May 22, 2019. Don't forget to read my new replies below!
Before all, I have already tag a number of images with "feet" and related tags. Feel free to fix them after reading my points of view about it!
(English is not my mother tongue. I am sorry for a potentially uncomfortable reading process.)
I am trying tagging some images which do focus on feet in my personal thought. However, I found it impossible to find all the images and tag all of them on my own, as its amount keeps going all the time. After reading wiki feet, I still cannot get an undoubted stipulation on that. So I decided to open a forum to talk about my view and discuss it with you.
Let's quote first, (original definition on wiki) "Images that focus on one or both of a character's feet. This does not include feet fully covered by shoes. Feet covered by sandals, socks, thighhighs, or pantyhose still count."
The main problem is the definition of Focus. So there are my own ideas.
1.One or both feet is quality enough to watch comparing with the whole image.
First, the feet should be at least clear.
The tag "feet" should not be included in when an image does show "feet" but the quality does not match with the other part of image.
Example 1 : The feet of this image is of a bad quality. Tag "feet" is not recommended when "barefoot" can still be used.
Example 2 : In this image, character's main body is clear and good. However, the feet are of lower quality even the toes are clear. In that the tag "feet" is not recommended.
Example 3 : As for this one, character's feet is just a pass quality. But it matches the overall quality of the image, while it is also a important part of image. In that the tag "feet" can be used.
2.Different Sensitivity in different angle of view
A bottom angle of view to feet should have a higher sensitivity on "feet" tag.
A side angle of view to feet has a normal sensitivity.
A top angle of view to feet has a lower sensitivity.
Most viewers are tend to like the "feet" images with sole(the bottom of feet) most.
Then the shape of the feet, which is usually highlighted using a "profile" of feet.
And finally the instep(the top of feet) angle.
However, the boundaries of the three angle of view are little indistinct, somewhat "smoothly change from the bottom to the top".
Sensitivity here simply means your attention/extra-bonus to adding the "feet" tag. Not whether you should tag "feet" or not.
For example, when an image includes an "okay" foot/feet and you are wondering. Using this ranking can help you to determine.
You should tag "feet" on an image anyway where feet are good enough even though it gives you a top angle of view.
This ranking is still worth discussing.
3.Think twice when tags like "barefoot" and "toes" are used before a "feet" tag is likely to be rejected or ignored by you.
(Same where are just opposite)
(This is more likely to be a reminder)
Updated