HDR in Photoshop CS5

Blackhead Beach boulders, tone mapped HDR image from 3 exposures

HDR capabilities were available in Photoshop from the CS2 version. There were some limitations with the HDR creation processes, including the inability to deal with ghosting and the tone mapping options, especially for the local adaptation algorithm were limited. It was a useful tool for making natural looking tone mapped images with the global tone mapping algorithms but it was pretty much useless for easily creating that “HDR look” that has become popular over the last few years. That’s not to say it was a bad thing, just that it didn’t give the results a lot of people expected it to.

Adobe has included an extensive update to HDR capabilities in the recent release of Photoshop CS5. The most important are new controls under the local adaptation tone mapping algorithm. I done a quick review of the new HDR capabilities of Photoshop CS5 and made some comparisons with good old Photomatix.

Cost

Photoshop CS5 is simply unaffordable for a lot of hobbyist photographers. Unless you can take advantage of an education scheme discount you are looking at US$700 for Photoshop, this compares with US$99 for Photomatix. Although HDR is only a very small part of the overall functionality of CS5 a lot of people already have this functionality within a previous version of Photoshop or in their other image editing software. If you are looking at upgrading your image editing software Photoshop CS5 is the obvious choice, but to purchase solely for the HDR functionality would be crazy.

Processing speed

I was really surprised at how slow the HDR creation in Photoshop CS5 was. I’ve put together this table comparing the HDR creation processing times for Photomatix and Photoshop CS5 for 3 and 7 photo sequences in both RAW and TIFF formats.

Photomatix has a clear advantage. Even on my new MacBook Pro HDR creation with Photoshop feels incredibly slow. Slow enough that you could go grab a coffee and read the front page of the paper while it grinds away. I like instant gratification and Photomatix is the clear winner in the speed stakes.

Also timed the tone mapping speed using the local adaptation algorithm in each software. Again Photomatix is significantly faster. In both cases I selected ghost removal. Interestingly Photoshop CS5 takes longer to tone map a 7 photo HDR sequence than it does for a 3 photo HDR sequence. This knowledge, coupled with the option for ghost removal appearing on the tone mapping dialog suggests that Photoshop CS5 creates the final HDR image immediately before the tone mapping and not during the initial processing prior to the tone mapping dialog box opening.

Preview

Photoshop’s tone mapping preview appears to be pretty close, if not exactly, what you see is what you get. This is a real advantage compared to Photomatix that can change the image significantly between the tone mapping preview and final output image.

Alignment

Photoshop CS5 only includes the one option for image alignment. From my initial tests it appears to do a good job although in one of the tests there was a very slight (1 or 2 pixel) alignment error, although it is possibly an issue with chromatic aberration. I’ll do some more testing to see how it copes with hand held shots and other tricky situations.

200% crop of image aligned in Photoshop CS5

200% crop of image aligned in Photomatix

Ghost removal

Photoshop CS5 now includes ghost removal during HDR creation. There aren’t options for this setting as there are in Photomatix. I haven’t done any testing yet.

Noise

Where Photoshop CS5 really shines is the lack of noise in the tone mapped images. There are obvious differences between the images processed with Photoshop and Photomatix.

200% crop of image tone mapped in Photoshop CS5

200% crop of image tone mapped in Photomatix


Color

Photoshop CS5 does an excellent job at preserving the original color in the image. This one of my biggest complaints with Photomatix, it can really have a big effect on colors in image as you change the various tone mapping settings. This problems are largely avoided in Photoshop CS5’s tone mapping process.

File formats

Both Photomatix and Photoshop support the most common HDR file formats (Radiance RGBE and Open EXR). There’s little need to use anything else, although Photoshop does offer a couple of extra options.

Photoshop CS5

.psd Photoshop PSD

.hdr Radiance RGBE

.tif TIFF (floating point)

.exr OpenEXR

.psb Large Document Format

.pbm Portable Bitmap

Photomatix

.hdr Radiance RGBE

.tif TIFF (floating point)

.exr OpenEXR

Photomatix is limited to exporting files in 8 or 16 bit TIF or 8 bit JPG file formats. With Photoshop you can save your tone mapped image in any of the available file formats.

Photoshop CS5 Workflow

Photoshop CS5 has a few points of difference  compared to Photomatix. The HDR creation and tone mapping are integrated in order to save the HDR file it is necessary to save the HDR creation result as a 32 bit file and then re-open it and convert to a 16 or 8 bit file to initiate the tone mapping functionality. It would be nice to have the option to save the HDR file without having to go through these extra steps, especially after how long it takes to process in the first place!

Here’s a rundown of the work flow in Photoshop:

1. From Photoshop select File > Automate > Merge to HDR Pro. If you use Adobe Bridge or Lightroom it is also possible to export photos to the HDR processor directly from these applications.

2. In the dialog box browse to the files you want to create and HDR image from (you can select specific files or a whole folder containing just the images you want to process)

3. At this point you can check the box Attempt to Automatically Align Source Images. Use this settting if there is likely to be any alignment problems due to hand holding a wobbly tripod.

4. Press Ok

5. If the images don’t have exposure meta data you will now have the option of adding it.

6. Photoshop will now grind away merging your images into an HDR file.

7. Finally another dialog box will open showing a preview of the tone mapped file and thumbnails of the original photos below. On the right hand side you will find the file export and tone mapping options.

8. Start by selecting a bit depth for the final image

9. If you want to save the HDR file select 32 bit and press Ok. Once you have selected 32 bit you will note that a histogram and white point slider appear on the screen. Moving the white point slider only affects the preview image and has no effect on the image data in the HDR file.

10. If you want create a tone mapped image immediately select either 8 or 16 bit from the drop down list.

11. Then select one of the 4 tone mapping options and adjust the settings to your liking.

12. One last option is ghost removal. Only use this if you had moving objects such as people, cars, animals or vegetation in your image. Photoshop will do it’s best to identify the moving objects in each image and remove them from the final HDR file. You will note that in the thumbnails one of the images will have a green line around it. This represents the image with the best tonal balance. This is called the base image and moving objects found in other images but not in this one will be removed. In some situations it maybe necessary to change the base image to improve the ghost removal results. To do this just click on the thumbnail that you want to select.

13. After adjusting the settings press Ok.

14. For Mac users there seems to be a little bug with this dialog box that prevents the Ok and Cancel buttons from been shown at the bottom. You can get around this by using keyboard strokes instead (2 presses for Ok)

Tone mapping a 32 bit image

If you save a 32 bit image as one of the previous steps you can go back and tone map this at any stage. Simply open the image and then go to Image > Mode > 16 Bits/Channel or 8 Bits/Channel. The tone mapping dialog box will then open and you can make the required adjustments before saving the final tone mapped file.

Saving settings

Photoshop CS5 allows you to save the cameras response curve so that it can be applied to other HDR image sequences. The response curve is the equation that the camera users to convert actual light values to pixel tonal values. To save a response curve simply select the response curve menu from in the top right corner of the dialog box. From this menu you can also load an existing response curve.

Comparison with Photomatix workflow

In some ways the Photomatix workflow is a little simpler and more logical. The HDR creation is clearly separated from the tone mapping process. It’s a minor point, but it might take a little getting used to. I won’t go into detail with the Photomatix workflow because there are plenty of tutorials available on the web already.

Tone mapping in Photoshop CS5

Photoshop offers 4 different tone mapping methods. Perhaps the most useful is local adaptation, which is the equivalent of the details enhancer in Photomatix.

The table below contains a run down on each of the tone mapping options available in Photoshop.

Probably the most useful tone mapping algorithm in Photoshop is local adaptation. Previously only two options were available (radius and threshold), but now there’s a comprehensive range of options. The names are slightly different to what you find in Photomatix or other software and the specific algorithm and parameters it used are also likely to be different but ultimately similar results to Photomatix can be obtained. Here’s a run down of the local adaptation options in Photoshop.

The following images show the effect of varying some of the key settings described above.

Default settings, Photoshop select default settings based on the image properties.

Increase Strength to 4 (maximum). Increases detail and but no other apparent changes. Changing the Radius setting has little or no effect when Strength is at the minimum.

Increasing the Strength to 1 and the Radius to 50 pixels, gives a slightly painterly look and increases local contrast.

Increasing the Strength to 4 whilst leaving the Radius at 50 pixels increases the global contrast and introduces some halo effects at the transition between bright and dark objects. The size of the halos is related to the Radius setting (small halos with smaller Radius setting).

Increasing the Radius even more increases the global contrast and reduces any halo effects.

For the next few images I have left the Radius at 100 pixels and the Strength at 1. Decreasing the Gamma to 0.5 decreases the overall contrast in the image, compressing the tonal range, but at the same time preserving local contrast.

Decreasing the Gamma to 2 increases the overall image contrast.

Increasing the Detail setting to 250% increases the local contrast adding punch and bring back some of the perceived tonal range that the HDR process removes.

Decreasing the Detail setting to 30% reduces local contrast creating a flat looking image

As you can see there’s a lot of flexibility in the Local Adaptation tone mapping settings. The controls have more of a subtle effect that those in Photomatix and it seems that some of the more crazy “HDR look” settings that are possible in Photomatix might not be achievable in Photoshop CS5 – perhaps that is a good thing!

Results

I’ve processed a few different sequences of images to make some initial comparisons between Photoshop CS5 and Photomatix. There are many different ways of making these sorts of comparisons so to simplify things I decided to try and produce, as closely as possible, a tone mapped result from each software that was identical. This gives some indication of the strengths and weaknesses of each image and the style of HDR photography you might find each software useful for. As I do more experimenting with Photoshop CS5 I will post some other examples that explore different aspects of each software’s differences.

Example 1

This is an HDR created from 9 exposures at 1 stop intervals. Photomatix has created the better image here I think with a better balance between the sky and building exposure.

Tone mapped in Photoshop CS5

Tone mapped in Photomatix

Example 2

There’s a huge dynamic range in this scene. Photoshop has balanced the exposure better in the foreground area without the localized exposure variations that the Photomatix version has.

Tone mapped in Photoshop CS5

Tone mapped in Photomatix

Example 3

The following example is an HDR sequence from 7 exposures at 1 stop interval. Both Photoshop and Photomatix did a great job of the tone mapping. Possibly the Photomatix version has a little more visual interest in the grass areas but either image could easily be edited to look more like the other with some simple curve adjustments and maybe localized exposure balancing.


Tone mapped in Photoshop CS5

Tone mapped in Photomatix

Example 4

With this example I thought I would try and make a really ugly “HDR look” image just to see how far each package can be abused. Photoshop CS5 certainly produces more natural looking images and I guess for that reason might not suit people looking for that crazy “HDR look”

Tone mapped in Photoshop CS5

Tone mapped in Photomatix

Conclusion

Photoshop CS5 seems to excel at making natural looking, noiseless tone mapped images. Although Photomatix can often produce very similar results they will generally contain more noise or other artifacts. Vice versa, Photomatix is still the clear choice for easily producing “HDR look” in your photos.

I wouldn’t recommend buying Photoshop CS5 for its HDR capabilities alone, but if you need to upgrade your image editing software it is the natural choice.

Personally I think I will be using a combination of the Photomatix and Photoshop CS5 for HDR creation and tone mapping in the future. Each has its strengths and weaknesses. My biggest criticisms of Photoshop CS5 is the incredibly slow processing speed (although that might be the sacrifice for noiseless HDR images!) and the lack of a logical work flow for saving HDR images.

You must be logged in to post a comment.