Most typical aspect on porthole sets?

[cuteorkill]

I have yet to acquire a porthole set but have noticed the image being displayed a few different ways. Despite the source video of 4:3, the image is often seen distorted to fill the screen. Was there a usual default that the manufacturers set (see graphic)? Were controls for the vertical and horizontal size of the image typical for these sets?

I'm not too sure I'd want to distort or overscan too much. Choice D seems a decent compromise, but what are the rest of you doing?

[Eric H]

Sometimes you don't have a choice, the Horizontal width is pretty much fixed so you have to stretch the vertical to fill the screen, that's the way i do it.

Some models have the option of doing 4:3 or pressing a button and filling the screen.
I don't know how all of them do it but for instance the Stromberg Carlson "Opera Glass" button Zooms the picture cutting off the sides slightly.
I know some of the Zeniths have an expansion feature but I don't know if it's just the height or width too.

On a 10" screen you don't really notice a little vertical stretch unless a round object is shown.
This Teletone is an example, at 1:19 there's a circle that's slightly elongated but it's not really bothersome: http://www.youtube.com/watch?v=EykM_lam17c

One thing for sure, they built Portholes so they could have more square inches of picture, it was not intended to have blank areas top and bottom.

[wa2ise]

Just imagine the fun you'd have if you wanted to watch downconverted hi-def video on a porthole. 16:9 -> 1:1 anyone

[compucat]

I ran into this problem when I restored my Motorola 9VT1 which has the typical roundie shape you see on color sets. The only way to get a correct 4:3 aspect ratio was to shrink the horizontal and vertical. This leaves a small picture in the middle of the screen. The manufacturers intended for the entire mask to be filled so I adjust for that and do the best I can with respect to linearity. Vertical is the most noticeable. It is just a characteristic of these types of sets.

[M3-SRT8]

I choose "C".

Larry Fine likes it, too...

[David Roper]

I once had a 1951 model Zenith restored which had a picture switch. It only stretched the vertical, so your choices were C (normal) or B (full). Absent a switch I guess a D style compromise would be a good compromise between correct aspect ratio (rare enough these days but that's another story...) and the full circle screen expected.

[Penthode]

I like the compromise D. It fills the screen and yet you can see the sides of the image. I'd like to see how you'd fit a 16x9 image?

Which brings me to raise the question of linearity distortion in new 16x9 displays. Have any of you seen the displays which stretch only the left and right sides of a 4x3 image to fit a 16x9 screen? By playing with the horizontal linearity, width and horizontal drive controls, you could probably do the same to fit a 4x3 image to fit a porthole!

Funny, in the past the set designers and TV repair guys would try to get as linear a horizontal scan as possible and now we live in an age of intentional non-linearity and "stretch-o-vision" (stretching a 4x3 image on a 16x9 flat display).

[ChrisW6ATV]

Originally Posted by cuteorkill

I have yet to acquire a porthole set but have noticed the image being displayed a few different ways.

The Zenith I own has the normal/screen-fill switch but I need to restore mine before I know how it will work. Just about every working "porthole" TV I have ever seen has been displayed with the screen filled with video, probably to show off the difference between these sets and standard displays. Since I am a big fan of viewing things in their original aspect ratio with nothing lost if possible, I would adjust my set for, and use, version C among your choices, but I would want version A available for brief demonstration of a completely-lit CRT.

[John Marinello]

Originally Posted by M3-SRT8

I choose "C".

Larry Fine likes it, too...

Actually, Larry is displayed in "full circle" mode !