Wednesday, June 8, 2011

HDR Photography Tutorial

What is HDR Photography?

High Dynamic Range Imaging (commonly referred to as HDRI or just HDR) is a process in which a greater dynamic range of luminance is captured throughout the lightest and darkest areas of an image. High dynamic range photographs are generally created by shooting multiple photographs using exposure bracketing, and then merging them into an HDR Photograph.

What is High Dynamic Range and how is HDR Photography best captured?

Sensors in digital cameras capture much less dynamic range than the human eye. With digital imaging, many software applications have been developed to map the image differently in shadow and in highlight to better distribute the lighting range across the image. These applications overcome the limited dynamic range of a camera sensor by combining multiple exposures of the same scene in order to retain detail in light and dark areas. These exposure brackets are combined together to produce an HDR image.

Here’s a before and after example of an HDR Photograph:

HDR Photography Exposures Sample

How does HDR Photography compare to traditional imaging?

Information stored in high dynamic range images more closely corresponds to the physical values of luminance that can be observed in the real world. HDR also stores information closer to what is seen by the human eye; and often uses a higher number of bits per color channel than traditional images to represent many more colors over a much wider dynamic range. Traditional digital images only represent colors that should appear on a monitor or a paper print with much narrower dynamic range.

What does all this technical mumbo-jumbo mean?

It means that HDR Photography is used to more accurately display real life and reproduce an image that more closely resembles what is seen by the eye. It allows you to capture every bit of the lightest areas and every bit of the darkest areas of a scene. HDR Photography generates much more viewer emotion and is a great way to get people to feel like they can reach out and touch whats in the photo.
HDR gives us the ability to make people feel as though they were there. Since it captures a closer representation of what we perceive, many people have greater emotional responses to HDR imagery than to that of standard photography. HDR techniques by no means replace Standard photography techniques. It’s merely another tool set for us to achieve the best and most vivid imagery possible. High Dynamic Range also gives us the ability to further manipulate the results in Post Production. We can tweak and adjust the color and luminance spectrum way further than a SDR (standard dynamic range) photo. This allows for a much greater control over the look and feel of the final result and produces higher color and tonal contrast.
A simple example of when using HDR is key is when shooting an element over a sky background. We have all taken those photos with a blown out or white sky even though our subject looks great. Furthermore, if you re-meter the camera on the sky, it comes clearly into view while making our foreground subject dark and unrecognizable. This occurs because both the sky and the foreground require different exposures in order to capture all the dynamic range. HDR solves this problem by combining information from multiple exposures. In this case, one for the sky and one for the subject. Below are some examples of when HDR is used correctly:

HDR Photography Hardware

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Recommended Camera Features:

Bracketing & AEB (Auto Exposure Bracketing)

Since the main focus of the game is going to be HDR, make sure that your camera has a bracketing feature. Some standard DSLR Cameras can bracket up to three (3) exposures while professional grade DSLRs can bracket up to nine (9). Three bracketed exposures can usually produce a stunning HDR photograph, so it’s not always necessary to spend big bucks on the upgraded bracketing feature.

RAW Image File Format

Raw digital photography has a wider dynamic range or color gamut than the eventual final image format, such as a JPEG. Raw images also preserve most of the information of the captured photo and save, with minimum loss of information, the data obtained from the camera’s sensor. In other words: Raw = Higher Dynamic Range. Period. Thankfully nearly all DSLR Cameras have this feature.

Low Noise and ISO Range

When shooting for HDR it’s important to shoot at the lowest ISO possible. The higher the ISO, the more noise or grain will be in the image. Since HDR Processing always produces extra grain, brackets shot at high ISO ranges can look very poor after HDR processing. Some Cameras have improved ISO ranges that allow you to shoot at higher ISOs without losing quality to film grain. Pay close attention to these details when researching what camera is right for you.

What Camera?

Since I’m most familiar with Nikon Cameras, this list is comprised of… well, Nikon cameras. The following are listed in order from Beginner to Professional (conveniently enough, also from lowest to highest price.

Entry Level & DX Format:

Nikon Coolpix P7000 (Most Budget Friendly – It will get the job done):

10.1 Megapixels — ISO sensitivity from 200 to 3200

Nikon D90:

12.3 Megapixels — Brackets: 2 or 3 frames in steps of 1/3, 1/2, 2/3 or 1 EV — ISO sensitivity from 200 to 3200

Nikon D7000:

16.2 Megapixels — Brackets: 2 to 3 frames in steps of 1/3, 1/2, 2/3, 1 or 2 EV — Dynamic ISO range from 100 to 6400 (Expandable to 25,600 in “Hi2” Mode)

Professional Level & FX Format

(FX Format captures a higher dynamic range than DX)

Nikon D700:

12.1 Megapixels – Brackets: From 2 to 9 exposures in increments of 1/3, 1/2, 2/3 or 1 EV — Super low-noise performance from 200-6400 ISO (added versatility of Lo-1 (100 ISO) Hi-1 (12,800 ISO) and Hi-2 (25,600 ISO)).

Nikon D3:

Basically the same specs as the D700 with a full size body. You do get 100% viewfinder coverage (D700 has 95%), A larger battery that produces a higher frame rate, and dual memory card slots.

Nikon D3s:

12.1 Megapixels – Brackets: From 2 to 9 exposures in increments of 1/3, 1/2, 2/3 or 1 EV — Low Noise ISO Sensitivity from 200 to 12,800 (Renowned low-noise performance at 12,800, plus expanded settings to an astounding ISO 102,400 (equivalent) and ISO 100 (equivalent)). This doubles the ISO sensitivity of the D3

Nikon D3x:

24.5 Megapixels – Brackets: From 2 to 9 exposures in increments of 1/3, 1/2, 2/3 or 1 EV — Low noise ISO sensitivity from 100 to 1600 (Added ISO settings of Lo-1 (ISO 50 equivalent), Hi-1 (ISO 3200 equivalent) and Hi-2 (ISO 6400 equivalent)

What Lens you ask?

Some Lens Requirements:

Lenses are expensive. Very Expensive. Thankfully they are one time investments. If you treat them well and keep them in good condition you can usually recoup most of their value when reselling them.
An important thing to consider when selecting lenses for HDR Photography is the “Maximum Aperture.” The lower this magical number, the higher your Shutter Speed will be. It also allows shooting at lower ISOs.

Fixed Lenses VS Zoom Lenses:

The basic idea here is that a Fixed Lens usually has a Higher Maximum Aperture then that of a Zoom Lens (most Zoom Lenses have a range). The downside is that you cant zoom; at all. You’ll have to get used to repositioning yourself instead of greasing the lens. Another perk is better image optics. Though not always the case, fixed lenses can sometimes produce superior results at a lower price.
Zoom Lenses come in a variety of flavors ranging from: wide angle, mid-range, all around, and telephoto. These lenses offer the most freedom and flexibility while shooting. The downside is the Maximum Aperture. Most of these zoom lenses have ranges, for example, my favorite all around lens, The AF-S DX NIKKOR 18-200mm. This lens has a maximum aperture range of f/3.5-5.6. Remember, the higher that number, the longer the exposure. You can find zoom lenses with fixed maximum apertures but they always cost a pretty penny.

DX vs FX Lenses:

If you own a DX Camera and plan to continue purchasing DX Cameras, buy DX Lenses. They are cheaper than FX Lenses and are specifically engineered for DX Camera Bodies.
If you own a DX Camera Body and plan to upgrade to a FX Camera Body later, then you should start investing in FX lenses now. However, if you don’t, you can usually sell good condition used lenses on Ebay or Craigslist to recoup some of the cost. If you own a FX Camera body you must have FX lenses. DX Lenses only work in Crop Mode.

A few DX Lens Recommendations:

Nikon AF-S DX NIKKOR 18-200mm f/3.5-5.6G ED VR II

This is the best all around and travel lens for a DX Camera.

          Nikon AF-S DX Zoom-NIKKOR 12-24mm f/4G IF-ED
This is a great wide angle lens and it has a Fixed Maximum Aperture! You can also go even wider with the more affordable AF-S DX NIKKOR 10-24mm f/3.5-4.5G. You also trade the fixed max aperture for a variable.

Nikon AF-S NIKKOR 50mm f/1.4G

This is an FX lens and an absolute MUST HAVE for all Nikon Camera Owners both DX and FX. It has a Fixed Maximum Aperture of f/1.4 and produces stunning images. It’s also very affordable. This is truly a spectacular lens to have in your quiver.

A few FX Lens Recommendations:

Nikon AF-S NIKKOR 14-24mm f/2.8G ED

Simply WOW! Once you shoot with this lens you’ll understand. This lens in itself is a work of art. It produces stunning imagery and is down right fun to use! It is heavy though; couple it with a Full Frame Body and you got one heavy piece of camera.

Nikon AF-S NIKKOR 24-70mm f/2.8G ED

This is another amazing piece of optic goodness. Stunning imagery across the board with a Fixed Max Aperture of f/2.8. Many people refer to this as “the bread and butter” lens. I often find myself pulling this lens out of the bag first. It is pricey however but well worth it.

“NEW” Nikon AF-S NIKKOR 28-300mm f/3.5-5.6 ED VR

I haven’t had the pleasure of playing with this lens yet but so far the review are all positive. It’s around $800 less than the 24-70 and packs just as much optic punch. I think this will become the favorite FX all around lens solution.

Nikon AF-S NIKKOR 50mm f/1.4G

Again: Great Lens. Must Have!

“NEW” Nikon AF-S NIKKOR 85mm f/1.4G

I also haven’t been lucky enough to use one of these yet but it’s predecessor is amazing. This is an ideal lens for portraiture and produces beautiful bokeh.

How about a Tripod?

Yes. Get one! Sturdier and Lighter = Better. Also, try to purchase the legs and head separately. Make sure that the total weight of the tripod head, the camera, and the lens don’t exceed the maximum weight allowance of the tripod legs.
Another thing to consider while traveling is having a lighter set of tripod legs. You can find some legs that have an additional segment allowing you to collapse the tripod further, making it ideal for travel.

HDR Photography Software

Basic Recommendations for Creating HDR Images:

Adobe Photoshop:

Your One Stop Photoshop; arguably the most important tool in photography, design, and image manipulation & processing. Photoshop also has a built in HDR feature that achieves some pretty decent results. If you want to produce stunning imagery or you just want to put your friend’s head on a chicken’s body, this piece of software is an absolute must.
I remember when I took my first Photoshop class in 1999. I came early to class, started Photoshop Version 5, then opened a stock photo, and then uh, crap, buttons and stuff everywhere. I went to the filter menu and selected Distort, Pond Ripple. Instant digital bliss! What is this amazing thing I just discovered? Lets try some more. Filters: Distort, Twirl. Wow! I’m a photoshop master! I wonder what the watercolor effect does. Sweet!
“Class, I’m your teacher Mrs. V. Let’s get started,” announced the teacher. “Photoshop is a wonderful application that opens up a world of creative possablilites. It looks like some of you have already started playing with the interface; and some of you have already found the distort filters.”
“Oh Crap!”
She went on to explain that Photoshop is not about filtering images but It’s about manipulating and sweetening imagery to it’s fullest potential. She also explained that Photoshop is an extremely robust application that covers the tool sets for both graphic design and image processing and through the use of these tools one could go on to do amazing things in the professional world.
“Sounds boring, Like What?”
“Are any of you familiar with Playboy Magazine? (quizzical silence) One of my former student’s is a retouch artist. He’s the one who airbrushes the Playmate Centerfolds.”

Photomatix Pro:

This is the software I use to process my HDR images. It’s fast; and it’s reliable & cheap. It’s an all around HDR Photography Processing powerhouse that, in my opinion, produces a better result than Adobe Photoshop’s HDR engine.

Adobe Lightroom:

If you are going to be shooting HDR Photography, you are going to have a ton of pictures to sort through. Adobe Lightroom catalogues your image library for streamlined sorting, manipulation, and finishing.
It’s also a direct portal between Photoshop (all Adobe products) and Photomatix Pro. In addition you can quickly create web galleries and upload images directly to facebook, flickr, and smugmug.

Shooting for HDR Photography

So now that you have a camera, lens, and a tripod, your ready to start shooting for HDR Processing. Before we head out and fire off a bunch of photos though, let’s examine some of what goes into the shooting aspect of HDR Photography.

Should I shoot everything with Bracketed Exposures for HDR?

No, and not just because you shouldn’t… it’s actually impossible. There are a lot of times when you can’t fire off multiple exposures. Since this is probably the easiest problem area to identify, lets break it down.
Moving subjects and Portraits: If the scene is mostly moving objects or you have to move the camera to follow the subject, don’t bother trying to capture multiple exposures; it’s a post processing nightmare. If there are just subtle object shifts such as blowing leaves, drifting clouds, or moving water, then there are some post processing tricks to remedy the movement. I will cover these techniques extensively in another tutorial.
If you are shooting portraiture and want to experiment with HDR, it only works if your subject can stay as still as stone. Photomatix Pro has a feature that allows you to create a Pseudo HDR out of one raw exposure. I’ll get into this topic another time.
Low Dynamic Range Scenes: If there is not much dynamic range to capture in the first place the only thing HDR Processing will enhance is the texture. If increased texture is what your going for then bingo. Just don’t be disappointed when the scene still looks dull after HDR Processing. This becomes evident on dreary overcast days when everything looks flat. If you don’t see any shadows and highlights, HDR will probably not save the shot. Experiment with these types of shots at your discretion. Sometimes the enhanced texture and detail is enough to pump up the already bleak mood.

Well smarty pants, when should I shoot HDR then?

Remember all that technical mumbo-jumbo I explained in Intro to HDR Photography Part 1 Tutorial?
If not, backtrack a bit. I’m patient. I’ll wait for you to catch up before I move on.
HDR (High Dynamic Range) Images are composed of multiple exposure brackets. Each one of these exposure brackets contains, you guessed it, SDR (Standard Dynamic Range.) It’s the combining of all these exposures that creates a range of color and light more closely related to what we can see and perceive.
Try to find scenes that already contain a wide range of color and light in the shadows, mid tones, and highlights. Simply put, you want to shoot elements and scenes that seem dynamic in the first place. Try and find interesting lighting scenarios or interesting shadow casts. Remember that the HDR processing will add the detail back into the dark shadows and the light sky and highlights.
A simple formula is to work during those magical parts of the day at dusk and dawn. The last hour of the day is commonly referred to “Magic Hour” or “Golden Hour,” and has been the staple of many a photographer and videographer. It’s that time of day when shadows are most dramatic and the range of color is most vibrant in the sky. It’s at these times when we can find the most unique and beautiful lighting scenarios. A caution though is to be quick. Magic moments fade fast so grab them while you can.
Golden Hour is not the only time to capture HDR Photography. Most times of day can achieve equally stunning results. Try to capture the same scene at different times of day. It might surprise you how different the processed images look.

How many exposures should I take?

This question is a bit harder to answer since every scene is different. Basically, the more dynamic range in the scene, the more exposures you need to take. In most cases though, 3-5 exposures can be sufficient.
If your scene has really bright lighting or you happen to be shooting with the light source in your shot, crank the brackets up to 7 or 9.
Night photography also needs more exposure data. I’ve found that 7 exposures works better than 5 in most cases. Here are some examples of night time HDR Photography using 7 exposures:

Shooting 7 or 9 exposures doesn’t mean you have to process all 7 or 9 exposures. Sometimes it’s easy to over shoot a scene. Thankfully since we live in a digital age, we no longer have to spend money developing photos. You can easily discard unnecessary exposures later. A good rule of thumb is the old saying “better safe than sorry.” It’s always better to shoot more than you need than to be stuck with less than you need.
Other factors could be the availability of a tripod and/or the shutter speeds necessary to shoot the brackets. Very often I’ve found myself in a situation where I can’t use a tripod. Hand Held HDR is a whole different animal. I cover how to cope with these situations in depth in My “Shooting for HDR Photography Without a Tripod” Tutorial.
When you become a bit more advanced with these techniques you can even shift your EV values up and down the scale. This allows you to capture extra images either below or above your median exposure. For example 5 exposure brackets usually look like: -2, -1, 0, +1, +2. You could slide the scale and get, for example: -1, 0, +1, +2, +3. If this seems like too much information, just use regular EV spacing.

What are some basic camera settings to use?

Obviously if we are taking multiple exposure brackets we should enable: Exposure Bracketing on our camera. Most DSLR cameras have this feature; make sure you enable it and select your desired setting.
Make sure to shoot in “Aperture Priority Mode,” Aperture Priority (or Av) Mode allows you to choose a specific aperture value while the camera selects a shutter speed to match. This is different from manual mode, where you have to decide both values. Remember your camera’s bracketing function will automatically dictate the appropriate shutter speed for each exposure.
Another handy trick is to enable your camera’s auto shoot function. This enables you to hold the shutter button down and shoot your brackets in rapid succession. It also eliminates camera shakes caused from multiple button pressing.
You can take it one step further and get a remote shutter release for your camera. Then you don’t even have to touch the camera. This completely removes any possibility of camera shake.

ISO, F-Stop, and Shutter speed? Oh My!

This is where settings become extremely important. Let’s start with the basics.
ISO: The lower the better image quality. Easy right?
– If you have a solid tripod then yes, shooting with a low ISO is simple enough. Since our camera is completely static we can use any shutter speed we want, right?
Kind of.

Especially with low light or night photography, this is where that infamous High Maximum Aperture comes into the picture. The lower the F-Stop Number, the higher the Aperture. A high Aperture lets more light into the camera, increasing the shutter speed. Some lenses have Maximum Aperture ratings of f1.4 or f1.8 and can dramatically increase shutter speeds. Adjust accordingly.
A side effect of opening the Aperture is an increased depth of field which can make elements in your shot a bit softer. Double check and make sure your subject is correctly in focus before shooting the exposure brackets.

Carefully consider the shutter speed of your bracketed exposures.
Long exposures X multiple exposure brackets = a long time.
It also maximizes the possibility of objects moving in your scene and creating motion blur. Remember, blurry objects can be the enemy of HDR Photography.
If there is ample light in your scene then it shouldn’t be a problem to shoot at the lowest ISO setting. Make sure you crank the ISO down all the way 100% of the time.

Monkey Motto#1 = “Shoot First, Ask Questions Later.”

Now that all your settings are tweaked and the camera is set to auto fire, it’s time to shoot some exposure brackets!
Since we have spent all this time talking about how to get the best images possible it’s important to also do this one simple thing: review the images while you’re still on location.
Identify if each image captures the necessary dynamic range. Do I have all the information in the brightest areas? How about in the shadows? Do I maybe need to increase the amount of exposures from 5 to 7? Make sure you identify any possible issues especially when shooting travel photography. There is nothing more depressing than messing up a shot and being 10,000 miles away from a re-shoot.
If there is any question about the quality or integrity of the bracketed exposures,
make sure to re-shoot them.

Source : blamethemonkey

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