Author Topic: A 3200MP camera to unravel the mustery of the univers is being completed  (Read 623 times)

Akira

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BruceSD

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Amazing camera.  Thanks for posting the link to this article.

The feature of this camera that caught my eye was that this camera's giant sensor is made up of 189 individual 16MP "CCD" sensors.

I have long preferred CCD sensor image quality to CMOS sensor image quality.   In fact, of the 11 digital cameras that I currently own, all but 2 of them have CCD sensors.

Obviously, the designers of this giant camera also prefer CCD to CMOS sensors.

Do you think this giant state-of-the-art camera employing CCD sensors might lead to a return of CCD sensors in the prosumer digital camera marketplace in the future?   

Akira

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Hope you enjoyed the article, Bruce.

I guess the engineers chose CCD over CMOS sensors because CCDs are more sensitive to the infrared which is essential to observe the universe.  The sensors installed in James Webb Space Telescope are also CCDs made with a very exotic material:

https://jwst.nasa.gov/content/observatory/instruments/nircam.html

I also have some nostalgia for the rendition of CCD sensors and even sometimes look for a reasonable D3000, the last and latest Nikon body with the CCD sensors.  But I'm not sure if we would see the revival of CCDs in digital cameras.
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BruceSD

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I did not realize that CCD sensors "are more sensitive to the infrared". 

I recently purchased a like new Nikon D200 digital camera body whose sensor (identical to the D3000 ?) was permanently converted to full time IR.  As the D200's sensor is the CCD type, can I assume that it likely has better IR performance than if the sensor was a CMOS variety?


Akira

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I did not realize that CCD sensors "are more sensitive to the infrared". 

I recently purchased a like new Nikon D200 digital camera body whose sensor (identical to the D3000 ?) was permanently converted to full time IR.  As the D200's sensor is the CCD type, can I assume that it likely has better IR performance than if the sensor was a CMOS variety?

The range of the wavelength we typically use for the IR photography lies right next to the longest end of the visible range (deep red).  So, I'm not sure if the advantage of a CCD sensor, if any, would be apparent.  The Near Infrared Camera of James Webb covers between 600nm and 5000nm which is much longer than a normal digital camera, even modified, can handle (only the shortest range overlaps with the visible deep red and the range that can be captured by modified digital cameras). :

https://www.jwst.nasa.gov/content/observatory/instruments/nircam.html

I've tried to shoot IR with a very dense IR90 filter on D40 (CCD) that I had as well as my current SIGMA fp (CMOS), but both are unmodified and thus I cannot compare.

I would just hope you to share your images shot with the IR modified D200!
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BruceSD

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I have not yet taken any "serious" photos with my D200 IR camera.

However, attached is one I took with an IR converted Fujifilm FinePix S3Pro and a non-Ai 28mm f/3.5 Nikkor a few years ago.    The only lens that I will be using on the D200 IR body will be this very same lens.  I'll be sure to post some D200 IR images soon - likely in a new thread.

By the way, this photo is very special to me as it was taken at sunrise on the day after my father died.

Øivind Tøien

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That is a nice memory to associate with you father, Bruce.
I think comparison between IR bodies can be tricky as we usually do a lot of editing on IR shots, but here is one from my D40x IR-720nm (Lifepixel mod) and Nikon 12-24mm @ f/9. ISO 200. The D40x has a slightly modified version of the D200 CCD sensor. I have always liked the output of that sensor after IR modification - removal of the lowpass filter during conversion also helped bring out the best of the sensor.
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Øivind Tøien

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Regarding choice of CCD sensor, here is link to an article that explains some advantages/disadvantages. Apparently dark current is lower for long exposures, while read noise is higher than the CMOS sensor..
https://ui.adsabs.harvard.edu/abs/2021RAA....21..268Q/abstract

Cooling the CMOS sensor to these super low levels might also be an issue due to that more of the electronics is located on the sensor chip.
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Akira

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I have not yet taken any "serious" photos with my D200 IR camera.

However, attached is one I took with an IR converted Fujifilm FinePix S3Pro and a non-Ai 28mm f/3.5 Nikkor a few years ago.    The only lens that I will be using on the D200 IR body will be this very same lens.  I'll be sure to post some D200 IR images soon - likely in a new thread.

By the way, this photo is very special to me as it was taken at sunrise on the day after my father died.

Thank you, Bruce, for sharing this precious image related to a touching story.


Regarding choice of CCD sensor, here is link to an article that explains some advantages/disadvantages. Apparently dark current is lower for long exposures, while read noise is higher than the CMOS sensor..
https://ui.adsabs.harvard.edu/abs/2021RAA....21..268Q/abstract

Cooling the CMOS sensor to these super low levels might also be an issue due to that more of the electronics is located on the sensor chip.


Thank you, Øivind, for the link for the detailed explanation.


And this is an image shot with a very dence IR90 filter.  I needed to set the exposure time to 15 sec. @ISO 800 on my unmodified SIGMA fp.  The lens is an early single coated Nikkor 50/2.0 which is also known to be quite capable for IR without hot spot.
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Hugh_3170

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Great links and story Akira - many thanks for sharing these with us.

Your first link also refers to this link:  https://www.dpreview.com/news/1908840125/canon-australia-macquarie-university-supply-400mm-f2-8-lenses-huntsman-telescope

The Canon salesperson in Sydney must have pinched himself/herself when the order for ten Canon 400mm f/2.8 lenses for the Huntsman telescope array was received.  Their US counterpart even more so with the order for 120 of these lenses (~$US10k/each) for the US built Dragonfly array.  The Macquarie University's School of Mathematical & Physical Sciences team that put this telescope together have a great track record of laser and optical engineering.  Astronomy doesn't come cheap these days.
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Akira

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Great links and story Akira - many thanks for sharing these with us.

Your first link also refers to this link:  https://www.dpreview.com/news/1908840125/canon-australia-macquarie-university-supply-400mm-f2-8-lenses-huntsman-telescope

The Canon salesperson in Sydney must have pinched himself/herself when the order for ten Canon 400mm f/2.8 lenses for the Huntsman telescope array was received.  Their US counterpart even more so with the order for 120 of these lenses (~$US10k/each) for the US built Dragonfly array.  The Macquarie University's School of Mathematical & Physical Sciences team that put this telescope together have a great track record of laser and optical engineering.  Astronomy doesn't come cheap these days.

Hugh, thank you for the reminder.  I was aware of the article about Huntsman telescope but didn't start a thread for that.

I found that the original webpage for the Huntsman telescope linked from that dpreview article offers another link to the Dragonfly Telephoto Array by which the Huntsman was inspired.  The Dragonfly uses a total of 48 Canon 400mm f2.8 lenses!:

https://www.dragonflytelescope.org/
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Hugh_3170

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Actually we are both short of the planned final total of the Canon 400mm lenses:  https://www.dpreview.com/news/1895782682/canon-usa-to-provide-120-ef-400mm-f2-8-lenses-to-expand-dragonfly-telephoto-array

When/if fully developed there will be a total of 168 in the array!  What a beast!  ;D


Hugh, thank you for the reminder.  I was aware of the article about Huntsman telescope but didn't start a thread for that.

I found that the original webpage for the Huntsman telescope linked from that dpreview article offers another link to the Dragonfly Telephoto Array by which the Huntsman was inspired.  The Dragonfly uses a total of 48 Canon 400mm f2.8 lenses!:

https://www.dragonflytelescope.org/
Hugh Gunn

Akira

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Actually we are both short of the planned final total of the Canon 400mm lenses:  https://www.dpreview.com/news/1895782682/canon-usa-to-provide-120-ef-400mm-f2-8-lenses-to-expand-dragonfly-telephoto-array

When/if fully developed there will be a total of 168 in the array!  What a beast!  ;D

Wow, that's eye-opening and jaw-dropping!  One of major reasons of me intrigued by the astronomy is the insane idea for the equipment to observe the universe.  This Dragonfly is definitely one of such!
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Macro_Cosmos

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Using a CCD makes total sense to me.  Here is my 2 cents.
CCD sensors are not inherently more sensitive to IR, per se.  The structure has numerous advantages for this extremely niche yet astoundingly demanding application.

-Linearity
Due to the readout structure of CCDs, the linearity is 100% and data is 100% truthful.
sCMOS sensors feature an amplifier for each photosite, which means when a readout occurs, there are inherent non-linearity issues. 
The best sCMOS sensors claim >99.7%, which amazing, what does the 0.3% entail, and now, that is 0.3% for each pixel.  3200MP would give around 10 error pixels.  (edit: this is incorrect, I will fix it in a moment.) Bad point, I was mistaken.
Alright, different manufactures use different standards and methods to measure nonlinearity.  Regardless, a CMOS camera will come with some inherent nonlinearity while the best CCDs will not.  There are many situations where CCDs will yield a nonlinear output, so claiming it is strictly 100% is not correct.  Typical sCMOS cameras use two 11-bit readout amplifiers, resulting in 16 bits, this in itself causes some nonlinearity.  High end cameras use a single readout amplifier to improve linearity.
Considering the cost of this thing, the errors could just be critical.
CCDs utilise a single readout amplifier.  Think of this as photos queuing for a gate versus each photon being assigned a value and read out as an electric signal.  Yes -- CCDs are a lot slower because of this.

-Electron multiplication (EM-CCD)
Using the avalanche effect, CCDs can be boosted to yield extreme sensitivity when light is low.  Even though the boosting comes with inherent electron multiplication noise, CCDs are linear, and such noise is also linear.  This makes it easy to cancel out in post signal processing.  EM-CCDs use a frame transfer structure where the signals are stored for readout, situated below the detection area, this overcomes the inherent slowness but they are indeed still slower than sCMOS counterparts, which reach 100FPS easily at more than 30 times the resolution.  Andor practically owns the EM-CCD market (90% as of 2017), which leaves other companies to innovate in sCMOS technology to compete.  The EM-CCD is irreplaceable when light is very low, at below 4 photons per pixel, there is just no other choice.  Most applications have plentiful photons to spare.

-Cooling
IR is a long wavelength and comes with heat.  Long exposure generates a lot of dark current.  It is typical for a CCD sensor to be cooled to -70C (Andor does -100C!!!) which lowers dark current drastically.  Such levels of cooling could be problematic for CMOS.  I have never looked into this, but I can imagine the nonlinearity becoming a nuisance since different cooling levels correspond to slightly different readouts.  One would have to calibrate for each temperature.  All the SWIR cameras use CCDs.

Read noise is higher on CCD cameras, but just like readout, the noise is also linear!  Since they will be doing longer exposures, I do not think readout noise is as important as the top two of my list above.  The third one really is an added bonus.

Inevitably, someone may ask "so why can't Sony/Canon/Nikon offer cooled CMOS/EM-CCD".
- EM-CCDs top out a 1 megapixel.  Yeah.  I am sure we need more "but my bigmi 917XSProPlusAI++QuintupleCam does 500 megapixels" type remarks. 
- For cooling to work, the sensor is situated in a sealed chamber.  With people complaining that a Z3 is heavy, this will not bode well.
- The chamber becomes leaky over time.  When cooling is on, humidity laden air manifests itself as condensation.  The desiccants inside the chamber must be replaced every 2 years or so.  See below:
"Fix Your Andor Zyla with Four COVID-19 RATs"  (Not clickbait.)
https://macrocosmosblog.wordpress.com/2022/07/09/fix-your-andor-zyla-with-four-covid-19-rats/

I cannot think of a single consumer company that would want to deal with this conundrum. 
EM-CCDs typically use a hermetically sealed enclosure that is extremely expensive to do correctly. 
"Turn cooling off!"  -- Why have it in the first place then? 
Additionally, the kind of electronics to cool such massive sensors... yeah.  ;D
- Cost: See above.  Labour to fix that leaky box is not free.
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Øivind Tøien

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Interesting technical information. A note regarding your linked page is that one could likely have regenerated the original desiccant packs for the chamber by heating them to about 250°C/400°F (if the envelope could take that much heat) and then let them cool down in a dry environment. This applies both to silica gel and molecular sieve. It was certainly a good move to heat the ones from the RAT.
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