Hình này rất sắc nét.

In Vietnamese, demonstratives like này (this) usually come after the noun.

So:

• hình này = this picture/image
• not này hình

This is a very common pattern in Vietnamese:

• nhà này = this house
• xe này = this vehicle
• bàn này = this table

So Hình này literally follows the Vietnamese word order picture this.

Vietnamese often does not use a verb like is/are when describing something with an adjective.

So:

• Hình này rất sắc nét. literally works like
• This picture very sharp/clear.

That is a normal Vietnamese sentence.

You do sometimes see là, but là is generally not used before ordinary adjectives in sentences like this. For example:

• Cô ấy là giáo viên. = She is a teacher.
• Cô ấy đẹp. = She is beautiful.
  (not usually là đẹp)

So in your sentence, no is is needed.

Hình can mean picture, image, photo, or sometimes figure, depending on context.

It overlaps a lot with ảnh, but they are not always identical in nuance:

• ảnh often specifically means a photo/photograph
• hình is broader and can mean a picture/image in general

So Hình này rất sắc nét could be used for:

• a photo
• a digital image
• a screenshot
• a printed picture

If you said Ảnh này rất sắc nét, that would sound very natural too, especially if you are clearly talking about a photograph.

Rất means very.

So:

• sắc nét = sharp / clear / well-defined
• rất sắc nét = very sharp / very clear

It goes before the adjective it modifies, just like very in English:

• rất đẹp = very beautiful
• rất nhanh = very fast
• rất tốt = very good

So the structure is:

• Hình này
  • rất
    • sắc nét

It is written as two words: sắc nét.

Together, they form a very common adjective meaning:

• sharp
• clear
• crisp
• well-defined

It is especially used for:

• pictures
• photos
• screens
• video quality
• printed text

Examples:

• Màn hình này rất sắc nét. = This screen is very sharp.
• Ảnh chụp khá sắc nét. = The photo is quite sharp.

Learners often try to understand each part separately, but in practice it is best to learn sắc nét as a single expression.

It can refer to more than just a photo.

Because hình is broad, the sentence can describe:

• a photograph
• a drawing
• an illustration
• a graphic
• an image on a screen

The exact meaning depends on context. If someone is pointing at something on a phone, computer, or page, hình này can work naturally.

A rough English-friendly guide is:

• Hình ≈ hing
• này ≈ nye
• rất ≈ somewhat like zut / ruht depending on accent
• sắc ≈ suck with a sharp rising tone
• nét ≈ net with a rising tone

A few useful pronunciation notes:

• hình has the huyền tone, so it sounds lower/falling
• này also has the huyền tone
• rất has the sắc tone in spelling, though actual pronunciation can vary by region
• sắc and nét also have the sắc tone, which is rising

If you want to sound natural, the tones matter a lot more than exact English-like vowel matching.

It is neutral and very natural.

You could use it in everyday conversation when talking about image quality. For example:

• looking at a photo on a phone
• discussing camera quality
• commenting on a print or screen

It is not especially formal or slangy.

Yes. Bức hình này rất sắc nét is also correct.

Here, bức is a classifier often used for:

• pictures
• paintings
• drawings
• photos

So:

• Hình này rất sắc nét.
• Bức hình này rất sắc nét.

Both are natural.

The version without bức is a little shorter and very common in speech. Adding bức can sound slightly more explicit or complete.

You can add không before the adjective phrase:

• Hình này không sắc nét. = This picture is not sharp/clear.

If you want to say not very sharp, you can say:

• Hình này không được sắc nét lắm.
• Hình này không quá sắc nét.

These can sound a bit more natural in some contexts than a direct negative, depending on what you want to express.

Yes. Vietnamese has several common degree words you can use:

• Hình này khá sắc nét. = This picture is quite sharp.
• Hình này cực kỳ sắc nét. = This picture is extremely sharp.
• Hình này hơi sắc nét. = This picture is slightly sharp.
  This one is less common semantically, because sharpness is not always something described with slightly in a natural way.
• Hình này quá sắc nét. = This picture is too sharp / overly sharp.

So rất is just one common intensifier.

The pattern is:

• Noun + demonstrative + degree word + adjective

In this sentence:

• Hình = picture/image
• này = this
• rất = very
• sắc nét = sharp/clear

So the full structure is:

• Hình này rất sắc nét.
• This picture is very sharp.

This is a very useful Vietnamese pattern that you can reuse:

• Xe này rất nhanh. = This vehicle is very fast.
• Nhà này rất đẹp. = This house is very beautiful.
• Món này rất ngon. = This dish is very delicious.