10 Things You Probably Did Not Know About Shooting at High ISO
K Madhavan Pillai uncovers some interesting facts, tricks and practices that will help you make optimal use of the high ISO settings of your camera and reduce noise.
The fantastic ISO range in today’s digital cameras have expanded creative possibilities greatly, allowing photographers to make pictures in situations and ways that were otherwise almost impossible. In the words of the legendary S Paul… “Photography used to be about available light. Now, it is about available darkness”. Here are 10 ways to reduce noise and use high ISO settings more effectively.
1. Know Your Sensor
Most know the fact that smaller sensors are more noisy than larger ones. There are various types of noise though, some caused by situational factors. And each camera behaves differently. For instance, sensor heat (produced by fast, continuous shooting, or long video clips) increases the level of noise even at low or constant ISO settings. Knowing how your camera reacts will go a long way in controlling noise.
2. Do Not Underexpose at High ISO
While shooting in low light, a common tendency is to underexpose, rather than increase ISO, and then recover shadow details in postprocessing. This invariably leads to more noise rather than reducing it. Shadow areas in an image are always more noisy than midtones or highlights.
3. Not all Light Sources are Made Equal
Daylight or white light (flashguns) uses the entire visible spectrum of colour. Sodium vapour lamps (street lamps) reduce visible colour and detail because they operates on a narrow spectrum. Given low levels of white light and street light, noise would be higher with street light.
4. The Advantage of Auto ISO
The high ISO noise characteristics of recent cameras are excellent, allowing photographers the freedom to let the camera choose ISO automatically. The Auto ISO range can also be preset, depending on the maximum amount of noise a photographer is willing to accept. By default, the camera selects the lowest ISO and only pushes it up when all other options are exhausted.
5. Noise is Relative to Print Size
All it takes to get rid of noise is to print or view the same image at a smaller size. In fact, except when pixel peeping at 100%, an image shot at ISO 3200 will appear almost devoid of noise in a 8 x 12-inch print.
6. RAWs, Minimum Compression JPEGs
With the various kinds of High ISO noise in an image, you really do not need compression artifacts adding to it. So use the largest available file sizes for JPEGs. Better yet, shoot in RAW and process later.
7. Explore In-camera Noise Suppression
A level of noise reduction happens in all cameras by default, to correct certain kinds of unavoidable noise. The latest cameras have refined algorithms specific to the sensor, with levels of user-defined noise suppression at different ISOs. Try it out.
8. Adding Noise to Reduce It
During postprocessing, noise removal works by essentially blurring out grain, thus reducing critical detail. Strange as this may seem, it is often better to add uniform grain to a noisy image, to improve smoothness, rather than suppress existing noise and lose further detail.
9. Working with Longer Exposures
Using a shutterspeed one stop slower, or opening your aperture by a stop, will let you equivalently set a lower ISO, giving you a significant advantage over noise. While this is commonly known, it is rarely practiced. In situations where the shutterspeed is not critical, using a tripod makes a huge difference. There is a flip side to it too. Extremely long exposures of over 15 seconds are best done at settings of ISO 400 or lower. As the sensor heats up, noise creeps in. The effect is multiplied at higher ISO settings.
10. An Advantage for Flash Users
Shutterspeed and aperture remaining the same, increasing the ISO by two stops (for example, from 400 to 1600), will double the guide number or reach of a flash unit. Conversely, the intensity of flash required for a subject at a given distance will reduce by half. There are many creative uses for this, especially if you are shooting at low ambient light levels and in situations where you need to increase the exposure anyway without compromising on the shutterspeed.
Being able move to a higher ISO without compromising on image quality allows many opportunities that were otherwise unavailable to photographers a few years ago. Exploring possibilities while keeping these ten points in mind will go a long way in refining both quality and technique.Tags: High ISO, K Madhavan Pillai, September 2015