Digital BW, The Print

From my training as a printer many years ago I understand that ISO series is 
based on formulae on 1000 square centimetres equals A0 used in outdoor 
advertising hoardings in Europe down to A7 credit card size.  All dimensions 
are propionate to each other, wither your using SRA, RA or A sizes the 
diagonal length of the short side is always equal to length of the long 
side.  \ufffdA\ufffd sizes are standard finished sizes.  \ufffdRA\ufffd is a standard print 
production size that facilitates trimming to \ufffdA\ufffd size to give a clean 
professional finish.  \ufffdSRA\ufffd is used to accommodate registration marks, 
colour scale bars, which help monitor quality control in multicolour 
printing.  Most printing done today is not mono colour therefore most paper 
on the market is \ufffdSRA\ufffd.

>From: Ernst Dinkla <E.Dinkla@...>
>Reply-To: DigitalBlackandWhiteThePrint@yahoogroups.com
>To: DigitalBlackandWhiteThePrint@yahoogroups.com
>Subject: Re: [Digital BW] OT - U.S vs. Europe paper sizes???
>Date: Mon, 20 Sep 2004 21:50:50 +0200
>
>The Wogster wrote:
> > On 20 Sep 2004 at 13:07, Ernst Dinkla wrote:
>
> > There is a standard for raw paper stock as well, the A series sizes are 
>for finished
> > (trimmed) paper sizes, there is a RA standard for raw (untrimmed) sizes. 
>  An A4
> > sheet is 210 x 297mm A3 is 297 x 420.  RA4 is 215 x 310 RA3 is 305x430.  
>This
> > gives you 5-10mm for trimming, considering that presses most likely 
>across the
> > longer dimension, this gives adequate room.  There is also the larger 
>SRA sizes, but
> > unless you work in the press industry, it's unlikely that you would see 
>those.  Most
> > likely the printing company would buy rolls of SRA width stock, then 
>trim that to RA
> > size before feeding the press, and then the bindery would receive that, 
>and trim as
> > needed.
>
>Correct, that are the sizes for printing.  RA3 is 310x430
>however. In practice the paper suppliers here keep stock of all
>the (S)RA sizes  and as much of non ISO sizes, some of the sizes
>in two paper fiber directions and all in different weights.
>The printshops have the sizes in stock that run on their offset
>presses and cutting them in half before printing isn't done.
>Either the presses have all the same size or there are ISO (S)RA
>and B types. That you can design for one A size and use it on a
>sheet that has twice the size seems handy. But that can be done
>on any range of papers that share the same ratio between the
>sizes.  Then they can't be cut in half with the same ratio as a
>result but nobody does that in practice or its importance is
>limited to the paper industry. As I have written before I don't
>think the economy is in less waste or lower stock. Too many other
>formats still used here that show that demand isn't ISO A dictated.
>
>Cutting the (S)RA sizes to (multiple) A sizes after the press job
>is done on a large press is another matter. An American shop with
>a large offset press uses the same practice but doesn't get A
>sizes in the end.
>
>So I'm in favor of a standard ratio in sizes (if there has to be
>a standard) but the advantage that the sheet can be cut in half
>and keeps its ratio is minor in my opinion.
>
>
> > Now, in the darkroom, metric sizes make even more sense, each time you 
>increase
> > one size, you need one stop more exposure, due to light loss,  each time 
>you
> > decrease one size, you need one stop less exposure.  I used to know the 
>formula for
> > inch sizes, and man was it UGLY.
>
>That translates in print time on printers but feeding the sheet
>landscape style (if possible) will always be faster. BTW, I have
>not seen many darkrooms here that worked with A sizes. Not many
>darkrooms left either.
>
>
> > The only real holdout left is the United States, and you can get metric 
>sized paper
> > there.  What is also an issue though, is digital sensor sizes, there 
>should be
> > standards there as well, at this point, it would make sense to have 
>sensors with the
> > same aspect ratio as metric paper sizes, but I think 35mm aspect ratio 
>will probably
> > end up more likely.
>
>I find it difficult to set a ratio standard for image taking.
>Given the ever changing market for pro photographers, the
>difference of that market if compared with the amateur market,
>what the consumers expects for their wedding pictures, the change
>in use of digital pics compared to analogue pics (80% never gets
>printed) and what is changing in monitor and TV sizes and ratios,
>there's a long list of desired formats and they do not resemble
>one another.  I doubt that A paper sizes can be a reference for
>sensor sizes, it could have been for film formats over the last
>40 years but that is passed and ISO A never had an influence on
>that either. Kodak tries to set its standards again (with some
>Japanese companies) wonder whether that list of sensor formats
>will get as long as Kodak's film formats list. At this moment the
>wafer size is the dominant factor for consumer sensors, the more
>that fit the disc the better. The ratio and sizes of those
>sensors are still based on the old video camera vacuum tubes if I
>recall it correctly.  Nikon's latest 12 MP pro sensor isn't full
>frame 35 (0.66x) but has the 35 mm aspect ratio. Don't think I
>will see a standard image sensor size in my life.
>
>Ernst
>
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