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Equipment & Techniques => Digital Cameras & Shooting Techniques => Topic started by: Guillermo Luijk on April 03, 2010, 11:08:16 am

Title: Dynamic range of human visual system
Post by: Guillermo Luijk on April 03, 2010, 11:08:16 am

I am looking for some reliable resource (or figures) about the dynamic range of the human vision. Both static (without allowing the eyes adapt) and dynamic (total dynamic range including pupil adaption).

Anyone has some info or figures?

Thanks
Title: Dynamic range of human visual system
Post by: bjanes on April 03, 2010, 03:13:21 pm
Quote from: Guillermo Luijk
I am looking for some reliable resource (or figures) about the dynamic range of the human vision. Both static (without allowing the eyes adapt) and dynamic (total dynamic range including pupil adaption).

Anyone has some info or figures?

Thanks
Guillermo,

Do a Google Scholar search with the key words "eye dynamic range" and look at the links to PDF files. There are a number of links that address the problem. Two different sources (e.g. Seetzen & Heidrich: High Dynamic Range Display Systems) state that eye can capture approximately 5 orders of magnitude of dynamic range effectively simultaneously and up to 9 orders of magnitude with adaption. Orders of magnitude are log base 10. 10^5 = 16.6 stops and 10^9  = 29.9 stops.

Regards,

Bill
Title: Dynamic range of human visual system
Post by: Guillermo Luijk on April 03, 2010, 04:57:04 pm
Thanks, I will keep those figures: 5 orders of magnitude static (16,6EV) and 9 orders adaptive (29,9EV), although I think specially the last could be a bit optimistic depending on how demanding we are about distinguising detail and colour.

I was doing some tests to find out the EV between the max and min luminance (i.e. the maximum displayable DR) on my monitor and on a print copy, and found lower values than some of the figures found in the literature.

For my monitor (I shot a black and white pattern) I found a difference between pure white and pure black of about 6,7EV:

(http://www.guillermoluijk.com/article/mpdrange/monitor.gif)

For the print copy (same pattern displayed on the monitor) I measured a difference of about 4,3EV:

(http://www.guillermoluijk.com/article/mpdrange/papel.gif)

Of course the figures may vary depending on many parameters such as monitor calibration, ambient lighting, type of paper, ink,... but these should be the standard order of magnitude.

In the reference: HDR images (http://www.isisimaging.com/LIBRARY_files/HDR_Image_White_Paper.pdf) we find this table:

• 100,000:1. The ratio of an outdoor scene from shadow to a sunlit area. About 100 orders of magnitude.
• 10,000:1. The ratio for the human eye’s dynamic range is at least an eight order of magnitude luminance range with adaptation and five orders of magnitude of dynamic range without adaptation.
• 300:1 to 500:1. The ratio of an LCD monitor. The ratio is usually referred to as the contrast ratio. About 3 orders of magnitude.
• 300:1. The ratio of a display with sufficient range for medical diagnosis.
• 160:1. The ratio of a printer page from paper white to the black colorant.
• 150:1. The ratio for the HVS local contrast at high spatial frequencies and at small regions where very high contrast cannot be perceived. It is this ratio that allows the HVS to view the dynamic range of the printed page as acceptable.
• 90:1. The ratio of encoding for sRGB is less than two orders of magnitude.

I don't understand very well the matching between the contrast figures on the left, and the orders of magnitude they talk about. E.g. 100,000:1 for 100 orders of magnitude???
For the LCD monitor they say 300:1 to 500:1, i.e. 8,2EV and 9EV, I wonder if they include changing monitor adjustments from its purest black to its brightest achievable white.
They give 160:1 (7,3EV) for the printer page, that seems too much for me.

I was wondering how ambient lighting could affect DR of devices.
Just to think a bit about. Regards
Title: Dynamic range of human visual system
Post by: bjanes on April 03, 2010, 06:10:11 pm
Quote from: Guillermo Luijk
In the reference: HDR images (http://www.isisimaging.com/LIBRARY_files/HDR_Image_White_Paper.pdf) we find this table:

• 100,000:1. The ratio of an outdoor scene from shadow to a sunlit area. About 100 orders of magnitude.
• 10,000:1. The ratio for the human eye’s dynamic range is at least an eight order of magnitude luminance range with adaptation and five orders of magnitude of dynamic range without adaptation.
• 300:1 to 500:1. The ratio of an LCD monitor. The ratio is usually referred to as the contrast ratio. About 3 orders of magnitude.
• 300:1. The ratio of a display with sufficient range for medical diagnosis.
• 160:1. The ratio of a printer page from paper white to the black colorant.
• 150:1. The ratio for the HVS local contrast at high spatial frequencies and at small regions where very high contrast cannot be perceived. It is this ratio that allows the HVS to view the dynamic range of the printed page as acceptable.
• 90:1. The ratio of encoding for sRGB is less than two orders of magnitude.

I don't understand very well the matching between the contrast figures on the left, and the orders of magnitude they talk about. E.g. 100,000:1 for 100 orders of magnitude???
For the LCD monitor they say 300:1 to 500:1, i.e. 8,2EV and 9EV, I wonder if they include changing monitor adjustments from its purest black to its brightest achievable white.
They give 160:1 (7,3EV) for the printer page, that seems too much for me.

Guillermo,

Some interesting observations. Your reference does not use orders of magnitude in the sense they are used in the scientific community, where it is a log 10 scale. 100,000:1 = 5 orders of magnitude. See this Wikipedia (http://en.wikipedia.org/wiki/Order_of_magnitude) link.

Regards,

Bill
Title: Dynamic range of human visual system
Post by: ErikKaffehr on April 03, 2010, 07:02:16 pm
Hi,

Density rang on paper may be like 2.2 (D-MAX) - 0.05 (DMin), something like 140. Slightly higher DMAX than 2.2 is possible. My interpretation of 1:100000 is also five orders of magnitude, or 16.6 stops.

BR
Erik



Quote from: bjanes
Guillermo,

Some interesting observations. Your reference does not use orders of magnitude in the sense they are used in the scientific community, where it is a log 10 scale. 100,000:1 = 5 orders of magnitude. See this Wikipedia (http://en.wikipedia.org/wiki/Order_of_magnitude) link.

Regards,

Bill
Title: Dynamic range of human visual system
Post by: Guillermo Luijk on April 03, 2010, 07:05:15 pm

Yes, from school an 'order of magnitude' has always been x10 for me. But never in a very strict way, just a commonly accepted criteria.
Title: Dynamic range of human visual system
Post by: ErikKaffehr on April 03, 2010, 07:09:21 pm
Hi,

I agree with what you say. Just want to mention that perceived contrast increases with illumination level. So a well done print can really shine under good (strong) illumination but get murky under less than optimal viewing conditions.

BR
Erik


Quote from: Guillermo Luijk
I was wondering how ambient lighting could affect DR of devices.
  • For instance in a projector, ambient light definitively reduces contrast (that is why lights are to be switched off during projections).
  • The same could apply to a monitor, where blacks could easily become 'washed' because of ambient light while whites do not benefit so much from it.
  • On the contrary I think ambient light shouldn't affect contrast on a printed copy, or it could even benefit of a higher contrast the higher the ambient light is, I don't know.
Just to think a bit about. Regards
Title: Dynamic range of human visual system
Post by: ErikKaffehr on April 03, 2010, 07:11:30 pm
Hi,

Well I guess that we could also have a "binary order of magnitude", meaning times 2.

Have a good night!

BR
Erik


Quote from: Guillermo Luijk
Yes, from school an 'order of magnitude' has always been x10 for me. But never in a very strict way, just a commonly accepted criteria.
Title: Dynamic range of human visual system
Post by: Ray on April 03, 2010, 09:35:25 pm
Quote from: Guillermo Luijk
I was wondering how ambient lighting could affect DR of devices.
  • For instance in a projector, ambient light definitively reduces contrast (that is why lights are to be switched off during projections).
  • The same could apply to a monitor, where blacks could easily become 'washed' because of ambient light while whites do not benefit so much from it.
  • On the contrary I think ambient light shouldn't affect contrast on a printed copy, or it could even benefit of a higher contrast the higher the ambient light is, I don't know.
Just to think a bit about. Regards


Interesting topic. The methods used to calculate contrast ratios for displays is not clear to me. For plasma displays one often sees two sets of figures, one described as the 'native' contrast ratio, and the other the 'dynamic' contrast ratio.

I imagine that the 'native' CR figure, which is the much lower figure, refers to the ratio of the blackest black to the whitest white possible within a single scene, as measured in a dark room with no ambient lighting. The dynamic CR of my Panasonic plasma TV is claimed as being '2 million to 1'. I'd really like to know how such a figure is derived. However, it seems clear that whatever the CR claimed by the manufacturer, the ambient lighting conditions play havoc with the perceived contrast.

I would actually have preferred to have bought an HD projector instead of my 65" Plasma because 65" is a bit small in a large room when viewing 'true' HD material, if you want to see all the detail. Fortunately for the viewer, the average 'so-called' HD broadcast is mush, hardly better than good quality standard definition or an upscaled DVD, and sometimes not even as good as a high quality upscaled DVD. When viewing such material, the further away you are, the better.

An advantage of the projector is, one can use the zoom to change the size of the image according to quality. If the source is true HD, then one can zoom out (or is that in) to fill the entire screen. If the source is crap (technically) one can make the image smaller to hide the defects, without the need in either case to change one's seating position.

The disadvantage of the projector is its low contrast ratio and the consequently greater requirement to view images in a darkened room. This was the main reason I chose a plasma screen in preference to a projector.

However, I now realise that in order to appreciate the full dynamic range of a high quality HD source, viewing either a Blu-ray video of a high quality TV series such as the HBO 'Rome', or one of my own jpeg images, I still need a darkened room, even with the Panasonic plasma with its amazing contrast ratios.

I think perhaps an analogy with audio is relevant here. One can have the most expensive hi fi system that money can buy, however, if one's room acoustics are poor, one is wasting one's money and not deriving the benefit of such exotic equipment.

Room acoustics in relation to hi fi is analagous to ambient lighting in relation to images on the wall, whether transmissive or reflective.
Title: Dynamic range of human visual system
Post by: feppe on April 04, 2010, 04:58:50 am
Quote from: Ray
Interesting topic. The methods used to calculate contrast ratios for displays is not clear to me. For plasma displays one often sees two sets of figures, one described as the 'native' contrast ratio, and the other the 'dynamic' contrast ratio.

Veering off-topic, but dynamic contrast ratio is done by turning off the backlight and measuring a black, then turning it on to full and measuring a white. Current displays don't work this way in real life, in other words dynamic contrast ratio is entirely useless for measuring the real-world contrast ratio of a screen. This is the one usually used by marketing people because it's a more impressive, if implausible, number. More info (http://www.cnet.com/8301-17914_1-9985085-89.html).

That's only one way you get mislead with numbers. And it doesn't stop there: I was with my parents buying a HDTV for them last Christmas, and they ran HD content on only the most expensive models at the shops. The ones costing half those ran SD content although they were 1080p TVs! So it was impossible to compare the quality side-by-side. And don't get me started on factory presets which crank up the backlight, brightness, contrast and saturation to 11 to make them pop more than the display next to it.

And yes, projector for movie viewing is fantastic. The current generation has enough firepower to view in a dim (not fully dark) room with good contrast ratio. And you can get a 100+ inch screen for much less than the price of a 65" plasma. I have one from the previous gen (Panasonic PT-AX200E) and it looks gorgeous in a darkened room.
Title: Dynamic range of human visual system
Post by: elf on April 04, 2010, 05:02:05 am
Quote from: Guillermo Luijk
Thanks, I will keep those figures: 5 orders of magnitude static (16,6EV) and 9 orders adaptive (29,9EV), although I think specially the last could be a bit optimistic depending on how demanding we are about distinguising detail and colour.

I was doing some tests to find out the EV between the max and min luminance (i.e. the maximum displayable DR) on my monitor and on a print copy, and found lower values than some of the figures found in the literature.

For my monitor (I shot a black and white pattern) I found a difference between pure white and pure black of about 6,7EV:

   
Title: Dynamic range of human visual system
Post by: Guillermo Luijk on April 04, 2010, 07:12:54 am
Quote from: ErikKaffehr
I agree with what you say. Just want to mention that perceived contrast increases with illumination level. So a well done print can really shine under good (strong) illumination but get murky under less than optimal viewing conditions.

Quote from: Ray
The disadvantage of the projector is its low contrast ratio and the consequently greater requirement to view images in a darkened room. This was the main reason I chose a plasma screen in preference to a projector.

However, I now realise that in order to appreciate the full dynamic range of a high quality HD source, viewing either a Blu-ray video of a high quality TV series such as the HBO 'Rome', or one of my own jpeg images, I still need a darkened room, even with the Panasonic plasma with its amazing contrast ratios.
I will put these two comments together just to agree.
One possible rule to explain the facts would be that self illuminated devices (projector, monitor) get worse with added ambient light. On the contrary devices  that need to reflect an external source of illumination in order to be viewed (print paper in this case) can maximise contrast with an optimised source of light (I guess both the intensity and angle of incidence are important here).


Quote from: feppe
Veering off-topic, but dynamic contrast ratio is done by turning off the backlight and measuring a black, then turning it on to full and measuring a white.
I guess many measures are done that way (specially those from manufacturers interested in giving huge figures), but I think that is not the way to get useful DR figures. In a real situation, we won't change monitor/projector/paper settings to visualize a single picture. That is why I think measuring reflected/projected levels of light from the final image we are really viewing without any change in the settings is the right way, because this will be real the contrast entering our eyes, and hence the contrast we can expect to perceive regularly using that device.
Title: Dynamic range of human visual system
Post by: Ray on April 04, 2010, 08:30:09 pm
Quote from: Guillermo Luijk
One possible rule to explain the facts would be that self illuminated devices (projector, monitor) get worse with added ambient light. On the contrary devices  that need to reflect an external source of illumination in order to be viewed (print paper in this case) can maximise contrast with an optimised source of light (I guess both the intensity and angle of incidence are important here).

Yes. That's true. In a completely dark room you won't see the print at all. Zero contrast! Yet the monitor will look close to its best   .

But perhaps we should distinguish between contrast and dynamic range. I don't get any sense that shadow detail is lost on a monitor when ambient light levels are increased. The contrast of the scene is simply reduced. One can compensate for this, at least to some extent, by increasing the contrast of the display.

However, when viewing a print, a lowering of ambient light levels actually reduces the perception of dynamic range in the print because shadow detail becomes less discernible.


Title: Dynamic range of human visual system
Post by: Ray on April 04, 2010, 09:05:52 pm
Quote from: feppe
Veering off-topic, but dynamic contrast ratio is done by turning off the backlight and measuring a black, then turning it on to full and measuring a white.

I must admit I've never noticed the 'dynamic' CR claims for any LCD. Turning off the backlight certainly does not seem relevant to any real-world viewing experience.

However, the plasma display does not have a backlight. Each of the 2 million pixels on a plasma HD display can be switched off in real time during the display of any scene to indicate total black. That's why plasma displays tend to have much better contrast ratios than LCDs; no backlight. They are a bit like CRTs in this respect.

If one switches off a plasma screen to measure the blackest black, then the result will surely depend on the level of ambient lighting in the room where the measurements are made. If the room is turned into a 'black body' for the purpose of measurement, and such measurements are compared with the brightest level the display is capable of (with contrast controls at their maximum) then the results would surely be astronomical; far greater than 2 million to 1.
 
The 'native' contrast ratio of my Panasonic plasma, which I presume refers to the maximum CR within a single scene at a given instant, is claimed as 40,000:1.
Title: Re: Dynamic range of human visual system
Post by: davidKane on May 27, 2013, 10:02:47 am
Take a look at this paper.

It argues the stead-state dynamic range of the visual system is 3.7 log units.

http://www.cs.bris.ac.uk/~reinhard/papers/kunkel_apgv2010.pdf

DAve
Title: Re: Dynamic range of human visual system
Post by: Jim Kasson on May 27, 2013, 10:53:18 am
...this paper...argues the stead-state dynamic range of the visual system is 3.7 log units.

Thanks, Dave. It is an excellent paper. I like the control of the spatial frequencies of the target, and the use of 1/f noise in the adapting field. For photographers, maybe we should restate the conclusions in log(2) terms, rather than log(10): the steady-state dynamic range of the visual system is 12.3 stops.

Jim
Title: Re: Dynamic range of human visual system
Post by: theguywitha645d on May 28, 2013, 11:24:51 am
CCD Arrays, Cameras, and Displays by Holst, 2nd edition, defines display contrast as:

Contrast = Lwhite + Lambient * reflectivity / Lblack + Lambient * reflectivity

where L is luminance.

I am not sure how you are defining contrast, but a standard outdoor scene in daylight was always defined by Kodak as about 160:1. A silver print topped out at about 30:1. Contrast should be logarithmic.
Title: Re: Dynamic range of human visual system
Post by: thierrylegros396 on May 28, 2013, 11:31:16 am
My personal vision is about 14 Ev static and 28 Ev Dynamic.

But my left eye is 10/10 and my right only 6/10 ;)

Thierry
Title: Re: Dynamic range of human visual system
Post by: BobDavid on May 28, 2013, 02:55:59 pm
Age of the human factors into the equation. I've read that human eyesight decreases in brightness by one f/stop every ten years.
Title: Re: Dynamic range of human visual system
Post by: digitaldog on May 28, 2013, 03:24:46 pm
You might ping Karl Lang, the author of this paper which discusses the subject a bit.

http://wwwimages.adobe.com/www.adobe.com/products/photoshop/family/prophotographer/pdfs/pscs3_renderprint.pdf

http://www.lumita.com
Title: Re: Dynamic range of human visual system
Post by: bjanes on May 28, 2013, 03:33:29 pm
CCD Arrays, Cameras, and Displays by Holst, 2nd edition, defines display contrast as:

Contrast = Lwhite + Lambient * reflectivity / Lblack + Lambient * reflectivity

where L is luminance.

I am not sure how you are defining contrast, but a standard outdoor scene in daylight was always defined by Kodak as about 160:1. A silver print topped out at about 30:1. Contrast should be logarithmic.


Those contrast ratios do not seem realistic to me. Karl Lang, Rendering the print: the art of photography (http://wwwimages.adobe.com/www.adobe.com/products/photoshop/family/prophotographer/pdfs/pscs3_renderprint.pdf), demonstrates an outdoor scene with luminances of 10-30,000 cd/m^2 for a range of 3,000:1, and states that a typical silver print has a contrast ratio of 250:1. The 160:1 to which you refer may represent the daylight scene as rendered to a silver print (output referred, not the scene referred contrast).

Regards,

Bill
Title: Re: Dynamic range of human visual system
Post by: BJL on May 28, 2013, 03:54:31 pm
Karl Lang, Rendering the print: the art of photography (http://wwwimages.adobe.com/www.adobe.com/products/photoshop/family/prophotographer/pdfs/pscs3_renderprint.pdf) ... states that a typical silver print has a contrast ratio of 250:1.
I am skeptical about that second number: numerous sources suggest that the reflectivity of pure black on a glossy silver print is about 1.5% (the darkest natural substances, like fine charcoal, reflect about 4%). Meanwhile pure white anything reflects no more than 90%, and the baryta base of printing paper is not quite the whitest thing around. These two numbers limit the contrast ratio of a silver print to 60:1, or about six stops --- a range often discussed as a target in B&W printing from high contrast negatives.
Title: Re: Dynamic range of human visual system
Post by: bjanes on May 28, 2013, 05:02:40 pm
I am skeptical about that second number: numerous sources suggest that the reflectivity of pure black on a glossy silver print is about 1.5% (the darkest natural substances, like fine charcoal, reflect about 4%). Meanwhile pure white anything reflects no more than 90%, and the baryta base of printing paper is not quite the whitest thing around. These two numbers limit the contrast ratio of a silver print to 60:1, or about six stops --- a range often discussed as a target in B&W printing from high contrast negatives.

That figure may be a bit optimistic. For comparison, the ICC PRMG uses a high quality virtual print with a 288:1 DR, having maximal and minimum reflectances of 89% and 0.30911% respectively. The corresponding densities are 0.05 and 2.51.

Ilfobrom Galeria fb (http://www.ilfordphoto.com/Webfiles/2011427953242632.pdf) chemical print paper has a Dmax of 2.2. Assuming that the maximal reflectivity is 89% or a density of 0.05, the DR would be 2.15 logs or 141:1.

Regards,

Bill

Title: Re: Dynamic range of human visual system
Post by: theguywitha645d on May 28, 2013, 06:08:38 pm
Those contrast ratios do not seem realistic to me. Karl Lang, Rendering the print: the art of photography (http://wwwimages.adobe.com/www.adobe.com/products/photoshop/family/prophotographer/pdfs/pscs3_renderprint.pdf), demonstrates an outdoor scene with luminances of 10-30,000 cd/m^2 for a range of 3,000:1, and states that a typical silver print has a contrast ratio of 250:1. The 160:1 to which you refer may represent the daylight scene as rendered to a silver print (output referred, not the scene referred contrast).

Regards,

Bill

You need to use a logarithmic scale. That better represents our perception of light values. I can check my texts again, but I remember the values very well--they were kind of drilled into us at RIT.
Title: Re: Dynamic range of human visual system
Post by: bjanes on May 28, 2013, 06:47:36 pm
You need to use a logarithmic scale. That better represents our perception of light values. I can check my texts again, but I remember the values very well--they were kind of drilled into us at RIT.

You do not need a log scale to calculate contrast ratios. Density is log based. If you want perceptual values, you should use L* or at least gamma 2.2, which can easily be done with Bruce Lindbloom's Companding Calculator.

You should recheck your texts, as I think your recalled values are way off as demonstrated in my previous post using Ilford photographic paper. Your outdoor scene contrast ratio is way off. Karl Lang is a serious guy who knows his stuff.

Bill
Title: Dynamic range of printing papers: up to about 7.5 stops?
Post by: BJL on May 28, 2013, 07:01:41 pm
That figure may be a bit optimistic. ...
Ilfobrom Galeria fb[/url] chemical print paper has a Dmax of 2.2. Assuming that the maximal reflectivity is 89% or a density of 0.05, the DR would be 2.15 logs or 141:1.
Thanks Bill: it seems my information was not up to date with the latest papers. At http://www.imatest.com/guides/image-quality/print-dmax/ it is suggested that the new record might be a minimum print reflectivity of Dmax=2.3:
"There have been reports that the new Epson Ultrachrome K3 printers have Dmax as high as 2.3 with Premium Luster paper".
That would be a minimum reflectivity of about 1/200, so then allowing for at best 90% maximum reflectivity gives a contrast range of about 180:1. (But that is not a silver print, which is what I was Karl Lang and I were talking about.)

Note: Dmax is log base 10, so in the log base 2 units of "stops" more familiar to photographers, that Dmax=2.2 for Ilfobrom Galeria fb is about 7.3 stops below 100% reflectivity, or 158:1, and so a contrast range a bit less: probably a bit over 7 stops and no more than 150:1. Given that this is the highest Dmax we can find for a silver print paper, I still maintain that Karl Lang is overstating the numbers a bit.
Title: Re: Dynamic range of human visual system
Post by: Bart_van_der_Wolf on May 28, 2013, 07:16:05 pm
I am skeptical about that second number: numerous sources suggest that the reflectivity of pure black on a glossy silver print is about 1.5% (the darkest natural substances, like fine charcoal, reflect about 4%).

Hi,

But glossy surfaces can reach a much higher D-max, because less light is scattered (also back to the observer) and more is reflected away from the observer. An interesting thing is that an extremely black object can be created by folding a glossy(!) black surface into a deep cone shape ... Part of the light will be absorbed when it hits the surface, and the reflected component will be absorbed a few times more before it can ever return to the observer.

Cheers,
Bart
Title: Re: Dynamic range of printing papers: up to about 7.5 stops?
Post by: bjanes on May 28, 2013, 08:19:24 pm
Note: Dmax is log base 10, so in the log base 2 units of "stops" more familiar to photographers, that Dmax=2.2 for Ilfobrom Galeria fb is about 7.3 stops below 100% reflectivity, or 158:1, and so a contrast range a bit less: probably a bit over 7 stops and no more than 150:1. Given that this is the highest Dmax we can find for a silver print paper, I still maintain that Karl Lang is overstating the numbers a bit.

Yes, I don't know what paper Karl is using. For those who don't have Excel or a scientific calculator that does log base 2 calculations, one can calculate log base 10 and multiply by log(10, base 2) or 3.32.

Bill
Title: Re: Dynamic range of human visual system
Post by: bjanes on May 28, 2013, 08:40:19 pm
Hi,

But glossy surfaces can reach a much higher D-max, because less light is scattered (also back to the observer) and more is reflected away from the observer. An interesting thing is that an extremely black object can be created by folding a glossy(!) black surface into a deep cone shape ... Part of the light will be absorbed when it hits the surface, and the reflected component will be absorbed a few times more before it can ever return to the observer.

Cheers,
Bart

Bart, thanks for pointing that out. I see that you supplied Norman Koren with a link (http://www.imatest.com/docs/veilingglare/) to a post by Roger Clark on rec.photo.digital describing such a light trap. I understand that the camera looks into the cone from the apex. What should one use for the base of the cone and what is the optimum angle for the cone?

Best regards,

Bill

PS. I see that this news group still exists. Does anyone on LuLa follow them? I abandoned them long ago when my favorite newsreader (Gravity) ceased production at that time.

Title: Re: Dynamic range of printing papers: up to about 7.5 stops?
Post by: Schewe on May 28, 2013, 11:56:21 pm
Yes, I don't know what paper Karl is using. For those who don't have Excel or a scientific calculator that does log base 2 calculations, one can calculate log base 10 and multiply by log(10, base 2) or 3.32.

So, given a D-max and D-min, exactly how does one calculate contrast ratio? Also, I believe that certain Epson papers with UltraChrome HDR inks can hit a D-max of 2.5-2.7 (with EFP being near 2.5 and Ultra Premium Glossy being close to 2.7 (I remember 2.68 as a number but not where I read that and I didn't measure that).
Title: Re: Dynamic range of printing papers: up to about 7.5 stops?
Post by: Bart_van_der_Wolf on May 29, 2013, 03:44:30 am
So, given a D-max and D-min, exactly how does one calculate contrast ratio?

Hi Jeff,

Contrast Ratio =10 ^ (D-max - D-min)
Where ^ denotes the power function

So, e.g. with a D-max of 2.20 and a D-min of 0.05, we'd get 10^2.15 = 141, or as a ratio 141 : 1.

Cheers,
Bart
Title: Re: Dynamic range of human visual system
Post by: Bart_van_der_Wolf on May 29, 2013, 04:32:11 am
Bart, thanks for pointing that out. I see that you supplied Norman Koren with a link (http://www.imatest.com/docs/veilingglare/) to a post by Roger Clark on rec.photo.digital describing such a light trap.

Hi Bill,

That's correct, I got that suggestion from a discussion with Roger.

Quote
I understand that the camera looks into the cone from the apex. What should one use for the base of the cone and what is the optimum angle for the cone?

I'm not sure if there is an optimal angle, because it also depends on how directional the light is that enters the cone, and it's dimensions. However, the angle should be narrower than 45 degrees (less is better), in other words the 'depth' must be at least half of the base diameter, but I'd go for at least as deep as it is wide, if it must remain compact.

It would help if the incident light cannot enter the cone at an angle of more than 45 degrees off-normal, by attaching a glossy black tube that functions as a light shade at the base where the light enters, and that would be at least as deep as its diameter. To keep that light shade more compact and more effective, one could use a short reversed cone with the tip cut off for letting the light in (see attachment).

Cheers,
Bart
Title: Re: Dynamic range of printing papers: up to about 7.5 stops?
Post by: Schewe on May 29, 2013, 04:51:01 am
So, e.g. with a D-max of 2.20 and a D-min of 0.05, we'd get 10^2.15 = 141, or as a ratio 141 : 1.


Pardon my lack of understanding (I don't do math all that well) so if one had a d-min of .0318 and a d-max of 2.2639, the difference would be 2.2321...so, in a calculator, how do you calculate 10 ^ (D-max - D-min)...using a calculator?
Title: Re: Dynamic range of printing papers: up to about 7.5 stops?
Post by: francois on May 29, 2013, 05:03:00 am
…how do you calculate 10 ^ (D-max - D-min)...using a calculator?

Since you're using a Mac, simply paste 10 ^ (2.20 - 0.05) in the spotlight field and you'll get the result.
Title: Re: Dynamic range of printing papers: up to about 7.5 stops?
Post by: Bart_van_der_Wolf on May 29, 2013, 05:28:15 am
Pardon my lack of understanding (I don't do math all that well) so if one had a d-min of .0318 and a d-max of 2.2639, the difference would be 2.2321...so, in a calculator, how do you calculate 10 ^ (D-max - D-min)...using a calculator?

Hi Jeff,

No problem, many hand (or smart phone) calculators have a 10x key (may need to press a shift key).
Just calculate the D-max - D-min difference and once you have the result press that 10x key.

When you have a computer at hand, the suggestion from Francois gives the result as well.

Cheers,
Bart
Title: Re: Dynamic range of human visual system
Post by: AlfSollund on May 29, 2013, 06:13:32 am
My personal vision is about 14 Ev static and 28 Ev Dynamic.

But my left eye is 10/10 and my right only 6/10 ;)

Thierry

Thanks. How did you measure this?
Title: Re: Dynamic range of human visual system
Post by: AlfSollund on May 29, 2013, 06:20:16 am
Take a look at this paper.

It argues the stead-state dynamic range of the visual system is 3.7 log units.

http://www.cs.bris.ac.uk/~reinhard/papers/kunkel_apgv2010.pdf

DAve

Thanks for sharing,

Great paper. But what it really show is that "under specific conditions" for the chosen set-up the steady-state dynamic range of the visual system is 3.7 log units. Please note "This display has a backlight consisting of individually modulated LEDs" and "Our results therefore indicate that current display technologies do not yet adequately match the human visual capabilities".

So I really would have loved to see a very different set-up without back-light monitor to measure the dynamic range of the human vision. But one cannot have all for free  8).
Title: Re: Dynamic range of human visual system
Post by: bjanes on May 29, 2013, 07:05:52 am
Thanks for sharing,

Great paper. But what it really show is that "under specific conditions" for the chosen set-up the steady-state dynamic range of the visual system is 3.7 log units. Please note "This display has a backlight consisting of individually modulated LEDs" and "Our results therefore indicate that current display technologies do not yet adequately match the human visual capabilities".

So I really would have loved to see a very different set-up without back-light monitor to measure the dynamic range of the human vision. But one cannot have all for free  8).

Yes, the paper is of interest. I see that the maximal luminance of the display is 3548 cd/m^2. This would drive the Digitaldog (Andrew Rodney) crazy, since he recommends that one should set the luminance of the monitor to about 140 cd/m^2 (Why are my prints too dark (http://www.luminous-landscape.com/tutorials/why_are_my_prints_too_dark.shtml)).

For softproofing prints one does not need a monitor with a very high contrast ratio, but the contrast ratio should be greater than that of the target print.

Best wishes,

Bill
Title: Re: Dynamic range of human visual system
Post by: hjulenissen on May 29, 2013, 08:13:00 am
Yes, the paper is of interest. I see that the maximal luminance of the display is 3548 cd/m^2. This would drive the Digitaldog (Andrew Rodney) crazy, since he recommends that one should set the luminance of the monitor to about 140 cd/m^2 (Why are my prints too dark (http://www.luminous-landscape.com/tutorials/why_are_my_prints_too_dark.shtml)).

For softproofing prints one does not need a monitor with a very high contrast ratio, but the contrast ratio should be greater than that of the target print.

Best wishes,

Bill
Soft-proofing is only one, specific usage of displays.

I see no point in holding back display technology to the limits of prints. Rather, it should strive for "realism", and those that needs to simulate print on screen should use profiles and calibration to accomplish good simulation.

If I look out of my window on a bright summer day, the visual appearance is a very bright image compared to the (probably) relatively darker inside of my room. Should a reproduced image (print, display or whatever) be capable of reproducing that sensation, or should its maximum brightness be normalized to the in-room lighting (such as reflective media)?

-h
Title: Re: Dynamic range of human visual system
Post by: digitaldog on May 29, 2013, 09:45:59 am
This would drive the Digitaldog (Andrew Rodney) crazy, since he recommends that one should set the luminance of the monitor to about 140 cd/m^2 (Why are my prints too dark (http://www.luminous-landscape.com/tutorials/why_are_my_prints_too_dark.shtml)).

Actually he doesn't say to set cd/m2 to any other setting than the value which produces a visual match to the print:

Quote
The correct value for luminance is one that produces a visual match. You can start at the so-called “recommended” value, which is often in the neighborhood of 120-140cd/m2. That value may need to be lower or higher. You will need to adjust the display luminance until you get that visual match.
Title: Re: Dynamic range of human visual system
Post by: BJL on May 29, 2013, 10:10:36 am
Bart,
    Thanks for the explanation of how the latest glossy papers can have albedo (diffuse reflectivity) as low as 1/200, about eight times lower than than any natural substance. (This also explains why matte papers have far less impressive Dmax.)

But glossy surfaces can reach a much higher D-max, because less light is scattered (also back to the observer) and more is reflected away from the observer.

Anyway, whatever the details it is clear that no print paper come close to matching the subject brightness range [SBR] that can often occur in natural scenes when there is significant variation in incident light levels. To which I will add that no part of a displayed image (on print or screen) gets close to matching the luminosity of the brightly lit parts of the outdoor scenes that produce those examples of high SBR, so any attempt to reproduce the contrast range of such a scene in a displayed image must have the maximum brightness far lower than it was in the actual scene, so that the shadows are also far darker, and so will disappear into the murk. Also, I am fairly sure that only the static contrast range of the eye is relevant to viewing displayed images, not the far greater dynamic range available when we move our eyes from sunlit to deeply shaded parts of a scene. This partly relates back to the fact that no part of a displayed image will be bright enough to cause our irisis to close down as much as they do in bright sunlight, or to cause the chemical adjustments to "lower ocular sensitivity".
Title: Re: Dynamic range of printing papers: up to about 7.5 stops?
Post by: BJL on May 29, 2013, 10:21:09 am
Since you're using a Mac, simply paste 10 ^ (2.20 - 0.05) in the spotlight field and you'll get the result.
Or put it into the Mac OS app called "Calculator", which is where Spotlight takes you.

Going even further OT, it is strange to me that some people use complicated software that costs actual money like Excel for tasks that I am used to handling with basic tools included with the OS.

By the way, is there a reliable source for a print paper Dmin value, like the Dmin=0.05 used here?
Title: Re: Dynamic range of printing papers: up to about 7.5 stops?
Post by: Bart_van_der_Wolf on May 29, 2013, 11:36:18 am
By the way, is there a reliable source for a print paper Dmin value, like the Dmin=0.05 used here?

Hi,

That would require a calibrated densitometer, or a spectrophotometer.

You could also use the data from e.g. Ernst Dinkla's SpectrumViz (http://www.pigment-print.com/spectralplots/spectrumviz_1.htm) application, and take an average reflection % of paper white and calculate:
Optical Density = - Log10(reflection%), e.g. 90% reflection is - Log10(0.90) = 0.046 or 4.6%.

Cheers,
Bart
Title: Re: Dynamic range of printing papers: up to about 7.5 stops?
Post by: bjanes on May 29, 2013, 12:14:22 pm
Or put it into the Mac OS app called "Calculator", which is where Spotlight takes you.

Going even further OT, it is strange to me that some people use complicated software that costs actual money like Excel for tasks that I am used to handling with basic tools included with the OS.

By the way, is there a reliable source for a print paper Dmin value, like the Dmin=0.05 used here?

I already have Excel and it is pinned to my Windows task bar for easy and rapid access. Since I have already paid for it, why not use it? BTW, if I enter 10^2.4 into google search, a calculator also pops up with the result. Windows also has a calculator with the needed function.

Bill
Title: Dynamic range of human visual system -- way OT
Post by: BJL on May 29, 2013, 12:56:35 pm
Bill, my comment was not a Mac vs Windows thing; I just used the Mac OS example because that is what had already been mentioned, and what I have in front of me at the moment.

It was a matter of my preference for using a simple, free tool that starts instantly and has an interface optimized for the simple task at hand over using a complex (and for many of us, costly) "kitchen sink" tool that opens more slowly (for those who do not have it constantly open) due to all the unneeded "plumbing". Sort of like when people use bloatware like Word to produce simple notes and memos that for me are more quickly and easily handled by nice little "free" tools like Mac's Textedit or Windows' Notepad(?). Or using the currently notorious PhotoShop when alternatives like Lightroom or Aperture or whatever deal with most photographers' needs better and cheaper.
Title: Re: Dynamic range of printing papers: up to about 7.5 stops?
Post by: Schewe on May 29, 2013, 01:30:00 pm
Since you're using a Mac, simply paste 10 ^ (2.20 - 0.05) in the spotlight field and you'll get the result.

That is way cool!!! Many thanks.
Title: Re: Dynamic range of human visual system
Post by: theguywitha645d on May 29, 2013, 04:36:52 pm
You do not need a log scale to calculate contrast ratios. Density is log based. If you want perceptual values, you should use L* or at least gamma 2.2, which can easily be done with Bruce Lindbloom's Companding Calculator.

You should recheck your texts, as I think your recalled values are way off as demonstrated in my previous post using Ilford photographic paper. Your outdoor scene contrast ratio is way off. Karl Lang is a serious guy who knows his stuff.

Bill

From Photographic Materials and Processes by Les Stroebel, John Compton Ira Current, and Todd Zakia (all former teachers, BTW), on page 359 clearly state the average scene has a luminance ratio of 160:1. They supply data where the White clouds come in at 1,114 candela/sq ft or 3,500 footlambert all the way down to the base of a tree in heavy shade at 12 and 38 respectively. I would say these authors know their stuff as well. Zakia in his book Photographic Sensitometry: The Study of Tone Reproduction on page 7 list the average scene has a luminance range of 160X.

It might be worth noting that scenes don't have density.
Title: Re: Dynamic range of human visual system
Post by: bjanes on May 29, 2013, 06:02:20 pm
From Photographic Materials and Processes by Les Stroebel, John Compton Ira Current, and Todd Zakia (all former teachers, BTW), on page 359 clearly state the average scene has a luminance ratio of 160:1. They supply data where the White clouds come in at 1,114 candela/sq ft or 3,500 footlambert all the way down to the base of a tree in heavy shade at 12 and 38 respectively. I would say these authors know their stuff as well. Zakia in his book Photographic Sensitometry: The Study of Tone Reproduction on page 7 list the average scene has a luminance range of 160X.

It might be worth noting that scenes don't have density.

I don't know about the average scene, but many scenes have a much higher luminance ratio, or else we wouldn't need to use HDR techniques with our D800s or your Pentax MF digital. 160:1 is only 7.2 stops. Look at the examples in Karl's treatise. You are correct about scenes not having density. I got side tracked from the discussion of the print.

Bill
Title: Re: Dynamic range of human visual system
Post by: hjulenissen on May 29, 2013, 06:45:17 pm
Does it make any sense to talk about "scene DR" without mentioning patch sizes? Are we talking about the brightest/darkest 1% of the scene? 0.00001%? Surely, many landscapes must contain some small birds holes in a tree off to one corner where the luminance is minimal compared to highlights or the sun?

-h
Title: Re: Dynamic range of human visual system
Post by: Jim Kasson on May 29, 2013, 06:55:24 pm
Does it make any sense to talk about "scene DR" without mentioning patch sizes? Are we talking about the brightest/darkest 1% of the scene? 0.00001%? Surely, many landscapes must contain some small birds holes in a tree off to one corner where the luminance is minimal compared to highlights or the sun?

Good point. How long is the coastline of England? Depends on the scale. Lens flare, diffraction, etc will fill in a lot of the small holes, but that's not a function of the scene itself. I guess the bottom scene-referred scale is on the order of the wavelength of blue light.

Jim
Title: Dynamic range of ... 160:1 (7.3 stops) for typical sunlit scene with shadows
Post by: BJL on May 29, 2013, 07:04:14 pm
From Photographic Materials and Processes by Les Stroebel, John Compton Ira Current, and Todd Zakia (all former teachers, BTW), on page 359 clearly state the average scene has a luminance ratio of 160:1.
That seems reasonable for a typical scene with clear sunlight and significant shadows:
- the reflectivity of natural materials varies over a range of about 20:1 (from 4% for fine charcoal and fresh asphalt to 80-90% for fresh snow) http://en.wikipedia.org/wiki/Albedo
and
- there is an EV range of about three stops from a typical scene in bright sunlight (EV15) to open shadows in a scene with clear sunlight (EV12) for another factor of 2^3 = 8  http://en.wikipedia.org/wiki/Exposure_value
together getting to 160:1.

The 100,000:1 extreme case mentioned elsewhere seems to require a variation in incident light of about 5,000:1, or 12 stops (12 EV).
Title: Re: Dynamic range of human visual system
Post by: hjulenissen on May 30, 2013, 05:19:16 am
Good point. How long is the coastline of England? Depends on the scale. Lens flare, diffraction, etc will fill in a lot of the small holes, but that's not a function of the scene itself. I guess the bottom scene-referred scale is on the order of the wavelength of blue light.

Jim
If you want to be really nerdy, what is the probability that a really dark and small spot will emit zero photons in our way within a given time-window, and what is the DR of X/0 ?:-)

But perhaps the discrete nature of light should be seen as "noise" in this case, what we really are interested in is the linear reflectance*illumination?

-h
Title: Re: Dynamic range of human visual system
Post by: theguywitha645d on May 30, 2013, 11:18:03 am
I don't know about the average scene, but many scenes have a much higher luminance ratio, or else we wouldn't need to use HDR techniques with our D800s or your Pentax MF digital.

I never use HDR techniques with either my D800 or Pentax 645D. The need for these techniques is not that common. I have found most folks that use HDR extensively either have trouble controlling their process or simply like the look.
Title: Re: Dynamic range of human visual system
Post by: bjanes on May 30, 2013, 11:27:13 am
I never use HDR techniques with either my D800 or Pentax 645D. The need for these techniques is not that common. I have found most folks that use HDR extensively either have trouble controlling their process or simply like the look.

I don't have the luxury of a 645D, but I too rarely feel the need for HDR with my D800e landscape images. Their DR is less than I had thought as shown by the preceding discussion. Thanks for your input. Erik Kaffer often states that the need for very high DR is overblown for most imaging and I would agree.

Bill
Title: Re: Dynamic range of human visual system
Post by: hjulenissen on May 30, 2013, 02:07:20 pm
I never use HDR techniques with either my D800 or Pentax 645D. The need for these techniques is not that common. I have found most folks that use HDR extensively either have trouble controlling their process or simply like the look.
I like to talk about these two separately:
1) High dynamic-range capture. Possible by exposure stacking or single shots from very good sensors
2) Tone-mapping to map HDR to LDR displays/print

HDR capture does not have a "look" to it. It is about recording the scene more accurately. If anything, the highlight clipping and shadow noise of regular sensors is a "look".

Tonemapping certainly can have a distinct "look", but that look should also be possible when processing good sensors in modern raw developers.

-h
Title: Re: Dynamic range of human visual system
Post by: mouse on May 30, 2013, 05:19:57 pm
Age of the human factors into the equation. I've read that human eyesight decreases in brightness by one f/stop every ten years.

My guess is that not a result of diminished sensitivity of the "sensor" but rather increased attenuation of light by the intervening elements.
Title: Re: Dynamic range of human visual system
Post by: BJL on May 30, 2013, 08:44:45 pm
My guess is that not a result of diminished sensitivity of the "sensor" but rather increased attenuation of light by the intervening elements.
Also, our irises lose its ability to open as far in low light, so we lose some of the low end of our dynamic range. (I use the first person, because I am experiencing this process, as I suspect are many of this forum's participants.)
Title: Re: Dynamic range of human visual system
Post by: 250swb on June 02, 2013, 04:57:29 pm
When it comes to 'reality' there is a divergence between scientific tests of what an eye, or a camera, records. And the difference is in what the brain remembers.

The accuracy of a photograph to represent the moment it was made has little to do with dynamic range of the eye, or the DR of the camera. While the eye has a vast DR, the memory for a scene is much less discerning. The memory remembers the bright light that made you squint, it remembers dark corners that made you peer, but it doesn't do it all in one go, because the eye is never adapted across a wide DR scene all in one go. So an accurate photograph, one that 'remembers' the scene as the eye saw it has a smaller dynamic range. Which is where modern digital cameras start to render reality as it appears to the camera, not the photographer. In a scene, a sunset perhaps, we shield the eyes, we look down, we look up, we don't take all the detail of a wide DR scene in the one hit, unlike the camera, so while we remember the glare, or the deep shadows as the light falls, it is done on separate levels. The camera renders them on one level, especially if some mild HDR is done. So it is a moot point if a very high DR camera is any good at representing a human connection to a scene because just like the high pitched sounds a dog can hear, we can't see what the camera can see even if the overall DR of the eye is as wide as the camera's.

The danger of course is that photographers chase the things technology can give and forget that their photographs are starting to bear no resemblance to what the viewer might expect. An extreme HDR photograph may elicit the question 'that can't be right can it?', while a clearly artistic rendering will be accepted for what it is, as will B&W, they are clearly not reality. But even on a lower subliminal level high DR of modern cameras makes the brain distrust the image if the intent of the image is the accurate recording of reality, and reality is entirely what the brain remembers or expects, not how a camera records it. But that is a bigger philosophical discussion.

Steve
Title: Re: Dynamic range of human visual system
Post by: Iliah on June 03, 2013, 01:04:51 pm

> 5 orders of magnitude static (16,6EV) and 9 orders adaptive (29,9EV)

1000 and 101 technically are of the same order of magnitude. If the result of division is less than 10, numbers are of the same order of magnitude. This may cause quite a difference in EV, like subtracting up to 3 stops from the result.

> For my monitor (I shot a black and white pattern) I found a difference between pure white and pure black of about 6,7EV

Have you tried to check the number using exposure meter, and measuring from the screen off to have reference, filled with just black, and filled with just white, to avoid additional flare?
Title: Re: Dynamic range of human visual system
Post by: joneil on June 04, 2013, 09:59:19 am
  An article form the UK Guardian I was interviewed for - over ten years ago now, that might be of interest to this topic:
http://www.guardian.co.uk/science/2001/feb/01/technology2

  Deals more with the range of human colour vision than the actual dynamic range of human vision, but I think it ties in, especailly since colour can influence how the "brain" sees brightness.

  The range of human vision varies greatly.