Barthes makes use of two terms, anchorage and relay; these crop up frequently in discussions about what pictures mean and what they do.
I have found many detailed explanations of these terms online, but the graphic above seems to summarise the terms quite neatly. I do understand that this is quite a superficial view but it’s a good start.
Anchoring describes the effect that the combination of text and contents might have on the viewer. The effect is not that of the text on the image, but the effect on the way the viewer understands the meaning of the two together.
In the above example some assumptions have been made: that the viewer can read, understands written English and has a passing acquaintance with fruit. With these conditions satisfied the text can anchor the meaning of the green thing above it – it is an apple. This example is a bit too simple here because this item couldn’t really be anything else, so the anchorage is not having to work particularly hard.
The relay examples are better because they serve to direct the viewer to make particular associations – again this assumes familiarity with Biblical teaching and popular electronic devices.
Relay works differently to anchorage because it “opens up” the possible interpretations rather than “closing down”, the anchorage effect. Newspaper captions are a good example of this, particularly where readers are likely to be unfamiliar with the picture contents. There’s probably little need for a caption to state “Grenfell Tower” given the widespread visual coverage, but “Gas explosion Riyadh” would be more useful.
I’m more likely to go for a relay function in any use of text with my work. I feel it is best applied to serve to add intrigue and suggestion whereas anchorage would be more helpful in a factual sense.