Tôi phóng to chủ thể.

• Tôi = I
• phóng to = to enlarge, to zoom in, or to magnify depending on context
• chủ thể = subject (for example, the main subject in a photo, image, or discussion)

So grammatically, it is:

I + enlarge/zoom in on + the subject

Vietnamese often keeps a simple Subject–Verb–Object order, which is what you see here.

Here, phóng to functions together as a verb phrase.

Even though to by itself means big, in phóng to the combination means to enlarge / magnify / zoom in. So you should learn it as a set expression in this context.

A useful contrast is:

• phóng to = enlarge / zoom in
• thu nhỏ = reduce / shrink / zoom out

So yes, learners should treat phóng to here as a unit of meaning.

Because Vietnamese usually follows Subject + Verb + Object, much like English.

So:

• Tôi = subject
• phóng to = verb
• chủ thể = object

That gives:

Tôi | phóng to | chủ thể
I | enlarge/zoom in on | the subject

Vietnamese does not need a word like on in every case the way English sometimes does.

Sometimes yes, depending on what you want to sound like.

• phóng to chủ thể focuses on enlarging the subject
• zoom vào chủ thể focuses more specifically on zooming in on the subject

In everyday speech, especially with cameras, phones, or editing, many speakers would say:

• Tôi zoom vào chủ thể.
• Tôi phóng to ảnh của chủ thể.
• Tôi phóng to phần chủ thể.

So your sentence is understandable, but if you specifically mean camera-style zoom in on, zoom vào chủ thể may sound more natural.

Not necessarily.

Chủ thể has several possible meanings depending on context, such as:

• the subject of an image or photo
• the main entity involved
• the agent or actor in a formal context
• the subject/theme in some academic writing

So yes, it can sometimes overlap with English subject, but it does not always mean the grammatical subject of a sentence.

In visual or artistic contexts, chủ thể often means the main thing being shown. In casual speech, though, people may also say:

• đối tượng
• nhân vật chính
• vật thể chính

depending on what kind of subject they mean.

It is understandable, but it may sound a little stiff or context-dependent.

Why? Because chủ thể is somewhat formal or technical in many situations. Also, phóng to chủ thể can sound slightly compressed, as if taken from instructions, editing language, or a translation.

Depending on context, more natural alternatives could be:

• Tôi zoom vào chủ thể.
• Tôi phóng to hình của chủ thể.
• Tôi phóng to phần chủ thể.
• Tôi làm chủ thể to hơn.
  This one is less technical and more conversational.

So the original sentence is not wrong, but it may not be the most everyday phrasing.

Yes, very often.

Vietnamese frequently drops pronouns when the subject is clear from context. So instead of saying:

• Tôi phóng to chủ thể.

you might simply say:

• Phóng to chủ thể.

This is especially common in:

• instructions
• software menus
• conversations where it is obvious who is acting

But if you want to clearly say I am the one doing it, keeping tôi is perfectly fine.

You usually know from context.

For example:

• In photo editing, phóng to often means enlarge
• In camera use, it may be understood as zoom in
• In general visual description, it can mean make bigger / magnify

Vietnamese often allows one expression to cover several related English meanings. English separates them more strictly than Vietnamese sometimes does.

So you should not expect a perfect one-to-one match every time.

No, not by itself.

Vietnamese verbs do not change form for tense the way English verbs do. phóng to stays the same. Time is usually understood from context or shown with time words.

For example:

• Tôi đang phóng to chủ thể. = I am enlarging / zooming in on the subject.
• Tôi đã phóng to chủ thể. = I enlarged / have enlarged the subject.
• Tôi sẽ phóng to chủ thể. = I will enlarge the subject.

So the basic sentence Tôi phóng to chủ thể is tense-neutral unless context tells you more.

Because Vietnamese does not use articles like a, an, and the in the same way English does.

So chủ thể can mean:

• a subject
• the subject

depending on context.

If the speaker and listener both know which subject is meant, English would usually say the subject, but Vietnamese often just says chủ thể with no article at all.

That is completely normal in Vietnamese.

Yes.

While chủ thể is correct, native speakers may choose different words depending on the situation:

• đối tượng = object/subject
• người này / vật này = this person / this object
• nhân vật chính = main character / main person
• mẫu = model, in photography contexts

For example, if you are talking casually about a person in a picture, you might hear:

• Tôi zoom vào người này.
• Tôi phóng to nhân vật chính.

So chủ thể is useful and correct, but it can sound more formal or technical than some everyday alternatives.