atw: Re: Dpi for various screenshot uses
- From: "Daryl Colquhoun" <atw@xxxxxxxxxxxxx>
- To: "austechwriter list" <austechwriter@xxxxxxxxxxxxx>
- Date: Mon, 20 Jun 2005 22:31:51 +1000
Nigel said,
>Daryl, I'm not sure if this is applicable to your circumstance, but thought
it worth mentioning. A point to note when working with bitmap images is that
because they are one bit images their resolution should always match that of
the output device. This ensures they print at the best possible quality.
Well, it's not my circumstances, remember we're trying to answer Sonja's
questions (message 119). Since she asked about printing screenshots, this
point _is_ worth mentioning, so much so that I already mentioned it.
But as it happens it isn't quite right, or rather isn't quite as useful as
it could be. What I said was...
>The dpi for printing will depend on the printer. If you have a 600dpi
printer and want to make use of its full capability, prepare your work at
600dpi...If you're happy to use a lower resolution in order to reduce file
sizes, then...
So say you have a screen shot, and say it's 600 by 600 pixels, which is just
a bit smaller than the window I'm typing in right now. If you have a 600dpi
printer and render the shot at 600dpi, your image in your manual will be 1
inch square, which is almost certainly too small. So you can find yourself
using a lower resolution not to reduce file size but to make your manual
readable! And in that case,
>...for preference and in principle you should choose a submultiple, like
300, 200, etc. to avoid moiré effects.
Those resolutions (300, 200) will give you images of 2 inches and 3 inches
square respectively, which will probably still be rather small. 150dpi would
give 4 inches, 120 would give 5 inches -- this is 127mm so it's probably
about right for a printed manual.
All the calculations have to be redone if your printer isn't as above. The
outcome if the printer is coarser is that you end up with less choice. If
you had the same image but a 300dpi printer, 300 dpi would give 2 inches
square, 150 dpi 4 inches, 100 dpi 6 inches and so on. I have been known to
resize windows before capturing them to give a nice sized illustration at a
desirable dpi. Although as I said last time, even if you don't use a
submultiple it often looks OK anyway.
This only addresses one part of Sonja's question. Moving briefly to the
question of PDFs (another small part), it does depend on the fate of the
PDF. If your customer is going to print it, then you take into account all
the above (supposing you know what sort of printer your customer has) and
further, what sort of compression you have opted for in your Acrobat
settings. For screenshots, this will ideally be a lossless one, but that's
really another story.
By the way, the info from scantips.com relates to the converse process of
scanning things and so isn't relevant to Sonja's question.
Emails direct to this address are deleted unread as an anti-spam measure.
**************************************************
To post a message to austechwriter, send the message to
austechwriter@xxxxxxxxxxxxxx
To subscribe to austechwriter, send a message to
austechwriter-request@xxxxxxxxxxxxx with "subscribe" in the Subject field.
To unsubscribe, send a message to austechwriter-request@xxxxxxxxxxxxx with
"unsubscribe" in the Subject field.
To search the austechwriter archives, go to
www.freelists.org/archives/austechwriter
To contact the list administrator, send a message to
austechwriter-admins@xxxxxxxxxxxxx
**************************************************
Other related posts:
