Ican tell - you can tell

 "I can tell" is an idiom used to say that you know something after you see it, touch it or hear it, recognise it, you can recognise the difference, change, characteristic or particularity1. In English (US), "I can tell" means that the speaker has already come to the conclusion that has been spoken2. For example, the speaker says "I can tell!" to show that the speaker has noticed the hard work put into the presentation2.