searching for visually similar images

[muranod]

No matter which options I choose, I rarely get a visual duplicate of an image to turn up in the result window.
Favor images withe the same orientation shows both horizontals and verticals. Search by shape and color and Search for similar colors returns both black and white and color images. Even with the result number turned up to 1,000, it often misses a similar image for those that are wildly different. Wondering if there are any tips to making this work better, or maybe just an explanation of how this actually works?

As for speed, it executes quickly through a 10,000+ photo database.

[Mario]

A Visual duplicate is an image that has the same pixel data as the original image, but may have different metadata. IMatch compares the image "fingerprint" it has created with the fingerprints of other images.
The dupe checker compares the file size and checksum to find binary identical files.

Which search do you use, exactly? Visual duplicate, copy and visually similar are all different things.
Also, make sure your result window uses the default sort profile or a profile which sorts by similarity. Else similar images may show anywhere in the File Window.

See Finding Duplicate Files and Visual Queries for more info.

As always, more details in the form of "I use this command to find ... for this image (screen shot)) and that are the first 20 results (screen shot) helps a lot.