Saturday, March 6, 2010

Practical HDR

What to do when the light is too extreme for one shot?
HDR, or high dynamic range, is a digital imaging technology that allows us to go beyond the limitations of our cameras and their sensors. With this technique, we can make pictures that are closer to what we actually saw with our eyes - photographs that represent the world in more realistic renditions that simply weren't possible in the past, even with film.

How HDR Works
With HDR, start by taking multiple exposures of the same scene - exposures that vary from underexposed to overexposed - then use software to combine the tonal information from that range of exposures into a single final image. This allows you to capture detail, color and tones and merge them into one image that couldn't be captured by a single exposure. By using HDR technique and software, you can bring out more detail in the shadows, midtones and highlights. Cibodas_series
First Steps
To get started with HDR, you'll need several exposures of the same scene. Each of these exposures must be framed identically or you'll have problems assembling the final image.
Here are some ideas that work well for HDR shoots:
1. Shoot at least 3 photos, each with a difference of one or more f-stops in exposure.
2. Use a sturdy tripod and lock down your camera on the scene.
3. Avoid shooting anything with movement, including wind blowing your subject around.
4. Try using the auto-exposure bracketing function (AEB) on your camera. AEB allows you to shoot at least 3 exposures in a row with a variation in exposure for each.

How Many and How Much?
In general, you can try for a minimum of a one-stop difference between exposures, then use three to five exposures for the scene. Sometimes, the result are great using 3 frames with a 1.5- to 2-stop difference in exposure, other scenes work better using 5 frames with 1-stop difference in exposure.
I wish I could give you specific information on what exposures would work in every situation, but "every situation" is different and will require you to modify your approach. However, with experience, you'll start to know what seems to work best for the specific subjects that you like to photograph.

Into The Computer
Once you've captured your scene with multiple exposures, you need to upload them onto the computer and work on them with software that allows you to combine the pictures into a final HDR image. You don't actually have to do a lot, other than open your series of exposures into the program. The software then automatically examines your exposures and puts them together into a final HDR shot.
Most of the programs also allow some adjustments as to how the exposures come together. Sometimes these adjusments can be done before you do the HDR conversion and almost always can be done afterward. A number of software programs allow you to do this. 
Adobe Photoshop CS versions have an HDR capability. And the picture below show you what I did with Photoshop to create an HDR image from 3 bracketed images.image

And this is the result:image Other softwares you can use to create  HDR images are Essential HDR, LR/Enfuse (it's a Lightroom plug-in), and Photomatix.

HDR Processing On Other Images
Another way of using many HDR programs is to double-process RAW files. Take a single RAW image and process it twice, first to optimize the highlights (while ignoring what happens to the shadows) and again to optimize the dark areas (whike ignoring what happens to the highlights). You can even triple-process an image, creating a third version that optimizes midtones only.
Then put those processed RAW files together into a single file by using one of the HDR programs.
HDR is changing the way we photograph, giving us new opportunities for capturing the world. We now can create images that more closely render our world and more truthfully communicate what we see.
Written by Rob Sheppard, as appeared on Digital Photo Mag. June/July/August 2009. You can see more of his works at his website,


How To Use Flash Effectively?

Light is basic to photography, obviously. When the light isn't at it's best, it's a serious challenge. Poor light consistently makes potentially good photos go bad. One strategy for success is to use flash. Yet, using flash can be challenging, as well. It can be bold and beautiful, but also harsh and unappealing. Flash Basic
There are some things you can do to make your flash work more in your favor, so you get pictures more often on the bold and beautiful side than the other. This article will explore some tips that can point you in the right direction to do exactly that.

Turn On Your Built-In Flash During The Day
When the sun is out, and the shadows are harsh, turn on that flash! When the light is dull from heavy clouds (and even rain), turn on that flash!
With harsh sunlight, that daylight fill-flash brightens shadows and makes dark shadows, such as those under hat brims, come to life. If the flash is too strong, try using flash exposure compensation to reduce the flash output.
When the light is dull, use the flash to brighten colors and make your subject stand out from the background. A quick way to get drama is to go to manual exposure, set the camera to slightly underexpose based on your meter reading, then use the flash normally. This will give properly exposed flash light on your subject while the surrounding are darker.

Use The Ceiling For More Natural Flash
One of the challenges that flash has is that it can look harsh indoors. This is because the light is small in size (which makes for contrasty shadows) and is close to the camera lens when the flash is on the camera (which can make the light less than flattering).
With an accessory flash that allows tje flash head to tilt to the ceiling, you can bounce light indirectly to your subject. That way the light that hits your subject comes from a big light "source" - the light bounced from the ceiling. This immediately softens the look of the flash. In addition, the light will come from a natural direction above your subject.
You need a white ceiling for this to work, and lower ceilings work better than high ones. If you're very close to your subject, you may run into a problem of the light from above causing unwanted shadows under the subject (dark eye sockets can be a problem). In this case, place a white card at the back side of your upward-pointing flash so that a little light is kicked forward toward your subject, even though most of the light heads to the ceiling.

Get Your Flash Off The Camera
Get your flash off the camera to get more control. You'll immediately see a change in the light - it will become more multidimensional and far more attractive. You can buy a dedicated flash cable to tether your flash to the camera for complete automatic control (and control that works in all conditions). Or using wireless triggers for cameras with wireless flash capabilities.
An easy way to handle this flash is to hold it in your left hand with your "pointing finger" on top of the flash. Now just point that finger at your subject and you're also pointing your flash. Experiment with flash coming from all sorts of angles just to see what the possibilities are.

Bounce The Light From A Reflector Or Through A Diffuser
Two things consistently help you get better flash results: changing the angle of the light to your subject and increasing the size of the light.
You increase the size of the light by bouncing it onto a large surface (such as the ceiling mentioned earlier) or shooting through a large diffuser (a small diffuser has little effect). You need to have the light that's hitting your subject come from a large surface area.
An easy way to get started is to get a piece of foam board about 2x3 feet in size. Have someone hold it, or clamp or tape it to something on one side of your subject. Then use your off-camera flash and point it at the foam board from a distance of a couple of feet. You need to have it far enough from the reflector that it spreads out the light, but not so far that it spills over the edges. Move the reflecting board up and down, as well as side to side for different effects.
If you get serious about this, you can then buy a folding reflector or diffuser. Use it in the same way described for the foam board. The diffuser requires a little different technique. You must position it in between your flash and subject. Keep the flash far enough back to fill up the diffuser with light without spilling over. If you're too close to the diffuser, the light won't spread out much, so the effect will be greatly reduced.

Use Flash For Sharper Close-Ups
Close-up and macro photography always challenge our abilities to get a sharp photo. First, up-close depth of field is vey narrow, often severely limiting sharpness. Second, at close distances, the effect of camera movement or shake during exposure is exaggerated, so sharp photos become more difficult. Third, if you use a small apperture or f-stop for more depth of field, you'll be saddled with a slower shutter speed, making camera movement worse. Finally, gear such as macro lenses and extension tubes will reduce light, so even slower shutter speeds are required.
Flash can help. Flash gives such a brief burst of light that it's usually like using shutter speed of 1/1000 second and even faster. This effectively limits the effects of camera movement. In addition, when flash is used up close, there's a lot of light to work with, allowing you to use small f-stop such as f/16 or f/22, resulting in more depth of field.
A key to gettimg better flash photos up close is to get the flash off the camera as described above. When your subject is close to your camera, even a slight change in flash position can give you noticeably different results. You can even try putting the flash somewhat behind the subject for dramatic effect. You can aim the flash right at the subject; you can aim it so the flash hits both the subject and the background; or you can aim the flash so it just hits the subject and not the background.
The key to learning all these techniques is to try them. Test them out with a willing subject, even if that's just a statue that can't complain. Check your results in your LCD and experiment. Don't worry if every shot isn't a winner. As you explore using flash, however, you'll find flash becomes a potent tool for making more winners!
Source : Digital Photo Mag. June/July/Auust 2009.
Written and photography by Rob Sheppard.

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