> I was thinking about the "traditional dye and gelatine optical
> filters" used by "professional photographers", not high-Q optical
> filters used by scientists. Wedding pictures and stock images can be
> post-processed for color and effects.
Commercial photographers still use ND3 to ND5 filters even today to get
the motion blur effects on waterfalls and sea scapes. It could be done
by taking loads of shots and combining them in post processing.
There are some effects that are easier to do with a filter in front of
the lens especially if they are using large cameras and sheet film.
The other one is graduated density filters for managing bright skies.
You can do it with digital HDR but the image can look very artificial.
--
Martin Brown
Reply by Phil Hobbs●January 23, 20232023-01-23
John Larkin wrote:
> On Mon, 23 Jan 2023 11:26:02 +0000, Martin Brown
> <'''newspam'''@nonad.co.uk> wrote:
>
>> On 21/01/2023 03:00, bitrex wrote:
>>> Before they were built into your phone's camera. From a Seattle
>>> Filmwork's catalog found among a late relative's personal
>>> effects. Winter, 1985:
>>>
>>>
>>> <https://imgur.com/a/YDakITI>
>>
>> Analogue traditional dye and gelatine optical filters are still
>> available to professional photographers today. eg
>>
>> https://www.srb-photographic.co.uk/square-filters-1222-c.asp
>
>
> Is there any reason to use a filter in digital photography?
Sure, many reasons, some of which are similar to why you use analog
filters in electronics.
-- Eliminating large unwanted signals (e.g. the pump light in a "black
light" image)
-- Glint elimination using linear or circular polarizers
-- Dynamic range reduction by emphasizing dimmer spectral regions.
> Imager chip pixels have extreme dynamic range and one can digitally
> post-process an image.
>
"Extreme dynamic range", e.g. 50k electrons full-well. That's a shot
noise limited SNR of 47 dB--enough for a good image, certainly, but not
for a good image plus a lot of reserve for high contrast situations.
Postprocessing is fine, but it won't fix inadequate SNR or dynamic range.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.nethttp://hobbs-eo.com
Reply by bitrex●January 23, 20232023-01-23
On 1/23/2023 6:26 AM, Martin Brown wrote:
> On 21/01/2023 03:00, bitrex wrote:
>> Before they were built into your phone's camera. From a Seattle
>> Filmwork's catalog found among a late relative's personal effects.
>> Winter, 1985:
>>
>>
>> <https://imgur.com/a/YDakITI>
>
> Analogue traditional dye and gelatine optical filters are still
> available to professional photographers today. eg
>
> https://www.srb-photographic.co.uk/square-filters-1222-c.asp
>
> Edmund Scientific have an even wider range for filters for science and
> industry including dopes glasses and dichroic filters (for a price).
>
> https://www.edmundoptics.co.uk/c/optical-filters/610/
>
$40 for the "Fog" filter in 1985 dollars! Highway robbery!
Reply by John Larkin●January 23, 20232023-01-23
On Mon, 23 Jan 2023 16:35:40 +0000, Martin Brown
<'''newspam'''@nonad.co.uk> wrote:
>On 23/01/2023 15:23, John Larkin wrote:
>> On Mon, 23 Jan 2023 11:26:02 +0000, Martin Brown
>> <'''newspam'''@nonad.co.uk> wrote:
>>
>>> On 21/01/2023 03:00, bitrex wrote:
>>>> Before they were built into your phone's camera. From a Seattle
>>>> Filmwork's catalog found among a late relative's personal effects.
>>>> Winter, 1985:
>>>>
>>>>
>>>> <https://imgur.com/a/YDakITI>
>>>
>>> Analogue traditional dye and gelatine optical filters are still
>>> available to professional photographers today. eg
>>>
>>> https://www.srb-photographic.co.uk/square-filters-1222-c.asp
>>
>> Is there any reason to use a filter in digital photography? Imager
>> chip pixels have extreme dynamic range and one can digitally
>> post-process an image.
>
>Yes. The most common reason would be to photograph in some narrow
>wavelength band to isolate particular elements. Scientific imaging
>tends to be done with monochrome CCDs and very well characterised glass
>filters in astronomy and fluorescence microscopy for example.
>
>https://astrobackyard.com/narrowband-imaging/
>
>Most colour Hubble shots are in SII, Halpha, OIII narrow band as R,G,B.
>
>You can get a roughly plausible colour image from Halpha to R and OIII
>496nm to a turquoise green using two bandpass filters.
>
>Single shot colour imaging is popular with hobby astronomers, but even
>there many push the technique using narrowband filters (which helps cut
>out a lot of the light pollution).
>
>In discussions about lights near observatories they offered to use
>yellow LEDs as an alternative to LPS - missing the point that it wasn't
>the yellow light so much as the very narrow waveband it pollutes (and
>sodium is so ubiquitous there is always some sky glow at sodium D lines.
I was thinking about the "traditional dye and gelatine optical
filters" used by "professional photographers", not high-Q optical
filters used by scientists. Wedding pictures and stock images can be
post-processed for color and effects.
Reply by Jan Panteltje●January 23, 20232023-01-23
On a sunny day (Mon, 23 Jan 2023 07:23:42 -0800) it happened John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote in
<8f9tsh90kbiualvhbqrqee5dd3hfq0fs01@4ax.com>:
>On Mon, 23 Jan 2023 11:26:02 +0000, Martin Brown
><'''newspam'''@nonad.co.uk> wrote:
>
>>On 21/01/2023 03:00, bitrex wrote:
>>> Before they were built into your phone's camera. From a Seattle
>>> Filmwork's catalog found among a late relative's personal effects.
>>> Winter, 1985:
>>>
>>>
>>> <https://imgur.com/a/YDakITI>
>>
>>Analogue traditional dye and gelatine optical filters are still
>>available to professional photographers today. eg
>>
>>https://www.srb-photographic.co.uk/square-filters-1222-c.asp
>
>
>Is there any reason to use a filter in digital photography? Imager
>chip pixels have extreme dynamic range and one can digitally
>post-process an image.
> On Mon, 23 Jan 2023 11:26:02 +0000, Martin Brown
> <'''newspam'''@nonad.co.uk> wrote:
>
>> On 21/01/2023 03:00, bitrex wrote:
>>> Before they were built into your phone's camera. From a Seattle
>>> Filmwork's catalog found among a late relative's personal effects.
>>> Winter, 1985:
>>>
>>>
>>> <https://imgur.com/a/YDakITI>
>>
>> Analogue traditional dye and gelatine optical filters are still
>> available to professional photographers today. eg
>>
>> https://www.srb-photographic.co.uk/square-filters-1222-c.asp
>
> Is there any reason to use a filter in digital photography? Imager
> chip pixels have extreme dynamic range and one can digitally
> post-process an image.
Yes. The most common reason would be to photograph in some narrow
wavelength band to isolate particular elements. Scientific imaging
tends to be done with monochrome CCDs and very well characterised glass
filters in astronomy and fluorescence microscopy for example.
https://astrobackyard.com/narrowband-imaging/
Most colour Hubble shots are in SII, Halpha, OIII narrow band as R,G,B.
You can get a roughly plausible colour image from Halpha to R and OIII
496nm to a turquoise green using two bandpass filters.
Single shot colour imaging is popular with hobby astronomers, but even
there many push the technique using narrowband filters (which helps cut
out a lot of the light pollution).
In discussions about lights near observatories they offered to use
yellow LEDs as an alternative to LPS - missing the point that it wasn't
the yellow light so much as the very narrow waveband it pollutes (and
sodium is so ubiquitous there is always some sky glow at sodium D lines.
--
Regards,
Martin Brown
Reply by John Larkin●January 23, 20232023-01-23
On Mon, 23 Jan 2023 11:26:02 +0000, Martin Brown
<'''newspam'''@nonad.co.uk> wrote:
>On 21/01/2023 03:00, bitrex wrote:
>> Before they were built into your phone's camera. From a Seattle
>> Filmwork's catalog found among a late relative's personal effects.
>> Winter, 1985:
>>
>>
>> <https://imgur.com/a/YDakITI>
>
>Analogue traditional dye and gelatine optical filters are still
>available to professional photographers today. eg
>
>https://www.srb-photographic.co.uk/square-filters-1222-c.asp
Is there any reason to use a filter in digital photography? Imager
chip pixels have extreme dynamic range and one can digitally
post-process an image.
Reply by legg●January 23, 20232023-01-23
On Sat, 21 Jan 2023 07:49:54 -0800, John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote:
>On Fri, 20 Jan 2023 22:00:04 -0500, bitrex <user@example.net> wrote:
>
>>Before they were built into your phone's camera. From a Seattle
>>Filmwork's catalog found among a late relative's personal effects.
>>Winter, 1985:
>>
>>
>><https://imgur.com/a/YDakITI>
>
>There's a story in
>
>https://www.amazon.com/Genius-Life-Science-Richard-Feynman/dp/0679747044
>
>about multilayer optical filters. Feynman was surely an alien life
>form.
>
A simple fader is usefull in getting relative lux/power measurements
for emitters, while keeping detector in linear range.
RL
Reply by Martin Brown●January 23, 20232023-01-23
On 21/01/2023 03:00, bitrex wrote:
> Before they were built into your phone's camera. From a Seattle
> Filmwork's catalog found among a late relative's personal effects.
> Winter, 1985:
>
>
> <https://imgur.com/a/YDakITI>
> On 2023-01-21 20:17, John Larkin wrote:
>> On Sat, 21 Jan 2023 19:14:03 +0100, Jeroen Belleman
>> <jeroen@nospam.please> wrote:
>>
>>> On 2023-01-21 16:49, John Larkin wrote:
>>>> On Fri, 20 Jan 2023 22:00:04 -0500, bitrex <user@example.net> wrote:
>>>>
>>>>> Before they were built into your phone's camera. From a Seattle
>>>>> Filmwork's catalog found among a late relative's personal effects.
>>>>> Winter, 1985:
>>>>>
>>>>>
>>>>> <https://imgur.com/a/YDakITI>
>>>>
>>>> There's a story in
>>>>
>>>> https://www.amazon.com/Genius-Life-Science-Richard-Feynman/dp/0679747044
>>>>
>>>>
>>>> about multilayer optical filters. Feynman was surely an alien life
>>>> form.
>>>>
>>>>
>>> He looks quite human to me, even though he did his own thinking.
>>> What did he have to say about multilayer optical filters?
>>>
>>> Jeroen Belleman
>>
>> As I recall, someone suggested something to him in a hallway
>> encounter. A few days later he delivered a complete theory of
>> multilayer optical filters.
>>
>> He was far more intelligent than humans can be. His hobby, as a kid,
>> was seeking out difficult differential equation to solve.
>>
>> At 13.5 nm, nothing refracts and nothing reflects... except extreme
>> multilayer coatings. That makes for interesting mask reducing optics.
>>
>
> Multi-layer optical filters obey the same laws as consecutive
> pieces of coax alternating between two impedances, except that
> the working frequency is much lower, and the coax is just a
> single pixel.
>
> Jeroen Belleman
And optical coatings have to work at different angles of incidence and
two polarization states.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.nethttp://hobbs-eo.com