color filter in B&W: do they affect dynamic range

[ymc226]

Reading that the Leica Monochrom has more DR than the M9 among other attributes, forum members also write about the improved contrast that would be expected akin to film.

Since it does increase contrast, could it be said that color filters could also dampen DR (one of the advantages of the MM) or am I wrong?

 

[michaelwj]

I'm not quite sure what you're asking?
Dynamic range is really the difference between the darkest and brightest areas on the image. Contrast is related to that but different. I think of DR as a global attribute, while contrast can be local.
Colour filters are used to change the relative brightness of different areas of the scene, so they can be used to increase the dynamic range of the scene (blue filter turning the sky almost white) or reduce the dynamic range of the scene (red filter darkening the blue sky).
To try and answer the question, yes, colour filters could be used to dampen the dynamic range. But the converse is also true.
I'm sure others will chime in.

 

[willie_901]

Reading that the Leica Monochrom has more DR than the M9 among other attributes, forum members also write about the improved contrast that would be expected akin to film.

Since it does increase contrast, could it be said that color filters could also dampen DR (one of the advantages of the MM) or am I wrong?

In general you are right if you meant the color filter array or Bayer filter.

Removing the CFA means more light reaches the sensor. More signal always good (up until th sensor site's electon capacity is exceeded). More light means more signal. At the same time, the sensor read (electronic) noise reminds essentially constant.

The S/N increases and therefore the dynamic range increases. Nothing beats S/N. If you look at quantitative measurements of DR vs ISO, as ISO increases DR decreases. As ISO increases the S/N for the shadow regions decreases because those sensor sites are now under exposed.

The sensor only has one sensitivity... the base ISO. increasing the ISO in order to decrease the shutter speed means less light, which means less signal for everything but highlights that were clipped at the slower shutter speed.

It is not possible to increase the sensor's sensitivity. The sensor sensitivity depends primarily on the sensor well capacitor size (how many electrons can it store) and the sensor's quantum efficiency.

After the shutter closes (exposure is completed) the voltage from the sensor is amplified in order to make the most of the analog to digital converter. But the sensor was under exposed. The image appears bright because ADC outputs large numbers to raw file. The final brightness and the exposure when the shutter was open are not the same thing.

 

[Exdsc]

B&W film, something like Tri-X has more dynamic range on the highlights than the shadows, that is why the rule for B&W film, expose for the shadows.

Digital is the complete opposite. With digital all the dynamic range is in the mid to shadows while the highlights have a very narrow range... You can have a 14 stop DR digital like D800 but it does not tell you how many stops of that is in the highlights.


But to answer your question, the dynamic range of your MM will not be affected by contrast filters, unless you're using a graduated ND filter.

 

[willie_901]

If you meant a colored lens filter, there would be no effect unless you changed the inherent dynamic range of the scene enough to no longer exceed the dynamic range of the sensor.

Otherwise, all you can do is maximize exposure which makes th most of the sonsor'ssensitivity inherent dynamic range.

Removing highlights vis a color filter means you could increase exposure, but the S/N would not change because during exposure the best you can do is maximize the signal in the sensor sites that record the light amplitude for the new highlights.

 

[kossi008]

Some of the statements above seem to indicate that color filters do not change the dynamic range of the scene; others indicate changes that I believe will go the other way:

Any scene in direct sunlight will be increased in global contrast by a yellow, orange, or red filter, because the shadow areas are predominantly blueish stray light from the sky, while the highlights receive the full spectrum. A blue filter will work in reverse, suppressing the shadows less than the highlights.

Not that I think it would be of much practical importance with respect to dynamic range...

 

[willie_901]

Some of the statements above seem to indicate that color filters do not change the dynamic range of the scene; others indicate changes that I believe will go the other way:

Any scene in direct sunlight will be increased in global contrast by a yellow, orange, or red filter, because the shadow areas are predominantly blueish stray light from the sky, while the highlights receive the full spectrum. A blue filter will work in reverse, suppressing the shadows less than the highlights.

Not that I think it would be of much practical importance with respect to dynamic range...

Reducing light amplitude selectively via a lens filter from any portion of the EV scale removes information. The EV span beomes compressed.

The dynamic range of the light exiting the filtered lens is less demanding. The sensor has less information to record. At some point the dynamic range of the light reaching the sensor will be within the range the sensor can measure.

Is it possible IR lens filters on the M8 did more than attenuate color artifacts?

 

[Calzone]

I think the term "useful" has to be included in this discussion. I use a 2X yellow filter on my Monochrom. My reason is to compress the dynamic range as to avoid or minimize clipping in both the shadows and in the highlights. The result is less contrast and more mid-range which is a bit counter intuitive. I find the information "recorded" better matches the sensor of the Monochrom because clipping is exceeding the ability of the sensor.

BTW in B&W film generally I use filters. To me it is always best to record the contrast I want upon exposure rather than in the darkroom or in post.

Cal