OSTC Sport Character size
Posted by: obetz ()
Date: August 08, 2019 07:45PM

Hi,

what is the approximate character size of the smallest numbers on the screen (e.g. temperature, @+5 time) with the default layout?

Re: OSTC Sport Character size
Posted by: Ralph ()
Date: August 08, 2019 08:08PM

Hi,

that's the small font with character boxes of 24px hight x 28px width. Note: the actual characters are a little bit smaller as the box includes the spacing between two chars as well as some space for the descenders.

The legends are even smaller, their boxes are 14x18 px.

Re: OSTC Sport Character size
Posted by: obetz ()
Date: August 09, 2019 08:55AM

Thanks for the information.

Is the character box really wider than high? Usually it's vice versa!

Assuming square LCD pixels, I calculate from the specs a pixel pitch of 63mm/sqrt(320²+240²), IOW 0,158mm or 6.35px/mm. Is this correct?

Then 24x28 would be a 3,78mm x 4.4mm character box. Still right?

Characters smaller than 4mm seem to be hard on the border for people over 50. No one escapes presbyopia.

Re: OSTC Sport Character size
Posted by: Ralph ()
Date: August 09, 2019 05:53PM

Well, there are about 4 different displays in use with OSTC 2 family dive computers, all are a little bit different. The one in the latest Sport model is even a little bit bigger in size than the others. Anyhow, that's why all the important numbers are displayed in larger fonts. Additionally, the OSTC computers use anti-aliased fonts to improve readability.

Re: OSTC Sport Character size
Posted by: obetz ()
Date: August 10, 2019 10:53AM

would you mind to check whether the box is really 24px high and 28px wide which I consider "unusual"? Could it be you switched height and width?

Even more interesting would be:
* The digit size in mm
* Reports from people >50 whether they can read everything without lenses

Re: OSTC Sport Character size
Posted by: Ralph ()
Date: August 10, 2019 03:22PM

That's what it says in the source code... I don't know if the pixels are really square, but as said: there are different displays in use, and each one is a little bit different. So best, you measure yourself: the chars and digits have a fixed box size, so you can measure any text string on the display and divide by the number of chars it contains.

Sure people ask for readability, that's why (again as said) all important stuff is using bigger fonts, and in the Tech there is even an alternative layout mode with once again bigger Fonts / less content on the screen.

May i ask what's your specific interest? Are you owning an OSTC, or are evaluating to buy one?

Re: OSTC Sport Character size
Posted by: heinrichsweikamp ()
Date: August 10, 2019 03:35PM

obetz Wrote:
-------------------------------------------------------
> * The digit size in mm

In the current OSTC2/plus with the Seiko TFT pixel size is 0.153 x 0.153 mm². The other screen generations are very similar to that with the new OSTC sport having the biggest one (But it's actually only ~1% bigger).

The old OSTC3 and old Sport with the 2.0" screen had 0.1275 x 0.1275 mm²

> * Reports from people >50 whether they can read
> everything without lenses

Yes, an inevitable issue. But as Ralph said having (hand-optimised) anti-aliased fonts and high contrast colors helps a lot here.

regards,
Matthias

Re: OSTC Sport Character size
Posted by: obetz ()
Date: August 10, 2019 07:38PM

@Ralph: Yes, it's about whether to consider buying an OSTC.

In the mean, I grabbed the sources (uh small PIC are sooo ugly) and find for the "small" font these equates:

aa_font28_height EQU .24
aa_font28_width EQU .14

This looks more plausible than "24px hight x 28px width".

I also scaled some screen images and measured the character size.

The "small" digits (deco time and depth) are roughly 4mm high which seems to be acceptable.

The "tiny" digits (temperature, @+5..) are approximately 2.4mm, that's rather small.

The green legends are yet smaller, less than 2mm, but you don't need to read them.

Re: OSTC Sport Character size
Posted by: Ralph ()
Date: August 10, 2019 09:18PM

The tiny font (aa_font16_block) is the smallest one, it is used for the green legends.
The small font (aa_font28_block) is e.g. used for the time, pressure and temperature in surface mode.
The standard font (aa_font34_block) is e.g. used for the max depth (full meters), the dive time (full minutes) and the decimeters of the current depth in dive mode.
The rest of the bigger fonts is used for NDL & TTS time, stop depth (medium) or depth full meters (large). In the alternative "big" layout, most of these numbers are shifted one font up, so e.g. depth will come in font 'huge'.

In all the code, horizontal sizes and positions are encoded in 1/2 of actual position to stay within 1 byte size. So you have to multiply by 2 to get the real screen x-coordinate.

Re: OSTC Sport Character size
Posted by: obetz ()
Date: August 11, 2019 06:45PM

Well, then the "standard font" digits (numerical values) are 4mm high and the "small font" digits are 2.4mm high.

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