La nitidez mejora con la lente.

Spanish often uses the definite article with abstract nouns more than English does. So la nitidez is completely natural.

Here, la nitidez refers to the sharpness as a quality or result being discussed. English often drops the article, but Spanish usually keeps it in sentences like this.

So:

• La nitidez mejora... = natural Spanish
• Nitidez mejora... = not natural here

Nitidez is a noun meaning sharpness, clarity, or crispness, especially in visual contexts.

You will often see it in:

• photography
• optics
• screens
• image quality

It comes from the adjective nítido/a, meaning sharp, clear, or well-defined.

Examples:

• una imagen con mucha nitidez = an image with a lot of sharpness
• La foto tiene más nitidez = the photo has more sharpness

Because its grammatical gender is feminine: la nitidez.

There is no simple rule that lets you predict the gender of every noun from its ending, so this is something you mostly learn with the word itself. Even though -ez nouns are often feminine, it is best to memorize the whole phrase:

• la nitidez
• la rapidez
• la sencillez

That helps you remember the correct article automatically.

Here, mejora is a verb.

It is the third person singular present form of mejorar:

• yo mejoro
• tú mejoras
• él/ella mejora

So La nitidez mejora means sharpness improves.

It is true that mejora can also be a noun meaning improvement:

• una mejora = an improvement

But in this sentence, it is clearly the verb because it follows the subject la nitidez.

Because the sentence is built around what improves.

In La nitidez mejora con la lente, the thing that changes is la nitidez. So la nitidez is the subject.

A useful comparison:

• La nitidez mejora con la lente.
  = The sharpness improves with the lens.

• La lente mejora la nitidez.
  = The lens improves the sharpness.

Both are correct, but they focus on different things:

• first sentence: focus on the result
• second sentence: focus on the lens as the cause

Yes, con literally means with, but here it can imply more than simple accompaniment.

In this sentence, con la lente can mean:

• with the lens
• using the lens
• when using the lens
• sometimes even thanks to the lens, depending on context

So con is often used in Spanish to show the tool, means, or condition involved in the result.

In Spain, lente normally means lens.

Depending on context, it could refer to:

• a camera lens
• an optical lens
• a contact lens
• one lens in a pair of glasses

If you mean glasses as a whole, Spain Spanish usually prefers gafas, not lentes.

So in Spain:

• gafas = glasses
• lente = lens

In standard Spain Spanish, lente is normally feminine: la lente.

However, in some parts of Latin America, people often say:

• el lente
• los lentes for glasses

So if you are learning Spanish from Spain, la lente is the form to use.

Yes, you could, but it changes the nuance a little.

• con la lente = neutral, practical, with / using the lens
• gracias a la lente = more clearly thanks to the lens

So con is more neutral and common in technical or descriptive language.
Gracias a puts more emphasis on the lens as the reason for the improvement.

Yes. Spanish word order is flexible.

You could also say:

• Con la lente, mejora la nitidez.

This is still correct, but it gives more emphasis to con la lente.

The original version:

• La nitidez mejora con la lente.

is the most neutral and straightforward.

Because mejorar works very naturally here as a normal intransitive verb.

• La nitidez mejora = the sharpness improves

That is already complete and idiomatic.

If you say se mejora, the structure changes and it does not sound as natural for this simple statement. For a learner, the best forms to remember are:

• La nitidez mejora con la lente.
• La lente mejora la nitidez.

Those are the clearest natural options.