What are accepted figures for signal/noise (SNR) and dynamic rangefor CRT? LCD? Film? Human eye?

In article , Roger N. Clark (change username to
rnclark) wrote:
At one time I worked on a project finding black coatings for cameras and
other EO sensors. It is amazing how hard it is to get a truly black
black. Even the famed 3M Black Velvet was a 2% reflectance. The only
thing we found was a coating by Martin Marietta that was close to 1%.


Not only isn't it black, it's yellow, or blue or red ... Black, like
white seems to be an imaginary concept.


Carbon lamp black is probably the darkest diffuse
reflector. It's reflectance in the visual range is
about 1.6%:

The BBC's Test Chart No 57 included (includes?), for the purpose of setting
the flare-correction circuitry, a "superblack" rectangle that is actually a
box a few inches deep, lined with black velvet. A small rectangular aperture
at the front opens onto the surface of the test chart. Any light striking
this rectangle enters the dark box and has to undergo several successive
reflections by the black velvet before emerging, thus giving the rectangular
opening an effective reflectance much lower than would be achievable by any
actual surface.

Any value of the output signal above dark current level corresponding to this
part of the chart is deemed not to have come from the chart at all but from
light scattered in the lens, and the circuitry is adjusted accordingly.

Rod.

"Roderick Stewart" wrote in message
om...

The BBC's Test Chart No 57 included (includes?), for the purpose of
setting
the flare-correction circuitry, a "superblack" rectangle that is actually
a
box a few inches deep, lined with black velvet. A small rectangular
aperture
at the front opens onto the surface of the test chart. Any light striking
this rectangle enters the dark box and has to undergo several successive
reflections by the black velvet before emerging, thus giving the
rectangular
opening an effective reflectance much lower than would be achievable by
any
actual surface.

Any value of the output signal above dark current level

Why not just test with the lens cap on?

"Roderick Stewart" wrote in message
om...

The BBC's Test Chart No 57 included (includes?), for the purpose of
setting
the flare-correction circuitry, a "superblack" rectangle that is actually
a
box a few inches deep, lined with black velvet. A small rectangular
aperture
at the front opens onto the surface of the test chart. Any light striking
this rectangle enters the dark box and has to undergo several successive
reflections by the black velvet before emerging, thus giving the
rectangular
opening an effective reflectance much lower than would be achievable by
any
actual surface.

Any value of the output signal above dark current level

Why not just test with the lens cap on?

In article , Roger N. Clark

Carbon lamp black is probably the darkest diffuse
reflector. It's reflectance in the visual range is
about 1.6%:

The color of the lamp black varies with the source of the paraffin.
North Sea Brent produces a different color than West Texas Light,
produces a different color than ....

This just for plain-ole black paint.

1.6% is quite a bit of reflectance - 1.8 oD, 6 stops down from
white.

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
To reply, remove spaces: n o lindan at ix . netcom . com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

In article , Jjs wrote:
The BBC's Test Chart No 57 included (includes?), for the purpose of
setting
the flare-correction circuitry, a "superblack" rectangle that is actually
a
box a few inches deep, lined with black velvet. A small rectangular
aperture
at the front opens onto the surface of the test chart. Any light striking
this rectangle enters the dark box and has to undergo several successive
reflections by the black velvet before emerging, thus giving the
rectangular
opening an effective reflectance much lower than would be achievable by
any
actual surface.

Any value of the output signal above dark current level

Why not just test with the lens cap on?

Test what? The superblack box is for setting flare correctors, which of course
won't do anything if there isn't any flare. All you can test with the lens cap
on is black balance, clamp balance ("pulse cancellation") and black shading.
Superblack has to be visible simultaneously with a large area of high
brightness in order to set and balance the flare correctors.

Rod.

In article , Jjs wrote:
The BBC's Test Chart No 57 included (includes?), for the purpose of
setting
the flare-correction circuitry, a "superblack" rectangle that is actually
a
box a few inches deep, lined with black velvet. A small rectangular
aperture
at the front opens onto the surface of the test chart. Any light striking
this rectangle enters the dark box and has to undergo several successive
reflections by the black velvet before emerging, thus giving the
rectangular
opening an effective reflectance much lower than would be achievable by
any
actual surface.

Any value of the output signal above dark current level

Why not just test with the lens cap on?

Test what? The superblack box is for setting flare correctors, which of course
won't do anything if there isn't any flare. All you can test with the lens cap
on is black balance, clamp balance ("pulse cancellation") and black shading.
Superblack has to be visible simultaneously with a large area of high
brightness in order to set and balance the flare correctors.

Rod.

"Roderick Stewart" wrote in message
om...
In article , Roger N. Clark (change username
to
rnclark) wrote:
At one time I worked on a project finding black coatings for cameras
and
other EO sensors. It is amazing how hard it is to get a truly black
black. Even the famed 3M Black Velvet was a 2% reflectance. The only
thing we found was a coating by Martin Marietta that was close to 1%.


Not only isn't it black, it's yellow, or blue or red ... Black, like
white seems to be an imaginary concept.


Carbon lamp black is probably the darkest diffuse
reflector. It's reflectance in the visual range is
about 1.6%:

The BBC's Test Chart No 57 included (includes?), for the purpose of
setting
the flare-correction circuitry, a "superblack" rectangle that is actually
a
box a few inches deep, lined with black velvet. A small rectangular
aperture
at the front opens onto the surface of the test chart. Any light striking
this rectangle enters the dark box and has to undergo several successive
reflections by the black velvet before emerging, thus giving the
rectangular
opening an effective reflectance much lower than would be achievable by
any
actual surface.

Any value of the output signal above dark current level corresponding to
this
part of the chart is deemed not to have come from the chart at all but
from
light scattered in the lens, and the circuitry is adjusted accordingly.

Ah - so that's where my licence fee goes......

"Roderick Stewart" wrote in message
om...
In article , Roger N. Clark (change username
to
rnclark) wrote:
At one time I worked on a project finding black coatings for cameras
and
other EO sensors. It is amazing how hard it is to get a truly black
black. Even the famed 3M Black Velvet was a 2% reflectance. The only
thing we found was a coating by Martin Marietta that was close to 1%.


Not only isn't it black, it's yellow, or blue or red ... Black, like
white seems to be an imaginary concept.


Carbon lamp black is probably the darkest diffuse
reflector. It's reflectance in the visual range is
about 1.6%:

The BBC's Test Chart No 57 included (includes?), for the purpose of
setting
the flare-correction circuitry, a "superblack" rectangle that is actually
a
box a few inches deep, lined with black velvet. A small rectangular
aperture
at the front opens onto the surface of the test chart. Any light striking
this rectangle enters the dark box and has to undergo several successive
reflections by the black velvet before emerging, thus giving the
rectangular
opening an effective reflectance much lower than would be achievable by
any
actual surface.

Any value of the output signal above dark current level corresponding to
this
part of the chart is deemed not to have come from the chart at all but
from
light scattered in the lens, and the circuitry is adjusted accordingly.

Ah - so that's where my licence fee goes......

In message ,
"jjs" wrote:

That should be slightly different, as the black rectangle will pick up
light not meant to be focused in that area (the stuff that lowers
contrast).

Why not just test with the lens cap on?


--


John P Sheehy

In message ,
"jjs" wrote:

That should be slightly different, as the black rectangle will pick up
light not meant to be focused in that area (the stuff that lowers
contrast).

Why not just test with the lens cap on?


--


John P Sheehy