Talk:ZX Spectrum graphic modes

Archives (Index)

1

Too bright 'dim' RGB values suddenly – “PAL gamma”?

I am quite worried after 4throck's « PAL gamma approximation » that has set 224 as potential RGB values for the dim colors, lately.

→ MY SUMMARY:

I am not convinced at all from this undocumented and rough method, so I'd like to know more about the applied conversion, in scientific terms hopefully. From what I humbly know as a long-term pixel artist and coder, almost all the related users on the real hardwares and via emulators are pretty fine with the medium 192, even the brighter 205 at times, for at least 14 years…

→ MY QUESTIONS:

• What are the proofs of this sudden correction?
• Where is the paper of this possible research?
• Is your system original or modded?
• What is your display and which settings?
• Are you fine with these faulty dim colors?
  

→ MY DOUBTS:

• The difference looks too big and new to be true.
• The dimming looks flawed, not less inaccurate as expected.
• We won't edit millions of RGB conversions after a one-man decision.
• I remember my opposite experience here.

--_{d^⠚p^⠖l^⠃a^⠒.fr} 02:09, 13 September 2021 (UTC)

75% voltage (a linear value) corresponds to DN 192 of course, but that value was then PAL encoded and displayed on a CRT. That assumes a non-linear display gamma of 2.4. Today's displays are sRGB with gamma 2.2 (that's the web standard), so we need to change the values for proper display on Wikipedia. That's what I did, I simply gamma corrected the original value. Of course, I might have done a mistake somewhere. Feel free to apply a better correction or change it back, I'm not "territorial" about my contributions.

But one thing is certain, on an sRGB display the correct value won't be 192. Likewise the Spectrum's RGB primaries are BT.601 (PAL) and need to be converted to Rec.709 (sRGB) for accurate display. In practice the difference is minimal (ex: green will be something like 0,255,32 ), but mathematically it's there. So yes, all emulators are wrong unless you connect them to a PAL TV.

The point here is that Wikipedia is a web based, and web colors are sRGB (unless you use images with ICC profiles...)

Hope it helps 4throck (talk) 08:57, 14 September 2021 (UTC)

I'm replying to here to temporarily stop the archiving of this section by ClueBot III. Ignore this post. Z80Spectrum (talk) 05:05, 26 March 2024 (UTC)

Archive settings

I was going to add archiving to this talk page, but I realised that if I did it would archive most of Z80Spectrum's remaining comments, and as I don't want to be accused of having ulterior motives, I'll wait until the discussion has run it's course. I've added <nowiki></nowiki> tags that can just be removed when done. I also added a header to the Demo scene comment, otherwise that will never be archived when the time comes. Chaheel Riens (talk) 15:02, 10 January 2024 (UTC)

Is archiving good or bad, in the sense that I would like, of course, this discussion to remain as visible as possible? Z80Spectrum (talk) 16:19, 10 January 2024 (UTC)

WP:ARCHIVE I prefer Cluebot III, which is the code I've added to the top of the page. Inclusion of the minkeepthreads=3 parameter stipulates that there will always be at least three topics left on the talk page, even if they're eligible for archiving. So - at this time of writing - all threads before Grammar error near start of "ULAplus" section will be archived. Remember that archived comments don't disappear - they can still be seen (and searched) in the archive itself. Chaheel Riens (talk) 17:13, 10 January 2024 (UTC)

Perhaps, If I want this issue "decided", I should post it now to WP:DRN, before it is archieved. I think we have enough arguments posted, sufficient for a decision.

However, I'll probably be a bit busy now, but I'll try to go to [WP:DRN] in less than 24 hours. I hope that is OK with you, and that you can postpone the archieving for 24 hours. Z80Spectrum (talk) 17:59, 10 January 2024 (UTC)

Just to make it clear:

I would like some topics of the talk page to be archived.

The topics that should be archived are:

- Epilepsy?

- Shock Megademo

- Grammar error near start of "ULAplus" section

Everything else should stay on the talk page. Z80Spectrum (talk) 07:23, 11 January 2024 (UTC)

I removed ClueBot III. I'm against adding any bots to this page. The topics should be archived manually. Z80Spectrum (talk) 07:39, 11 January 2024 (UTC)

I'm replying to myself here to temporarily stop the archiving of this section by ClueBot III. Z80Spectrum (talk) 05:06, 26 March 2024 (UTC)

The removal at [1] looks unsurprising given the WP:FORUM nature of the comments. @Z80Spectrum: the content remains available in the history for you to copy to a more appropriate (non-Wikipedia) location. I see no value in keeping any of the sections above on the talk page and I think they can be safely archived immediately. The section Someone has just deleted all of my suggestions is too rambling to be useful. If there are unresolved issues there a new, less verbose, section should be started. all parties are encouraged to keep discussion tightly-worded and focused on article content. VQuakr (talk) 20:48, 11 January 2024 (UTC)

Z80Spectrum, as I've explained already - the |minkeepthreads=3 setting means that regardless of the age of the threads - and even if they meet archiving criteria - there will always be 3 threads active on the talk page. Also - don't edit war. You've already agreed that you don't understand how archiving works, so please don't mess around with things you don't understand. Chaheel Riens (talk) 07:12, 26 March 2024 (UTC)

Engvar edits

I've reverted your latest edits for the following reasons:

• WP:Engvar is policy - please read and understand it. Your reversion - and subsequent manual changes - missed some engvar instances
• There is no preference between scientific notation and ASCII representation, but the article as it stands mixes usage of both styles. My edit consolidated this to a single style of ASCII "x", which is better represented off-wiki such as translations and PDF creation etc. Your reversion obviously undid this and reinstated usage of both ASCII and scientific notation - sometimes in the same sentence.
• The article itself is not disputed. Your edits on the talk page are disputed.
  • This is the second time the disputed template was added after it was removed by a completely uninvolved editor. Simply adding it again is the first step in edit warring

Chaheel Riens (talk) 13:21, 11 January 2024 (UTC)

I wouldn't quite agree to the simplistic description of the events that you have provided, but I'll skip my side of the story, for brevity. I don't think it matters much.

The only real contention is "x" vs multiplication "×". I'm stronly for multiplication symbol, so if your only complaint is consistency, then I'll change the entire article so that only multiplication symbol is used.

Is that OK? Z80Spectrum (talk) 15:59, 11 January 2024 (UTC)

I have another un-related proposal. It is about solving our dispute, hopefully, easily. I have posted it on your talk page a few hours ago.

I had this idea: the removed parts of this talk page, which are the object of dispute, can be archived.

I have nothing against archiving that entire computation of mine, and the rest that was removed. Would that be acceptable to you as a resolution of our dispute? Z80Spectrum (talk) 16:04, 11 January 2024 (UTC)

I've replied on my talk page as to why I'm against your archiving proposal, and as I make clear above consistency is not my only complaint about the mix of ASCII and scientific notation - the scientific notation character is not a standard ASCII value (215), and outside the usual 32-127 set, which causes issues when transcoding. There are occasions when either scientific notation or indeed any >127 ASCII values should be used, but this isn't one of them as there's an acceptable alternative - "x" (120). Chaheel Riens (talk) 08:11, 12 January 2024 (UTC)

Ok. I now understand that issus with non-ASCII characters are also important to you.

What I don't understand now is this:

The much more popular and important page "ZX Spectrum" also contains non-ASCII multiplication symbol, all over the place.

I also see that you were active on the talk page of "ZX Spectrum".

So, why don't we agree on one standard for both pages, and work towards that goal?

We could ask other editors, on this talk page and on "ZX Spectrum", and see if we can reach some kind of a consensus policy, or we can perhaps agree to abide by majority's decision.

I think that such an agreement would be far better than having the two of us constantly revert and correct each other over minor issues. I don't think that we are in an edit war, perhaps our opinions just happen to be different. Z80Spectrum (talk) 17:22, 12 January 2024 (UTC)

I'm replying to myself here to temporarily stop the archiving of this section by ClueBot III. Z80Spectrum (talk) 05:07, 26 March 2024 (UTC)

Sources for INT on vertical sync

I've got a problem: an user with an IP address is now, for the second time, reverting the text for Z80 INT signal on vertical synchronization.

The newest change he did is still wrong (he claims that Spectrum used IM2). IM2 is just an interrupt mode of INT, which can be modified by Z80 software to either IM0, IM1, or IM2.

Unfortunately, I can't find good sources that EXPLICITLY say that the vsync was hooked onto INT. Can someone help me? Obiously, I can't notify the user who uses an IP address.

If someone could find a good source for INT on vsync, it would be great. Z80Spectrum (talk) 19:18, 11 January 2024 (UTC)

Found a source, page 224 of:

11. Smith, Chris (2010). The ZX Spectrum ULA: How to Design a Microcomputer (1st ed.). United Kingdom: ZXDesign Technology and Media. p. 74. ISBN 978-0-95-650710-5.

It's a book, non-free, but hopefully this will be good enough to stop the user. Z80Spectrum (talk) 19:32, 11 January 2024 (UTC)

Yes, made it! Z80Spectrum (talk) 19:54, 11 January 2024 (UTC)

I'm replying to myself here to temporarily stop the archiving of this section by ClueBot III. Z80Spectrum (talk) 05:07, 26 March 2024 (UTC)

Comparisons with Commodore 64

Could it be outlined why some features of the Spectrum graphic modes get compared to the Commodore 64, while others do not? Is the Commodore 64 some kind of baseline? Do reliable sources make this comparison? In the Spectrum's home market, the Commodore 64 was outsold through most of the 80s by the Spectrum, Vic20 and BBC b, so what is it that makes this comparison relevant? Thanks. Escape Orbit ^(Talk) 13:26, 12 January 2024 (UTC)

In Europe, both C-64 and ZX Spectrum were about equally popular. There are some differences from one country to another, they were both present in many countries at the same time.

A fact is that C-64 is micro-computer with the highest sales in 1980's.

For those two reasons, C-64 and ZX Spectrum do often get compared. Comparisons are all over the today's Internet, it is easy to find them on Google.

So, yes, C-64 is a common baseline for comparison, and, yes, other sources do make the same comparison.

Also, many readers want to know what are the differences between those two. Even after 40 years, people are still seeking information on the comparison. Z80Spectrum (talk) 17:35, 12 January 2024 (UTC)

I think it is also interesting for the readers of the article to see two different engineering perspectives compared.

It is interesting to provide answers to questions like: in what ways was ZX Spectrum unique; how was it different from the rest; how it compares to the market leader. Z80Spectrum (talk) 17:43, 12 January 2024 (UTC)

If I wanted to do it technically and more in-depth, then I would have mentined in the article that C-64 has an 8 KiB framebuffer, while ZX Spec has 6.8 KiB framebuffer. Those two are very close, with a slight advantage to C-64.

Then, C-64 has sprites and scrolling, but Spectrum has a slightly faster CPU.

Well, overall, for games and graphics, C-64 certainly beats ZX Spectrum, in my opinion, but I would never mention that in the article.

However, ZX Spectrum beats C-64 in other ways: A more "capable" CPU (it is just slightly faster, but Z80 is much more modern than 6502 with regards to style of programming, stack and registers).

Also ZX Spectrum's BASIC is better than C-64 Microsoft 2.0 BASIC, in my opinion.

Better not to mention any of that in the article, in my opinion. Z80Spectrum (talk) 18:02, 12 January 2024 (UTC)

Even if it is a comparison based on facty only, like framebuffer size, it is still better to not mention it, because dry facts cannot tell the whole story.

The story of differences should be based mostly on the differences in electronic design and concept. Even then, only the most important differences in the design and concept should be mentioned in the article, because you can't have the entire article turned into an A vs B comparison. Z80Spectrum (talk) 18:37, 12 January 2024 (UTC)

So, for example, I find the shared graphics memory vs. discrete graphics memory a very interesting comparison, because we still have exactly the same situation in our computers today. Z80Spectrum (talk) 18:43, 12 January 2024 (UTC)

I'm replying to myself here to temporarily stop the archiving of this section by ClueBot III. Z80Spectrum (talk) 05:08, 26 March 2024 (UTC)

Original research on this article

There are a lot of problems with this article that are down to it becoming somewhere for people, who no doubt are very knowledgeable on the subject, to publish their knowledge and opinions. Wikipedia is not the place to publish original research or unpublished opinions by unidentified contributers of unverifiable authority and expertese. As a encyclopedia, it should only contain what has already been published by reliable sources. Escape Orbit ^(Talk) 10:39, 13 January 2024 (UTC)

You have to differentiate "original research" and unsourced (but true) statements.

"Original research" is a narrower term than "unsourced statements". If a statement is unsourced, it might be just a reflection of some well-known fact that is hard to find an explicit reference to.

Such a situation is far better than the situation of most articles on Wikipedia, which contain obviously false but sourced statements. Then you get big fights.

I am of the opinion that the best course of developing an article is to first add statements that are obviously true. That can be done by an expert or by a group of experts. Then, later, sources for those statements can be found.

Therefore, we should first make a good attempt to find the missing references for the unsourced statements. It might not be easy, it might take some time. Z80Spectrum (talk) 12:47, 13 January 2024 (UTC)

@Z80Spectrum Sorry, Wikipedia doesn't make any such distinction, and that is not how Wikipedia works. The criteria for inclusion is verifiability, not truth. Wikipedia is not interested in what self-proclaimed experts can contribute themselves, but in what they can identify and select from within reliable sources. Otherwise articles could be filled with what well meaning, but wrong, people believed was right, and not what recognised authorities and experts have already published. If no good sources can be found, then the question must be "is this notable and suitable for Wikipedia"? To which the answer is usually no. Remember, this is an encyclopaedia, not a technical manual. Escape Orbit ^(Talk) 13:51, 13 January 2024 (UTC)

Well, that is fine, but the real question is: how much time to allow for the good sources "to be found", as you say? Z80Spectrum (talk) 14:42, 13 January 2024 (UTC)

I'm replying to myself here to temporarily stop the archiving of this section by ClueBot III. Z80Spectrum (talk) 05:09, 26 March 2024 (UTC)

As a general rule of thumb, if you can't find sources of information for facts, it probably means that it's not important information to include in the encyclopedia. For example, the fact "User Ritchie333 wrote a utility in Z80 machine code to load any Speedlock game, decrypt it, and return a pointer to the start of the executable code" is true (well, you'll just have to trust me that it is), but without multiple sources mentioning it, it's not going in any article.

I appreciate though, for topics that pre-date the internet explosion, lots of important information is published in long out-of-print media that is hard to access, and that is a problem. Ritchie333 ^{(talk) (cont)} 10:59, 17 January 2024 (UTC)

I want to 2nd the observation that this article needs a hard scrub for its original research issues. For example, there are a bunch of images that note they are a "Simulation of ZX Spectrum graphics output". Is that a simulation the editor did? If so, those images should not be in the article. VQuakr (talk) 18:45, 18 January 2024 (UTC)

Split Proposal

In my opinion, the article should be split into two, because it is extremely confusing as it is. One article should be titled "ZX Spectrum Basic Graphics Mode", and the second article "ZX Spectrum Non-Basic Graphics Modes" (note: the split is not related to the BASIC programming language). The first article should contain everything up to the "Hicolour 8x1" section.

This second article can contain the descriptions of both the graphics modes of the ZX Spectrum's successors, and the various software-assisted modes, and other quirks that were used to enhance the output image. 02:19, 2 February 2024 (UTC)

Posted on behalf of Z80Spectrum per their request at [2]. VQuakr (talk) 02:19, 2 February 2024 (UTC)

• Thank you. Z80Spectrum (talk) 02:54, 2 February 2024 (UTC)

Also: at the time when my proposal was originally made, the section Dithering and Blur was in the top half of the article. So, I believe that the "Dithering and Blur" should go into the first half of the split ("ZX Spectrum Basic Graphics Mode").

I'm also unsure about the title of the first part. Perhaps a better title would be "ZX Spectrum Standard Graphics Mode". Z80Spectrum (talk) 02:59, 2 February 2024 (UTC)

• Oppose. This is already a quite overly detailed subarticle from ZX Spectrum, and at 3400 words of prose is it not approaching the "too long" region of WP:SIZERULE. The concern about it being confusing is better addressed by pruning, editing, and otherwise improving the article. In any case, the substantial issues with sourcing and original research should be addressed before they are propagated into an article split. Personally I am unconvinced that much of the emulated or otherwise kludged "non-basic modes" merit mention anywhere in Wikipedia, but that's beyond the scope of this split discussion. I would likely support a move to the more generalist ZX Spectrum graphics, but again that's beyond the scope of this discussion I think. VQuakr (talk) 03:48, 2 February 2024 (UTC)
• Oppose. The pages and "see also" sections of comparable computers of the era, such as the Commodore VIC-20 and the Atari 400/800 series, do not have separate pages for the graphics mode, character set or specifications of the memory. Splitting the page up will just add more pages about the technical side of the ZX Spectrum that aren't exactly necessary. Keep this page as is. GarethBaloney (talk) 23:40, 16 February 2024 (UTC)
• Oppose Page is too small for a size split, and I see no case for a WP:CONTENTSPLIT. If the article is confusing, and a split is really the only remedy to make it not confusing, then the same effect can be achieved by creating two sections ZX Spectrum graphic modes § Basic modes and ZX Spectrum graphic modes § Advanced modes, or somesuch. Paradoctor (talk) 08:11, 26 March 2024 (UTC)