Learn Hardcore Portuguese (Portugal): O brilho do ecrã está alto demais; isso cansa os olhos ao fim do dia. - The screen brightness is too high; that tires the eyes at the end of the day.

o brilho = the brightness
Just brilho (without article) is possible, but it sounds more like a title, a label, or very telegraphic style (e.g. in menus, notes, headlines).
In a normal sentence describing something, o brilho do ecrã sounds natural and complete, whereas brilho do ecrã está alto demais would sound a bit like a note you wrote on a Post-it.

So, in standard, neutral speech, you normally include the article: O brilho do ecrã está alto demais…

What is happening grammatically in do ecrã?

do is a contraction:

de + o = do

So do ecrã literally means de o ecrã (of the screen), but native speakers always contract it to do ecrã.

Structure:

o brilho do ecrã = the brightness of the screen

The word ecrã is masculine in European Portuguese, so we use o ecrã, not a ecrã.

What exactly does ecrã mean, and is it specific to Portugal?

Yes, ecrã is the standard European Portuguese word for screen (of a computer, phone, TV, etc.).

In Portugal: ecrã is what you’ll hear and see in interfaces, manuals, etc.
In Brazil: the usual word is tela, not ecrã.

So:

EP: o ecrã do computador
BP: a tela do computador

Both mean the computer screen.

How do you pronounce ecrã, and what does the ã mean?

Approximate pronunciation (European Portuguese):

ecrã ≈ eh-KRÃ
- e like e in get
- cr as in English cream (but shorter)
- ã is a nasal vowel; you don’t pronounce a final “n” or “m”, you just nasalise the vowel.

The ã indicates a nasal a sound, similar to French an in enfant or the -on in some English pronunciations of wrong, but with the tongue more forward. There is no exact English equivalent, so you mainly have to learn it by ear.

Why is it está alto demais and not é alto demais?

This is the usual ser vs estar contrast:

ser (é) is used for more permanent, inherent characteristics.
estar (está) is used for temporary or current states.

Here, the idea is that the current setting of the brightness is too high (something you can change), so estar fits:

O brilho do ecrã está alto demais.
The screen brightness is too high (right now / at the moment).

If you said:

O brilho do ecrã é alto demais.

it would sound more like By nature, the screen’s brightness is too high (a more permanent property of that specific screen), which is less likely here.

What’s the nuance of alto demais vs demasiado alto vs muito alto?

All three can be used, but there are differences:

alto demais
- Very natural in everyday speech.
- Means too high, excessively high.
- Slightly more colloquial/relaxed than demasiado alto.
demasiado alto
- Also too high, excessively high.
- Sounds a bit more neutral or careful, and is very clear in writing.
- Common in European Portuguese, especially in more formal contexts.
muito alto
- Literally very high.
- In context it can imply it’s too high, but grammatically it doesn’t mean “too”, just “very”.
- If you really want to say too high, alto demais or demasiado alto is safer.

Here, alto demais communicates clearly: it’s higher than it should be.

Can demais mean something other than “too (much)”?

Yes, demais has two main uses:

“Too much/too (adjective)” when it comes right after an adjective or adverb:
- alto demais = too high
- rápido demais = too fast
“A lot/very much” when it follows a verb:
- Gosto demais deste filme. = I really like this film / I like this film a lot.

In your sentence, demais comes after an adjective (alto), so it has the “too (much)” meaning: too high.

Why is there a semicolon (;) instead of a comma or a full stop?

The semicolon links two closely related clauses:

Clause 1: O brilho do ecrã está alto demais;
Clause 2: isso cansa os olhos ao fim do dia.

You could also write:

O brilho do ecrã está alto demais. Isso cansa os olhos ao fim do dia.

That’s perfectly correct; it just separates them more strongly.

A comma here (alto demais, isso cansa…) would be less standard in careful writing, because each part is a full clause with its own subject and verb. Semicolon keeps the connection clear while respecting that separation.

Why is it isso and not isto or ele?

In this context, isso refers back to the whole idea “the brightness of the screen is too high”.

isso = that (idea/thing we just mentioned)

The usual distinctions:

isto – this (something very close, or something you’re about to introduce)
isso – that (something just mentioned, or associated with the listener)
ele/ela – normally refer to specific nouns (he/she/it), not whole situations.

Here we are not referring to a physical object like the screen (o ecrã), but to the whole situation (“the brightness being too high”), so isso is the natural choice:

Isso cansa os olhos… = That (fact/situation) tires the eyes…

Why is it cansa os olhos and not cansam os olhos?

Verb agreement in Portuguese follows the subject, not the closest noun.

Subject: isso (singular)
Verb: cansa (3rd person singular of cansar)
Object: os olhos (direct object, plural)

So:

isso cansa os olhos = that tires the eyes

If the subject were plural, the verb would change:

Essas luzes cansam os olhos.
Those lights tire the eyes.
(subject essas luzes, verb cansam)

Why is it cansa os olhos and not cansam-se os olhos or os olhos cansam?

All of these are possible in different formulations, but they’re not equivalent:

Isso cansa os olhos.
- Focus: the thing (isso) is actively tiring the eyes.
- Direct, natural way to say “That tires the eyes.”
Os olhos cansam.
- Focus shifts to the eyes themselves: The eyes get tired.
- You could say: Os olhos cansam ao fim do dia., but it doesn’t mention the screen anymore.
Cansam-se os olhos.
- Grammatically possible (the eyes get themselves tired), but in everyday speech this order sounds quite formal or literary.
- In more natural order you’d say: Os olhos cansam-se ao fim do dia.

The original sentence wants to keep a clear cause-effect structure: Isso (cause) → cansa os olhos (effect), so the chosen form is the most straightforward.

Why is it os olhos and not os teus olhos (“your eyes”)?

Portuguese often uses the + body part instead of your/my/his when it’s clear from context whose body we’re talking about.

cansa os olhos literally: tiring the eyes
Implied: your / one’s / our eyes, depending on context.

If you say os teus olhos, you highlight specifically your eyes (and not someone else’s):

Isso cansa os teus olhos. = That tires your eyes (in particular).

The generic statement cansa os olhos is more neutral and natural here, meaning it’s tiring on the eyes in general.

What’s the difference between ao fim do dia and no fim do dia?

Both can be used with time expressions and are often interchangeable, but there is a slight nuance:

ao fim do dia
- Literally “at the end of the day”.
- Very idiomatic in European Portuguese to mean by the end of the day / when the day is finishing.
- Has a bit of a routine / habitual feel.
no fim do dia
- Literally “in/at the end of the day”.
- Also possible and understood as a time expression.
- Can sound a bit more “static” or literal: at that time point, at the end of the day.

In this sentence, ao fim do dia is very natural, giving a sense of “as the day wears on and by the end of it”.

Is this sentence specifically European Portuguese? How would Brazilians usually say it?

Yes, some choices are clearly European Portuguese:

ecrã (EP) vs tela (BP)
ao fim do dia is much more typical in Portugal; Brazilians are more likely to say no fim do dia.
demais is fine in both, but demasiado is more common in Portugal than in Brazil.

A natural Brazilian Portuguese version might be:

O brilho da tela está muito alto; isso cansa os olhos no fim do dia.

Or:

O brilho da tela está alto demais; isso cansa os olhos no fim do dia.

Could you rephrase the sentence in other natural ways in European Portuguese?

Yes, here are a few natural variations with slightly different word choices:

O brilho do ecrã está demasiado alto; isso cansa os olhos ao fim do dia.
A luminosidade do ecrã está alta demais; isso cansa os olhos ao fim do dia.
Se o brilho do ecrã estiver alto demais, cansa os olhos ao fim do dia.
O brilho do ecrã é muito forte; isso acaba por cansar os olhos ao fim do dia.

All keep the same essential idea while slightly changing vocabulary or structure.