High pixels, low DPI ??
Ted Shoemaker
Our church is doing a photo directory.
The picture quality of the last directory was about half that of the
pictures that I supplied. That is, the printed pictures look as if
they have the same resolution as my on-screen photos when I view them
at 50%.
In response to this concern, someone (presumably the publisher) wrote
that I should send pictures at 220 DPI.
Well . . . last time they were at 220 dpi, IF a printer's dot is the
same as a screen pixel. That is, a 4-inch-wide photo was 880 pixels
wide. Is this the right way to get 220 dots? If not, what is the
right way? If so, why was the print resolutino about half that of the
screen picture? Should I use a higher resolution?
Thank you for all advice.
Ted Shoemaker
mianileng
> Hello,
>
> Our church is doing a photo directory.
>
> The picture quality of the last directory was about half that
> of the
> pictures that I supplied. That is, the printed pictures look
> as if
> they have the same resolution as my on-screen photos when I
> view them
> at 50%.
>
> In response to this concern, someone (presumably the publisher)
> wrote
> that I should send pictures at 220 DPI.
>
> Well . . . last time they were at 220 dpi, IF a printer's dot
> is the
> same as a screen pixel.
Strictly speaking, dpi is the number of dots the printer prints
per inch. It is a measure of the printer's resolution and has
nothing directly to do with how many pixels of digital image are
used to fill one inch of print. The latter is PPI - pixels per
inch (of print) - and is probably what the publisher meant.
> That is, a 4-inch-wide photo was 880 pixels
> wide. Is this the right way to get 220 dots?
Strictly speaking again, no. Try to visualise the distinction
between dot and pixel. I assume you know what a pixel is. A dot
in this context is the tiniest blob of ink the printer squeezes
onto the paper. However, you and your publisher seem to be mainly
concerned with how many pixels of picture should go to make up
one inch of print. In that case, your math is correct, except
that you're mixing up pixels and dots.
The dpi may be the same as, or lower or higher than the ppi. As
an extreme example, you may print a single pixel as one square
inch of uniform color. The ppi is 1, but if the printer was set
to 600 dpi, then 600x600 dots of ink would be needed to fill up
that square inch of print.
> If not, what is the
> right way? If so, why was the print resolutino about half that
> of the
> screen picture? Should I use a higher resolution?
>
Not sure what you mean here. Do you mean that the printed output
looked coarse, that you could see individual pixels as tiny
squares on the print? 220 ppi should be adequate for the
purpose.Maybe they downsized the images while composing the print
layout (reduced ppi) or used a coarse print resolution (low dpi).
If it's the former, individual pixels may be noticeable. If the
latter, the picture would look coarse without individual pixels
being visible, as in a newspaper.
John McWilliams
Your photos were probably fine enough- in fact, way too fine- for a
cheap printing job, at the 220 *PPI* you sent them.
DPI is what the printer puts down, with home inkjets capable of over
1440 DPI. More than likely, the "printing" method was a cheapo, not able
to achieve anywhere near the resolution you provided.
Can you find out what the Printer used for his "printer"? (It may have
been a higher end copying machine.)
--
John McWilliams
Bob Williams
As others have pointed out, that is a printing term and is controlled by
the printer itself.
If you are using PhotoShop to edit your pictures, I'd suggest that you
use the CROP TOOL to crop the picture to the size it will appear in your
photo directory, say 3" x 4". Also set the Crop Tool's resolution to 220
ppi. The image you get will print out at exactly 3x4 @ 220 ppi and 220
dpi I would check with the publisher about the 220 dpi requirement
because that is very modest resolution for a professional printer.
That said,however, 220dpi should be satisfactory for a 3 x 4 or smaller
picture
Bob Williams
Focus
news:STJvl.151609$fM1....@newsfe14.iad...
I think it's the other way around: the bigger the picture, the less dpi you
need, because it's looked at from a distance.
Billboards have a very low dpi of less than 100, while magazines use at
least 300 dpi.
--
---
Focus
Don Stauffer
The problem is that many of these folks at publishers and printer places
are not that computer literate. In prepress work for a printing press, a
(halftone) dot IS the same as a pixel. The problem is that an inkjet
printer dot is NOT the same as a pixel.
The problem with someone asking you to submit a picture as so many dots
per inch (assuming they mean pixels) is that they are ASSUMING you will
send a picture of a given dimension, without telling you what that
dimension IS! You then need to ask them what physical size as well is
ppi. By specifying how many pixels in each direction this is taken care
of, but they do not seem to understand that. They are talking printing
presses, halftoning, pre-press, and such, not computer lingo.
John McWilliams
>
> Sorry, but I need to ask a total newb question. The very
> simple photo editors I've used in the distant past (such as
> LView) only dealt with the size of the pictures in H/V
> pixels, such as 640x480. Is the "resolution" of the picture
> in terms of pixels per inch actually specified in the jpeg
> itself by better editors? Would that value have any effect
> on how a picture would be displayed on a monitor (as opposed
> to being printed)?
The resolution is a function of the number of pixels and the size at
which it's displayed/sent to the printer.
Thus your example would be about 300 ppi at a size of 2" x 1.6". 0r ca.
2 1/2" x 2" at 240 ppi.
--
John McWilliams
John McWilliams
> John McWilliams <jp...@comcast.net> wrote:
>
>> Your photos were probably fine enough- in fact, way too fine- for a
>> cheap printing job, at the 220 *PPI* you sent them.
>>
>> DPI is what the printer puts down, with home inkjets capable of over
>> 1440 DPI. More than likely, the "printing" method was a cheapo, not able
>> to achieve anywhere near the resolution you provided.
>>
>> Can you find out what the Printer used for his "printer"? (It may have
>> been a higher end copying machine.)
>
>
> version of the image used in the layout program. I've seen that happen
> plenty of times in catalogues, newspapers etc.
That's a possibility, for sure.
However, to the OP: was your photo about the same 'quality' as the
others? If so, it suggests to me a poor printing method. Using 'printer'
in its loosest terms.
--
John McWilliams
Dave Cohen
The printer should tell the customer at what pixel resolution he would
like the submission.
Dave Cohen
Ted Shoemaker
The pictures I submit are in grayscale TIFF format, at the publisher's
request. I did use PhotoShop and cropped them before submitting, as
well as making aesthetic adjustments. I did specify via a PhotoShop
widget that the pictures should be 220 PPI. (I can't control DPI on
my end, only PPI; hence these questions.) I did the math and got the
appropriate number of pixels for the various sizes of pictures (e.g.
880 pixels wide for a 4-inch-wide photo).
The printed result looks far coarser than the same pictures on my
computer screen. I can too easily see individual inkdots. In order
to make my screen look as coarse as the printed version, I have to
reduce the pictures to half the width & half the height (e.g. 440
pixels wide for a 4-inch picture, 293 pixels wide for a 1 1/3 inch
picture, etc.)
There were about 120 photos in the directory, of different sizes, and
the same effect is true for each of them.
The publisher tells me that the solution is for me to give him
pictures at 220 DPI. If I already gave him 220 PPI, that's as close
to doing it as I know how to do.
I'm puzzled.
I hope this added info clears things up.
All advice will be appreciated.
My guess is that this is already as good as it's going to get until we
use a different printing operation -- and that's not my decision to
make. Even so, I don't want to pass the buck; I want my contribution
to be as good as possible.
Again, thank you for all help.
Ted Shoemaker
(Original Poster)
John McWilliams
There's nothing to indicate that you're not doing your part just right.
You could submit photos at 400 ppi and wouldn't get any better result.
The publisher either doesn't know his technical stuff, or does but isn't
being upfront with you.
--
John McWilliams
D-Mac
Most off-set printers - actually most are just duplicators, used by
church and social clubs are barely able to handle a screen of 120 LPI
over a photo which makes the photo about the same as a high quality monitor.
It sounds to me like the printer is not capable of "screen to plate"
work and they are still using cameras to make the printing plates. If
this is the case, you might have the DPI mixed up.
When you make a plate by photographing artwork, there is a LPI "screen"
of dots imposed over the art so the printing press can print a picture
as a half tone image. These screens vary from 120 to 220 LPI or DPI. The
actual resolution of the picture has nothing at all to do with those
measurements.
John McWilliams
> Peabody <waybackNO...@yahoo.com> wrote:
>
>> John McWilliams says...
>>
>>> The resolution is a function of the number of pixels and the size at
>>> which it's displayed/sent to the printer.
>>> Thus your example would be about 300 ppi at a size of 2" x 1.6". 0r
>>> ca. 2 1/2" x 2" at 240 ppi.
>> the jpeg?
>
> Yes it is (or at least it can be). Some programs take notice of it whilst
> others don't. For instance if you drag and drop a photo into Word, it will
> read the ppi (actually listed as "dpi" I think) value and display the image
> in the document at the appropriate size, ie. pixel size divided by ppi. You
> can resize it afterwards, thus changing the effective ppi, but initially
> Word will size it using the embedded data. Photoshop does this too IIRC, at
> least when it comes to trying to print an image.
>
> Unfortunately digital cameras are inconsistent in setting this field. IME,
> some set 300dpi whilst others set nothing, and unfortunately many programs
> default to assuming 72dpi if nothing is specified, leading to pretty crazy
> results with today's high-megapixel cameras (defaulting to a poster sized
> image or even bigger). In reality the dpi field in the EXIF data is
> meaningless since how can the camera know what size you intend to print the
> picture at? Without this info the image has no "dpi" as such, only an
> absolute size in pixels.
>
> IMHO it would be better if (a) cameras did not set a dpi in the EXIF data
> and (b) programs did not assume 72dpi when this information was absent. At
> one time 72dpi was the dot screen used by newspapers, and in the early
> 1980's it was also the resolution of the original Apple Mac monitor, but
> nowadays the figure is a completely stupid default which simply causes
> problems. If you set a 17" monitor to 800x600 resolution, that is 72dpi.
> But no-one who works with photos would use such a low resolution monitor
> setting.
All your mentions of dpi should read "ppi". That Word may have it wrong
is not surprising.
--
john mcwilliams
canon.user
'Peabody' wrote this:
>Bob Williams says...
>
> > You cannot SEND images at 200dpi. As others have pointed
> > out, that is a printing term and is controlled by the
> > printer itself.
>
> > If you are using PhotoShop to edit your pictures, I'd
> > suggest that you use the CROP TOOL to crop the picture
> > to the size it will appear in your photo directory, say
> > 3" x 4". Also set the Crop Tool's resolution to 220 ppi.
> > The image you get will print out at exactly 3x4 @ 220
> > ppi and 220 dpi I would check with the publisher about
> > the 220 dpi requirement because that is very modest
> > resolution for a professional printer. That
> > said,however, 220dpi should be satisfactory for a 3 x 4
> > or smaller picture
>
>Sorry, but I need to ask a total newb question. The very
>simple photo editors I've used in the distant past (such as
>LView) only dealt with the size of the pictures in H/V
>pixels, such as 640x480. Is the "resolution" of the picture
>in terms of pixels per inch actually specified in the jpeg
>itself by better editors? Would that value have any effect
>on how a picture would be displayed on a monitor (as opposed
>to being printed)?
Resolution usually refers to the H/V pixel size of an image.
PC monitors and digital cameras use this term too.
Thus, an image of 640hx480v will display on your monitor in full
screen using an image viewer like Irfanview, if your monitor
resolution is also set to 640hx480v. If you send that same image
to a friend who uses a higher resolution on his monitor, the image
will not fill the screen.
PPI (or dpi) defines how many of those pixels will be printed
per inch when you print it. The higher the ppi, the smaller the
printed output will be for the same size image.