Crop to A4 paper size

The top popup in the layout section (ruler units) allows you to choose between many different units.

How do I set Lightroom to give me metric measurements in the page setup?

As I noted above, the idea behind the A sizes is that doubling them up along the length direction will create the next size up (or cutting one in half creates two of the next size down). This is done geometrically by using the ratio of square-root of two to 1. Since square-root of two is an irrational number there is no number you can type in the field that is exact, but 1.414:1 is close. 210 x 297 is slightly closer to square-root 2 to 1 though. You're never going to notice the difference though and both should be fine.

Well a true A4 does sound like it equals a true PA4..

The ratio for a PA4 is 4:3 and a A4 is 1.414:1 .
Is that a correct statement.

I'm not sure which one to use?
Well I guess I'll go with the A4 1.414:1 and hope for the best.

Does A4 equal PA4 Wikipedia say so..
PA series
PA4-based series Name mm × mm Ratio
PA0 840 × 1120 3:4
PA1 560 × 840 2:3
PA2 420 × 560 3:4
PA3 280 × 420 2:3
PA4 210 × 280 3:4
PA5 140 × 210 2:3
PA6 105 × 140 3:4
PA7 70 × 105 2:3
PA8 52 × 70 ≈3:4
PA9 35 × 52 ≈2:3
PA10 26 × 35 ≈3:4

A transitional size called PA4 (210 mm × 280 mm, 8¼ in × 11 in) was proposed for inclusion into the ISO 216 standard in 1975. It has the height of Canadian P4 paper (215 mm × 280 mm, about 8½ in × 11 in) and the width of international A4 paper (210 mm × 297 mm). The table to the right shows how this format can be generalized into an entire format series.

The PA formats did not end up in ISO 216, because the committee felt that the set of standardized paper formats should be kept to the minimum necessary. However, PA4 remains of practical use today. In landscape orientation, it has the same 4:3 aspect ratio as the displays of traditional TV sets, some computer displays and data projectors. PA4, with appropriate margins, is therefore a good choice as the format of presentation slides. At the same time, PA4 is the largest format that fits on both A4 and US/Canadian Letter paper without resizing.

PA4 is used today by many international magazines, because it can be printed easily on equipment designed for either A4 or US Letter.

Every pack of A4 paper says sheets are 210 x 297 mm.

So just create a custom crop size of 210 x 297.

A3 would be twice as big at 420 x 297 and A3Plus would be whatever it says on the pack (can't remember offhand).

I suppose the real question is why doesn't Lightroom have these as standard ratios. That way Adobe could claim it had customized the product for the European market to justify it's foreign pricing strategy.

Ian

Being a nerd, it's one of things I really like about the A formats. You can always make the next size by simply putting two of the smaller together because of the sqrt(2) thing, so two A4s create an A3, and so on, and all A formats have the same length to width ratio. It does come at the price of one of the dimensions always being an irrational number.

11.69/8.26=1.4152... is just a tad too long

Absolutely correct! Always get an error message when printing that there will be a clip. Amounts to 1mm so not a worry. Didn't know about the sqrt(2)to 1 ratio. Got the figures from the CS3 print dialog box that gives you the paper size in inches when you choose A4 paper. Thanks for the clarification.

Dana

>11.69 x 8.26 (inches)

Actually that is almost as good as entering 1.414x1. Remember the crop has no units! All A sizes have a length to width ratio of sqrt(2) to 1, which equals 1.414213..., so 11.69/8.26=1.4152... is just a tad too long and 1.414 is very close to it.

Bring up the custom crop dialog box and enter 11.69 x 8.26 (inches)and you will get a nice A4 crop. Works perfectly for me.

Dana