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Author Topic: MF Digital, myths or facts? A bit of drilling down  (Read 8615 times)
ErikKaffehr
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« Reply #60 on: November 14, 2012, 10:43:27 PM »
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Hi,

Actually that does not matter at all as far as you expose consistently, especially not if you expose to the right, thus fully utilizing the sensor.

Best regards
Erik


Totally agree with you Bernard.  The amount of light reaching the sensor will be a function of the gathering power of the lens, the internal transmission losses and the percentage of the image circle that actually falls on the sensor.  Perhaps an interesting test would be to compare various 35mm lenses with various MFD lenses in a test rig on both types of sensors so that these variables can be eliminated. 

I shoot with both MFD (H4D-60) and 35mm (D800E).  Both are fine instruments and very often I could use either camera for a job.  There are situations however where the ease of use and portability of the Nikon make it my tool of choice and situations where the Hasselbald is my preferred option - usually in the studio.  They are both very very good.

However from a subjective point of view I like what the combination of Hasselblad back and lenses and their Phocus software producing in a large format print.
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bjanes
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« Reply #61 on: November 15, 2012, 08:01:43 AM »
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Well, I have no idea what 'flux density' is.  Is it in any way related to the flux capacitor from "Back to the Future"?

Luminous flux = Lumens

Exposure = Lumens * integration time (lux seconds)
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BJL
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« Reply #62 on: November 15, 2012, 04:47:19 PM »
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It would be feasible to build a sensor that has binary pixels either black or white. If there was enough of those pixels the sensor would form a good image. As far as I know such sensor designs have been proposed.
Such sensors exist: they are called "film", where each sensel is a cluster of silver halide crystals that is either "exposed" or "not exposed" as far as the subsequent processing is concerned. All shades of gray seen in a traditional monochrome negative are dithering of a mixture of pure black at exposed "sensels" and pure white elsewhere. By any practically relevant definition, the resulting dynamic range is vastly greater than any "per sensel" value, and cannot determined at all from per sensel measurements. Dithering and blurring of the signal from multiple sensels each covering an angular part of the viewed image too small for the viewer's eye to resolve must be taken into acccount.

By the way, thanks for your effort on this.

Also, the Kodak/Truesense 50MP CCD has read noise of 12.5 e-, about the best for any of that brand of sensors, so your value is reasonable for CCDs as used in DMF. One source of such data is
http://www.truesenseimaging.com/products/full-frame-ccd
and the product summaries linked to in there.

P. S. TeledyneDalsa just released details of a 60MP sensor which is presumably the same as or similar to the one that was originally exclusive to Phase One, only now offered openly to all customers:
http://www.teledynedalsa.com/public/sensors/datasheets/FTF9168C_datasheet_20120306.pdf
This reports signal and noise specs in a different way, but you can convert back from well capacity (50,000e-) and DR (73 dB) to SNR in electrons, and I get just over 11e-.
« Last Edit: November 15, 2012, 05:01:39 PM by BJL » Logged
ErikKaffehr
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« Reply #63 on: November 15, 2012, 10:25:58 PM »
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Thanks for the good comments!

Erik



Such sensors exist: they are called "film", where each sensel is a cluster of silver halide crystals that is either "exposed" or "not exposed" as far as the subsequent processing is concerned. All shades of gray seen in a traditional monochrome negative are dithering of a mixture of pure black at exposed "sensels" and pure white elsewhere. By any practically relevant definition, the resulting dynamic range is vastly greater than any "per sensel" value, and cannot determined at all from per sensel measurements. Dithering and blurring of the signal from multiple sensels each covering an angular part of the viewed image too small for the viewer's eye to resolve must be taken into acccount.

By the way, thanks for your effort on this.

Also, the Kodak/Truesense 50MP CCD has read noise of 12.5 e-, about the best for any of that brand of sensors, so your value is reasonable for CCDs as used in DMF. One source of such data is
http://www.truesenseimaging.com/products/full-frame-ccd
and the product summaries linked to in there.

P. S. TeledyneDalsa just released details of a 60MP sensor which is presumably the same as or similar to the one that was originally exclusive to Phase One, only now offered openly to all customers:
http://www.teledynedalsa.com/public/sensors/datasheets/FTF9168C_datasheet_20120306.pdf
This reports signal and noise specs in a different way, but you can convert back from well capacity (50,000e-) and DR (73 dB) to SNR in electrons, and I get just over 11e-.
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opgr
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« Reply #64 on: November 16, 2012, 02:52:14 AM »
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Such sensors exist: they are called "film", where each sensel is a cluster of silver halide crystals

And the million dollar question obviously is: how many of those clumps fit in the space of a modern sensel at equivalent ISO?
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Regards,
Oscar Rysdyk
theimagingfactory
hjulenissen
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« Reply #65 on: November 16, 2012, 04:54:23 AM »
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And the million dollar question obviously is: how many of those clumps fit in the space of a modern sensel at equivalent ISO?
How many of those clumps can be fit into a film size that is economically viable to manufacture and shoot images with, compared to many sensels can be fit into a digital sensor that is economically viable to manufacture and shoot images with?

-h
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BJL
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« Reply #66 on: November 16, 2012, 09:09:27 AM »
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And the million dollar question obviously is: how many of those clumps fit in the space of a modern sensel at equivalent ISO?
I am fairly sure that there are many billions of them in a 36x24mm frame of a typical fine-grained monochrome film. One hint is the very high extinction resolution of such films, indicating that the chemical sensels are far smaller than the photosites of any current DSLR sensor, though of course at that resolution limit, dynamic range and measurement of luminosity levels is very poor.

Eric Fossum, originator of the modern active pixel CMOS sensor, has proposed sensors based on one-bit electonic sensels, which he calls "jots". Some of his writings at his site http://ericfossum.com/ are
http://ericfossum.com/Presentations/2012%20March%20QIS%20London.pdf
where he suggests that one bilion to 100 billion one-bit sensels would be needed, and
http://ericfossum.com/Publications/Papers/Gigapixel%20Digital%20Film%20Sensor%20Proposal.pdf
He also speculates about repeated reading of sensels during an exposure.
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ErikKaffehr
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« Reply #67 on: November 17, 2012, 04:34:53 AM »
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Hi,

There are two problems with silver halide crystals. One is that quantum efficiency is low (about 2% if I recall) the other is that it takes a lot of crystals to replace a single pixel. A single pixel can take detect 30000-60000 photons. It would take 30000 crystals to detect 30000 photons.

Best regards
Erik


I am fairly sure that there are many billions of them in a 36x24mm frame of a typical fine-grained monochrome film. One hint is the very high extinction resolution of such films, indicating that the chemical sensels are far smaller than the photosites of any current DSLR sensor, though of course at that resolution limit, dynamic range and measurement of luminosity levels is very poor.

Eric Fossum, originator of the modern active pixel CMOS sensor, has proposed sensors based on one-bit electonic sensels, which he calls "jots". Some of his writings at his site http://ericfossum.com/ are
http://ericfossum.com/Presentations/2012%20March%20QIS%20London.pdf
where he suggests that one bilion to 100 billion one-bit sensels would be needed, and
http://ericfossum.com/Publications/Papers/Gigapixel%20Digital%20Film%20Sensor%20Proposal.pdf
He also speculates about repeated reading of sensels during an exposure.

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