I can't find any authoritative source information on which prepositions to use when describing a background something is positioned on. Is it correct to say for example "photography of a wall clock on a warm, pastel background"? Or should it be "a clock with a pastel background" , or "against a pastel background"? Sometimes many options are possible but one or two are more widely used, so if "with" or "against" is preferred in this case, is the expression "on a pastel background" grammatically correct?
The Oxford Collocation Dictionary suggests the following usages:
- 2) facts connected with a situation/event
Preposition: against the ~ Against that general background I shall give you a more detailed view of current medical practice. | ~ to the technical background to the report.
- 3) part of a view/picture behind the main parts
Preposition: against a/the ~ The areas of water stood out against the dark background. | in the ~ The mountains in the background were capped with snow. | on a/the ~ bright blue on a red background.
All the usages in the question are correct, although they do not all mean the same thing.
Photography of a wall clock on a warm, pastel background describes a photograph showing a clock, and behind the clock, in the photograph, is a warm, pastel background. Actually, the phrase is slightly ambiguous, and could mean that the photograph itself is displayed on a pastel background, but if that is what is meant it should be phrased differently for clarity.
A clock with a pastel background describes a clock that has, as part of itself, a pastel background. For example: a typical 12-hour analog clock with an hour hand and minute hand which has a pastel face.
The choice of using "on" versus "against" to describe the relationship between the foreground object and the background is largely stylistic (meaning either one is acceptable). I would use "against" to emphasize a contrast, while "on" is neutral about the relationship between the foreground and background.
For other readers, note that besides the usage indicated here, where "background" refers to something visibly behind something else, there are other uses of the word with corresponding specific prepositions. Journalists can talk to a source on background. A radio can be playing in the background. In order to better understand an event, you may want to be filled in on the background leading up to it. People who have studied a subject are said to have a background in the topic, an in fact any kind of personal history, such as cultural or economic situation in which they were raised, can be considered part of a person's background, leading to the phrase people from different backgrounds or people of different backgrounds. There are other cases, too, so if you see a usage not covered here, look it up.