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SE/30 Historically accurate screen adjustments
- Thread starter tbohen
- Start date
All B&W Compact Macs have a specified measurement of exactly 7.11" wide and 4.47" tall. This is based on 72 dpi, so that 512x342 should display WYSIWYG accuracy: an inch on your paper will match an inch on screen. Which of course means there's going to be a black border. This is the proper adjustment for a compact Mac display. Nothing else is correct.
That said, enlarging the image to fill the entire screen will not necessarily harm the Mac (however, enlarging it will cause a larger power draw and the voltages should be adjusted afterwards to avoid putting stress on the system), and thus is a personal preference. If you want to defeat WYSIWYG, then feel free to enlarge the window as far as you can. But keep in mind you are distorting the native pixel size, upscaling as it were, so that the screen will be less sharp. You also run the risk of distorting the square shape of the pixels so that the images are slightly stretched.
Also, be sure to synchronize the voltages after you set the display. It may take several attempts as enlarging the display will draw more power, raising the voltage may enlarge the display even more, and thus the display size must be reduced, and the voltage brought up slightly, and so on. In some instances, you will quickly see the limits (and state) of your PSU, as you may find you cannot expand the display to fill the entire screen and maintain the proper voltages. In the case of the original 128K & 512K, I would not recommend adding to the PSU load in any way. But an SE/30 with the most robust PSU and fan should be fine. You may also have to center and focus the resulting display for optimum picture.
That said, enlarging the image to fill the entire screen will not necessarily harm the Mac (however, enlarging it will cause a larger power draw and the voltages should be adjusted afterwards to avoid putting stress on the system), and thus is a personal preference. If you want to defeat WYSIWYG, then feel free to enlarge the window as far as you can. But keep in mind you are distorting the native pixel size, upscaling as it were, so that the screen will be less sharp. You also run the risk of distorting the square shape of the pixels so that the images are slightly stretched.
Also, be sure to synchronize the voltages after you set the display. It may take several attempts as enlarging the display will draw more power, raising the voltage may enlarge the display even more, and thus the display size must be reduced, and the voltage brought up slightly, and so on. In some instances, you will quickly see the limits (and state) of your PSU, as you may find you cannot expand the display to fill the entire screen and maintain the proper voltages. In the case of the original 128K & 512K, I would not recommend adding to the PSU load in any way. But an SE/30 with the most robust PSU and fan should be fine. You may also have to center and focus the resulting display for optimum picture.
I wonder if that's why my picture started to get a little wobbly when I expanded it to fill the entire space, insufficient voltage...
I looked it up, according to my Classic II service manual the image on ones screen should be exactly 177.8 mm wide by 119.38 mm high
I can't believe they actually go to 10 µm accuracy. Unaided human vision is on average no more accurate than ~50 µm. One would need to use a 5x loupe to even be able to adjust it at that level, and I highly doubt most people would be able to move their hands accurately enough with the analog adjustment to make adjustments that fine.
I looked it up, according to my Classic II service manual the image on ones screen should be exactly 177.8 mm wide by 119.38 mm high
I can't believe they actually go to 10 µm accuracy. Unaided human vision is on average no more accurate than ~50 µm. One would need to use a 5x loupe to even be able to adjust it at that level, and I highly doubt most people would be able to move their hands accurately enough with the analog adjustment to make adjustments that fine.
The other major factor is that CRTs back then weren't as high quality, especially at the edges, as later CRTs. The black borders weren't just there for size considerations (they could have used a physically smaller CRT,) they were also there because the edges of CRTs tend to have worse picture quality than the centers. This is true even on the latest CRTs, but they are made to be "good enough" at the edges, while earlier CRTs they were perfectly happy saying "leave a big black border". (You don't notice as much on TVs simply because TVs usually don't have a need to display sharply defined lines near the edges all that often.)
Or a fabric (or even paper) seamstress measuring tape works great.
To get the screen geometry right, ie the height:width ratio, change the desktop pattern to the one that looks like a checkerboard close up (ie grey, alternating black/white pixels). Then hold up the corner of a fresh sheet of office paper (letter or A4, whatever) at a 45 degree angle, turning it until the edges lines up diagonally with the background pattern. If the geometry is correct, you will be able to eliminate the fringing effect on both edges of the paper.
The corner of a floppy disk works for this too.
The corner of a floppy disk works for this too.
There used to be a utility called Test Pattern Generator that had some great patterns built in. However, a ruler in MacDraw works well too if you're looking for accuracy of inches.
One of the tools I use with CRTs is a soft measuring tape. If you've ever been to a tailor, you've probably seen one of these--he will use it to measure waist size, hem length, etc. These work well on any screen not only to check size accuracy, but also to center the screen with the yoke, as the straightness of the black border can be examined closely with the tape next to it.
A lot of people actually did stretch out their screens at some point to use the entire viewable area. Most did not, however, and finding a Mac with the exact specifications really isn't that hard provided its power supply has remained sound.
One of the tools I use with CRTs is a soft measuring tape. If you've ever been to a tailor, you've probably seen one of these--he will use it to measure waist size, hem length, etc. These work well on any screen not only to check size accuracy, but also to center the screen with the yoke, as the straightness of the black border can be examined closely with the tape next to it.
A lot of people actually did stretch out their screens at some point to use the entire viewable area. Most did not, however, and finding a Mac with the exact specifications really isn't that hard provided its power supply has remained sound.
If I'm doing display alignment on a compact Mac, I find it easiest to cut a sheet of white paper to the correct image size. Just hold the paper up to the display and adjust the image to match the size of the paper sheet. It also helps confirm that the geometry is correct (parallel top/bottom and left/right sides).
Metal rulers can mar the display surface. Plastic rulers solve this, but, are still too long to fit flat against the CRT.
Metal rulers can mar the display surface. Plastic rulers solve this, but, are still too long to fit flat against the CRT.
I know this was posted over 13 years ago, but the information is wrong, and I want to fix it for anyone who might come across this later (and hopefully reads down to the bottom of the thread). The correct dimensions are 7.11" wide by 4.75" tall.
I’ve been trying to answer this question and your answer makes the most sense. 7.11 x 72 = 512 and 4.75 x 72 = 342.
It would be nice to see an official Apple document that references this, but my search foo let me down. The best I could do was Macintosh Repair & Upgrade Secrets (archive.org) by Larry Pina.
In the Service Source from Apple for the Macintosh SE/30, on the video size adjustments page it does mention 7 inches wide and 4.7 inches high.
Thank you! I take great pride in my ability to make sense
