|This article is brought to you by the "Ask B&H Photo" Forum. B&H New York kindly has supported Nikonians by providing this article written by Allan Weitz.
The ability to dial in ISO sensitivities in the five- to six-figure range in 1/3-stop increments is pretty heady stuff. With the exception of some of the highest ISO ratings, the image quality of the resulting imagery remains surprisingly decent and is equal to or better than the image quality of the fastest film stocks, which speed-wise were nowhere near the ISO sensitivity levels we can squeeze out of our (H)DSLRs.
Getting the best image quality out of your camera is another matter however, because as cool as it is to be able to take sharp, blur-free photos under the lousiest lighting conditions, for optimal sharpness, tonal gradations and maximum detail in the shadows and highlights it's far wiser to stick to the camera's base, or native ISO rating, which for most cameras is ISO 100. But depending on your camera, even here we have some wiggle room.
One of the side benefits of nosebleed-level ISO ratings is an expanded window of opportunity in terms of how far we can goose the ISO range before noise and artifacting start becoming noticeable. Not all that long ago, image quality started becoming compromised before you climbed a stop above the camera's native ISO rating, which for most cameras meant by ISO 200 you started seeing noise and artifacts. Today, most DSLRs can be pumped 3-4 stops before noise levels start becoming visible—though still quite acceptable—and depending on the make and model, you may or may not be able to push the limits a few additional stops further before things start falling apart.
Even point-and-shoot cameras, which fall victim to the ravages of increased ISO sensitivity levels sooner than DSLRs containing larger imaging sensors, hold up well to ratings in the ISO 400, 640, and 800 range, which is something we couldn't claim three or four years ago.
Figuring out the window of acceptability of your camera's ISO range is pretty straightforward and requires little more than a tripod and a well-lit subject containing a range of colors, textures, shadows and highlights.
ISO Comparison Test*
- Secure your camera to a sturdy tripod, and make sure you turn off any image stabilization functions, or if your camera is so enabled, set the IS function to Tripod mode.
- Focus on a subject (or subjects) containing a combination of fine details, a broad range of colors, as well as highlight and shadow detail. If you have access to a color chart designed for calibrating printers, scanners or computer monitors, make sure you include it in the frame. Bright sunlight is preferable, but any bright, even light source will suffice.
- Establish your exposure using a gray card, set your shutter mode to self-timer in order to further reduce any measure of camera vibration.
- Once everything is in place, set your ISO to the lowest setting (most likely ISO 100), take a picture, set the camera's ISO to the next higher ISO rating and repeat this process through the camera's entire ISO range. When progressing through your camera's ISO range, take the time and effort to test the camera at the smallest increments, which for almost all DSLRs and advanced point-and-shoots are in 1/3-stop increments.
- Once you've finished this exercise, open the image files to pixel resolution, and depending on the editing program you're using, open them up in order, side by side if possible and examine the details of the images and take note as to at what ISO setting you start to notice elevating levels of noise or artifacting. You should also take note of at what point you start losing shadow and highlight details, and if you included a color patch, at what settings you start losing separation between the brightest and darkest patches.
If you take the time and effort to run this simple test, you will have a far better handle on using your camera optimally when shooting under challenging lighting and/or working conditions.
*Note: If you're performing this test using a kit lens, make sure you set the lens somewhere between mid-range and the telephoto end of the zoom range. Generally speaking, the edge sharpness of many kit zooms can be less than optimal, especially at the widest apertures. For that reason you should zoom in to better ensure accurate results.
|This article has been brought to you by the "Ask B&H Photo" Forum. B&H New York kindly has supported Nikonians by providing this article written by Allan Weitz.
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