[LONG] Theoretical estimates for film-equivalent digital sens

David Littlewood wrote:
[]
"mkm"? Not a recognised unit; could you please clarify.

David

He says it's micrometres but he refuses to use "um".

David

David Littlewood wrote:
[]
"mkm"? Not a recognised unit; could you please clarify.

David

He says it's micrometres but he refuses to use "um".

David

In article , David J
Taylor writes
David Littlewood wrote:
[]
"mkm"? Not a recognised unit; could you please clarify.

David

He says it's micrometres but he refuses to use "um".

David


Ah! Bernard's irregular verb from "Yes Minister" springs to mind.

Thanks.

David
--
David Littlewood

In article , David J
Taylor writes
David Littlewood wrote:
[]
"mkm"? Not a recognised unit; could you please clarify.

David

He says it's micrometres but he refuses to use "um".

David


Ah! Bernard's irregular verb from "Yes Minister" springs to mind.

Thanks.

David
--
David Littlewood

David Littlewood wrote:
In article , David J
Taylor
writes
David Littlewood wrote:
[]
"mkm"? Not a recognised unit; could you please clarify.

David

He says it's micrometres but he refuses to use "um".

David


Ah! Bernard's irregular verb from "Yes Minister" springs to mind.

Thanks.

David

Unfortunately it doesn't improve the credibility of anything else he says.
I presume we're in for a few weeks of "Yes, Minister" speak ourselves over
the next few weeks!

Cheers,
David

David Littlewood wrote:
In article , David J
Taylor
writes
David Littlewood wrote:
[]
"mkm"? Not a recognised unit; could you please clarify.

David

He says it's micrometres but he refuses to use "um".

David


Ah! Bernard's irregular verb from "Yes Minister" springs to mind.

Thanks.

David

Unfortunately it doesn't improve the credibility of anything else he says.
I presume we're in for a few weeks of "Yes, Minister" speak ourselves over
the next few weeks!

Cheers,
David

Hi Ilya,


BTW, there are also such devices like Electron Multiplying CCDs
which tackle that. No reason why these will not appear eventually in
consumer electronics.


(snip)


However, note that in other thread ("Lens quality") another limiting
factor was introduced: finite capacity of sensels per area. E.g.,
current state of art of capacity per area (Canon 1D MII, 52000
electrons per 8.2mkm sensel) limits the size of 2000 electrons cell to
1.6mkm. So without technological change, there is also a restriction
of sensitivy *from below*.
One advantage of the EMCCDs is there speed: up to 100fps. One could use that
speed for example for smart averaging including motion compensation, depth of
focus manipulation in combination with moving the focus, have stop here
before getting carried away....

Combining two estimages, this gives the low limil of cell size at
1.6mkm. However, I think that the latter restriction is only
technological, and can be overcome with more circuitry per photocell.
ok


'Resolution' is a rather vague term, usually it is taken as Half
Intensity Width of the point spread function, or using the Rayleigh
criterion. Both are not the same as the highest spatial frequency
passed by the lens,


Right. However, my impression is that at lens' sweet spot f-stop, all
these are closely related. At least I made calculations of MTF
functions of lenses limited by different aberrations, and all the
examples give approximately the same relations between these numbers
at the sweet spot.
The theoretical bandlimit is not affected by the aberrations, but the 50% MTF
point of course strongly.


To keep sensitivity when scaling down the sensor, keeping the pixel
count and not being able to gain sensitivity, you need to keep the
aperture diameter as is, resulting in a lower f/d number, costs
extra.


What happens is you keep the aperture diameter the same, and want to
keep the field of view the same, but the focal length smaller. This
"obviously" can't be done without addition additional elements.
yes
However, these "additions" may happen on the "sensor" side of the
lens, not on the subject side. So the added elements are actually
small in diameter (since sensor is so much smaller), so much cheaper
to produce. This will not add a lot to the lens price.
Looking at prices for microscope lenses I'm not so sure :-)

Hmm, maybe this may work... The lengths of optical paths through the
"old" part of the lens will preserve their mismatches; if added
elements somewhat compensate these mismatches, it will have much
higher optical quality, and price not much higher than the original.
I don't know much about lens designing, but I think that as soon as you add a
single element, make one aspherical surface or use some glass with special
dispersion properties you have to redo the entire optimization process. That
might be not so hard provided the basic design ideas are good, but probably
it is much pricier to manufacture the whole scaled up design to sufficient
accuracy.

Cheers, hans

Hi Ilya,


BTW, there are also such devices like Electron Multiplying CCDs
which tackle that. No reason why these will not appear eventually in
consumer electronics.


(snip)


However, note that in other thread ("Lens quality") another limiting
factor was introduced: finite capacity of sensels per area. E.g.,
current state of art of capacity per area (Canon 1D MII, 52000
electrons per 8.2mkm sensel) limits the size of 2000 electrons cell to
1.6mkm. So without technological change, there is also a restriction
of sensitivy *from below*.
One advantage of the EMCCDs is there speed: up to 100fps. One could use that
speed for example for smart averaging including motion compensation, depth of
focus manipulation in combination with moving the focus, have stop here
before getting carried away....

Combining two estimages, this gives the low limil of cell size at
1.6mkm. However, I think that the latter restriction is only
technological, and can be overcome with more circuitry per photocell.
ok


'Resolution' is a rather vague term, usually it is taken as Half
Intensity Width of the point spread function, or using the Rayleigh
criterion. Both are not the same as the highest spatial frequency
passed by the lens,


Right. However, my impression is that at lens' sweet spot f-stop, all
these are closely related. At least I made calculations of MTF
functions of lenses limited by different aberrations, and all the
examples give approximately the same relations between these numbers
at the sweet spot.
The theoretical bandlimit is not affected by the aberrations, but the 50% MTF
point of course strongly.


To keep sensitivity when scaling down the sensor, keeping the pixel
count and not being able to gain sensitivity, you need to keep the
aperture diameter as is, resulting in a lower f/d number, costs
extra.


What happens is you keep the aperture diameter the same, and want to
keep the field of view the same, but the focal length smaller. This
"obviously" can't be done without addition additional elements.
yes
However, these "additions" may happen on the "sensor" side of the
lens, not on the subject side. So the added elements are actually
small in diameter (since sensor is so much smaller), so much cheaper
to produce. This will not add a lot to the lens price.
Looking at prices for microscope lenses I'm not so sure :-)

Hmm, maybe this may work... The lengths of optical paths through the
"old" part of the lens will preserve their mismatches; if added
elements somewhat compensate these mismatches, it will have much
higher optical quality, and price not much higher than the original.
I don't know much about lens designing, but I think that as soon as you add a
single element, make one aspherical surface or use some glass with special
dispersion properties you have to redo the entire optimization process. That
might be not so hard provided the basic design ideas are good, but probably
it is much pricier to manufacture the whole scaled up design to sufficient
accuracy.

Cheers, hans

Hi Ilya,


BTW, there are also such devices like Electron Multiplying CCDs
which tackle that. No reason why these will not appear eventually in
consumer electronics.


(snip)


However, note that in other thread ("Lens quality") another limiting
factor was introduced: finite capacity of sensels per area. E.g.,
current state of art of capacity per area (Canon 1D MII, 52000
electrons per 8.2mkm sensel) limits the size of 2000 electrons cell to
1.6mkm. So without technological change, there is also a restriction
of sensitivy *from below*.
One advantage of the EMCCDs is there speed: up to 100fps. One could use that
speed for example for smart averaging including motion compensation, depth of
focus manipulation in combination with moving the focus, have stop here
before getting carried away....

Combining two estimages, this gives the low limil of cell size at
1.6mkm. However, I think that the latter restriction is only
technological, and can be overcome with more circuitry per photocell.
ok


'Resolution' is a rather vague term, usually it is taken as Half
Intensity Width of the point spread function, or using the Rayleigh
criterion. Both are not the same as the highest spatial frequency
passed by the lens,


Right. However, my impression is that at lens' sweet spot f-stop, all
these are closely related. At least I made calculations of MTF
functions of lenses limited by different aberrations, and all the
examples give approximately the same relations between these numbers
at the sweet spot.
The theoretical bandlimit is not affected by the aberrations, but the 50% MTF
point of course strongly.


To keep sensitivity when scaling down the sensor, keeping the pixel
count and not being able to gain sensitivity, you need to keep the
aperture diameter as is, resulting in a lower f/d number, costs
extra.


What happens is you keep the aperture diameter the same, and want to
keep the field of view the same, but the focal length smaller. This
"obviously" can't be done without addition additional elements.
yes
However, these "additions" may happen on the "sensor" side of the
lens, not on the subject side. So the added elements are actually
small in diameter (since sensor is so much smaller), so much cheaper
to produce. This will not add a lot to the lens price.
Looking at prices for microscope lenses I'm not so sure :-)

Hmm, maybe this may work... The lengths of optical paths through the
"old" part of the lens will preserve their mismatches; if added
elements somewhat compensate these mismatches, it will have much
higher optical quality, and price not much higher than the original.
I don't know much about lens designing, but I think that as soon as you add a
single element, make one aspherical surface or use some glass with special
dispersion properties you have to redo the entire optimization process. That
might be not so hard provided the basic design ideas are good, but probably
it is much pricier to manufacture the whole scaled up design to sufficient
accuracy.

Cheers, hans

Alfred Molon wrote:
In article , Ilya Zakharevich says...


Are there actual back-illumination sensor used in mass-production
digicams?


To my knowledge no - they are all used for astronomy. The production
Good camera's for fluorescence microscopy use them too. I guess the
efficiency gain is not sufficient to justify the current price difference (
$1) for use in digicams.

-- hans