Shutter Speed, ISO, and Digital Noise
Shooting these leopards in low light presented challenges, especially with a long telephoto lens. The most important element for getting sharp images with a moving subject is shutter speed. In order to use a higher shutter speed in low light, I had to make a trade-off somewhere else, by moving to my lowest aperture and by increasing the ISO. For the leopards, dialing to a higher ISO allowed me to use the faster shutter speed I needed. The trade-off with using a higher ISO is the added digital “noise” in the image.
Digital noise in an image appears as speckled, errant bits of color. (Noise tends to be more pronounced in darker areas.) In-camera noise reduction settings can help to minimize noise in your image. Plus, there are tools available with image optimization software to minimize the appearance of noise. We use Adobe’s Lightroom 3 and the tools there are quite impressive. (See before and after photos at bottom of this page.)
Please Note: Any shooting/settings advice needs to be considered in relation to the model and performance of your own camera. On the subject of ISO, newer camera models keep improving image quality at higher ISO’s. In general, compact cameras show much more noise at higher ISO’s (400, 800+) than SLR cameras due to the small size of their sensors. The consumer and pro-sumer SLRs with cropped (mid-size) sensors will show less noise at higher ISO’s (800+) than compact cameras, a definite advantage. Full-frame SLR sensors have the ability to shoot at much higher ISO’s while maintaining good image quality.
To accommodate using a higher shutter speed in the rapidly diminishing light, I turned my camera to Auto ISO. [A hush falls over the room as the tried and true rule of shoot at the lowest ISO possible is shamelessly ignored…] Most wildlife encounters like this one with the leopard cubs are somewhat fleeting, so Auto ISO can be a terrific help when you need to be shooting fast in changing light, hand-held. With Auto ISO, the camera will automatically make the ISO as low as possible to allow for your shutter and/or aperture setting, or move it higher to accommodate a higher shutter speed or aperture. (Note: Not all SLRs have Auto ISO.)
Shooting the leopard cub when she was sitting close by, I chose my Nikon D700 so I had the advantage of a full-frame sensor. My number one concern was my shutter speed vs. my focal length. I was shooting with 420mm (a Nikkor f/4 300mm plus 1.4x teleconvertor), hand-held in a very awkward position, and with other movement in the vehicle, so I knew I could not hold the camera very steady. To compensate, I turned my shutter speed to 1/1600 sec. The Auto ISO pushed my ISO up to 1600 to support that shutter speed. I’m happy to say that these images are sharp enough, but they do have noise.
If you want sharp images of moving objects, and you’re shooting telephoto hand-held, you need to shoot at fast shutter speeds and do everything you can to brace yourself to steady your camera. For shutter speed settings, think in terms of 2 to 4 times your focal length. For example, if you’re shooting a 300mm lens, you’ll want a shutter speed of at least 1/640 sec., but the faster you go, say 1/1200 sec., the better your chances for very sharp images. Remember, the more telephoto you use, the faster the speed needs to be. Remembering this will help you get sharp images when shooting hand-held whether you are working from a safari vehicle or on a Zodiac cruise.
As you learn about using these settings, always check your image on your LCD screen to make sure you are getting a good exposure. Zoom in on the playback to check that the image is sharp. With compact cameras, it is really challenging to get good results using the built-in super-telephoto (500mm+) lenses except in bright daylight.
I am less concerned about digital noise these days because the newest tools for minimizing noise are really impressive. Software in Adobe’s Photoshop and Photoshop Elements work well. There are a variety of products available to help with noise reduction including Photoshop Plug-ins from Neat Image and Noise Ninja. We’re using Adobe’s Lightroom 3 and it does a very impressive job.
How great is this software? Well, that final shot of the cubs, when the little girl was grabbing her brother’s tail, it was dusk, and they were in fairly deep shadow. I had turned my ISO up to 6400, knowing I would have noise, but I wanted to try to get the image sharp. The images below show a detail view of the top photo at 100% pixels to illustrate how the software has minimized the affects of noise.
Without optimization you can see the colorfully speckled and grainy effect of digital noise. Optimization with noise reduction software significantly reduces the appearance of noise. Using noise reduction software does take away some sharpness overall, but looking at the full image, it is not too noticeable.
Click here for a link to read the story of this leopard encounter.