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Author Topic: Dynamic Range War  (Read 9044 times)

dtaylor

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Re: Dynamic Range War
« Reply #15 on: March 09, 2012, 05:36:34 PM »
If you look at DxoMark scores for dynamic range

Don't. Their scores are all over the place and do not concur with standard transmission step wedge tests or real world results. The fact that their DR values change between the screen and print reports suggests that they don't even know what DR is, as harsh as that may sound.

I've stayed out of the other thread but I got a good laugh out of the first couple pages. Nobody can tell you the 5D3's DR by shoving some IR samples into a piece of software. IR's samples are very good for other things, but not that. We won't know the 5D3's DR until someone performs a transmission step wedge test (DPR does this). Even then, digital DR is highly sensitive to the RAW converter used. I have a funny feeling, based on initial review of IR high ISO RAW and JPEG files, that our RAW converters will need an update to get the most out of the 5D3's sensor.

Quote
Right now, Nikon's full frame sensor from 2008 and crop sensor from 2010 beat Canon's best full frame sensor by a wide margin (almost 2 full stops).

It's about 1 stop (11 vs. 12, RAW, ACR maximized for DR).

Quote
I am not very knowledgeable about film photography, but my recollection is that, beyond the reported dynamic range, film is more forgiving than digital; with digital, if you blow a highlight, it is blown completely and utterly beyond recovery (your Spinal Tap brand amp won't go to 12, no matter how hard you try).  With film, since it is analogue, it is a more gradual process; it becomes progressively harder to distinguish between different highlight areas, but there is still some minuscule difference.

True, but print film quickly fell apart on the shadow side.

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Re: Dynamic Range War
« Reply #15 on: March 09, 2012, 05:36:34 PM »

awinphoto

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Re: Dynamic Range War
« Reply #16 on: March 09, 2012, 06:03:58 PM »
I think you got your print film and slide film mixed... Slide film typically had much wider DR than color negatives... So much so that many pro's who shot color would shoot slides, and then try reexposing the slides on negative film when needed to print. 

Slide film never had wider DR than color negative. Check the characteristic curves published by manufacturers. The best slide film I'm aware of, in terms of DR, was Astia at roughly 8 stops. That's where print films began.

The only reason slides were ever shot to negatives and then printed is because you can't directly print a slide with standard darkroom printing processes. The resulting print would be a negative of the slide.

While you technically are right in the essence that the negative had more range it all came down to the fact, in order to be seen in final output, any way you slice it, it had to be printed which paper only had 5-6 stops whereas slides had much more.  In the darkroom you could add contrast filter, dodge/burn/ etc but you were still limited in that regard... Also while negatives had more DR, they were not as vibrant, they had more grain, they were not as contrasty/punchy, and in the end, you were still limited by the paper, whether it was magazine, or photographic paper, it really boiled down to that. 

Color, low grain, contrast... these were the reasons many pro's chose to shoot with slides over film, and simply when you dealt with final output, projecting the slides just looked better than prints from negatives, especially color.  They could, if it came down to a client wanting to use their photos, expose slide to negative then to print, but they had the best of both worlds by going that route.  I loved film and that era, but in the end, I love digital more because I prefer to work in my office, rather than a dark, smelly dark room. 
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Re: Dynamic Range War
« Reply #17 on: March 09, 2012, 06:10:17 PM »
This image shows why we would like more dynamic range in a camera.  I took this on a bright day, and the camera exposed for the bright sky.  I then switched to manual exposure and exposed for the person, but kept the image as a example.

A higher dynamic range might let you get good detail from both the bright and the shadow areas, without enough dynamic range, you must chose the area you want to be able to show the detail.


Were you able to use Digital Photo Professional or another image processing tool to adjust the shadows, highlights and contrast in RAW? 

But I agree that you shouldn't have to take a HDR image in order to get what the human eye can see.  Either have a setting mode that will apply the settings to artificially make a HDR image, or have it automatically adjust the settings in such a way as to bring out the mid-darks, and to under expose the mid-brights.
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dtaylor

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Re: Dynamic Range War
« Reply #18 on: March 09, 2012, 06:31:28 PM »
While you technically are right in the essence that the negative had more range it all came down to the fact, in order to be seen in final output, any way you slice it, it had to be printed which paper only had 5-6 stops whereas slides had much more.

The capture range is what is at issue. It was easy to compress the detail from a negative into the DR of a print in the darkroom, and is trivial today with scanners and PS.

Slides never had much more. As I said, Astia hit 8 stops, but others were 5-6, maybe 7.

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Also while negatives had more DR, they were not as vibrant, they had more grain, they were not as contrasty/punchy,

All of this really depends on the emulsion. While probably nothing tops Velvia for contrast and saturation, I remember Kodak Supra 100 and 400 as very vibrant films. Grain also wasn't one sided. Slide films generally had less grain at ISO 50-100, but couldn't touch print films at 400 or higher.

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Re: Dynamic Range War
« Reply #19 on: March 09, 2012, 07:04:58 PM »
Fantastic thread! I always highly respect great teachers! DTaylor is obviously among the best. I enjoyed your comments like cool water in a hot sunny day: all these heated and merely preliminary discussions about DR from a IR RAW download should be stopped and discarded immediately.
I enjoyed your explanation, thank you, now some practical points:
Do you consider a particular RAW converter more suitable for DR "rescue"? You mentioned ACR optimized for DR, what is that?
Do you think the current RAW converters are incapable of delivering optimal results with the 5D3 sensor and need to be adjusted/updated? Is this offered in Canon's proprietary RAW converter?
We had a discussion about the "best" RAW converter and obviously no one addressed these points. Please, DTaylor, specify how do you convert your RAWs and why. Thank you again! 
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Re: Dynamic Range War
« Reply #20 on: March 29, 2012, 01:53:20 PM »
Monitors have more DR than prints. Some may even exceed sensors.

Sorry, but thats not true. Some extreme monitors might but generally if you look at a monitors specs it will show you differernt.
For example, I looked up one monitor and it shows a 1:20,000 (and you can find ones up to a 1:1,000,000), but in the specs it says 1:1000 typical.

The backlight intensity can vary which gives you the difference between the two specs. So for a movie that moves between bright and dark, you might get 1:20,000 difference between the darkest pixel in a dark scene and the brightest pixel in a bright scene. However for a stationary picture, your limited to the amount of filtering the foward layer can provide...in this case 1:1000.

For those who haven't left already, how many stops are in these ratios?  Remember a stop is a doubling of light and that 1 stop of DR represents 2x between the darkest and lighest. So we start with DR of 1 equal to 1:2 and we double each time....

Stops Ratio
1       1:2
2       1:4
3       1:8
4       1:16
5       1:32
6       1:64
7       1:128
8       1:256
9       1:512
10     1:1024   (typical for most monitors)
11     1:2048
12     1:4096
13     1:8192
14     1:16384
15     1:32767
16     1:65536
17     1:131072
18     1:262144
19     1:524288
20     1:1048576 (the largest "nonsense" number I have ever seen for a monitor)

I should make a special mention for LED monitors. Instead of one light source for the whole monitor, they have LEDs that can be individually adjusted brighter/darker.  As such, you actually might get those 1:1000000 ratios on the screen, but a single LED controls a group of pixels so a white pixel next to a black pixel would generally be back at that 1:1000 figure.

TMI?  ;D

keithfullermusic

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Re: Dynamic Range War
« Reply #21 on: March 29, 2012, 02:18:19 PM »
This image shows why we would like more dynamic range in a camera.  I took this on a bright day, and the camera exposed for the bright sky.  I then switched to manual exposure and exposed for the person, but kept the image as a example.

A higher dynamic range might let you get good detail from both the bright and the shadow areas, without enough dynamic range, you must chose the area you want to be able to show the detail.

Black and white film typically had very good dynamic range, and you routinely got good prints from a bit of under or over exposure.  Digital is not so forgiving, its because there is less dynamic range.

Most of the discussion involves how much range you can theoritically extract from a raw image, and is not necessarily related to the quality of the final image.




If DR was that high then they wouldn't make any money selling flashes!!!

Also, You can just use grad filters for things like this.  Granted, it wouldn't be ideal right here where the top half of the guy would be darker than the lower, but grad filters solve this problem with ease when taking landscape shots.  Polarizers also do a good job of darkening the sky and water more than other things, so that might help in situations like this.

I bet you could lighten the shadows in LR/Aperture and get tons of info back on the darker parts also.

Granted, more DR would be sweet, but there are some ways around it.
« Last Edit: March 29, 2012, 02:26:47 PM by keithfullermusic »
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Re: Dynamic Range War
« Reply #21 on: March 29, 2012, 02:18:19 PM »

helpful

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Re: Dynamic Range War
« Reply #22 on: March 29, 2012, 02:26:33 PM »
For the record, slide film has a smaller dynamic range than negative film.

However, it still held at least as much "data" as did negative film.

Therefore, there was much more detail in the image coming from a slide, but exposure latitude was not as forgiving. Blown highlights, and lost shadows were more likely with slide film. Overexposure in particular is much less of a problem with negative film, because there was a lot of headroom with negative film. Not so with slide film.

The way this compares to digital images is as follows:

Approximately the brightest 1/2 of the image data (i.e., the right side of the histogram) represents one stop. Therefore, the most image detail is in this area. Subtle variations between brightness are easily discernable.

The darkest 1/2 of the image data is divided up as if it was another image, like this:

* the brightest 1/2 of the remaining 1/2 of the image data (i.e., the upper half of the bottom half of the histogram) contains another stop of brightness data. There is slightly less detail, since not as much data is used to represent one stop of light.

The remaining quarter of the image data is divided up again, recursively:

* the brightest 1/2 of the remaining 1/4 of the image data contains another stop of brightness. There is significantly less detail, etc.

Let's assume that your image data is stored as 16 bits per pixel, and the primary part of your image is exposed at EV 16.

Then the top 8 bits contain a detailed view of the brightest one stop of the image from EV 16.0 to 16.9.
The  next 4 bits contain a moderately detailed view of the next brightest stop of the image from EV 15.0 to 15.9.
The next 2 bits contain a poorly detailed view of the next brightest stop of the image from EV 14.0 to 14.9.
The final 1 bit contains a very low detail view of the darkest stop of the image from EV 13.0 to 13.9.


This is how it works, simplified, with "linear gamma."

All modern cameras use non-linear gamma systems to expand the dynamic range of linear gamma from the maximum of four stops to many more stops of dynamic range.

But the principle is the same.

If you want to get the most detail from your images, then the major area of your image's histogram should be towards the right.

Try taking a photo of a subject with little dynamic range, like a a square foot in the middle of a field of green grass. If the image is underexposed, the histogram will make a narrow band towards the left side. The size of the band represents the detail recorded from the grass.
If the image is properly exposed, the band will be a little bit larger showing that more detail is being recorded in the upper area of the histogram which is more detailed because more bits are used to record each stop of light.
« Last Edit: March 29, 2012, 02:28:33 PM by helpful »
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Marsu42

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Re: Dynamic Range War
« Reply #23 on: March 29, 2012, 02:36:58 PM »
If you want to get the most detail from your images, then the major area of your image's histogram should be towards the right.

Thanks for pointing that out, I only discovered this fact after some try and error - maybe they should have put a  sentence like this in the manual :-p

neuroanatomist

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Re: Dynamic Range War
« Reply #24 on: March 29, 2012, 02:39:13 PM »
If you want to get the most detail from your images, then the major area of your image's histogram should be towards the right.


Thanks for pointing that out, I only discovered this fact after some try and error - maybe they should have put a  sentence like this in the manual :-p


The concept is termed ETTR.
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Marsu42

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Re: Dynamic Range War
« Reply #25 on: March 29, 2012, 02:43:53 PM »
The concept is termed ETTR.

While it might not make me seem like a pro (hey, I am not!): I didn't know about that, thanks again dr. neuro!

The only thing left for me to wonder when shooting at low light is if it's better to have a properly exposed histogram at higher iso or a histogram that leans to the left at lower iso. Using lr4 and its smart shadow recovery, I'm tending towards the latter with my aps-c sensor, because higher iso than 800 really ruins the picture while 1ev underexposure does not.

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Re: Dynamic Range War
« Reply #26 on: March 29, 2012, 02:58:46 PM »
The concept is termed ETTR.

While it might not make me seem like a pro (hey, I am not!): I didn't know about that, thanks again dr. neuro!

The only thing left for me to wonder when shooting at low light is if it's better to have a properly exposed histogram at higher iso or a histogram that leans to the left at lower iso. Using lr4 and its smart shadow recovery, I'm tending towards the latter with my aps-c sensor, because higher iso than 800 really ruins the picture while 1ev underexposure does not.


That is a question that there may never be a definitive answer for.

In my experience it depends on the camera. Some cameras whose high ISO modes are just "software enhanced" are better used at lower ISOs with slight underexposure, and then pushed on the comupter with software that is better designed and can increase the brightness without resulting in as much nosie as the in-camera "software-enhanced" ISO boosting.

For other cameras that really do have the ability to increase their light sensitivity, it is absolutely better to increase the ISO to get more bits of detail in the file, and then try to decrease noise later. Underexposing reduces the actual amount of data that is captured in the scene. So in an ideal world, you would get the proper exposure by increasing the ISO, and then reduce the nosie in post-processing, and your image would have higher quality than shooting underexposed and then boosting the ISO with software.

It all depends on whether the ISO level that you are shooting at is provided by the intrinsic analog/physics capabilities of the image sensor physics (in which case you should shoot at high ISO and reduce noise afterwards), or by the camera's image processing (in which case you should shoot at lower ISO and increase brightness afterwards).

Boosting ISO with software always reduces the amount of usable data in the image (which is why the Nikon D4 only has 6-8 bits of DR at ISO 200,000, because it is software boosted). So that is what you always want to avoid.
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TrumpetPower!

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Re: Dynamic Range War
« Reply #27 on: March 29, 2012, 03:00:16 PM »
I'd caution strongly against expose to the right and even bothering with thinking about linear encoding and the like. Even if that's still what's going on in the silicon, it's been ages since that sort of folk wisdom has had any practical application. Unless you've got a very specific, uncommon, awkward, and carefully-crafted workflow, you're just going to risk blowing your highlights and wind up with unnatural and weird-looking tonal and color shifts.

Expose properly, ideally with a well-calibrated incident meter.

If you've still got crushed shadows and blown highlights in critical areas of the image, you either need better light or you need to go to HDR -- and that's assuming that the crushed shadows and blown highlights are a problem in the first place...the kinds of photography where it's a problem but you can't either fix the light or use HDR are basically nonexistent.

Don't forget that there's a great deal more DR to be had in any well-exposed RAW image than what comes right out of the converter with the default settings. Much more, in fact, than any of the various numerical tests would lead you to believe. And, unless your printer is too big to fit on a tabletop, noise simply isn't a factor any more. Those whose printers take ink by the gallon have to worry about it, but they also generally know how to capture good exposures such that noise again doesn't become a problem or is at least manageable / acceptable.

And that's why the whole brouhaha over the wider dynamic range of the D800 over the 5DIII is meaningless. In the real world, you're never going to find yourself in a situation where the 5DIII has insufficient DR but the D800 is good enough. That minuscule set of scenes where it could theoretically apply still requires either better light or HDR for proper results, even if you've got the D800 in hand.

It's also why Canon went the better route this time 'round: the 5DIII's non-sensor qualities (AF, FPS, etc.) are significantly better than the D800's, and those qualities have the potential for significantly more improvements in image quality than just a few extra megapickles. At least, they do if you're shooting something other than dollar bills taped to brick walls....

Cheers,

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Re: Dynamic Range War
« Reply #27 on: March 29, 2012, 03:00:16 PM »

helpful

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Re: Dynamic Range War
« Reply #28 on: March 29, 2012, 03:01:21 PM »
If you want to get the most detail from your images, then the major area of your image's histogram should be towards the right.


Thanks for pointing that out, I only discovered this fact after some try and error - maybe they should have put a  sentence like this in the manual :-p


The concept is termed ETTR.


Great point, I would like to add a link a really cool article on the subject as well:

http://www.luminous-landscape.com/tutorials/expose-right.shtml

In summary,

"For Maximum S/N Ratio [i.e., image quality]

"The simple lesson to be learned from this is to bias your exposures so that the histogram is snugged up to the right, but not to the point that the highlights are blown. This can usually be seen by the flashing alert on most camera review screens. Just back off so that the flashing stops."

There are photos of the histograms in the article.

Note that for a dark subject, you still need the image to be darker than for a bright subject, so it is overly simplistic to say "always have the histogram snugged up to the right." But to get the most details out of all the data that is available in the light coming from the subject, that is the way.
« Last Edit: March 29, 2012, 03:04:31 PM by helpful »
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Aglet

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Re: Dynamic Range War
« Reply #29 on: March 29, 2012, 03:20:58 PM »
This image shows why we would like more dynamic range in a camera.  I took this on a bright day, and the camera exposed for the bright sky.  I then switched to manual exposure and exposed for the person, but kept the image as a example.

A higher dynamic range might let you get good detail from both the bright and the shadow areas, without enough dynamic range, you must chose the area you want to be able to show the detail.

Black and white film typically had very good dynamic range, and you routinely got good prints from a bit of under or over exposure.  Digital is not so forgiving, its because there is less dynamic range.

Most of the discussion involves how much range you can theoritically extract from a raw image, and is not necessarily related to the quality of the final image.




This image is a good example of how to make use of the full DR of a sensor - altho it hasn't yet been processed to do so for final ouput if one wanted to achieve that look.

You expose for the hilites so they're not blown.  Then you tone-curve adjust to lighten the dark areas.  There are numerous ways to do this but Adobe's FILL LIGHT is one of the simplest and most effective.

Where the DR limitations come in, shadows at low iso, is NOISE.
When you start to brighten those shadows you may also start to see more chroma noise show up in those areas.  If the noise is random it's more acceptable and easier to minimize its appearance.

If the noise has a pattern to it, banding, cross-hatching or similar, then it's very difficult to impossible to remove the appearance of this noise.

This is where the Canon vs Sony-Nikon sensor argument arrises.
One company's sensors have more pattern noise at low iso shadows than the other company's, thus limiting the ability to boost shadows and achieve an effective HDR image from one exposure.

Other than that, they all make pretty good cameras and each has their respective compromises.  you choose the one that works the way you need it to.


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Re: Dynamic Range War
« Reply #29 on: March 29, 2012, 03:20:58 PM »