Càng phóng to, hình càng mờ.

It means the more …, the more … or as … increases, … also increases/changes.

So in this sentence:

• Càng phóng to, hình càng mờ.

the structure shows a relationship between two changes:

• when the zoom gets greater,
• the image gets blurrier.

This is a very common Vietnamese pattern for comparisons of change:

• Càng học càng giỏi. = The more you study, the better you get.
• Càng lớn càng đẹp. = The older she gets, the prettier she becomes.

Because each càng marks one side of the correlative comparison:

• first part: the changing condition
• second part: the changing result

So:

• Càng phóng to = the more you enlarge/zoom in
• hình càng mờ = the blurrier the image gets

Using càng twice is the normal way to build this pattern.

Phóng to means to enlarge, to blow up, or to zoom in / make bigger.

Depending on context, it can refer to:

• enlarging a photo
• zooming in on an image on a screen
• printing something at a larger size

In this sentence, it most naturally means to enlarge an image or zoom in.

Vietnamese often leaves out subjects when they are obvious from context or when the sentence is stating a general fact.

So Càng phóng to, hình càng mờ does not need to say:

• you enlarge it
• we enlarge it
• the image is enlarged

It just gives the general relationship:

• the more it is enlarged,
• the blurrier the image becomes.

This kind of omission is very normal in Vietnamese.

Here, hình means image, picture, or photo.

It is a very common everyday word. Depending on context, hình can mean:

• a picture
• a photo
• an image on a screen
• a figure/shape

In this sentence, it clearly means the image/picture.

Mờ usually means blurred, unclear, fuzzy, or not sharp.

In image-related contexts, mờ is very naturally translated as:

• blurry
• pixelated / unclear depending on the situation
• not sharp

So here, hình càng mờ means the image becomes less clear as it is enlarged.

Vietnamese often does not need a separate verb like become when a change is already clear from the pattern.

In English, we usually say:

• the image becomes blurrier
• the image gets blurrier

In Vietnamese, the càng … càng … structure already implies a changing relationship, so hình càng mờ is enough.

If you translated word-for-word, it might look like:

• image more blurry

but the real meaning is:

• the image gets blurrier

Yes. That is also natural.

Adding thì can make the sentence feel a little more explicit:

• Càng phóng to thì hình càng mờ.

This is similar to saying:

• The more you enlarge it, then the blurrier the image gets.

In many cases, thì is optional in this pattern. Both versions are natural:

• Càng phóng to, hình càng mờ.
• Càng phóng to thì hình càng mờ.

The comma is not always strictly necessary, but it is very helpful.

It separates the two halves of the pattern:

• Càng phóng to,
• hình càng mờ.

In writing, the comma makes the structure easier to read. In speech, there is usually a small pause there.

In modern casual speech, some people do use English-influenced expressions, but phóng to is the standard Vietnamese way to say enlarge.

If you are talking about a digital image, other context-specific verbs may appear, but phóng to is a very normal and correct choice.

So for learners, phóng to is the safest and most useful phrase to remember.

It is best understood as the image in a general sense.

Vietnamese nouns usually do not show singular/plural the way English nouns do. The context tells you what is meant.

Here, hình most naturally refers to:

• one image,
• or an image in general.

If needed, Vietnamese can add words for specificity, but in this sentence it is not necessary.

Yes, that is possible, but it changes the feel slightly.

• hình càng mờ = the image gets blurrier
• hình càng bị mờ = the image increasingly gets blurred / is affected by blurring

The version without bị is simpler and more natural for a general statement like this.

Use bị when you want to emphasize that something is affected in an undesirable way, but here it is not necessary.

It is natural and easy to understand, especially in contexts like:

• talking about photos
• digital images
• printing
• screen resolution

It sounds like a concise general statement, almost like a rule or observation. Very normal Vietnamese.

A speaker might also say slightly longer versions such as:

• Càng phóng to thì hình càng mờ.
• Phóng to càng nhiều thì hình càng mờ.

But your original sentence is perfectly good.

Yes, very often. Càng … càng … is a highly productive pattern in Vietnamese.

Examples:

• Càng đọc càng hiểu.
  The more you read, the more you understand.

• Càng đợi càng sốt ruột.
  The longer you wait, the more impatient you get.

• Càng nói càng sai.
  The more you talk, the more mistakes you make.

So Càng phóng to, hình càng mờ is a good model sentence for learning this grammar pattern.