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On the bottom left area of this image, we can see a very prominent pattern of straight lines in two directions crossing each other

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Full version of the pic is available at https://i.sstatic.net/NC5Ft.jpg

Is there a technical term for this? What could have caused these patterns?

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    \$\begingroup\$ The crossing patterns are odd, but even more odd, IMO, is the brownish diagonal line crossing the bottom of the photo. Do you know that this photo hasn't been photoshopped? \$\endgroup\$
    – D. Lambert
    Commented May 14, 2011 at 10:09
  • \$\begingroup\$ @D. Lambert: This picture is straight out of the camera.. very strange! \$\endgroup\$
    – Lazer
    Commented May 14, 2011 at 10:22
  • \$\begingroup\$ @Lazer: It is only 1024x653 pixels. I don't believe it is produced by a camera; it has certainly gone through some post-processing. Could you perhaps post the original photo? \$\endgroup\$
    – Jukka Suomela
    Commented May 14, 2011 at 11:43
  • \$\begingroup\$ Does this happen with all images or was this one an exception? RAW or compressed in camera? I've seen this before out of damaged point and shoot camera but all pictures would come out like that. \$\endgroup\$
    – Jakub Sisak GeoGraphics
    Commented May 14, 2011 at 13:12
  • \$\begingroup\$ @Jukka: I think that is the max Flickr supports. Here is the full version. \$\endgroup\$
    – Lazer
    Commented May 14, 2011 at 16:22

3 Answers 3

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Looking at the original at https://i.sstatic.net/NC5Ft.jpg - the pattern is caused by an obstructing diamond-mesh fence in the lower part of the photo. The 'brownish diagonal line' across the lower-third appears to be twisted two-strand wire, holding the mesh up.

The fence, being much closer to the camera than the subject, is outside the depth of field, thus blurry. The resulting uniform'ish line pattern is most likely an affect of moire.

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    \$\begingroup\$ I disagree with this assessment, given that the "diamond mesh" extends beyond the top of the diagonal wire in the corner of the bay. The grid also does not appear on any land or buildings, only the water. If it was just a mesh, it would stop where the wire was and appear over land/buildings...but that is not the case. The grid, whatever it is, definitely appears to exist ON or UNDER the water, and does not really appear to be an out-of-focus mesh. \$\endgroup\$
    – jrista
    Commented May 14, 2011 at 20:09
  • \$\begingroup\$ @jrista, might it just be that over detailed backgrounds like buildings or the rocky land, the pattern is hard to distinguish? \$\endgroup\$
    – mattdm
    Commented May 14, 2011 at 21:56
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    \$\begingroup\$ I understand @jrista, however this Google Map link might explain the situation. \$\endgroup\$
    – Leorex
    Commented May 14, 2011 at 22:28
  • \$\begingroup\$ @jrista - anti submarine net? ;-) \$\endgroup\$
    – ysap
    Commented May 14, 2011 at 22:28
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    \$\begingroup\$ Well, @Leorex's google map link settles it. :P I am still a bit confused as to why you can't see ANY part of the OOF fence overlayed on the land or sidewalk around the outer edge of the bay. If it wasn't for that fact, I would have agreed up front. @ysap: I used to live near the beach in California, and there are plenty of regular structures to be found under the waters surface around bays and the like, remnants of some past thing abandoned. I admit, this would be rather large...but you never know. \$\endgroup\$
    – jrista
    Commented May 14, 2011 at 23:20
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My first thought it is some sort of structure under the water in the harbour as the lines stop where the water is clear of the harbour wall on the lower right of the image.

The angles of the lines appear to marry up with the perspective of the shot so it seems unlikely to have been caused by anything on the sensor as these would run up/down and left/right across the frame.

That said, it also seems remarkably uniform for such a large expanse... very odd!

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After giving this photo some thourough examination, I can arrive at a few conclusions.

First, the funky line that streaks through the lower 1/3rd of the image appears to be a slightly out of focus cable or something...it may have just been on the inside border of the depth of field, and did not get entirely blurred away.

As for the "grid", I can't say anything definitively. Here are some facts that I see about it:

  • It only exists within a very specific area of the water...only in the area with the boats.
  • It has a VERY specific size, structure, and shape unfettered by any measurable degree of randomness.
  • It does not seem to appear on any non-water part of the photograph.

Some thoughts that come to mind are the following:

  1. Its actually something real..."design" of part of the bay there. Something under the surface of the water that was picked up by your exposure.
    • Could be tested by just looking at the same scene with your own eyes and see if the grid pattern is visible without the camera.
  2. It is the result of something closer to your camera, outside of the bounds of your depth of field, that has been blurred just enough to be nearly invisible, but visible enough that it affected the lower portion of your photo.
    • Might be possible, however outside of the slightly blurred cable through the lower part of the scene, I can see nothing else that might hold up such a mesh or grid only in the lower part of your scene, and not in the upper parts.
  3. It is the result of an odd wave-interference pattern in the water itself.
    • Rather unlikely, given that such a clear and regular interference pattern would require a rather specific underlying waveform to occur...and the waves on the water otherwise look quite random.
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  • \$\begingroup\$ The size of the mesh cells is quite uniform, disregarding any perspective distortions. This makes me doubt the fact that it is some underwater structure. Additionally, you can identify the pattern extending all the way to the right side of the image, outside of the lagoon. \$\endgroup\$
    – ysap
    Commented May 14, 2011 at 22:39
  • \$\begingroup\$ @ysap: Yup...hence option #2. \$\endgroup\$
    – jrista
    Commented May 14, 2011 at 23:21

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