I can’t put 200pt for character size cos after 3,5pt I loose some text … 

 I am not sure I understand your problem. Your text is very long and if you want to show it bigger you have to split your text in several (depending of the size of the font) part and show every part one behind the other or to use the scroll function in the text draw actor. You can also use the "bounds width" input to set some space left on right of your text if you don't want the text touch the border of the screen.

or with several screens:

I m outputting preview in 1920x1080 in the preview full size mode

I can’t put 200pt for character size cos after 3,5pt I loose some text … 

are you looking your text only in preview mode or in the fullscreen/projection mode? the preview mode is a reduced size

Preview

Full-size on second monitor

same with  a text size of 200

I used your text with the same font "Avenir"

best

Jean-François

thanks

Some of the Office Hours crew will be doing a workshop on Isadora on Tuesday and they had asked me this question, so I will pass along the answer!

Any tips or tricks on rendering sharp text? 

TL;DR: the rule of thumb is to the width of the Text Draw actor to match the width of your stage, and the height as small as possible to contain your text, you should get acceptable output. (I mean, I'm not a broadcaster, but it looks sharp to me.)

DETAILS:

The first and most important step is to set the resolution in the 'output width' and 'output height' inputs of the Text Draw actor. If you leave these set to 0, then Isadora uses the default resolution as set in the Isadora Preferences (Video > Video Image Processing > Default Resolution) which is set to 640 x 480 unless you modify it. Compare these images rendered to a 1920x1080 stage can captured by the Capture Stager To Picture Actor:

'output width' = 0, 'output height' = 0, which means the default resolution of 640 x 480 is used:

and this version where 'output width' = 1920, 'output height' = 1080

and this version where 'output width' = 3480, 'output height' = 2160

Cropping these so we can see more closely:

640 x 360

1920 x 1080

3840 x 2160

As you can see, there is a big difference between the 640x360 version and the 1920x1080 version. But since the stage size is 1920x1080, you don't gain much by doubling the resolution.

However, if we set the stage size to 3840 x 2140, then you will see a difference between the 1080p and 2140p outputs.

Resolution = 1920x1080, Stage Size = 3840x2160:

Resolution = 1920x1080, Stage Size = 3840x2160:

EFFICIENCY:

In this example, a huge portion of the 1920 x 1080 image is not used because you are only displaying a single line. So, you can improve efficiency somewhat by reducing the height while keeping the width the same.

Here's the output when for a 1920 x 1080 stage with 'output width' = 1920, 'output height' = 400. You'll see that it looks the same as when the height was 1080:

text-draw-1920x1080stage.izz

text-draw-3840x1080stage.izz

Best Wishes,
Mark