Skies and high dynamic range images

[MalcolmL]

I have a long standing difficulity with the large smooth areas of skies - both cloudy and blue when it comes to tonal manipulation to attain a better tonal zoning in digital photographs.
This is a problem I have encountered both with HDR suites and also with the shadow and highlight sliders of standard photoeditors such as Adobe Photoshop Elements or Silkypix.
In attempting to bring down the highlights so I have some detail in the sky or even darken a sky,what starts out as a full spectrum of tonal gradation of gets squeezed down to perhaps a gamut of 6-12 tones with awfully pixelated demarcations bewteen each zone.

This often gives a semi- solarised type effect. I was advised to stop shooting io JPEG to avoid compression issues that might cause this, but even in RAWs converted to TIFFs I cannot resolve this issue.

This is now the ONLY issue I have personally yet to solve now in terms of image quality in digital files.
Should I just be exposing for the skies and lightening the shadows of is there somethong more fundamental I am missing ??

[Jack Varney]

Are your TIFFs 16 bit images?

[MalcolmL]

I have batch converted in XN view which I believe saves in 8 bit - I will need to check that when I get back to my home PC. Does 16 bit get round this issue ??
Maybe I should be doing my dynamic range adjustment in RAW and then saving as 16 bit TIFFS ??

Maybe exposing for the skies rather than averaging EV for the whole scene is the way because I doubt that the issue of limited gamut range arises in the shadow areas ?
Thanks

[Schewe]

Maybe I should be doing my dynamic range adjustment in RAW and then saving as 16 bit TIFFS ??

Ya think? Seriously, you need to get to the point where the raw files (not JPEGs) are as close as you can get them BEFORE processing the TIFF files and yes, 16 bit is a lot better for post processing than 8 bit.

[MalcolmL]

Thanks - sounds like good advice - will try that way.
malcolm

[ErikKaffehr]

Hi,

That can also depend on your monitor. Or you highlights being clipped. If you posted one of the raw files for download it would help.

One you convert to 8 bits you loose a lot of information which cannot be regained using 16 bit processing. One of the good reasons to shoot raw.

Best regards
Erik

I have a long standing difficulity with the large smooth areas of skies - both cloudy and blue when it comes to tonal manipulation to attain a better tonal zoning in digital photographs.
This is a problem I have encountered both with HDR suites and also with the shadow and highlight sliders of standard photoeditors such as Adobe Photoshop Elements or Silkypix.
In attempting to bring down the highlights so I have some detail in the sky or even darken a sky,what starts out as a full spectrum of tonal gradation of gets squeezed down to perhaps a gamut of 6-12 tones with awfully pixelated demarcations bewteen each zone.

This often gives a semi- solarised type effect. I was advised to stop shooting io JPEG to avoid compression issues that might cause this, but even in RAWs converted to TIFFs I cannot resolve this issue.

This is now the ONLY issue I have personally yet to solve now in terms of image quality in digital files.
Should I just be exposing for the skies and lightening the shadows of is there somethong more fundamental I am missing ??

[MalcolmL]

My TIFF files are all 24 bit. I checked
I have cracked this one. I edited the dynamic range of a RAW file in a RAW editor and converted to a TIFF. I then took the original RAW and converted to a 24 bit TIFF and gave it the same overall treatment. Attached are crops from the sky (I tweaked the contrast in the crops to magnify any aberrations). I have also included thumbs of the whole files.
Thanks for your help

[LKaven]

Working straight through in 16-bit is necessary if you're to preserve tonal gradations.  Absence of red-channel information is already a challenge.  But there is another factor in HDR to consider.

HDR involves supersampling a scene.  This process depends in most cases on the scene being static across the range of samples.  While blue sky gives the appearance of being a static field of blue, it is anything but.  You can mitigate this a bit by making a separate HDR for the sky, lower the strength, and adding some smoothing in Photomatix.  You would want to maintain a 16-bit workflow throughout.

[EricV]

My TIFF files are all 24 bit. I checked.

You do realize that 8-bit and 24-bit are the same thing?  So you are losing bit depth in the TIFF conversion.  If you saved from raw to 16-bit (48-bit counting 3x color) TIFF, there should be no problem.

[MalcolmL]

No I did not realise this at all.

I need to do some homework !

However by editing in RAW (see above) it seems that I have solved most of the issues. However this still leaves the issue of the final convertion to a TIFF which  really needs to be in 16 bit. I can print from RAW however using the Sony RAW editor. But other editors have features that Sony RAW does not
Malcolm

[ronkruger]

The biggest problem I found when switching from film/slides to digital is how it treats skies. There are a great number of software aproaches to combat this, but I haven't really been satisfied with any of them.
This site seems to be mostly about things one can do with computer and printing technology, with very little attention to actually taking pictures. But my approach is to get it right, or as close as possible, at time of capture.
This includes lens selection (some lenses treat skies better), use of filters (CPL and GND) and exposure manipulation. I'll expand upon these, if anyone is interested, but I doubt it.
From the computer play perspective, the best thing I've found is combining two widely exposed images with a simple cut-and-paste merger in Photoshop. This only works if you have a distant and flat horizon, with no trees or other items running vertically though both parts.
An example is posted here. The sky, by the way, was gray and almost flat. Exposer difference between rocks and sky were almost three stops.

[LKaven]

Also be sure to use the "linear" or "neutral" control to get the most linear capture you can for HDR purposes.  Using tone curves with images input HDR is a mess, and the data just doesn't shake out right.

[MalcolmL]

Thank you  !! - I can but agree. This is where I have too have thoughts - digital is great - image quality is FAR better than film (per unit area of sensor / film in terms of sharpness alone). But we all know there is more to it than sharpness. Tonal range has always been the issue despite the higher intrinsic dynamic range of good sensors (that is about 11-12 EV). It is pointless capturing that 11-12 EV unless it can be carried through post processing to print and this is where the current nemesis lies in digital. It is a thorny issue that has been conveniently ignored by the industry (mostly).
HDR was an attempt to address this  - but as has just been said  ""Using tone curves with images input HDR is a mess, and the data just doesn't shake out right"". I would never input tone modulated images into HDR. I am not sure if HDR fully addresses the issues and I need to do some in depth testing to see if HDR wins over simple tonal adjsutment in RAW exposed for the skies (see below)

So we are left with ""my approach is to get it right, or as close as possible, at time of capture"". Yes and yes !

BUT you say  ""This only works if you have a distant and flat horizon, with no trees or other items running vertically though both parts."" - well OK but that rather restricts what you can do does it not ??
Not really ideal at all is it (??)

My contention is this - in those shots where there is a lot of sky and we want to get that data into the final print we expose for the sky. The shadows areas will be dark but there seems to be little VISIBLE loss of image quality when shadows are lightened in the sliders. All this done in RAW of course. I am totally prepared to accept that there IS data loss when the shadows are lightened but its is not that visible. What counts is what the eye can see on thhe final print. Horribly banded skies DO show on the print - I have rejected many a print on that basis.

Then there is converting the image for other manipulations in standard photoeditors (I do not use full Photoshop although maybe I need to bite that bullet).

Saving as a 16 bit TIFF from RAW for a FF camera gives file sizes of about 135 megabytes - I tried that for the first time today. I have just bought a 2 terrbyte external drive to store these huge bloated files. Maybe we will all be buying 10 terabyte drives to store all this quality, or maybe we should all go back to large fomat film and pay 300 dollars a single drum scan (I personally never had the luxury of large format film).
One thing I feel pretty sure about is that the issue of tonal quality in digital photography has been to a large extent sidelined as its rather troublesome and uncomfortable.

[ErikKaffehr]

Hi,

You can alway try the graduated filter in Lightroom or Photoshop ACR. You could also checks this article:

http://echophoto.dnsalias.net/ekr/index.php/photoarticles/46-fixing-sky-with-luminosity-mask

Photoshop CS5 has an option for HDR tonemapping 16 bit images, I normally use local adjustment with default values.

Here are some of my HDR images: http://echophoto.smugmug.com/Special-methods/HDR/HDR/ but these are made from multiple exposures.

Best regards
Erik

Thank you  !! - I can but agree. This is where I have too have thoughts - digital is great - image quality is FAR better than film (per unit area of sensor / film in terms of sharpness alone). But we all know there is more to it than sharpness. Tonal range has always been the issue despite the higher intrinsic dynamic range of good sensors (that is about 11-12 EV). It is pointless capturing that 11-12 EV unless it can be carried through post processing to print and this is where the current nemesis lies in digital. It is a thorny issue that has been conveniently ignored by the industry (mostly).
HDR was an attempt to address this  - but as has just been said  ""Using tone curves with images input HDR is a mess, and the data just doesn't shake out right"". I would never input tone modulated images into HDR. I am not sure if HDR fully addresses the issues and I need to do some in depth testing to see if HDR wins over simple tonal adjsutment in RAW exposed for the skies (see below)

So we are left with ""my approach is to get it right, or as close as possible, at time of capture"". Yes and yes !

BUT you say  ""This only works if you have a distant and flat horizon, with no trees or other items running vertically though both parts."" - well OK but that rather restricts what you can do does it not ??
Not really ideal at all is it (??)

My contention is this - in those shots where there is a lot of sky and we want to get that data into the final print we expose for the sky. The shadows areas will be dark but there seems to be little VISIBLE loss of image quality when shadows are lightened in the sliders. All this done in RAW of course. I am totally prepared to accept that there IS data loss when the shadows are lightened but its is not that visible. What counts is what the eye can see on thhe final print. Horribly banded skies DO show on the print - I have rejected many a print on that basis.

Then there is converting the image for other manipulations in standard photoeditors (I do not use full Photoshop although maybe I need to bite that bullet).

Saving as a 16 bit TIFF from RAW for a FF camera gives file sizes of about 135 megabytes - I tried that for the first time today. I have just bought a 2 terrbyte external drive to store these huge bloated files. Maybe we will all be buying 10 terabyte drives to store all this quality, or maybe we should all go back to large fomat film and pay 300 dollars a single drum scan (I personally never had the luxury of large format film).
One thing I feel pretty sure about is that the issue of tonal quality in digital photography has been to a large extent sidelined as its rather troublesome and uncomfortable.

[LKaven]

[...] as has just been said  ""Using tone curves with images input HDR is a mess, and the data just doesn't shake out right"". I would never input tone modulated images into HDR. I am not sure if HDR fully addresses the issues and I need to do some in depth testing to see if HDR wins over simple tonal adjsutment in RAW exposed for the skies (see below)

So we are left with ""my approach is to get it right, or as close as possible, at time of capture"". Yes and yes !

So when you used ViewNX, you were using the "linear" picture control, and not the "standard" as I suggested?  You would want to do that.  Just double checking.  So you would go on to now make a set of 16-bit (x3=48) captures and take those into Photomatix. 

Then you can do several things in Photomatix.  There's exposure fusion and averaging, none of which require tonemapping.  There is HDR with the many possible applications of tonemapping, starting from the lightest strength.

But in the end, you might get away with a good camera and a full 14-bit capture as the starting point.

[Schewe]

One thing I feel pretty sure about is that the issue of tonal quality in digital photography has been to a large extent sidelined as its rather troublesome and uncomfortable.

Not at all...there are many, many threads here on LuLa about just this subject; controlling scene contrast within the dynamic range of a sensor and how to process raw files to optimize the final tone curve of the image for printing. It's definitely one of the top 5 topics...

You are indeed hamstrung by using the tool set you have...Camera Raw in Photoshop and Lightroom can easily do local tone and color corrections at the raw processing stage...there are also methods of bracketing and blending the multiple exposures to control the tonal range.

The other thing you need to understand is that if you under expose and image to maintain a "normal sky" you will be underexposing the capture and the shadows will indeed start blossoming with noise. Depending on the ISO is may or may not be exaggerated...but what you also don't seem to grasp is that there is far more data and detail in the brightest portions of raw captures...as long as you don't clip the highlights, you can easily tone them down in the raw processing. So you need to adjust how you expose digital to get the most from your sensor.

[ErikKaffehr]

Hi,

To fully utilize the sensor expose to the right using the histogram. Maximum exposure without clipping. Jeff Schewe had some nice demo on the issue somewhere.

The classic article is here: http://www.luminous-landscape.com/tutorials/expose-right.shtml

The reasoning may not be absolutely scientifically stringent but the suggestions are good,

Best regards
Erik

Not at all...there are many, many threads here on LuLa about just this subject; controlling scene contrast within the dynamic range of a sensor and how to process raw files to optimize the final tone curve of the image for printing. It's definitely one of the top 5 topics...

You are indeed hamstrung by using the tool set you have...Camera Raw in Photoshop and Lightroom can easily do local tone and color corrections at the raw processing stage...there are also methods of bracketing and blending the multiple exposures to control the tonal range.

The other thing you need to understand is that if you under expose and image to maintain a "normal sky" you will be underexposing the capture and the shadows will indeed start blossoming with noise. Depending on the ISO is may or may not be exaggerated...but what you also don't seem to grasp is that there is far more data and detail in the brightest portions of raw captures...as long as you don't clip the highlights, you can easily tone them down in the raw processing. So you need to adjust how you expose digital to get the most from your sensor.

[Schewe]

Jeff Schewe had some nice demo on the issue somewhere.

Here it is: Un-debunking ETTR

There's also an example of just how much image detail can be contained in the extreme highlights of an image...

[MalcolmL]

Thank you Schewe - . There are quite powerful controls in Sony RAW which include dynamic range, histogram adjustments and shadow / highlight adjusters I can use,  so perhaps I am not so hamstung as might be.
Howerver I am only just starting to grasp some of the basics of dynamic range physics and I clearly have my homework cut out for a while.
Malcolm

[Schewe]

Thank you Schewe - . There are quite powerful controls in Sony RAW which include dynamic range, histogram adjustments and shadow / highlight adjusters I can use,  so perhaps I am not so hamstung as might be.

Well, it doesn't have localized raw processing adjustments like ACR or LR...but you can certainly learn how to process multiple version of the raw file into different TIFF files for blending using layers...the problem there is that ideally you want to be using 16 bit and I think Element's 16 bit functionality is more limited than Photoshop's...I'm thinking you might want to look into upgrading to Photoshop if you want the optimal control over your images...