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My name is Kitao Nakamura, the developer of the PC Engine emulator Ootake.

In recent years, many re-released retro games—especially classic arcade titles— have been
published with their pixel aspect ratios (the shape of each character pixel) either ignored or
determined incorrectly.

As a result, the true quality of these masterpieces is often not fully conveyed.

In Gradius II, a pixel‑by‑pixel display is exactly the world
the designers intended.  * pixel‑by‑pixel = 1:1 pixel mapping

Gradius II is a masterpiece that has been re-released many times over the years. However, in three of the recent re-releases—Arcade Archives Gradius II, Arcade Classics Anniversary Collection, and Gradius: Origin Collection—the default setting stretches the original 320x224 game image to fill a 4:3 virtual TV screen. This results in the pixels being vertically stretched by a factor of 1.07, making the character designs appear unnaturally tall. This is clearly incorrect. Anyone who has actually played the game may notice that the artificial sun in Stage 1 looks far too thin vertically. And those who own the original PCB will immediately see that the square test grid pattern shown at boot is no longer square under this display method—it becomes noticeably elongated vertically ↓The default display in the Origin Collection.    The test grid becomes vertically elongated. Source：『Gradius: Origin Collection』（© Konami Digital Entertainment） ↓Display using the Origin Collection’s "Dot by Dot (pixel‑by‑pixel)" setting.    The test grid now appears as perfect squares. Source：『Gradius: Origin Collection』（© Konami Digital Entertainment） This white mesh test grid was the key tool arcade staff used to adjust the pixel aspect ratio on CRT monitors. By tuning the display so that this test pattern appeared as perfect squares, the staff ensured the game looked as natural as possible—exactly as the developers intended. In Gradius II, each black square in the test grid is displayed as 14x14 pixels—perfect squares with the same number of pixels vertically and horizontally. This strongly suggests that the developers intended the CRT to be adjusted so that each pixel appears as a square pixel. * On modern PCs and consoles, this corresponds to a true pixel‑by‑pixel (1:1) display. Once the display is adjusted correctly, the artificial sun in Stage 1 no longer looks unnaturally thin. Even that slight roundness makes a surprisingly big difference in how the game feels—the sun simply has more visual impact. Naturally, this also changes how enjoyable the game feels after playing. ↓The default display in the Origin Collection.    The artificial sun appears vertically stretched. Source：『Gradius: Origin Collection』（© Konami Digital Entertainment） ↓Display using the Origin Collection’s "Dot by Dot (pixel‑by‑pixel)" setting.    The artificial sun now appears properly round. Source：『Gradius: Origin Collection』（© Konami Digital Entertainment） There is another decisive piece of evidence that Gradius II was meant to be displayed pixel‑by‑pixel. It lies in Stage 7’s boss, the Covered Core. According to design materials from the original character artist, the Covered Core was drawn as a perfect circle. This clearly indicates that the intended aspect ratio was one in which circles appear truly circular. ↓Design materials from the original artist. The rotating cover of the    Stage 7 boss, the Covered Core, is drawn as a perfect circle. Source：『Gradius: Origin Collection』（© Konami Digital Entertainment） ↓Display using the Origin Collection’s "Dot by Dot (pixel‑by‑pixel)" setting.    The cover also rotates as a perfect circle in‑game. Source：『Gradius: Origin Collection』（© Konami Digital Entertainment） In the three currently available versions of Gradius II, the Covered Core is slightly horizontally compressed by default, causing it to appear vertically stretched. As a result, the cover no longer rotates as a perfect circle, breaking the intended visual effect. Earlier releases had similar issues due to hardware limitations: the PC Engine version (horizontal pixel ratio x1.14), the PlayStation version (x0.80), and the Sega Saturn version (x0.91) all deviated noticeably from true square pixels. Of course, even with incorrect pixel aspect ratios, the game is still highly enjoyable—it’s a masterpiece with far more to offer than just visuals. But when it comes to truly falling in love with the experience, I personally feel that an inaccurate pixel aspect ratio becomes a significant handicap. One more thing I noticed while capturing images from the Gradius: Origin Collection was the way certain sound effects behaved. In particular, the Ripple Laser in Gradius II normally has a very satisfying sound, but in this release it consistently felt unpleasant to my ears. I sincerely hope this can be improved in a future update. Another issue was that lowering the volume below 100 caused the overall sound pressure to drop significantly. I personally worked around this by raising the volume from the default value of 70 up to 100. That said, the large amount of included materials and the extensive sound gallery are truly excellent.

For Andor Genesis in Xevious, the designer’s intended world is one
built around perfect squares.

Let’s look at another title—Xevious, the classic that introduced players to its world with its imposing boss characters. In the recent Arcade Archives release of Xevious, the default setting stretches the original 224x288‑pixel game screen to fill a virtual 3:4 vertically oriented display. As a result, the pixels are horizontally compressed to about 0.96x, making the character designs appear slightly elongated vertically. The distortion is small enough that many players may not notice it. However, longtime Xevious fans will likely spot it the moment they face Andor Genesis—realizing that it’s not quite the perfect square it’s supposed to be. Anyone who owns the original arcade PCB would also notice that the square test‑grid pattern (the white mesh shown at boot) no longer appears as true squares under this display method, but instead becomes slightly vertically stretched. ↓Left: image horizontally compressed to 0.96x (equivalent to the    Arcade Archives default).  Right: pixel-by-pixel (1:1 pixel mapping). Source：『Windows 95/98 version of Xevious (publisher: MediaKite)』（© Bandai Namco Entertainment Inc.） The test grid in Xevious also displays black squares at 14x14 pixels, meaning each square has the same number of pixels vertically and horizontally. This strongly suggests that the developers intended the CRT to be adjusted so that each pixel appears as a true square. * On modern PCs and consoles, this corresponds to a 1:1 pixel-mapping (pixel-by-pixel) display. When adjusted this way, Andor Genesis becomes a perfect square, matching exactly how we remember it. Its presence — that distinctive look it has precisely because it is a square — finally returns. For players who experienced the game through retro PC ports, this accuracy can bring back old memories and even change how enjoyable the game feels after playing. ↓Left: image horizontally compressed to 0.96x (equivalent to the    Arcade Archives default).  Right: pixel-by-pixel. Source：『Windows 95/98 version of Xevious (publisher: MediaKite)』（© Bandai Namco Entertainment Inc.） There is another decisive reason why pixel-by-pixel display is the correct way to view Xevious. Andor Genesis was also released as plastic model kits and stickers, and in every case it is depicted as a perfect square. By contrast, earlier ports such as the PC Engine version and the Famicom version (with a horizontal pixel ratio of 1.14x) deviated significantly from a true square due to hardware limitations. To repeat the point: even if the pixel aspect ratio is incorrect, Xevious is still an outstanding game with so much going for it that you can absolutely enjoy it. However, whether you end up loving the game as deeply as many fans do can be heavily affected if the pixel aspect ratio is wrong. That is my personal view. One possible reason this 'close enough is fine' mindset has spread is that the default settings in MAME, the arcade-board emulator, use a similar aspect-ratio calculation. Because of that, more and more recent releases seem to assume that if others are doing it this way, then it must be acceptable for them as well. Both the Arcade Archives version and the Origin Collection version allow you to switch to a pixel-by-pixel display, so it is not a fatal issue. However, most players will naturally start by playing with the default settings. So, does a correct method for determining the proper pixel aspect ratio actually exist? We will explore that in the next chapter.

What should be used as the basis for determining
the correct pixel aspect ratio

【1】．For games that display a test grid pattern at startup or in test mode, aligning it to a perfect square is almost always correct. The very fact that the game displays a test grid pattern is essentially the developer’s way of saying, 'Please adjust this so the squares are perfectly square.' Back in the day, arcade operators would look at this white grid pattern and adjust the aspect ratio accordingly. * Update (January 14): I found an article that documents how these adjustments were actually done in real arcades. Another Day at Hey, Day 21 Game Culture Preservation Institute According to it, what I refer to here as the test grid was often called a 'crosshatch' on site, which also matches how many arcade PCB manuals described it." If the test grid pattern contains square cells with the same number of pixels vertically and horizontally, it means the developers intended the game to be displayed pixel-by-pixel. Therefore, when such a game is re-released or ported, a pixel-by-pixel display is the optimal choice. (Examples include the original Gradius, Gradius II, and Xevious.) * The only major exception is Capcom’s CPS hardware (Daimakaimura, Final Fight, Street Fighter II, etc.). If you align its test grid to a perfect square, the characters become noticeably wide, so a different method of adjustment is required." Home consoles of the Famicom and PC Engine era did not output square pixels due to cost constraints. However, many arcade boards—where higher manufacturing costs were acceptable—were designed from the beginning to display each pixel as a true square (pixel-by-pixel). For games that do not display a test grid pattern, the pixel aspect ratio must be determined using the following method. 【2】．Connect the arcade board to a CRT monitor set to its standard settings, and treat the pixel aspect ratio that appears without any adjustment as the correct one. In this context, 'standard settings' refers to a state in which a CRT monitor displays a television broadcast without any vertical or horizontal distortion. Most CRT monitors were shipped in this condition. If a game does not provide a test grid pattern, there are no other reliable reference points, so the pixel aspect ratio seen under these standard settings is treated as the correct one. * Capcom’s CPS hardware (Daimakaimura, Final Fight, Street Fighter II, etc.) is an exception. When displayed under these standard settings, all characters appear noticeably thin. Since this hardware provides no clear reference for adjustment, the aspect ratio was likely left entirely to the discretion of arcade staff. * Irem’s M72 hardware (R-Type, Ninja Spirit, etc.) is also an exception. Under standard settings, characters likewise appear thin, and because the board offers no test grid or other reference points, operators probably had to rely on their own judgment. For both CPS and M72 boards, arcade staff may have adjusted the aspect ratio by looking at round elements on screen—such as the circular dots in the R-Type title logo—and tuning the image until those shapes appeared correct. 【3】．Arcade staff would adjust the monitor so that the image appeared as large as possible while keeping the aspect ratio intact. Once the aspect ratio had been determined, arcade staff would typically enlarge the image as much as possible to make it look appealing. However, during this process, slight variations in aspect ratio often occurred depending on the operator’s personal judgment. Some operators may have ignored the intended aspect ratio altogether and simply stretched the image to fill something close to a 4:3 television screen. In fact, this incorrect approach is essentially how MAME—the arcade-board emulator—determines its aspect ratio. From an implementer’s perspective, stretching the image all the way to a 4:3 frame can appear reasonable at first glance. Because of this, not only MAME but even early versions of my own emulator, Ootake, expanded the image too far using this method, and several emulators still rely on this incorrect approach today. The reason this full‑screen expansion is not correct is that many arcade boards include black borders—non‑active display areas—either at the top and bottom or on the sides. When the image is stretched to fill these inactive regions, the intended aspect ratio becomes distorted. Because some developers of modern re-releases have used this incorrect method as their reference, many titles end up being sold with an inaccurate pixel aspect ratio as the default setting. 【4】．The pixel aspect ratio determined using the method described in 【2】 can be calculated simply by referring to the arcade board’s specifications, even without physically connecting the hardware. Ideally, developers working on modern re-releases should verify the results using the method described in 【2】. However, the same results can be obtained through calculation without physically connecting the hardware. In practice, when creating a port, using these calculated values is likely the most accurate approach. In the next section, we will look at the specific calculations used to determine the correct pixel aspect ratio.

　
How to Calculate the Correct Pixel Aspect Ratio

【1】．Calculate the pixel aspect ratio based on the value defined by ATSC (the Advanced Television Systems Committee) during the digital transition of NTSC: the 6.136 MHz pixel clock. This is the only true reference for pixel aspect ratio in the CRT era. It defines that, on a television screen displaying an undistorted broadcast image, a signal output with a horizontal frequency of 15.734 kHz, a vertical frequency of 59.94 Hz, and a pixel clock of 6.136 MHz will always produce square pixels (1:1). Even before this value was formally defined, actual measurements suggest that the effective pixel clock was already very close to 6.136 MHz. Since the explanation above may still feel abstract, the following section describes the actual calculation process. 【2】．What Formula Is Used for the Calculation Older arcade boards and home consoles were designed to output video compatible with NTSC CRT televisions, which were originally intended for broadcasting. As a result, their output signals use a horizontal frequency of 15.734 kHz and a vertical frequency of 59.94 Hz, or values extremely close to these. NTSC CRTs have a fixed vertical line count of 262.5 lines in non‑interlaced mode. Therefore, the only parameter that varies between different arcade boards and consoles is the horizontal resolution. And the factor that determines this horizontal resolution is the pixel clock. The pixel clock can be thought of as the speed at which the hardware’s drawing cursor processes pixels—not how fast it moves, but how fast it performs its work. A higher pixel clock (a faster rate) allows the system to draw more finely detailed pixels, resulting in higher horizontal resolution. From the pixel clock, the hardware’s pixel aspect ratio can be calculated immediately. The calculation is as follows: 6.136 ÷ [the pixel clock of the arcade board being evaluated] The result of this calculation is the pixel aspect ratio. This value represents how much the hardware’s “one pixel” is stretched vertically or horizontally compared to the square pixel defined by ATSC at a 6.136 MHz pixel clock. ・Less than 1.0 → a vertically elongated pixel (narrower width) ・Greater than 1.0 → a horizontally elongated pixel (wider width) This follows from the fact that a higher (faster) pixel clock allows more pixels to be packed into a single scanline, which in turn makes each individual pixel narrower in width. The pixel clock values for various arcade boards and game consoles can be found in the MAME source files or on sites such as the one below. Page by Pin Eight (administrator of a long‑standing video‑technology site active since the early 2000s): Dot clock rates Note: “Dot clock” refers to the pixel clock." When this method is applied to the PC Engine, the resulting pixel aspect ratio matches extremely well with the image displayed on real hardware, as well as with the output of Ootake (Real Stretched) and Mednafen. Although Pin Eight’s table is not a primary source, it compiles values based on real hardware behavior and the MAME source code. It also includes values such as the Famicom’s 8:7 ratio, which many emulators actually adopt. Given how few people still publish technical information today, this resource is genuinely invaluable. It is also possible to derive the pixel clock from the precise horizontal frequency and the total horizontal pixel count (including blanking regions). In the next section, we will calculate the pixel aspect ratios for the arcade boards of the original Gradius, Gradius II, and Xevious.

Calculating the Pixel Aspect Ratios of Gradius, Gradius II, and Xevious

【1】．Calculating "Gradius" Pixel Aspect Ratio ・Pixel clock: 6.14 MHz  6.136 ÷ 6.14 = 0.9993 The pixel aspect ratio is 「0.9993」 (approximately 0.07% narrower than a perfect square pixel, effectively square) The result shows only a 0.07% deviation, which is visually indistinguishable from a perfect square pixel. In practical terms, it can be treated as square. Since the original Gradius displays a test grid pattern at startup, arcade operators likely used the adjustment knobs to compensate for individual CRT variations so that the grid’s squares appeared correctly proportioned. Because the black squares in the test grid are 14×14 pixels (already perfectly square at the pixel level), a pixel‑by‑pixel (1:1 pixel mapping) presentation is effectively the recommended approach when porting the game to modern systems that use square‑pixel displays, such as contemporary consoles or PCs. 【2】．Calculating "Gradius II" Pixel Aspect Ratio ・Pixel clock: 6.14 MHz (TWIN16 board)  6.136 ÷ 6.14 = 0.9993 The pixel aspect ratio is 「0.9993」 (approximately 0.07% narrower than a perfect square pixel, effectively square) As a result, because the pixel clock is identical to that of the original Gradius, the pixel aspect ratio is exactly the same. The test grid pattern is also identical, so a pixel‑by‑pixel (1:1 pixel mapping) presentation can be considered the manufacturer‑intended display method. Gradius II (320‑pixel horizontal output) expands the horizontal visible area compared to the original Gradius (256‑pixel horizontal output). The areas that appeared as black borders on the left and right in the original Gradius now fall within the visible region. The important point here is that even though the horizontal pixel count (listed as "resolution" in specification sheets) increases, the aspect ratio of each individual pixel remains unchanged from the original Gradius. Pixel aspect ratio is determined by the pixel clock, not by the number of pixels. 【3】．Calculating "Xevious" Pixel Aspect Ratio ・Pixel clock: 6.14 MHz  6.136 ÷ 6.14 = 0.9993 The pixel aspect ratio is 「0.9993」 (approximately 0.07% narrower than a perfect square pixel, effectively square) As it turns out, Xevious also uses the same 6.14 MHz pixel clock as Gradius, so its pixel aspect ratio is identical. The test grid pattern is likewise the same, meaning that a pixel‑by‑pixel (1:1 pixel mapping) presentation can be considered the manufacturer‑intended display method. While many home consoles did not provide true pixel‑by‑pixel output due to cost constraints, a large number of arcade boards produced displays that were much closer to 1:1 pixel mapping. This pixel‑accurate output on arcade hardware likely made it easier for graphic designers of the time to perform their paint‑based workflow on the high‑end computers used for asset creation. That concludes this section. Using the same method, it is also possible to determine the pixel aspect ratios (PAR) of home consoles, not just arcade boards. Next, as noted in the caution section, let’s calculate the pixel aspect ratios of Capcom’s CPS hardware and Irem’s M72 hardware.

Calculating the Pixel Aspect Ratios of Daimakaimura and R‑TYPE

【1】．Calculating "Daimakaimura (Ghouls’n Ghosts)" Pixel Aspect Ratio ・Pixel clock: 8.00 (CPS1 board)  6.136 ÷ 8.00 = 0.767 The pixel aspect ratio is 「0.767」 (approximately 23.3% narrower than a perfect square pixel, resulting in a vertically elongated pixel shape) As a result, the pixels appear significantly vertically elongated, being 23.3% narrower than perfect square pixels. With this uncorrected presentation, many viewers would likely feel that character sprites look noticeably too thin. Although the test mode provides a test grid, aligning it to perfect squares produces characters that appear excessively wide, which is clearly incorrect. In the case of Capcom’s CPS hardware—an outlier in this regard—it is likely that arcade operators ultimately relied on visually adjusting the image by looking at round characters or items on screen, leaving the final tuning entirely in their hands. 【2】．Calculating "R-TYPE" Pixel Aspect Ratio ・Pixel clock: 8.00 (M72 board)  6.136 ÷ 8.00 = 0.767 The pixel aspect ratio is 「0.767」 (approximately 23.3% narrower than a perfect square pixel, resulting in a vertically elongated pixel shape) As it turns out, the pixel clock is the same as that of Daimakaimura, so the pixel aspect ratio is identical. However, unlike Daimakaimura, this hardware provides no test grid display at all. On the CPS hardware used for Daimakaimura, the presence of a test grid actually led to incorrect adjustments, but Irem appears to have avoided this issue by omitting the test grid entirely. For the M72 hardware as well, it is likely that arcade operators ultimately relied on visually adjusting the image by looking at round characters or items on screen, leaving the final tuning entirely in their hands. In R‑TYPE, the title screen displays “R・TYPE,” with a large round dot between the R and T. Because this screen alternates frequently with the demo play sequence, operators could easily use this dot as a reference to adjust the aspect ratio. The engineers who developed the CPS and M72 hardware appear to have prioritized achieving the highest possible resolution within the constraints of the NTSC standard, even at the cost of making screen adjustment more difficult. Because NTSC fixes the vertical resolution at 262.5 lines including the blanking interval, they pushed the horizontal resolution as far as practical. Increasing it any further would have required more expensive CRTs, so it is reasonable to assume that this led to the choice of a 384‑pixel horizontal display. Unlike Namco, Konami, Sega, and Taito—who tended to keep their pixel aspect ratios close to 1:1—these two companies pursued their own distinctive graphics specifications. As a result, the pixel art created for these systems still retains its unique brilliance today.

To Preserve the Appeal of These Classics for Future Generations

If, during the development of the port, the actual arcade board had been connected to a CRT monitor for verification, the default setting would likely not have ended up vertically stretched. That said, it is also possible that the developers thoroughly tested the game and intentionally chose the vertical stretch for their own reasons. There may have been circumstances we are not aware of, and therefore it cannot be criticized outright. Today’s home consoles and PCs have more than enough performance to scale images without blurring. As long as either the vertical or horizontal axis is scaled by an integer factor, visual artifacts remain minimal. We are no longer in an era where "hardware limitations make it impossible to reproduce the correct aspect ratio." Most players experience a game in its default settings. For that reason, I strongly hope that the very first screen is presented in a way that does not diminish the appeal of these masterpieces. Through such continued efforts, the appeal of these classic masterpieces will be conveyed deeply to younger generations, allowing the works to keep living on for many years to come — and far beyond.

2026.1.3-2026.1.15 Written by Kitao Nakamura.



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