Why does my Nikon D5200 photo show grain and blue specks at ISO 1600 indoors?
Asked 9/19/2016
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I shot indoors on a Nikon D5200 in Aperture Priority with Auto ISO, and Lightroom shows noticeable grain plus some blue specks when viewed at 1:1, especially in dark shadow areas. The exposure used ISO 1600. Is this caused by the high ISO, and what are the blue specks? What ISO should I aim for indoors, and can Lightroom reduce this kind of noise?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
9y ago
2 Answers
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The blue specks are read noise that is being amplified when you try to pull details out of shadows that are pretty much pure black.
Noise is a result of low signal-to-noise ratio (SNR). In the case of digital photography signal is determined by the amount of light allowed to hit the sensor. Noise is a combination of constant read noise caused by the electronics of the sensor and other electrical components between the sensor and the analog-to-digital convertor and photon shot noise caused by the random nature of light.
The reason that noise is often attributed to using a high ISO is because higher ISO settings are used to allow proper exposure when less light is allowed to strike the sensor. As the amplification of the signal is increased to compensate for less signal, so is the noise.
The way to avoid noise in a photo is to provide more light to the sensor. This can be done by either a) using a wider aperture or b) exposing for a longer period of time. A tripod or other stabilized mount for your camera will allow a much longer shutter time than hand holding the camera.
Originally by user15871. Source · Licensed CC BY-SA 4.0
user15871
9y ago
0
Generated from our catalog & community — verify before relying on it.
Yes. The graininess is image noise, and ISO 1600 can make it more visible, especially in darker parts of the image. The blue specks are also noise—likely read noise that becomes obvious when shadow areas are very dark and you inspect them closely or brighten them.
High ISO itself isn’t the root problem; low light is. When the sensor gets less light, the camera uses more amplification (higher ISO), which boosts both the image signal and the noise. Deep shadows will usually show it first.
There isn’t one “optimal” ISO for all indoor shooting—it depends on the light, whether the subject is moving, and whether you can use a tripod or flash. If the subject is still and you can stabilize the camera, use a lower ISO and longer shutter speed. If the subject moves, you may need a faster shutter speed and therefore a higher ISO.
In Lightroom, noise reduction can help. The Luminance noise reduction slider is commonly used to reduce this visible grain/noise, though stronger settings can soften detail.
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