4

When I recently imported photos from iPhone into LR, I noticed that every photo had evenly balanced histogram, so I guess that after you take a picture with iPhone, it is immediately processed and colors are altered to be more pleasing.

Am I right?

3

All digital cameras not only correct tone and color, they actually create it.

Digital cameras are calibrated to sense light and produce an analog electronic signal which is converted to a digital signal with a digital to analog converter. Almost all digital cameras are calibrated to produce a signal with a linear relationship to the original scene luminance values. This is important for the capture phase of the imaging system but would make for an ugly image reproduction. Further, almost all digital sensors produce an image with only one image channel. Color is created by overlaying color filters on individual pixels and using knowledge of the filter placement to create a three channel image using subsequent image processing.

Image processing is usually done with a image signal processor (ISP). ISPs are dedicated integrated circuits (ASICs) built to apply a series of image processing algorithms to the sensor data. The pipeline of algorithms varies but usually includes steps to correct for manufacturing defects in the sensor, reduce noise, determine black levels associated with the sensor signal, white balance, apply color correction, and a tone reproduction algorithms based on the captured dynamic range and assumptions about the ultimate display medium. Finally color primary and device encoding algorithms are applied before the data is compressed and written to a file. Most of these operations are reserved for cameras that produce "output referred" image data such as that found in JPG and TIFF files, but some subset may also be applied to RAW camera data as well.

Individual camera companies often market their image processing algorithms by naming their ASICs. Names like "Digic", and "Expeed" are proprietary names for digital camera ASICs.

Long story short ... Yes automatic color and tone correction is applied to images created with an iPhone.

  • Do you know any algorithms for color correction used in stage raw -> modified jpeg ? I guess there isn't just randomness, or is it just heuristic "evenly balanced histogram ~ good average photo" ? – Martin May 10 '15 at 23:04
  • Color correction is usually done by characterizing the digital camera sensor, converting the raw color image to an estimation of the scenes colorimetry, then occasionally using a creative adjustment. Methods vary but you can get a sense of the types of methods used by reading the DNG specification. Tone scale adjustments are often based on image heuristics. There's many papers and patents covering various methods. – agf1997 May 10 '15 at 23:10
  • By the way. If you're interested in reading a algorithms for doing white balance google "color constancy" – agf1997 May 10 '15 at 23:12
  • @martinerk0 if you like this answer please check it off so i get credit. Thanks ;-) – agf1997 May 12 '15 at 2:13
-1

iOS does some correction behind the scenes, yes.

  • Could you elaborate on what type of correction is applied and possibly provide sources. – damned truths May 10 '15 at 10:34
  • @damnedtruths like any camera set to automatic, it is doing color temperature, exposure, toning, highlight and shadow adjustments. – philberndt May 10 '15 at 10:37
  • @damnedtruths if you would like more control Camera+ app lets you save images in tiff format, letting you have more control over the post production. – philberndt May 10 '15 at 10:41
  • 1
    @philberndt Can you edit your answer to include these points? And if possible, link to any reference material (e.g. how do we know the iPhone uses toning, highlight and shadow adjustments?) – NickM May 10 '15 at 10:43

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