A Mr. Richard Fader of Fort Lynn, New Jersey writes and says, “Dear Roseanna Roseannadanna, What the heck is this HDR stuff I keep hearing about?”
Well, HDR stands for High Dynamic Range, a photography technique that allows you to capture both brightly lit and deep shadows within a single finished image. Think of it this way. You are standing inside your beautiful living room and want to take a picture of it as well as the view afforded through the bay window. At the most basic level, you are either left with a blown out landscape view and properly exposed interior or vice versa.
With HDR, you can capture both. But it does take a bit of learning how to shoot the scene. I wanted to write this quick lesson for those that are curious and may want to give this a shot. This “tutorial” is meant to allow you a starting point for capturing proper images in preparation for the post-processing of an HDR photograph.
First, the equipment (bare essentials):
1. Of course, your camera (one that allows for manual exposure)
2. A remote cable release
3. A tripod.
Let me preface this also that what I will be discussing is digital photography. While you can also use film, it would require scanning the images and probably providing exposure information to the program during post-processing.
Why do you call this equipment the “bare essentials”? I say that because you can probably get much deeper into the process, such as using a light meter to determine the varying exposure necessities. This is intended to be a basic tutorial.
So, if you have a tripod, why do you need a cable release? I have found that a tripod doesn’t necessarily mean your camera is perfectly stable. In that you are attempting to capture the exact copy of a scene, any camera shake may just destroy the whole sequence during post-processing. I use a pro Bogen set up and just by pushing the shutter button, get plenty of shake, especially when using a longer lens.
So it is imperative that you eliminate any and all movement of the camera, however slight. When using your buttons/dial to change your exposure values during the sequence, make sure you allow your camera to stabilize from any shake before depressing the shutter.
Okay, so now what? Well, the shot itself. First, what is the goal of your HDR shoot? Do you have a darkened interior through a window or doorway that you want to expose for? Or are you inside but want to capture both interior and a landscape? Or are you trying to capture a landscape that varies in light from bright areas to deep shadows with a setting sun?
Keep in mind you will need at least two different exposure values (Ev). But I find the more the merrier. I would say a minimum of three instead of two. Oftentimes, I use a minimum of 5. That would include +/-2, +/-1 and the mid-range shot. So in essence I would be shooting 5 different photographs of the same scene.
The whole goal of this technique is to capture detail in varying light. If you remember that rule, you will come away with a wonderfully exposed finished product. So, if the scene is stabilized (more on that later), why not use a full range of stops at 1/3rd instead of stopping up/down at full stop increments?
Next, you’ll need to remember that if you are in an area where the majority of your scene is bright (or dark), your on-board meter may be giving you a false impression of needed exposure values. So don’t merely think that you can on-board meter for a scene and just change your Ev based on that. This is another important thing to remember and be cognizant of while shooting.
Let’s say you have a dimly lit interior and only a fraction of the shot is a brightly lit area, such as my shot seen here: http://www.usefilm.com/Image.asp?ID=1375986
I was shooting this at an ISO of 100, f 32. The mid-range photograph had a shutter speed of 1/3 second. Since the meter was averaging between light and dark, this left me with a blown out landscape and a dimly lit room. So I bracketed my exposures by 5 full f-stops on either side of the normal exposure. With the underexposure f-stops, I was able to darken the landscape. With the overexposed f-stops, I was able to lighten the interior of the room.
But by understanding that the on-board meter is using an average, I decided not to leave it to chance that Ev’s of merely 1 or 2 f-stops would be adequate. So I exposed for 5 full stops on either side of the normal exposure. This later allowed for what I felt was a good finished product.
Of course, some may disagree with me and have. But I am learning this technique as well and I do so by visualizing my goal, practicing the technique and experimenting. Keep that in mind while shooting for an HDR processed photo. No sense getting back to your computer and finding out you should have bracketed just a little bit more.
And, in the processing of that finished product, remember, you can always drop out some of the bracketed exposure shots and see what happens. Digital is cheap, taking 20 shots of the same thing over and over again isn’t going to bankrupt you. The above noted photo, for instance, was the result of 11 different bracketed shots.
And what did I mean about “stabilized scene”? Remember, you are shooting multiple exposures of the same thing. So still-life subjects are most imperative. Moving objects, such as a horse, person, car, etc are going to be in different positions as you shoot and, when processed, are going to show that motion. Unless you are specifically after that effect, make sure you choose non-moving subjects.
Also in that regard, you are going to want to be cognizant of moving light. If you have too much of a light change during your photography, your results may be undesirable. So you want to make sure that once you have begun taking your sequence, you follow through with pretty rapid shots. Learn your camera and what you need to do to change the exposure levels. I know on my Canon 30D, three clicks on the wheel will drop me down (or up) 1 f-stop. But don’t forget to let your camera “settle” from the shake of changing settings.
Now that you have your shot and have a good grasp on the theory and technique, what next? The post-processing is next of course.
As far as I know, the only available software program for HDR is Photomatix. Please correct me if I am wrong. It is, however, what I use. It retails for $99 US but you can also find on-line coupons for 15% off bring the cost down to about $84. You can trial-use the program but it leaves watermarks on your photograph. It was worth it to me just to buy it.
Photomatix comes with both a quick tutorial and an Adobe Users Manual. So far, I haven’t had time to go through the users manual. The quick tutorial was enough to get me started and to start experimenting.
First you need to “generate” your image by choosing the files that you shot using the top menu under “HDR”. I have learned that it is much easier on your brain if, when shooting, you always start with the most underexposed (or overexposed) shot of the sequence. This way, when reviewing the thumbnails of the sequential shots in your file browser, you can easily identify which series represents the particular photograph you want to process. You would simply see them in exposure order and be able to select them for generating much easier than opening each file and reading EXIF data or trying to compare a slight camera position change from one series to another.
And, when you generate the sequential photos in Photomatix, you select file names instead of thumbnails. So having them in some easily identifiable order in your file browser, you will find, is going to be very helpful.
Believe me, if you have shot the first sequence of shots beginning with the underexposed and finishing with the overexposed and then gone on to the next series but start with the overexposed and work toward the underexposure, it will cause you to pull your hair out when trying to generate the HDR file. I always try to remember to go back to the opposite of what I finished one series with.
It also seems that you do not have the ability to select anything but a sequence of photographs when generating. In other words, if you had a sequence of photos number 100 to 110 but only wanted to use 100, 102, 104, 106 and 110, it will not let you select just those. At least not from what I’ve found. You may be able to put in the whole sequences of 100 through 110 and then delete unwanted files from the generating list but I have yet to try that.
Once you have generated the photo from your files, a box will appear that gives you an “un-toned” view of the merged files. This will typically look terrible, nothing like you expected. But it does give you a preview of the merged files and whether or not they are the correct files. If, for instance, you accidentally added a file from your next sequence after moving your camera, you will see that the pictures are not aligned. If they are, it is suggested you save the file (it saves as an HDR file). With that saved, you can always open it up later and make different tonal adjustments than what you initially make.
Considering that the new HDR file contains the sequential photos, you now select “tone mapping” from the “HDR” menu at the top of the program. This now opens up an adjusting box. Right from the start, you will see a major difference in the view of your finished product.
This tonal adjustment box has several sliders and adjustments to make. This tutorial is not intended to help you through that. The quick tutorial that comes with the program and the user manual should allow you the benefit of understanding what to do.
As a side note, one of the problems I see with the program is that the view of the photo during the adjustment phase is limited to 1024 maximum. When it opens, it will be in 512 view. You change the preview size to either choice of 768 or 1024 so you can see what you are doing. With a big screen I find it annoying to not be able to see a bigger view than the 1024.
In doing the tone mapping, I find that using only the Detail Enhancer mode (method) is best. When trial-using this program and following the quick tutorial, it instructed the user to make adjustments in detail enhancer mode and then switch to “Tone Compressor” mode (method). Try doing that. What you find after making all those adjustments is that it drastically changes your finished product.
The Tone Compressor mode gives you the ability to change the photograph on a global scale. It was very aggravating to then have to go back and make new adjustments within this mode. But if you are using the trial version, it will be your only option of getting a processed photo without a watermark.
Now that I am not using the trial version, I have learned to save the file once my “Detail Enhancer” mode adjustments are made.
Now that you are happy with the finished product, you select “apply” in the toning box. It goes through its magic, closes the box and brings up another wherein you can save it as a jpg file, renaming it if you want. I usually leave the name as assigned because it will give you the photo numbers of the files included and it is an easy way to determine how many you combined. Your original photos are not affected by this save, by the way.
Once I have finished saving the file, I then go to Photoshop and proceed with any touch-ups, etc. and complete it as I would any other photo (such as Unsharp mask, cropping, hot pixels, etc.) and then save it to conform to my file naming system.
I hope I have covered most of the basics here and gladly will answer any questions or welcome any other information anyone has.
As of this writing, here are some examples of some of the HDR photographs I have experimented with and completed:
Shooting from shaded exterior to dark interior with backlight coming through the opposing partially open door: http://www.usefilm.com/Image.asp?ID=1375959
Shooting totally shaded rocks with high glow of sunset in background:
http://www.usefilm.com/Image.asp?ID=1374609
Shooting landscape during sunset with many shaded areas and contrasting colors:
http://www.usefilm.com/Image.asp?ID=1373827
Combining three night shots wherein the “light painting” I had done was not complete in each photograph due to exposure length constraints:
http://www.usefilm.com/Image.asp?ID=1374341
(Night shots in HDR are very hit and miss; I’ve found most night shots don’t work with this technique)
Using a single photograph, copied three times with exposures manually set in the generating process:
http://www.usefilm.com/Image.asp?ID=1374463
Using a single photograph, copied three times but lightened and darkened in PS prior to generating the image in Photomatix:
http://www.usefilm.com/Image.asp?ID=1375781
I hope this helps as a beginner course for those interested in HDR technique.
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