I think that would be much more complex than the design Edmund has in mind.

I am impressed by the energy Edmund puts into this.

Best regards
Erik

How about a 3 CCD 36MP D800E sensor for true RGB color capture?
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eronald
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« Reply #92 on: March 08, 2014, 12:27:35 AM »
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Here is what happens when one of the world's best camera and sound companies tries to mess with CCD: They go broke.

http://nofilmschool.com/2013/05/aaton-new-owners-documentary-style-digital-camera/

And here is the incredible quality they managed to get, in case you think they were jokers:
http://vimeo.com/67811891

Edmund
« Last Edit: March 08, 2014, 10:40:14 AM by eronald » Logged
Ken R
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« Reply #93 on: March 08, 2014, 12:02:46 PM »
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Here is what happens when one of the world's best camera and sound companies tries to mess with CCD: They go broke.

http://nofilmschool.com/2013/05/aaton-new-owners-documentary-style-digital-camera/

And here is the incredible quality they managed to get, in case you think they were jokers:
http://vimeo.com/67811891

Edmund

As RED showed you need a LOT of money to design, make and market a new Digital Cinema Camera from scratch but more importantly whoever does it needs to do it in a unilaterally controlled way (with vision and strong will) like Jim Jannard did (the same can be said of Steve Jobs), none of this design by committee stuff (Detroit Auto Makers learned that the hard way).
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MichaelEzra
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« Reply #94 on: March 08, 2014, 12:19:45 PM »
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Oops.. by 3 CCD I surely meant 3 CMOS sensors of D800e:) The original implementation was via 3 CCD in video years ago.
The reason I mention this is that if the intent is to make a distinctly different/unique product, well this would be.
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jerome_m
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« Reply #95 on: March 08, 2014, 01:50:46 PM »
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This guys are doing an open source 4K movie camera based on a sensor a bit larger than APS-C: https://www.apertus.org.
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BJL
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« Reply #96 on: March 08, 2014, 01:54:08 PM »
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Oops.. by 3 CCD I surely meant 3 CMOS sensors of D800e:) The original implementation was via 3 CCD in video years ago.
The reason I mention this is that if the intent is to make a distinctly different/unique product, well this would be.
The video industry has used the approach of three small sensors with dichroic beam splitters with smiler sensors (up to 2/3" format) but has abandoned in favor of a single sensor with CFA when moving to larger sensors, and I believe that part of the reason is that those splitters cause problems with color accuracy and metamerism.

Let me just make my usual unpopular suggestion that the industry is well aware of the three-sensor approach, and yet has moved away from it except in video cameras that use small sensors in favor of using a single larger sensor, so putting aside paranoid conspiracy theories or the comforting internet forum arrogance that we know better how to design products that the companies with experience in actually competing to make sales to demanding professionals, it seems very likely that the theoretical advantages of three-sensor arrays are outweighed by their disadvantages when larger sensors are in use.  (The extra cost of two more sensors is unlikely to be the reason for makers of professional video cameras to abandon a technically superior alternative, since sensor cost is a small fraction of the price of such cameras.)
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EricWHiss
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« Reply #97 on: March 08, 2014, 02:21:27 PM »
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Ok, I already understand the extra challenges of working with a CCD sensor (for this ad hoc group in particular).  My point was rather to ask what CMOS sensors exist that we can buy that are bigger than 24x35mm, or better yet a sensor bigger than the new sony one?   I don't see any myself.

If this group decides that it's too much work or too difficult to approach a CCD sensor that has a large size such as the Truesense 50mp or one of the others pointed out, then what CMOS sensor could be used?   

I feel that if it boils down to only the new sony CMOS, we'd have a lot easier go buying the new pentax and hacking it than trying to build this from scratch components.
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eronald
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« Reply #98 on: March 08, 2014, 02:39:16 PM »
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You mean hack the Pentax, like take it apart?
I am not good at reverse engineering, like some people who disassemble firmware, although of course as part of my training I have reverse engineered VLSIs in  the sense of reconstructing how they work from the microscope images. Thinking inside the box is a skill I dont really have Smiley Design is more fun.



Edmund

Ok, I already understand the extra challenges of working with a CCD sensor (for this ad hoc group in particular).  My point was rather to ask what CMOS sensors exist that we can buy that are bigger than 24x35mm, or better yet a sensor bigger than the new sony one?   I don't see any myself.

If this group decides that it's too much work or too difficult to approach a CCD sensor that has a large size such as the Truesense 50mp or one of the others pointed out, then what CMOS sensor could be used?  

I feel that if it boils down to only the new sony CMOS, we'd have a lot easier go buying the new pentax and hacking it than trying to build this from scratch components.

« Last Edit: March 08, 2014, 02:48:00 PM by eronald » Logged
ErikKaffehr
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« Reply #99 on: March 09, 2014, 04:10:40 PM »
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Hi,

I guess that Eric means transplanting the sensor to another assembly that could be a digital back. I guess it would be possible but not feasible. It would also definitively not be open source. To be open source you would need to be in control of the source code.

Best regards
Erik

You mean hack the Pentax, like take it apart?
I am not good at reverse engineering, like some people who disassemble firmware, although of course as part of my training I have reverse engineered VLSIs in  the sense of reconstructing how they work from the microscope images. Thinking inside the box is a skill I dont really have Smiley Design is more fun.



Edmund

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