High Dynamic Range



Adobe's Photoshop was the first program to introduce a high dynamic range conversion way back in 2005 with CS2.

Since then High Dynamic Range images have been gaining more and more popularity and some of the images are absolutely stunning.

The HDR conversion is really quite straightforward and after it is done you may find that the application of some additional Photoshop adjustments is necessary.

This may include Levels, Curves, Hue and Saturation, Sharpening and maybe even a bit of local Dodge and Burn with a Soft Light Layer - or how about a black and white conversion or grayscale/duotone?

But first - Tone Mapping ...

Tone Mapping


One of the things that I didn't understand about high dynamic range conversions was tone mapping.  It just didn't make any sense to me so I did what any sane person with an internet connection would do - I typed Tone Mapping in the search bar and started reading the results.

What I found was a lot of bafflegab (at least it seemed that way to me) but there were a few great nuggets of information.

If tone mapping is confusing to you as well then here are a couple of definitions that may make some sense to you ...

  1. Tone mapping is a process that maps the colors in an HDR image to a normal image which decreases the dynamic range to what would be found in a normal image.

  2. Tone mapping compresses the tonal values of a high dynamic range image into a lower one. The result is an image with more visible details that would not be seen on an image with lower dynamic range.
What this means is that much more of the details of the HDR image become visible.

Toning an image will generally modify ...

  • Glow.
  • Tone and Detail.
  • Color.
in interesting, unique and wild ways ...

High Dynmaic Range Conversion - CS2 to CS4


Assuming you have three images that are one, two or three EV's apart this is how to do the conversion ...

File > Automate > Merge to HDR.  When the screen comes up click the Browse button to find the files you want to use or drop down the menu and choose Open Files if they are already open in Photoshop.

This is the screen that will appear with the names of the files in the Window ...


hdr photoshop 1


At the bottom of the screen is a place to put a check mark in Attempt to Automatically Align Source Images.  If there is the potential that some motion occurred when the images were taken then check the box.

When everything is set click OK.

It may take a few moments for the next screen to come up and it will depend on the speed of your computer.

The next screen includes thumbnails of the original images on the left, the resulting merge in the middle and a histogram with a slider to set the white point preview.


hdr photoshop


Just above the histogram is the Bit Depth selector.  It defaults to 32 Bit/Channel and when the drop down is selected are two additional selections for 16 Bits and 8 Bits.

When OK is selected without changing the Bit Depth you computer goes through the processing and the high dynamic range image pops up on your screen.

If either 16 Bit or 8 Bit is selected this is the screen that will appear and you can make some adjustments ...


hdr photoshop


The important  part of the dialogue is the Method drop down menu.  There are four choices in the menu ...

hdr local adaptionExposure and Gamma - allows you to manually adjust the brightness and contrast of the image with the sliders.

Highlight Compression - this adjustment compresses the highlight values in the HDR image so they fall within the luminance values range of the 8- or 16-bits-per-channel image file. There are no adjustments with this setting.
 
Equalize Histogram -Compresses the dynamic range of the high dynamic rage image while trying to preserve some contrast. There are no adjustments with this setting.

Local Adaptation - Adjusts the tonality of your high dynamic range image by adjusting the curve of the image.  This is the most useful adjustment of the bunch and it's very versatile.

Local Adaptation

When Local Adaptation is chosen the image will appear somewhat - well - weird 


hdr local adaption


but you have the ability to adjust the curves, the Radius and the Threshold ...


hdr-local adaption curves


Adjusting The Curve

The Curve for the high dynamic range image is adjusted like any curve dialogue - place some points on the line and move them up and down or left and right.

Comments about the curve ...

  • This curve modifies only the luminance of the image - there is no separate adjustment for the color channels.  The adjustments are applied to the whole image.
  • The first adjustment will probably be to bring the bottom of curve over to the start of the histogram.
  • A standard "S" curve will increase the contrast.
  • Putting a checkmark in the Corner box (bottom right) will smooth the transition between points on the curve.
  • Holding down the ALT key while in this dialogue will change the Cancel button to a Reset button if you need to go back to the beginning.  
  • Oh - and make sure that Preview is checked ...

Working with the Curve in Local Adaptation will probably take a lot of time so go slowly and make small adjustments.

Radius and Threshold

The Radius and Threshold adjustments will alter the degree of local contrast in the high dynamic range image.


high dynamic range radius threshold


The Radius controls the number of pixels that will be viewed as local.  A small number (like the default value of 16) will apply the adjustment to very tight regions which will produce hard edged enhancements in small regions.  This will enhance detail.

The range of the radius is between 1 and 250 pixels.  As mentioned a low value will enhance detail while a high value will look more natural but will lack details.

The way to approach this is to move the slider from one extreme to another, keeping an eye on the image.  Now slowly move the slider until you find a setting you like.

The Threshold sets the difference in luminance between adjacent pixels for them to be included or excluded from the current local region and the range is between 0.1 and 4.0.

When it is set too low then the image will be somewhat flat and setting it too high will make local details stand out unnaturally.

The best way to figure this out is to actually try it - so - grab three or more bracketed shots and run them through Merge to HDR in File > Automate, select Local Adaptation and have some fun with the Curve and the Radius/Threshold settings.

When you are satisfied click OK to complete the merge and then on to post processing ...


Post Processing

Creating a High Dynamic Range image from some bracketed shots can produce an amazing image but that is not the end of the story.

Like any image in Photoshop, the end result can be further modified with the normal Photoshop tools, such as ...

  • Curves
  • Levels
  • Hue and Saturation
  • Additional Dodge and Burn (which is, by itslef, a kind of High dynamic range conversion)
  • Sharpening, and maybe some neat effects from the ...
  • Filter Gallery

hdr photoshop cs2


This was done with Photoshop CS2.  The post processing was the addition of a Curves Adjustment Layer and a Hue and Saturation Adjustment Layer to bump up the colors.

The intent was to keep the HDR image as close to the original scene as possible.

For a more detailed look at Photoshop post processing of an HDR image - click here ...


High Dynmaic Range - CS5


Adobe has really stepped up with high dynamic range conversion in their newest release - CS5.

There are two High Dynamic Range modules in CS5 ...

  1. Merge to HDR Pro in the File > Automate menu, and
  2. HDR Toning in the Image > Adjustments menu.

Merge To HDR Pro

The first module, Merge to HDR Pro is an upgrade of the one in the previous versions of Photoshop and it includes a lot more adjustments and some great pre-sets.  It requires the typical bracketed shots and works best with RAW images from your digital camera.

This may be Adobe's answer to the stand-alone HDR conversion software packages that many digital editors believed did a better job at HDR conversion than the previous versions of Photoshop.

HDR Toning

This one is great because you can do a high dynamic range conversion on a single image.

Think about it - you have an old image that just isn't what it should be - run it through Image > Adjustments > HDR Toning and maybe the hidden gem will reveal itself!

Merge to HDR Pro

The new High Dynamic Range conversion in Photoshop CS5 starts out pretty much the same as previous versions.  Simply go to File > Automate > Merge to HDR Pro and either Browse to the images you want to use or select the files open in Photoshop (Add Open Files).

high dynamic range screen one
This is the screen that will come up ...

The selected files are listed in the box ...

By default a checkbox is entered in the box at the bottom of the screen - Attempt To Automatically Align Source Images.

Click OK to start the Merge process.



Depending on the speed of your computer you will be in for a short or maybe somewhat longer wait for the next screen where all of the magic will be happening.


high dynamic range screen two


This is where you will be doing all of the High Dynamic Range Toning (the panel on the right side of the screen).

The image thumbnails and the resultant image are also visible.  There is a little Zoom slider at the bottom of the resultant image screen if you want to zoom in closer.

Let's take a closer look at the Toning panel ...


Toning Panel

high dynamic range toning panelFrom top to bottom ...

Presets - Photoshop CS5 comes with a bunch of presets that you can apply (13 of them), choose one, click OK and you're done.

Remove Ghosts - when checked it attempts to remove any ghosts caused by moving objects.

Mode - the panel defaults to 16 Bit with Local Adaption.  The other options are still there but Local Adaptation is the most useful by far.

Edge Glow

Radius -  this slider controls the size of a Glow effect.

Strength - this slider controls the contrast of the Glow effect.

Tone and Detail

Gamma - adjusts the difference between highlights and shadows.

Exposure - the slider adjusts the overall image tone.

Detail - adjusts the amount of detail contrast.

Shadow - adjust the luminance of the shadow regions.

Highlights - adjusts the luminance of the the highlight regions.

Color

Vibrance - this slider adjusts the saturation while minimizing clipping.

Saturation - adjusts the color intensity.





Remove Ghosts

That small, little, unobtrusive checkbox (Remove Ghosts) at the top of the panel is really great. What it does is magically remove any ghosts that occur as a result of camera movement or movement in the scene.

high dynamic range ghosts high dynamic range no ghosts
Ghosts No Ghosts

Would you just look at that - this feature is amazing - should'a been called Ghost Busters ...

Back to Toning Panel




Back to the Panel

If you've ever used the previous versions of Merge to HDR in Photoshop will quickly realize how much more useful this Toning Panel is than the simple Local Adaption adjustments previously available.

At the bottom of the palette you can choose between Color and Curve.  Here are the two plaettes ...

high dynamic range color high dynamic range curves
Color Curves


With the Color panel you can adjust both the Vibrance and Saturation of the image and with the curves dialogue you can do anything that can be done with a normal curve dialogue.

All of the adjustments you do on the image in the panel will be immediately visible.  This is a procedure that can take a lot of time to complete so patience and a keen eye for what you want are required.

When everything is to your liking, click OK and Photoshop will process the HDR image.

Post Processing

The high dynamic range image can be saved as is or further processed with the normal Photoshop tools at your disposal -

  • Curves.
  • Levels.
  • Sharpening.
  • He and Saturation.
  • Filter Gallery for some cool effects.

High Dynamic Range On A Single Image

Photoshop did something good - they added an HDR Toning adjustment for single images. What this means is that you can dig through your old images - the ones you love - and do an HDR Toning on it.

It is easy to do - just select Image > Adjustments > HDR Toning and up will pop the panel to tone your image.

The toning palette is similar to the one found in the Merge to HDR Pro ...

HDR Toning Panel
high dynamic range HDR Toning panel Presets - Photoshop CS5 comes with a bunch of presets that you can apply (13 of them), click OK and you're done.

Method - the panel defaults to Local Adaption.  The other options are still there but Local Adaptation is the most useful by far.

Edge Glow

Radius -  this slider controls the size of a Glow effect.

Strength - this slider controls the contrast of the Glow effect.

Tone and Detail

Gamma - adjusts the difference between highlights and shadows.

Exposure - the slider adjusts the overall image tone.

Detail - adjusts the amount of detail contrast.

Shadow - adjust the luminance of the shadow regions.

Highlight - adjusts the luminance of the the highlight regions.

Color


Vibrance - this slider adjusts the saturation while minimizing clipping.

 Saturation - adjusts the color intensity.

A good way to start with HDR Toning is to choose a pre-set and then go from there.  The thing about the conversion is that it's all to your taste.

Here are a few single images that I converted ...

high dynamic range city original high dynamic range city toned
City Scape Original City Scape Toned


The toned image has more detail in the sky and more detail in the shadow area - which is typical of an High Dynamic Range image.


high dynamic range leafy wall original high dynamic range leafy wall toned
Leafy Wall Original Leafy Wall Toned


Perhaps a bit too green but ...


high dynamic range tower original high dynamic range tower toned
Tower Original Tower Toned


OK - so I went a bit wild with this one but it does give the idea of how powerful this HDR Toning adjustment really is - from mild to wild ...


high dynamic range sky original high dynamic range sky toned
Sky Original Sky Toned


The blue sky is better and there is some detail in the tall buildings to the right.


high dynamic range building original high dynamic range building toned
Building Original Building Toned


I like the looks of the toned building but it sure is beyond what would be considered "normal".

high dynamic range chess gamehigh dynamic range chess game
Chess Club OriginalChess Club Toned


HDR Toning can even be applied to a difficult image like the chess club.  The default setting only needed a bit of tweaking to get it right.

If you've got CS5 then give this conversion a go - it does a great job.

If you have an earlier version of Photoshop and you have a lot of great images that could use some tender lovin' care then maybe it's time to upgrade to CS5.



Page Links

Tone Mapping

CS2 to CS4 HDR Conversion

CS5 High Dynamic Range


HDR Toning a Single Image









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