HDR Archives - Infrared Conversions, IR Modifications & Photography Tutorials

“Dynamic Range” in photography refers to the ratio between the two most extreme values of light within an image. This is from the lightest to the darkest tones. So the “dynamic range” of a photograph is the difference between pure white and pure black. The term is also used to describe the “dynamic range” a particular camera has. Dynamic range is important to understand in photography to ensure you know the limitations of cameras and to make sure that your photos are correctly exposed. This quick beginners guide should help you understand the basics of dynamic range in photography.

Limitations in cameras

The dynamic range of a camera is measured in what are called “f/stops.” The brightness level of the camera doubles with a one-stop increase. Human beings can see about 20 stops, and a top of the range camera has about ten stops, 14 in some of the really high-end cameras. This means that the human eye sees a much more comprehensive range of tones.

For example, if you have ever taken a photograph on a sunny day and the photo has turned out nothing like what it looked like to you, you’ve experienced the limitations of the dynamic range of the camera compared to the human eye. But remember this is not your limitations as a photographer, it’s the limitation of the technology you are using.

The dynamic range of screens and printers is even less than that of a high-end camera. So, even if your camera can capture a high number of stops, you may have to edit the image to translate the dynamic range to that of a screen.

An example of a situation when the photograph doesn’t do the real scene justice in terms of tonal range. There are also areas that are underexposed on the rocks and overexposed in the sky.

Understanding the impact of dynamic range

As a photographer, running into dynamic range issues is something inevitable, but you get better at addressing the problems the more you come across them. If the dynamic range of the subject does not exceed that of the camera, your photograph will be correctly exposed. If the range is extensive, then it will affect one part of your photograph, and it will be under or overexposed.

When the dynamic range of the subject is broader, you need to choose where you want to lose detail, in the highlights or the shadows. Generally, it is better to expose the highlights so that they have more detail and sacrifice the details in the shadows as often you can recover these in post-production better than highlights.

Thankfully, there are techniques you can use to lift shadows like using a fill-in flash or lighting up the areas using a reflector. You can also invest in graduated neutral density filters (GND) to help balance out the dynamic range in some scenes. These filters are essential in say landscape photography where you often face a broad dynamic range. Below are some of the techniques you can use to ensure you get a better dynamic range in your photos.

The highlighted red area is overexposed and completely white. A GND would be useful in this type of scene.

Graduated neutral density filters

One of the major challenges when photographing landscapes during what is the best times of the day (early morning or late afternoon) is that the sun is low in the sky. Often this means you are faced with a bright sky and a dark foreground. This is one of those scenarios where the dynamic range of the scene might be too much for your camera. If you expose for the sky your foreground will be underexposed (too dark). If you expose for the foreground your sky will be overexposed (too bright).

In this scenario a GND filter is placed in front of the lens and can be rotated to reduce the brightness of the sky, allowing you to expose more of the shadows while darkening the sky. These filters come in a range of different strengths that can reduce the brightness of the sky by around three f/stops. These filters have a dramatic effect and are the quickest way of matching the dynamic range of the subject with that of your camera.

HDR Photography

One way of overcoming problems with dynamic range is High Dynamic Range (HDR) Photography, where you take the picture at multiple exposures and then combine the images into one final composite in post-processing (some cameras have an HDR setting that does this in-camera for you).

For this type of photography, a tripod is essential if your slowest image of the range is going to be at a slow shutter speed. A tripod will also ensure that you take the same image and there is no movement. If your camera doesn’t have HDR mode, you will need to set your camera on manual and then take the multiple shots adjusting your exposure from underexposing to overexposing.

Make sure you don’t adjust the aperture as the depth of field will be altered if you adjust the aperture. You need the images to be identical to merge them effectively.

Different time, weather, or from a different Angle

If the subject or scene you want to shoot is problematic because the sun is too bright, you can often overcome this by taking the picture at a different time of day, when for example it’s a bit cloudier or the position of the sun in relation to your scene has changed. This option will decrease the contrast and bring the dynamic range of the subject closer to that of the camera. Simply ensuring that you have your back to the sun when taking a photograph can make a difference in whether it is overexposed or not.

Use artificial lighting or a flash

You can use artificial lighting or a flash to add light to the darker parts of the image. This option decreases the difference between the lightest and darkest areas of the image and allows your camera to capture the entire gamut of light in one photograph.

When a flash is used, the light on the subject is closer to the amount of light in the background, and this narrowing of the dynamic range is often enough to capture the image effectively without any need for editing.

A flash is an excellent tool for capturing high contrast scenes, but it takes practice learning how to balance the light from the flash and the natural light. An off-camera flash is even better, but it can add to the amount of time it takes to take the shot as well as to the amount of camera gear you have to carry around.

Photo editing

There are some scenes when it is virtually impossible to deal with dynamic range problems in-camera, and you will need to use photo editing software to adjust the contrast. But the likes of Lightroom and Photoshop have come a long way in the last 10 years in being able to recover the areas which are underexposed or overexposed. So don’t be afraid to try to fix your images in post-production if needs be.

Cameras have limitations in the amount of light they can capture. When a scene’s lighting extends beyond the capabilities of the camera, these tools and techniques can still help you create a dynamic photograph of the scene. As you experiment with each of them, you will learn which is the best solution to use in a particular situation. You will soon be taking a dramatic high contrast image despite the constraints of the dynamic range of the subject or the camera you’re using.

What are bracketed exposures? If you’re familiar with this term, you know how useful they can be. There are multiple uses for bracketed exposures, but they are especially helpful in IR photography. Shooting bracketed exposures is where the camera is set-up to shoot the same scene, but at different exposures.

Nearly all stock cameras are meant to shoot in color. So when we get into the optics and start removing filters or adding other filters, the camera doesn’t work the same. The one area that really takes a beating is the metering. After a modification, the metering will still be fairly close. But shooting in IR or full spectrum will definitely change the way the camera’s metering system sees the world. I find that my full spectrum modified Canon 5D Mk II with a 740nm filter will usually meter a ½ to 1 stop (usually denoted by EV) brighter than a normal scene. Most of my other modified cameras were the same.

The shows a series of 3 bracketed exposures at -1, 0 +1 EV

When I shoot IR photos, I shoot bracketed exposures as a rule. I’ve had too many IR photos where I thought the metering was accurate only to find that there are highlights in the scene that are blown out (camera’s histogram is clipped on the RHS). Shooting bracketed exposures nearly always helps me recover these highlights or even allows me to process a different shot that is at the + or – end of the bracket.

How do you begin doing this? Well, most cameras these days will allow the use of bracketed exposures. This is where the camera will shoot 3 or more exposures for each image. Depending on how you set it up, the camera will typically shoot a normal exposure and one under exposed and another that is over exposed. Some cameras will shoot additional over/under frames and also allow you to skew how these different exposures are framed in the overall bracket. I like to set my camera to shoot the bracketed exposures in high speed mode, so I can get the 3 images in rapid succession with a single shutter button press.

This is the menu option for setting bracketed exposures on a Canon 7D. This one is set for -1, 0 +1 EV

My cameras (as to many) have several programmable settings where I can set f/stop, ISO, exposure mode, bracketed exposures, etc. So I have 2 custom settings that shoot only bracketed. On my camera, C1 is set up for 1 stop over and under. The camera will record 1 normally metered frame, one frame that is one stop under and one frame that is one stop over. C2 is the same operation except for 2 stops over/under. This makes it quick and easy for me to change the camera to different situations where 1 or 2 stops might be needed.

Many DSLR’s have the ability to set custom settings. This one is a Canon 5D MkII

So why else would I shoot bracketed exposures? One great feature is HDR. If you’re shooting a scene that has both bright and dark elements or the scene spans more dynamic range than a single shot can record, HDR or some other technique of exposure masking or blending is the way to do this. It’s also very helpful to have multiple exposures when shooting on the shadow side of the Sun, or toward the Sun. Many times you won’t see the need for HDR until after you return and are processing your images. It’s too late to do an HDR at that point. So by shooting bracketed exposures, you have the ability to do HDR or exposure blending on shots, after the fact.

This is an HDR of the 3 images shown above.

Isn’t shooting bracketed exposures going to wear out my camera? Won’t it take more memory? Yep, for both. Your shutter is now clicking 3 or more times for each scene. All of these shots have to be recorded on the memory card. Of the 7 modern DSLR’s I’ve owned, I’ve only replaced the shutter on one camera (my 30D), and that was at about 3700 clicks, for sure an anomaly. Most prosumer DSLR’s are good for 100k -150k shutter clicks. I’ve never shot 100k shots on any of my cameras. But I’m not a professional photographer. I venture to guess that most other casual shooters are the same. As for the memory consumption, memory cards are cheap.

Another example of scene that benefited from having more than a single exposure

There is a little good news. If you focus and shoot your IR like I described in my last blog, focusing through live-view, the mirror will stay locked up. So the wear associated with the mirror flipping up and down is removed from this operation. It also helps to use a tripod when shooting bracketed exposures, especially if you’re going to be using them for HDR. You can still align the images in post-processing. But it’s easier if the images begin with good alignment. I prefer to shoot all my IR with a tripod.

Scenes that are shot toward the Sun typically have a high dynamic range that benefit from having bracketed exposures

If you’re comfortable with shooting regular exposures with your IR photography, by all means proceed. I find that shooting bracketed exposures helps save many images that might have otherwise been unusable. Happy shooting.

What Is Dynamic Range In Photography?

Limitations in cameras

Understanding the impact of dynamic range

Graduated neutral density filters

HDR Photography

Different time, weather, or from a different Angle

Use artificial lighting or a flash

Photo editing

Bracketed Exposures for IR photography

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