HDR Tutorial

After completing the review series on various HDR software programs and talking about how well each could create realistic and grunge/surrealistic results, I figured it might be appropriate to put together a more in depth tutorial on how the results were obtained as well as some of my own, personal, approaches to shooting and editing for HDR.

The tutorial will concentrate on using Photomatix from HDRSoft but the techniques discussed for using PM apply to other HDR software programs as well. The names of the individual tonemapping operators may be different but the functionalities are much the same.

Shooting

When it comes to the capturing of images in the field, how you do it is really up to you.  There are a few tips that can be helpful though.  You can never capture too wide a set of bracketed exposures, but you can capture too narrow a set.  You don’t need to capture every 1/3 or 1/2 stop.  A tripod is very important and very helpful but not an absolute necessity.  Just because your camera may be limited to, say, a 3 shot AEB bracket doesn’t mean you’re limited to a 3 shot bracket.  Shooting RAW is best, but not an absolute necessity.

Let’s take each one of these in turn and go a little deeper.

You can never capture too wide a set of bracketed exposures, but you can capture too narrow a set. Just because you capture 9 or 11 shots in a bracket doesn’t mean you have to use all of them in the HDR merge.  You can toss out ones that are too overexposed or too underexposed.  What’s “too” over- or underexposed?  Practically, you want your brightest image to have your deepest shadow exposed as a middle value and you want your darkest image to have your brightest highlight exposed as a middle value. This will give you some ‘wiggle room’ in your bracketed set and you can decide whether to use all of the shots or to throw out the lightest and darkest.  Using more shots than this won’t help in the merging process and it’ll just slow down the merge time.  If your darkest and brightest shots still have some overexposed highlights and/or underexposed shadows respectively (i.e., you bracketed too narrow) then you’ll end up with a merged HDR that can have some problems.  You can end up with higher levels of noise than you might otherwise want.  Since the HDR process accentuates all aspects of your source images, if you’ve got noisy source images, your merged HDR (and tonemapped LDR) will be noisier.  Part of the reason for this is that the software is trying to ‘make up’ detail where it doesn’t exist.  The result is just noise.  Similarly, if you’ve got highlight areas that don’t have enough detail, you’ll have overexposed areas in your resulting image.  Having some overexposed highlights can sometimes be fixed with additional editing as I outlined in my Advanced HDR Editing tutorial.  Noise is more problematic and harder to fix.

You don’t need to capture every 1/3 or 1/2 stop. I used to think that the more information I fed into the HDR program, the better my results would be.  Turns out not to be the case.  As long as you’ve got the full brightness range covered with proper bracketing, 1 stop or even 2 stop separations between images give enough information for the HDR software to do its thing.  Bracketing at smaller increments just takes up card space and causes the HDR software to take longer to create the merged HDR file.

A tripod is very important and very helpful but not an absolute necessity. Of course camera movement causes problems with alignment in merging the source images.  But if your camera has a high enough frame rate (i.e., 6 fps or higher) and you’re shooting in a situation where your shutter speeds are high enough to take advantage of that frame rate and high enough that there won’t be blur from camera movement then you can get away with shooting hand held.  Using a tripod is still better but you can get away with it.  Also, if you’re in a situation where you have some other form of solid support, you can use that rather than a tripod.  A bench, a shelf, a window ledge, anything like that can provide solid support.  This can also be beneficial in situations where tripods aren’t permitted, like in a museum.

Just because your camera may be limted to, say, a 3 shot AEB bracket doesn’t mean you’re limited to a 3 shot bracket. Many cameras – most cameras – aren’t really ideal for HDR.  Only a relative few on the market have capabilities for more than a 3 shot bracket.  The folks at HDRSoft maintain an extensive list of bracketing features by manufacturer/model.  If you want to research your next camera with HDR in mind, that list is a good resource.  You can still get more than 3 shots though.  Using a combination of AEB and exposure compensation, you can capture 2 brackets that get you a wider sequence.  For example, if you set your AEB to +/- 2 stops and dial in 2 stops of -ve exposure compensation, you’ll get -4, -2, 0.  If you then dial in 2 stops of +ve exposure compensation you’ll get +4, +2, 0.  Toss out one of the 0 images and you’ve got a 5 shot sequence with 8 stops of brightness.  You can also capture your bracket manually.  Meter your scene then calculate 3, 4, 5 stops away from that meter reading.  Put the camera in manual mode, set your aperture to what you metered at and dial in your shutter speed at either the top or bottom of the range you calculated.  Take a shot and manually adjust the shutter speed to the next level.  For example, if you metered at 1/200 and f8 and you want an 8 stop bracket, your slowest shutter speed will be 1/12 (4 stops from 1/200).  In manual mode, set f8 and 1/12, take the shot then adjust the shutter speed to 1/25, repeat till you get to 1/3200 (4 stops from 1/200).  Now, there are some things to keep in mind using this method.  You’re touching the camera between shots.  Not the best situation.  You do risk camera movement.  A solid tripod is a must if you’re going to use these methods.  Even a bench or shelf isn’t advisable because the chance of moving the camera between shots is pretty high.

Shooting RAW is best but not an absolute necessity. The benefits of shooting RAW are, by this point, well known.  The flexibility RAW gives in editing for single image shooting can play the same role when shooting for HDR.  If you have to adjust white balance or otherwise make tweaks to the source images before merging, RAW is better for that.  But it’s not a necessity.  Some cameras simply don’t capture in RAW.  Sometimes you may want to conserve card space for a long shoot.  When, for example, I’m shooting for an HDR timelapse sequence, I may shoot in JPEG for a couple reasons.  One, to conserve card space so I don’t have to stop and replace a card part way through a capture sequence.  Two, due to the moving nature of the timelapse sequence and the low resolution of even full HD, ultimate quality of the source images isn’t as important.  So shooting JPEG is fine, you just have to be aware of the limitations.  And because adjusting JPEGs is more difficult than RAW, you have to do a better job of getting WB right in camera.

Pre-Merge Editing

Editing before merging?  Really? Yes, really.  At least to some extent.  Nothing major.  There are essentially three things to look for and correct before sending the source images into the HDR cooker.  White balance.  Chromatic aberration.  Dust spots.

Due to the enhancing effects of HDR, both good and bad aspects of your source images will be enhanced in the HDR merge process.  That means colour casts caused by a WB that’s off, the colour fringing effects of CA and dust spots on the sensor or lens.  Of the three, spotting is probably the least egregious.  If you’re using ACR or Lightroom to adjust your RAW files you can do your spotting on one file then sync the settings to the other files in the sequence so you’re only doing the corrections once.  Other RAW converters may have similar functionality.  Some HDR applications have the ability to apply CA correction during the merge process.  I think this is still something that’s better done before merging.  Again, you can do it on one file then sync the adjustment to the others depending on the RAW converter you’re using.  White balance is, in my opinion, the most important adjustment to make ahead of time.  A WB that’s off before merging can create a very unpleasant colour cast in the resulting HDR file and even though most HDR software programs have a white balance or temperature adjustment, it’s not always effective and can leave an unwanted colour cast after tonemapping.  Taking care of it ahead of time can help.

Does making adjustments mean not using RAW files in the merge? Maybe.  If you’re using ACR in Photoshop then importing directly into Photomatix, for example, Photomatix won’t pick up the RAW adjustments so you need to convert your RAW files to TIFFs.  Photomatix works better with TIFF files anyway, so this is something you should be doing.  Photomatix contains a RAW conversion engine and will convert your RAW files to TIFFs if you feed it RAW source images.  The conversion engine in Lightroom or ACR is better and will give you a better result if you do the conversion yourself.  If you’re using the Photomatix plugin for Lightroom, the plugin converts your RAW files to TIFF as a part of the export process and does pick up any adjustments you made to the RAW files.  Similarly, HDR Pro in CS5 will read the XMP file connected with the RAW image and take into account any adjustments.  As will the new Nik HDR Efex Pro plugin.  For other HDR software, you’ll need to do some testing to see if RAW adjustments get picked up or whether you need to convert your RAW files to TIFFs.  The easiest way to do this is to make a large, really evident adjustment; like converting the RAWs to black & white, to see if the adjustments get picked up.  Once you know that, you’ll know how to adjust your workflow.

A fourth correction you can consider pre-merge is noise reduction.  If you’ve shot at a high ISO, your merged image is going to show the effects of high ISO noise and noise, as with other things, can be exaggerated in the merge process.  There are noise reduction options at the merge stage of some HDR programs and in the tonemapping stage of some but taking care of it beforehand will be better because the noise reduction processes in your RAW converters is better than what’s in the HDR software applications.

Merging

Once you’ve made your adjustments to the source images, you’re ready to begin merging and creating your HDR file.  The process to load source images is pretty simple so I’m not going to go through that.

Photomatix (and other applications) offer you several choices before beginning the merge.  A screen capture of the PM merge dialogue is below.

Photomatix Merge Screen (click for larger version)

Whether you choose to align is up to you.  If you’ve shot on a solid tripod or with other support you’re confident in you can uncheck this and speed up the merging process.  If you do choose to leave this checked, you’ve got two options.  Correcting Horizontal and Vertical shifts only corrects for that type of movement, it doesn’t correct for rotational movement.  Matching Features also corrects for rotational movement.  The Matching Features option would be more applicable to hand held shots.  I don’t bother with cropping the merged file.  Although it may not take much time, anything that will save time in the merge process is a good thing so I leave this unchecked.

Next is deghosting.  If you’ve got elements in your scene that were moving then you want to turn this option on.  This can apply to major items like people or cars.  It can also apply to small items like leaves or branches moving due to wind.  If you were shooting indoors and know there’s no movement in the source images, leave this turned off and speed up the merge time.  Deghosting processes have improved a lot but may still leave unwanted ghost elements or other artifacting.  If that’s the case, you’ll need to clean those up after tonemapping by using layer masks and one or more of your source images.  Photomatix offers two types of deghosting – Automatic and Semi-manual.  My advice is to leave it on Automatic if you’re going to use it at all.  The Semi-manual method takes you into another screen where you draw a selection around the area(s) you want deghosted.  As noted in my Preview of PM4 the semi-manual method doesn’t seem to work as well as the automatic and it’s incredibly slow.  If you’re doing batch processing, the semi-manual isn’t an option anyway.  Automatic is the way to go.  You’re offered two degrees of ghost detection, Normal and High.  The default is High and is where you’ll want to leave it in most cases.

If you’ve already applied noise reduction to the source images, there’s no need to apply it here.  Similarly, if you’ve already cleaned up any CA, there’s no need to turn this option on.

You’ve already made any white balance corrections in your pre-merge edits so leaving the WB at the default As Shot is the choice.  The Color Primaries sets your colour space for the source and merged image.  If you’re importing directly into PM, choose the colour space that you tagged your TIFFs converted from the RAW files with.  If you’re using the LR plugin, it will pick up the colour space you have set up as your conversion default.  If you’re using a software other than Photomatix, you’ll need to test to find out how it handles colour spaces.

Once you’ve made your choices, you can click OK and start the merge process.  If you select to show the intermediary 32 bit image when loading your source images, you can save the 32 bit file for future use after the merge is done.  If you don’t select t his option, you’ll go straight to the tonemapping stage and the 32 bit file is gone.  I like to save my 32 bit files so that I can come back to them in the future; either to reinterpret the tonemapping in the same software application, or to try them out in new/different software.

Tonemapping

Once the merge is done you can move to the tonemapping stage.  Before starting to tonemap, you can get some interesting information about your 32 bit file by going to View>HDR Histogram.  A capture of the information screen that pops up is below.  It shows you your histogram in 32 bit and down at the bottom it shows you the ‘Estimated Dynamic Range’.  This is actually a contrast ratio.  In simple terms, each power of 10 is about 3.3 x  N stops; where N is the power exponent.  So 10:1 is 3.3 stops, 100:1 is 6.6 stops, 1,000:1 is 9.9 stops and 1,000,000:1 is about 20 stops.

The screen capture below, for example, shows an Estimated Dynamic Range of just over 49,000:1.  This translates into about 15.6 f-stops of brightness.  Obviously more than a digital camera sensor can capture in a single shot.

Photomatix 32 bit histogram view (click for larger version)

That image information and histogram relate to the image below which is one of the sample images used throught the software review series.

Photomatix Merge/Tonemap Realistic. (click for larger version)

Once you’ve had a look at the image information if you want to, you can move on to the actual tonemapping.

While called by different names, tonemapping controls – or operators – come in two basic types:  Local; and Global.  Local operators are those that affect contrast at the micro level, working on individual pixel level differences in contrast.  Global operators, on the other hand, are those that affect the entire image as a whole.

Global operators are those like temperature, saturation, brightness.  Local operators are those that have names such as microcontrast, detail, smoothing, light smooting.  Some HDR software will label the various controls or group them by global and local but many don’t.

Since we’re using Photomatix for this tutorial, I’ll walk through the tonemapping controls available and discuss whether each is a local or global control.  Photomatix has two ‘modes’ to choose from.  You’ve got the true HDR and the tonemapping types are called Details Enhancer and Tone Compressor.  Photomatix also has an Exposure Fusion mode.  This doesn’t create a 32 bit image but rather, simply (well, not exactly simply, but simpler than the 32 bit version) cretes a low bit depth exposure blend using the source images.  Since this is an HDR tutorial, I’m not going to discuss the Exposure Fusion mode of Photomatix.

When you’re in the tonemapping screen, you should see a small histogram display.  This is very useful for controlling white and black point clipping (i.e., making sure you don’t have any) and in seeing the overall distribution of tones in your tonemapped image.  If the histogram isn’t visible, go to View>8 bit Histograms to activate it.  The histogram will update as you make adjustments with the different tonemapping controls.  You can view the overall luminance of the image or click on the tabs for the individual colour channels to see if any one channel is clipped.  Unfortunately, PM doesn’t have individual colour controls to drop the saturation of reds, greens or blues separately if one channel is clipped.  This would be a nice upgrade in a future version.

I’ll start with the Details Enhancer since that’s the one that seems to be most used.  In some cases I’ll include sample screen captures to show the effects of the adjustments.

Strength.  The Strength operator controls the intensity of the contrast adjustments at both a local and global level.  Moving the slider to the right increases the contrast adjustments and moving it to the left decreases the contrast adjustments.  It would be considered, as far as I’m concerned, a global operator.

Color Saturation.  This one’s pretty obvious.  It controls the intensity of colours in the image.  Moving to the right increases saturation and moving to the left decreases saturation.  This would be considered a global operator.

Luminosity.  Not quite the same as an exposure or Brightness adjustment, the Luminosity operator is skewed toward the shadow end of the histogram.  Moving the slider to the right will open up shadow areas  and moving it to the left will darken down shadow areas.  It does this while having less impact on highlight areas, although it will still affect those areas somewhat.  The two screen captures below show the effect of this control at the extremes.  On the left, Luminosity is at its max. and on the right Luminosity is at its min.  You can see that the midtone and shadow areas have been affected most and the highlight areas in the sky and clouds have been less affected.  This would still be considered a global operator.

Maximum Luminosity (click for larger version)

Minimum Luminosity (click for larger version)

Microcontrast.  Microcontrast is a local operator.  It determines the enhancement of contrast at the pixel/edge level.  Sliding to the right increases local contrast.  Sliding to the left reduces local contrast.  This is somewhat similar to the Unsharp Mask (or other sharpening methods) we’re familiar with and use in our image editing workflow.  More contrast at the pixel/edge level gives a sharper appearance.  Conversely, less contrast at the pixel/edge level gives a softer appearance.

Smoothing.  The Smoothing operator controls the gradation of contrast in the image.  It determines whether the transition in contrast is gradual or quick.  It can almost be considered to be a radius control.  Moving the control to the right applies a greater amount of contrast smoothing (higher radius) and spreads the contrast over a wider area.  Moving the control to the left applies a lesser amount of contrast smoothing (lower radius) and makes the contrast differences more abrupt.  Higher amounts of smoothing will tend to give a more natural look whereas lower amounts of smoothing will tend to give the more surreal/grunge look.  This smoothing control would be in the global bucket.

Smoothing in Photomatix comes in two types.  The default is a slider, like the other controls.  Light Mode is a series of 5 buttons which can be clicked for the different effects.  The two are different.  The slider is a less extreme application of contrast smoothing and may be the option to choose if you want a more natural look.  Light Mode offers a more extreme range of smoothing and while a natural look can be achieved at the High or Max settings, using the Mid, Low or Min settings are typically where you want to go if you’re trying for the more surreal/grunge/overprocessed look.

The four screenshots below show the differences in the minimum and maximum values of each Smoothing mode.  The first two show the slider at Max and Min.  The second two show Light Mode at Max and Min.

Smoothing Slider Max Value (click for larger version)

Smoothing Slider Min Value (click for larger version)

Smoothing Light Mode Max Value (click for larger version)

Smoothing Light Mode Min Value (click for larger version)

White Point/Black Point.  These controls set the white value and black value in the image.  Think of them as the white and black points on a Levels or Curves adjustment in Photoshop.  It’d be nice if there were an eyedropper to set these quickly, but there isn’t so we go with the sliders.  Moving the White Point slider to the right raises the white point, brightening highlights and adding contrast.  Moving the Black Point slider to the right lowers the black point, darkening shadows and adding contrast.  Moving these sliders also affects other brightness values which are raised or lowered relative to the new black and white points you’ve set.  Be careful not to set these too high or you’ll end up with overly clipped highlights and shadows which is what we’re doing all this work to avoid.

Gamma.  This is, effectively, the midpoint slider on a Levels or Curves adjustment.  Sliding it to the left darkens the middle values, increasing contrast.  Sliding it to the right brightens the middle values, decreasing contrast.

Together these three operators are the Levels or Curves control equivalent in Photomatix.  Some other HDR software applications give you a Levels or Curves control directly – which is actually my personal preference – Photomatix implements it with these three slider controls.  These are global operators.

Temperature.  The Temperature control is the white balance adjustment in Photomatix.  Moving it to the left cools the image and moving it to the right warms the image.  In many cases, a small adjustment is all that may be necessary unless you’re going for a more extreme, unreal effect.  Temperature is a global operator.

Saturation Highlights. This is a finer control of the saturation of just the highlight areas of the image.  It works in conjunction with the Color Saturation control above.  It uses the master Color Saturation setting and adjusts the highlight saturation up or down relative to the master setting.  It can be likened, somewhat, to the Vibrance adjustment in ACR/LR or the Vibrance adjustment in Photoshop.

Saturation Shadows.  Does the same thing for shadow areas as the Saturation Highlights does for highlight areas.

Micro-smoothing.  Micro-smoothing works on the local contrast adjustments.  Similar to the overall Smoothing control above, it smooths or spreads out the contrast enhancements at the pixel/edge level.  Higher amounts spread the contrast enhancement over a wider area and lower amounts concentrate the local contrast enhancements.  If you’re working for the more edge-defined, surreal look, keeping Micro-smoothing at a lower level (i.e., below the default level of 2) is where you want to be.  For a more natural look, raising the Micro-smoothing operator will help in that regard.  It works in an inverse relationship with the Microcontrast control.  Higher Microcontrast/Lower Micro-smoothing = more detail, more surreal look.  Lower Microcontrast/Higher Micro-smoothing =  less detailed, more natural look.  That’s, of course, all within reason.  Setting Microcontrast at the minimum and Micro-smoothing at the maximum will tend to give a very flat, uninteresting result.  Micro-smoothing can also help with noise reduction.  If, as a result of cranking up the local contrast you end up with a heavy exaggeration of noise in the image, increasing the Micro-smoothing can help tone the noise down.  At the expense of the more surreal look you may be going for, of course.

Highlights Smoothness/Shadows Smoothness/Shadows Clipping.  These two controls have a similar effect to the Micro-smoothing control but work only in the selected areas.  Highlights on the highlight/lighter areas of the image.  Shadows on the darker/shadow areas of the image.

If you’ve lost a bit too much contrast in your highlights (i.e., highlights are too dark/dull) you can bring some of that back by increasing the Highlights Smoothness.  Doing this will remove some of the tonal range compression you’ve applied with the rest of the tonemapping adjustments.  Can’t you do this with the White Point control?  Not really.  White Point is a global operator and will increase all luminance values relative to the new white point you set.  Highlights Smoothness is localised on the highlight areas of the image.

If you’ve tried to open your shadows a bit too much and increased noise in those areas, you can try to fix that somewhat by increasing the Shadows Smoothness.  If noise is really excessive in your shadows, increasing the Shadows Clipping will work to darken just the dark/shadow areas of the image and help control the appearance of noise in those areas.

That’s the Details Enhancer side of things.  As you can see, it includes both global and local tonemapping operators.  Now we’ll switch to the Tone Compressor tonemapping option.

White Point/Black Point/Temperature/Saturation.  These perform the same functions here as they do with the Details Enhancer option.

Brightness.  This can be considered as an exposure adjustment.  This operator affects the overall brightness or darkness of the image.  Moving to the right increases brightness (exposure) and moving to the left decreases brightness (exposure).  This is a global operator.

Tonal Range Compression.  TRC determines how much the overall tonal range of the source images is compressed.  Moving to the right compresses more and moving to the left compresses left.  As you move to the right, the highlight and shadow values are moved inward toward the midtones.  This will have the effect of reducing oveall image contrast.  As you move to the left, highlights and shadows are moved further away from the midtones thereby increasing the dynamic range in the image and increasing contrast.  TRC is a global operator.

Contrast Adaptation.  Contrast Adaptation is a bit of an odd adjustment to describe.  It impacts both contrast and colour.  Moving the slider to the right decreases contrast and intensifies colour.  Moving the slider to the left increases contrast and reduces colour intensity.  In affecting the colour intensity it has more impact on colour brightness than colour saturation.  Having the slider more to the left will give a more natural look.  This can be considered a global operator.

What do we see as the biggest difference between the two tonemapping options?  As noted above, Details Enhancer includes both global and local operators.  Tone Compressor only uses global operators.  What does this mean?  In general, it means that the results from the Tone Compressor option are going to have a more natural or realistic look than with Details Enhancer.  You can get an overly bright, flat contrast result with the Tone Compressor but you’re not going to get that extreme result with the really crunchy details that you can get with the Details Enhancer.

With all those descriptions out of the way, how does it all play out?  What do we do with it?

Obviously, you can move the sliders around to your heart’s content to get a result you’re happy with.  The latest version of Photomatix, v4, includes a preset preview bar with thumbnails when you open the tonemapping screen.  You can switch between to get a look at what each will do.  You can use one of the presets as the final result or tweak more after applying a preset.  There are presets for both the Details Enhancer and Tone Compressor.

What if you like part of the image with one set of tonemap adjustments but not the whole image?  Then we need to do a little more work.  And this is where, as I’ve noted in past commentaries on this site about HDR and tonemapping, the idea that the tonemapped image is really just the starting point and not the ending point comes into play.  Take a look at the image below.

High Detail Tonemapping (click for larger version)

I liked the more extreme look in the car but didn’t like it so much in the trees and cedar fronds on the ground.  What to do?  I went back and processed the image again with a lighter touch (below).

Lower detail tonemapping (click for larger version)

This version, obviously, is a bit darker, less ‘crunchy’ overall but particularly in the trees and ground.  But the car was too soft and lacking the punch that I wanted it to have.  What to do?

I loaded both images into Photoshop, copied the softer version as a new layer into the more detailed version and created a Hide All layer mask of the softer version.  For more on layer masks, you can check out my tutorial.  Then I begain painting with white using a soft brush at a low opacity on the layer mask to gradually revealing the softer tonemapped trees and ground through the more detailed version.  The shades of grey on the mask are show where I’ve revealed the softer version through the original.  When I had it where I wanted it, I then applied a High Pass Sharpening layer and a Curves adjustment layer that is clipped to the softer tonemapped layer so that the Curves adjustment affected just that layer.  On the Curves adjustment I took the higlights up slightly and brought the shadows down around a locked midpoint.  the slope of the upper part of the curve is quite shallow while the lower part of the curve is more aprupt.  The layer stack for the image and the curve adjustment are both shown below.

PS Layer Stack

Clipped Curve Adjustment

The end result is that I got both the car and background the way I wanted them.  The final image is below.  The car is now clearly the point of focus.  The background has been softened and darkened to take attention away from those areas and bring the viewer back to the car with all of its wonderful colour and rust and texture.

Dual Tonemapped, Layered Final Image (click for larger version)

I talked a bit about noise possibly being a problem.  This takes us back to the beginning of the post where I outlined shooting considerations.  What can also be impacted by not having a wide enough bracket of source images is the dreaded (well, dreaded for most, some include them on purpose) halo effect.  Halos can develop in situations where the local contrast is pushed to high and smoothing is kept very low.  Having too narrow a bracketed set of images can cause these halos to be exaggerated.  In the example below, I originally captured a 9 shot bracket (+/- 4).  This was enough to give me the entire dynamic range of the scene.  If I’d only captured 5 shots, I might have been in trouble.  I’ve merged and tonemapped the darkest 5 of the 9 to show what I’m talking about.

Insufficient Bracketing (click for larger version)

What’s happened?  You can see halos around the clouds and the parts of the trees that extend into the sky.  In the highlight areas, such as the area on the side of the tow truck with no paint, it’s grey rather than white or slightly off-white.  Noise is very evident in the sky.  Why?  Because there wasn’t enough information in the source images for the software to do a proper merge, it’s tried to create detail where it doesn’t actually exist.  By trying to bring up the brightness of the sky, noise is enhanced.  In trying to get the brightness of lighter areas correct, we have blobs of grey.  Halos are created because I’ve tried to push the local contrast and smoothing too far.  In the image using the full 9 bracketed set, I can push the tonemapping to these extremes and while the result will still be ugly, it won’t exhibit as much of the same negative results as this one.  The image below is the same tonemapping applied to the 9 shot bracket.  There’s still some haloing, but much less.  There isn’t the noise in the sky.  And while the area on the side of the truck still shows some grey, there’s also more detail.  What you’ll also see is that the 9 shot result has more contrast and the colours aren’t as whacked out (relatively speaking) because the software had more information to work with.

9 shot bracket tonemapped (click for larger version)

So that’s it.  That’s the end of my HDR tutorial.  If you click the link, you’ll be able to download 3 Details Enhancer presets you can use yourself.

Deco is a slightly surrealistic look that I created to evoke an Art Deco era graphic illustration look.  It can work well with architecture, particularly of that design style.  This was the basis for the interior shots of the train station in the Colour gallery.

Realistic is a natural result that can work well with a variety of image types.

Grunge Extreme is the grunge of grunge.  It outgrunges the existing Photomatix Grunge preset.  To borrow a phrase from Jeff Schewe (who, I think, borrowed it from someone else but I can’t remember from whom) it’s the ‘Make my image look like crap’ setting.  But, one man’s crap is another man’s beauty.

Comments

comments

Powered by Facebook Comments