Inches, fractions, grids, rounding, accuracy and points.

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tylerdurden
Posts: 2322
Joined: Sun Apr 14, 2013 12:04 pm
Location: Michigan, USA

Inches, fractions, grids, rounding, accuracy and points.

Postby tylerdurden » Wed Aug 21, 2013 3:01 am

Hi All,

Thanks for the many helpful contributions, I would be lost without them.

I hope this post will help others too... I could not find this specific info via searching the board.

Backstory:
    I need to work in inches for many print-destined projects. (Clients use inches.)
    I wanted to use guides to align artwork for business cards, but the cursor coordinates only have two decimal places (setting with ordinal dimensions is a bit fiddly).
    I then realized I need to use grids to set the guides, but setting guides using fractions of inches (via decimal) is imprecise due to rounding (again too few decimal places).
    But: Since points per inch (72) are divisible by eight, they are excellent to use for setting the grid for work in fractions of inches.

Now I set my grids for 0.5625 points, which is 1/128".
That setting provides a handy, zoomable grid with enough precision for this type of work with no rounding errors. That grid helps me precisely set guides at fractional locations before I turn off the grid.

InchesToPointsGrid1.jpg
InchesToPointsGrid1.jpg (183.84 KiB) Viewed 4934 times

InchesToPointsGrid1a.jpg
Same settings, zoomed in.
InchesToPointsGrid1a.jpg (144.24 KiB) Viewed 4940 times

(The above example illustrates a business card 1-up layout with gutters for crop-marks and bleeds. Hence, my need for fractional guides set via grid.)

Have a nice day,
TD

Lazur
Posts: 4705
Joined: Tue Jun 14, 2016 10:38 am

Re: Inches, fractions, grids, rounding, accuracy and points.

Postby Lazur » Thu Aug 22, 2013 12:31 pm

Hi.

I may missed your point but
without any grid used, you can turn objects to guide lines by pressing Shift+G.
An even easier way to create accurate guide lines, is by double clicking on the guide line, then typing in the right values.

Maybe it's because I always use metrics, but why to mix pt-s with inches?
Why not to work entirelly with points?
Like, you set the right document size in inches, then set pt as the basic unit and as a grid distance.
1pt=1,25 px in inkscape, 0,3 pt at a 300 dpi print (~0,106 mm, about the thickness of a regular 80g paper).
Do you really need more precise work on a business card?
Last edited by Lazur URH on Thu Aug 22, 2013 9:43 pm, edited 2 times in total.

tylerdurden
Posts: 2322
Joined: Sun Apr 14, 2013 12:04 pm
Location: Michigan, USA

Re: Inches, fractions, grids, rounding, accuracy and points.

Postby tylerdurden » Thu Aug 22, 2013 2:20 pm

We work in fractions of inches or the decimal equivalents.

It wouldn't be any problem with a floating decimal entry in the grid and guide settings, but that ain't happenin.

Setting a grid with (inch) decimal equivalents < 1/16"... rounding will screw up the grid. Same with typing in a guide position - any value with more than four decimal places will be wrong.

This presents a way to work quickly and precisely in fractions of inches... so that zooming in with the grid visible is like having more functional tickmarks on the rulers that increase in resolution as zoom is increased.
Have a nice day.

I'm using Inkscape 0.92.2 (5c3e80d, 2017-08-06), 64 bit win8.1

The Inkscape manual has lots of helpful info! http://tavmjong.free.fr/INKSCAPE/MANUAL/html/


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