HDR tutorial – Appendices

HDR tutorial – Appendices 2017-01-17T20:45:02+00:00

Note: You can also download this tutorial as a free PDF eBook here in case you prefer to print or read it offline.

Table of Contents

Appendices

APPENDIX A: BATCH PROCESSING

I hope that everything is fine and clear up to now but how do you process HDR photos when you end up with a few hundreds to a few thousands of photos after a photo shoot? Opening each of them in Photomatix Pro, making adjustments, saving and then applying final adjustments sounds like a tedious and very long task, especially if a lot of images are similar (eg. taken in the same area, during same sunset).

Also it is rather difficult do pick the best images. When you have single images (i.e. not bracketed ones) you can compare them and choose one or few which you’re going to process. But how to compare images when each of them is in fact built from 3, 5 or 7 photos? Should you compare underexposed images, normal exposure or maybe all images? But what if the single image you picked is fine but after creating HDR you notice ugly ghosting or strong misalignment? This would complicate process of surveying very much.

Yet another thing is doing HDR timelapse which would also require quite a lot of time to process. And all the images would need to be processed using exactly same settings.

Luckily, the solution to above problems is quite simple – use batch processing feature in Photomatix Pro. Batch processing allows you to process similar images all at once using same settings for all of them. Photomatix Pro has this feature built-in and as you will see in a minute it’s very powerful and flexible.

CHOOSING AND PREPARING PHOTOS

As mentioned above, all photos in the batch will be processed with the same settings, so you first need to select photos for processing. Generally I try to choose photos which are very similar to each other, have similar tones and light. Most of the time I create new folder in Lightroom (or Windows Explorer) and move all selected photos there.

Then I take one bracketed sequence from this folder and open it in Photomatix Pro, choose preset and make adjustments to it, then I save it as a new preset (with a name like Batch) which I will then use in batch processing. Why this is necessary? Batch processing doesn’t allow you to preview your adjustments (this is same way as batch processing in Photoshop CS for instance) so you need to know in advance what settings to use (if you can’t decide you can use several different presets for all images and then choose your favorites).

I then close Preview mode with the X button (there is no need to process a photo) and open Batch Bracketed.

BATCH GUI

You can open batch processing by selecting Automate -> Batch Processing from main menu (or use CTRL + B shortcut on Windows; CMD + B on Mac).

Following window will appear. It might look quite complex at first but it isn’t.

batch_bracketed
Elements of the GUI are described below:
  1. This is Source files section, where you can choose files to process. Clicking on any file in the list will show small preview of it to the right. There is also option to remove file from the list (Remove file button) and filter files by type (Filter by combo box). Additionally:
    1. If you want to process whole folder choose Folder and then click on the Select folder button and navigate to your folder.
    2. If you, however, prefer to process only specific files, choose Selection by individual files and then click on the Select files button and in the opened window select files you want to process.
    3. If you want to process photos in subfolders be sure to check Process subfolders checkbox as otherwise those photos won’t be processed.
  2. This section allows you to specify number of exposures each of the bracketed sequences has. If you used sequences with 3 bracketed shots choose 3. If 5, select 5. But what if you used different number of exposures for some sequences and different for other ones? In such case select Advanced selection option, click on the Options… button and in a new window select Automatically detect number of bracketed frames option.
  3. In the bottom-left corner there are output settings.
    1. First you have to specify output directory and you have two options here:
      1. Subfolder within Source FolderPhotomatix Pro will create new folder in your source directory and save the output images there. The folder will have name in form PhotomatixResultsXX where XX is a number. For instance if there is already PhotomatixResults01, Photomatix will save result files under PhotomatixResults02.
      2. Custom Locationchoose this option when you want to save your images to destination of your choice.
    2. Save results as option allows you to specify output file format (JPEG or TIFF) and in case of JPEG files, you can also set output quality (80 by default).
    3. Create 32-bit unprocessed merged file – when checked, this option instructs Photomatix to create and store 32-bit HDR file on disk so you can use it later to tone-map it in Photomatix again or use it in another program. Skip HDR processing instructs Photomatix to skip all of the processing apart from merging photos to HDR.
  4. This panel contains controls that allow you to select processing settings that will be used to tone-map and/or fuse your images.
    1. You can either use preset (built-in or custom) by selecting it from the list if Preset radio button is selected or
    2. Use custom settings (or multiple presets) by clicking on the Set button when Custom settings or multiple presets option is selected. After clicking on the Set… button you can select as many presets as you wish.
  5. Merge with section lets you to specify how the images will be pre-processed. Most of these settings correspond to the settings from the Merge to HDR Options window so I won’t cover them here again. There is even more options available after clicking on the More Merge Options… button.
  6. Finish with section lets you add final touches to your images by applying some contrast and sharpening them.
  7. These buttons control the batch process:
    1. Run – starts the batch,
    2. Close – close the batch window,
    3. Stop – cancels the batch processing. Note: this button becomes visible after clicking on the Run button.
  8. Below there is large text section – it’s a batch log. Generally speaking all messages will appear here. Most of them will be various pieces of information to let you know what’s going on but also errors will appear here. Errors might appear when Photomatix could not process images for some reason (eg. when it couldn’t find bracketed sequences).

RUNNING BATCH

This is very simple, just:
  1. Set settings as desired,
  2. Click Run button,
  3. Wait (or eat a dinner or in case you have thousands of shots to process – go for a walk) as it might take a while, especially if you’re processing a few thousand HDR images.

APPENDIX B: PHOTOMATIX PRO GUI TIPS & TRICKS

Regarding tone mapping or fusion settings:
  • Double clicking on the setting slider resets it to its defaults.
  • You can click on a value next to the slider to edit it by typing it – useful when you know exactly what to put there.
  • Using mouse wheel on the settings window will scroll it vertically.
  • With CTRL key pressed when mouse pointer is over a slider you can use mouse wheel to control the value. It’s very useful if you want to move it just slightly as this method permits for very small value changes (like 1 or 2 increments – what I mean is it’s very precise).
  • Using mouse wheel on the presets window will scroll it (horizontally or vertically depending on its orientation).
  • When a preset is selected (marked by a white border in the presets window) you can move to the previous preset by using Up or Left arrow keys. To move to the next one you can use Down or Right arrow keys. This way you can quickly go through available presets to compare the results
Regarding image (all types of previews and final image):
  • Using mouse wheel on the image will scroll it horizontally (when horizontal scrollbar is visible). You can also use mouse wheel on the image scrollbars to scroll horizontally or vertically.
  • Using mouse wheel on the image while CTRL key is pressed will zoom it
Other:
  • You can also use a number of shortcuts like CTRL+O to open file or CTRL+L to load bracketed set – make sure to study menu items (as shortcuts are listed right to them).
  • You can set orientation of the presets window in preferences. Just open Preferences – General Tab -> Orientation of Preset Thumbnails. I always have it in vertical orientation.

APPENDIX C: NUMBER OF EXPOSURES AND ITS INFLUENCE ON IMAGE QUALITY

Most tutorials about HDR photography recommend taking 3 photos with 1.5 or 2 EV spacing in most situations to cover whole dynamic range of the scene. Although it is true in the majority of cases, there are scenes when 3 photos with even 2 EV spacing won’t cover whole dynamic range of the scene.In this section I will try to show differences in the final image look based on the number of exposures taken: 3, 5 and 7. All photos were tone-mapped in Photomatix Pro 4.2.3 using the same settings. No further editing was done on any of them. Also I used different EV spacing on some of the shots to give you an idea how it affects image quality.Here is a photo tone-mapped from only 3 exposures at 1.5 EV spacing:

Note how much detail is lost in this shot both in shadows and highlights. The sky is faded out (and the sun is almost completely blown out) and the forest lacks contrast. It is a sign that whole dynamic range of the scene wasn’t covered.

So now let’s try with 3 photos taken at 3 EV spacing (there are some cameras, not many, which allow to do this in auto-bracketing mode):

Much better (there is some blue in the sky, the sun doesn’t seem to be completely blown out and we have some contrast in the forest too). However, the tonal gradations aren’t smooth really. Look at the clouds in the left for instance – they are pretty much one colour making the clouds look rather flat and boring. Clouds also lack a bit of detail.

So to fix this we instead take 5 exposures at 1.5 EV spacing, this would ensure smoother tonal gradations:

Now it starts to look good 🙂 Note how clouds look more 3-dimensional now due to some extra tonal gradations.

Finally let’s try with 7 exposures at 1.5 EV spacing:

In this case the difference is rather subtle. There is a bit more detail in the clouds and also some of the highlights around the sun were restored. Although the difference seems to be insignificant it really matters when this image is viewed in large size.

APPENDIX D: DEALING WITH HALO ARTIFACTS

Halo artifacts.

One of the nightmares of HDR photographers. They appear between regions of different luminosity and virtually ruin any photo. You might have great composition, light and colours but if you have halos in your photo – it won’t be considered good – rather poorly executed.

It might be that even when you followed all my steps above and used low settings for Strength there are still some ugly halo artifacts. They can appear especially in the sunrise/sunset scenes and after using some Photoshop filters (like eg. Topaz or even Curves adjustments layer).

What you will need is Photoshop. First open your image with halo artifacts:

At full size it doesn’t look very bad but hit CTRL + MINUS keys several times to see nasty halo artifacts. Ugh…

As you see highlights in the sky are a way too strong and also shadows are a way too deep. So the easiest thing to do would be to adjust both by using Curves adjustments layer.

First make sure to select sky only (eg. with Wand selection tool) as the halos are present only in it. Then add Curves adjustment layer.

For this image I used following settings:

Note I darkened highlights and brightened shadows a little bit. After that adjustment the image looks like this:

It’s slightly better but still far from good.

So what we will do is to manually Dodge & Burn the sky to get rid of too dark regions and too bright ones too. Fear not – this tool is very easy to do (and powerful too!) but I admit one has to get used to using it.

You can use Dodge and Burn tools from the Photoshop toolbox for this but they have one serious disadvantage – they both are destructive tools. I prefer editing my images in a non-destructive way so I do the following:

  1. Press CTRL + SHIFT + N (CMD + SHIFT + N on Mac) to create a new layer. In a dialog box that appears, change Mode to Soft Light and also check the box at the bottom to fill the new layer with neutral grey colour.
  2. Press Ok, to create the layer.
  3. With your new layer selected select Brush tool and change its Flow to around 2 – 3%. Also make sure your brush is soft.
  4. Paint over dark regions with White colour and over bright ones with Black. Using White colour has effect of brightening the image, while using Black – of darkening it. So when you use White on Shadows you brighten them up. Similarly when you use Black on Highlights you darken them.
  5. While painting make sure to zoom out from time to time because it might be easier to see halos at smaller magnification.

Here is the final result:

Although still not perfect, it now does look a lot better 🙂

For your reference, here is also the Dodge & Burn layer I used. Note that the brightest parts of the image were painted with black and darkest with white colour.

Appendix E: Quick HDR Tips

  1. Make sure that brightest photo of your bracketed sequence has shadows in midtones to avoid enhancing noise in the final tone-mapped image.
  2. When there are very bright light sources in the image (like lamps for instance) make sure to clip the whites a little bit in your HDR app – otherwise you will lose effect of glowing.
  3. When creating HDR panoramas, it’s better to merge same exposures to panoramas first (eg. 0 EV exposures to one panorama; +2 EV to another) and then merge them to HDR and tone-map/fuse. It will help you avoid some artificats.
  4. One of the best things I learnt about HDR and tone-mapping in the recent years is that it’s the beginning of the process of developing a photo, not the final step. Many people would like to throw their photo into Photomatix, process it and share on the net. However, making a good HDR photo requires much more work.
  5. No matter how you deal with ghosts remember about one thing. If you remove ghost for given subject, make sure to fix it also for subject’s reflection and/or shadow. It looks quite strange (and sort of funny!) when shadow has completely different shape than subject that casted it.
  6. If you aren’t sure how many bracketed photos to capture, take a few more. Otherwise you might end up with noisy shadows or blown out highlights.
  7. There is an easy way of taking right number of bracketed photos for given scene. Set your camera to Aperture priority mode and set Metering Mode to Spot Metering. Now aim your camera at brightest spot of the scene and note down shutter speed (let’s call it A). Do the same with darkest spot of your scene (and let’s call this shutter speed B). Now starting with shutter speed of A take a photo and then increase shutter speed by your chosen EV spacing (eg. 2.0 EV). Take photo again. Repeat until you take photo with shutter speed B and then you’re done – you captured required number of bracketed photos for that scene.
  8. If you aren’t sure what given slider in Photomatix Pro is doing, just hover it with your mouse pointer and you will see short but helpful description often containing tips on proper usage (like move it to the left for natural results).

Go back to advanced HDR techniques on previous page…