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I took this picture in a soft box illuminated by three 5000k 10 watt LED flood lights (one on each side and a third on top)

I'm using a Samsung Galaxy S5 to take the picture, ISO 100 and Matrix Metering.

Why am I getting that blue hue? And why does it look like there are horizontal waves of white and gray throughout the picture?

Thank you for your help!

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Two main things apply here that affect the result you got.

  • When your camera meters a scene it assumes some of the scene is composed of lighter shades, some of it is composed of medium shades, and some of it is composed of darker shades. Absent of any instructions from you to the contrary, it will attempt to expose the scene so that the result is of medium brightness. But when you have a scene that is primarily white you probably don't want a medium gray result - you want the whites to look white. But your camera can't tell the difference between white and grey, and so it will normally expose for grey. You have to tell it to expose brighter using exposure compensation, probably at around +1.5 to +2 stops. The same is true of very dark objects, your camera can't tell grey from near black either. But in that case you need to dial in -1.5 to -2.0 stops of exposure compensation.
  • Fluorescent and some LED lights flicker. Not only does the brightness vary, but so does the temperature of the light. Peaks are bluer, valleys are yellower. Some people can actually see fluorescent lights flicker, but most of us can't. Cameras certainly can, though! If your images show the effects of flickering lights, the best way to combat this when neither the camera nor the subject is in motion is to reduce the ISO and aperture and use a longer shutter time. By catching several cycles of the peaks and valleys of the light flicker the light should even out. So if your image is showing the effects of flicker, slowing the shutter time down when possible will help.

In your image, though, I'm not convinced the variation in brightness is caused by light flicker. It may just be an indication that that your lights project an uneven pattern of brightness.

Even with the JPEG file, increasing brightness and using the eyedropper tool to "pick" the white balance gives a more natural looking result. If the raw file were available a true WB correction could be done. But WB is "baked in" when the data from the sensor is converted to JPEG. And the color cast near the hot spot in the upper right is another indication that you have uneven illumination from your lights.

semi-corrected image

  • LEDs may flicker. Even if they're run off a DC source brightness could be controlled by PWM, but in a light designed for photography (and most decent lamps) this should be at least an order of magnitude faster than fluorescent flicker. Even cheap mains-LED bulbs don't tend to flicker at mains frequency (or 2*mains frequency like many fluorescents). Even many fluorescents are high-frequency these days (kHz+). – Chris H Feb 16 '16 at 11:58
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    I don't think I said anything about the rate of flicker and how it related to mains frequency. Regardless of the rate of flicker, slowing down the shutter speed to less than that rate will result in more uniform color and brightness than selecting a shutter time shorter than a full cycle. So if your image is showing the effects of flicker, slowing the shutter time down when possible will help. – Michael C Feb 16 '16 at 13:30
  • You didn't relate it to mains frequency, but mains is around typical shutter speeds while high frequency stuff tends to be 10s of kHz. Even at 1kHz (i.e. really slow), shutter speeeds slower than 1/250 will get you 4 cycles. – Chris H Feb 16 '16 at 14:56
  • I guess it depends on what and where you're shooting. There are still a lot of older, slower oscillating lights in places I need to shoot sometimes. And if you're not experiencing flicker then you don't need to worry about slowing down the exposure time... but if you are getting the effects of flicker in your photos then slowing down will help. – Michael C Feb 17 '16 at 1:24

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