Keep the Noise Away
Aditya Nair gets into the world of high ISO photography and tells you some things to keep in mind while shooting, to keep the noise levels to a minimum.
The light levels have begun to drop. You have set the camera to the lowest shutterspeed you can handhold, and have also used a wide aperture setting. The picture is still too dark. Are you going to keep the camera inside and retire for the day?
Have you tried boosting a setting called ISO? This helps you increase the brightness of the picture, but most people avoid increasing it beyond a particular point because this introduces a lot of noise in the picture. While grain has always been an integral part of film photography, its digital equivalent, noise, has been reduced to nothing more than a profanity. How do you use this noise creatively? Or better still, how do you minimise the amount of noise in the final photo?
How ISO Works
The term ISO refers to how sensitive a film or sensor is, to light. Increasing this setting from 100 to 400, or 1600 or even a higher setting, simply amplifies the signal received by the camera, thus brightening the overall photograph.
Each sensor has a base ISO sensitivity which is usually from 80–200. At this ISO, the image has minimum noise. When the ISO is boosted, the base sensitivity is amplified digitally in the camera causing a variation in the brightness, colour tones and discolouration in the pixel information. As the ISO is further increased, noise becomes more apparent. It is quite like listening to music actually. As you start to amplify the volume, the static in the background builds up as well.
Textured Grain or Random Specks
When you shoot at high ISOs, it is not just about the amount of noise in the photograph, but also what that noise looks like. Sometimes, it may distract the viewer’s attention. At other times, it may add a gritty feel to the subject. Colour noise is usually more distracting—it consists of random specks of coloured dots that mar the quality of the overall photo. Luminance noise, on the other hand, is not too distracting and looks like film grain. In B&W photographs, it may even enhance the aesthetic quality of the image!
Test the Limits
Use the Aperture Priority mode, keep the aperture settings constant and shoot multiple images of the same scene, at different ISOs. The camera will automatically adjust the shutterspeed while shooting each frame, so that the overall exposure is constant.
Now, transfer these images to the computer and view them at full size. Are they too noisy? Have they become soft at higher ISO settings? This test will help you figure out at what setting luminance noise appears, when colour noise becomes overpowering and when the overall image becomes discoloured.
How Much is Too Much?
Whether the noise in your photograph is acceptable is subjective. Every camera performs differently and each person’s aesthetics are different. It also depends on the size you are printing your photos and the genre of photography that you wish to undertake.
Photojournalists, for example, will have no problem boosting the ISO as news photographs look impactful even when noisy. On the other hand, an extremely noisy photograph of a child posing with his grandmother may disturb the eye. You can even consider using high ISOs to stylise the look of a photograph or series.
Dealing with Shadow
Noise Noise is more easily visible in the shadow areas, which is why underexposure can really emphasise noise. While using high ISOs, expose to the right. This basically means that the exposure value must be such that you have enough detail in the shadows, without the highlights getting blown out.
Observe the camera’s histogram carefully while doing this. From left to right, the Histogram tells you how many pixels are in the shadow, midtone and highlight regions of the image.
Avoid Cooler Tones
If you are shooting in street light, avoid using the Tungsten White Balance setting. This setting corrects the colours and helps capture neutral tones, but it also exaggerates the amount of noise in the final picture. Colder subjects, in general, also look noisier. This is so because every digital photograph can be broken down into three different channels—Red, Green and Blue. The Blue channel always shows more noise.
For those who are using advanced compact cameras or DSLRs, shoot in RAW. This file format captures the maximum image information and detail, which comes in handy when you are shooting in extreme conditions.
However, if RAW is not available, shoot in a format that has minimum compression like TIFF or JPEG Fine. Other options may result in smaller files, but this causes its own share of problems in the form of JPEG artefacts which can increase the appearance of noise.
Keep In-camera Settings Conservative
If you prefer to shoot JPEG photographs, you should be extremely critical of the in-camera settings that are being used. Most cameras allow you to adjust values like Saturation, Sharpening and Contrast of a photograph before you shoot. While shooting at higher ISOs, keep the Sharpening values to minimum. Oversharpening tends to create ugly halos and also tends to make the image noisier. Similarly, keep the Saturation settings conservative as a high value may exaggerate colour noise further.
Increase the Contrast
On the other hand, boosting the Contrast setting is a great way to reduce noise in the shadows caused due to underexposure. Doing this may reduce the overall number of tones in your photograph and the shadow areas will become almost black. This will make the noise in the shadow areas less visible.
Resize the Picture
An overlooked factor for noise appearance is the size of the final picture. For instance, a photograph you have shot at ISO 6400 may look extremely noisy when seen at 100%, but if you are only uploading it on a social media website like Facebook, the noise will eventually not look so distracting. Similarly, a 6 x 4-inch print is quite forgiving of extremely high ISO settings.
Within the Camera or in Software?
Some cameras allow you to choose whether you wish to switch off in-camera Noise Reduction or not. While this feature is effective for those who do not want to be bothered with postprocessing, the downside is the fact that it is automated. The camera reduces the amount of noise by smoothening the overall photo. This robs the image of any fine detail that there may be, and gives it a smudgy paint-like look.
If you want finer control, you should switch off Noise Reduction and instead, do this entire process in a software. This helps you strike the perfect balance between minimal noise and maximum detail.
Get Your Shot Perfectly Right
As far as possible, try to get every aspect of your photograph right while shooting itself, including Exposure, White Balance and other such settings. Postprocessing an image will only amplify the noise. Once you have the perfect shot, you can concentrate on only reducing just the noise in later on.
Master photojournalist Raghu Rai once said, “An image may speak a thousand words, but thousand words also may be a lot of noise. Now, how about some silence?” But as we just find out, we do not have to be afraid of using high ISOs, just because the resultant image may be noisy. Increasing the ISO ensures that you capture a sharp picture even in low light. After all, a noisy picture of a beautiful moment is still better than no photo at all.
For Shooting High ISO Portraits
A simple technique you can use after you have shot a portrait at a high ISO is to duplicate the Layer in Photoshop and then exaggerate the noise reduction. Mask out the eyes. This will ensure that there is noise only in the eyes of the subject keeping it tack sharp while the skin becomes smooth due to the noise reduction.
Increase the ISO to Open up a World of Possibilities
Larger sensors, improved image processors and better noise reduction means that cameras today are capable of using ISOs like 1600 with great results. As a photographer, you can now experiment with many styles of photography that would earlier not have been possible.
Action in Low Light
With events that are held indoors or even in the night, it was earlier difficult to shoot sharp images without grain. With street photography you can now capture tack sharp photographs and minimise the blur by boosting the ISO setting. While blur will still have an aesthetic appeal to such images, now you can choose blur rather than be forced to use it.
To Increase Depth
Another feature of low light photography is shallow DOF. To accommodate for low light, it is common practice to set a wide aperture. Also, sports photographers often use the widest aperture setting, so that they can use a fast shutterspeed to freeze action. By using a higher ISO, however, you can now shoot these genres and still have a lot of elements in focus.
While Using Flash
If you are using a flash and find that there is not enough power for the flash to reach your subject, the easiest solution is to increase the ISO setting.
Since the sensor’s apparent sensitivity increases, it will appear as if the flash is more powerful and has a longer reach. This technique works not only with the in-built flash but can be used with external flash guns as well.
To Capture the Ambience
The biggest advantage of using a higher ISO, is the increased amount of ambient light it allows you to capture, which is especially useful while shooting in places that are lit interestingly. Even while using flash, you can use a higher ISO setting to capture the ambient light in the background instead of just having a black background. This is especially useful when you are shooting portraits in low light.
Three Creative Ways in Which You Can Use High ISO Settings:
1. For Black and White Imagery
Grain is the perfect ingredient for black and white images. It adds a gritty feel and also adds a texture that looks lovely in print. This can look even more appealing if the contrast is extremely high.
2. With Extremely Vibrant Subjects
Colour noise is certainly not as aesthetic as luminance noise or grain, but it can make strongly monochromatic photographs look even more interesting.
3. Choose a Theme
All the way up to the mid-nineties, grain was an integral part of photography. Use this to your advantage to recreate similar themes for your photographs and to create a retro feel.
Tags: Aditya Nair, contrast, February 2012, flash, High ISO, ISO, Low light, Low Light Photography, night, Raw, Shooting Technique, tones, white balance