Question

which rules do filters require in photoshop? ​

Answer 1

Answer:

For a filter to affect a layer, the layer must be visible and must contain pixels—for example, a neutral fill color. You can apply a filter to an individual channel, apply a different effect to each color channel, or apply the same filter but with different settings

Answer 2

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ғᴏʀ ᴀ ғɪʟᴛᴇʀ ᴛᴏ ᴀғғᴇᴄᴛ ᴀ ʟᴀʏᴇʀ, ᴛʜᴇ ʟᴀʏᴇʀ ᴍᴜsᴛ ʙᴇ ᴠɪsɪʙʟᴇ ᴀɴᴅ ᴍᴜsᴛ ᴄᴏɴᴛᴀɪɴ ᴘɪxᴇʟs—ғᴏʀ ᴇxᴀᴍᴘʟᴇ, ᴀ ɴᴇᴜᴛʀᴀʟ ғɪʟʟ ᴄᴏʟᴏʀ. ʏᴏᴜ ᴄᴀɴ ᴀᴘᴘʟʏ ᴀ ғɪʟᴛᴇʀ ᴛᴏ ᴀɴ ɪɴᴅɪᴠɪᴅᴜᴀʟ ᴄʜᴀɴɴᴇʟ, ᴀᴘᴘʟʏ ᴀ ᴅɪғғᴇʀᴇɴᴛ ᴇғғᴇᴄᴛ ᴛᴏ ᴇᴀᴄʜ ᴄᴏʟᴏʀ ᴄʜᴀɴɴᴇʟ, ᴏʀ ᴀᴘᴘʟʏ ᴛʜᴇ sᴀᴍᴇ ғɪʟᴛᴇʀ ʙᴜᴛ ᴡɪᴛʜ ᴅɪғғᴇʀᴇɴᴛ sᴇᴛᴛɪɴɢs.