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I am a longtime photographer but not such an expert on the technical aspects of optics and digital sensors.

I've been experimenting with my Nikon D200 and a home-made paper pinhole, coloured black on the 'inside'. The RAW images, when viewed at 100%, show a fine grid. Picture below of a very small portion of the image (exported without editing as a jpeg), showing the grid (upper half of the picture - the lower half is a bit of dust or other dirt on the sensor). Taken at (native) ISO200, 30-second exposure. Just out of curiosity, I wonder if any of ye know what it is that creates the grid?

enter image description here

Also, the sensor clearly needs a bit of a clean - and I am also very curious about how it comes that the edges of whatever it is that is on the sensor are diffracted.

Here's another part of the same image (this is of trees, so there could have been movement during the exposure): enter image description here

Update: I made some more images yesterday evening with the same pinhole setup on the Nikon D200, and headlights of a car showed some of the rainbow effect discussed here: What causes this bokeh / lens flare effect?

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  • \$\begingroup\$ Looks like you've got a tapeworm...should probably get that looked at...seriously though, have you cleaned the sensor and taken another shot to test yet? \$\endgroup\$
    – OnBreak.
    Commented Jun 3, 2018 at 13:47
  • \$\begingroup\$ You can't view a pre-demosaiced raw image at 100% without getting a grid unless the illuminating light is such that all three colored filters pass the exact same amount of light. \$\endgroup\$
    – Michael C
    Commented Jun 4, 2018 at 7:01
  • \$\begingroup\$ Alexandria - Are you really viewing the raw images? Or are you viewing an image that is created by your raw converter's default settings for converting raw data to a viewable image file? \$\endgroup\$
    – Michael C
    Commented Jun 4, 2018 at 7:02
  • \$\begingroup\$ Thanks for the comments. The two crops are from the same photo of trees outside (so, bit of sky, bit of trees). No, the camera has not been modified, so it does still have its anti-aliasing filter. And, yes, the image viewed and exported is not RAW anymore but rather imported into Photoshop and exported as a jpeg. \$\endgroup\$
    – user59085
    Commented Jun 4, 2018 at 8:00

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What you call a grid seems to be outlines of objects caused by diffraction. An example using a laser, shows the pattern more clearly. There's a nice series of photos by Chris Jones demonstrating diffraction in detail.

You might want to try multiple pinholes to investigate interference patterns, as well.

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