DPI / Pixels conversion?

Hi,

I've been asked to send high-res images in minimum 300 dpi to a print
publication. But I'm only familiar with the pixels concept. For example, I
have a set of images which are 1000x1500 pixels and another which are
3300x2200 pixels. Approximately, what dpi are these respective set of
images?

Thanks,
Tuxedo

On 03/12/2010 08:30, Tuxedo wrote:
Hi,

I've been asked to send high-res images in minimum 300 dpi to a print
publication. But I'm only familiar with the pixels concept. For example, I
have a set of images which are 1000x1500 pixels and another which are
3300x2200 pixels.

Divide by 300 so see the sizes in inches.

Approximately, what dpi are these respective set of
images?

Whatever value the software that created them decided to put in the dpi
field. It is an utterly meaningless number since the viewer can render
the image to any size they like and decoders most totally ignore it.
Print shops tend to be stuck in the dark ages.

Just edit the dpi fields to 300. They are idiots if the specify 300 dpi
without first telling you how big they intend to print the final image.

If they have specified a target image size then multiply size in inches
by dpi to see if your images are large enough. A decent publisher will
usually handle whatever you send them if the image is important enough.

Chances are they will have much better image upscaling methodology than
you do if the image is undersize so they are just being lazy here.

Regards,
Martin Brown

Hi,

I've been asked to send high-res images in minimum 300 dpi to a print
publication. But I'm only familiar with the pixels concept. For example,
I
have a set of images which are 1000x1500 pixels and another which are
3300x2200 pixels. Approximately, what dpi are these respective set of
images?

Thanks,
Tuxedo

(Number of pixels) x (pixels per inch) = (image dimension in inches).

If needed, set the PPI to produce the image physical size you want. Do it
in your image processing software. If you don't have enough pixels,
interpolate to get more pixels.

Cheers,
David

David J Taylor wrote:

[...]

(Number of pixels) x (pixels per inch) = (image dimension in inches).

If needed, set the PPI to produce the image physical size you want. Do it
in your image processing software. If you don't have enough pixels,
interpolate to get more pixels.

[...]

Thanks but I don't understand. I know my pixels but not my pixels p/inch.
In fact, I have a 15' monitor which is 1024x768 pixels. But of course, the
image file doesn't change if viewed on another screen or system, which may
have a different resolution. I use The Gimp, which is like Photoshop. I do
not see any option you mention, such as "setting the PPI to produce the
image physical you want". All I know are my number of pixels for which I
simply need to know if the number is large enough for this image size
requirements I just received from someone from the world of printing.

Perhaps there some convertors, such as web based tools, where I can simply
upload an image and it will identify and tell me its "dpi" value?

Thanks for any additional tips.

Toxedo

On 12/03/2010 10:23 AM, Tuxedo wrote:
David J Taylor wrote:

[...]

(Number of pixels) x (pixels per inch) = (image dimension in inches).

If needed, set the PPI to produce the image physical size you want. Do it
in your image processing software. If you don't have enough pixels,
interpolate to get more pixels.

[...]

Thanks but I don't understand. I know my pixels but not my pixels p/inch.
In fact, I have a 15' monitor which is 1024x768 pixels. But of course, the
image file doesn't change if viewed on another screen or system, which may
have a different resolution. I use The Gimp, which is like Photoshop. I do
not see any option you mention, such as "setting the PPI to produce the
image physical you want". All I know are my number of pixels for which I
simply need to know if the number is large enough for this image size
requirements I just received from someone from the world of printing.

Perhaps there some convertors, such as web based tools, where I can simply
upload an image and it will identify and tell me its "dpi" value?

Thanks for any additional tips.

Toxedo

DPI is a characteristic of the image rendering medium: screen, print...
A bitmap image itself has no intrinsic DPI. Some software may associate
a rather arbitrary number to it and call it DPI (for instance to produce
some default size when printing) but it can (and will) be ignored for
most purposes.

Now, if you know the DPI of your display medium and the physical size in
inch, you can compute how many pixels are necessary. If your picture is
the size of a postage stamp, 150x150 pixels will suffice. If it's a full
magazine page, it's more like 3000x2000 pixels. On the whole the
printshop is specifying a minimum value, they won't mind an image larger
than necessary (but don't upscale the image unless they specifically ask
you to do so).

--
Bertrand

Tuxedo wrote:
Hi,

I've been asked to send high-res images in minimum 300 dpi to a print
publication.

Does the magazine indicate how big the photographs
will be printed (6"x4" or A4 etc) ?

BugBear

bugbear wrote:

Does the magazine indicate how big the photographs
will be printed (6"x4" or A4 etc) ?

BugBear

No, I presume they don't know that ahead of having received the pictures,
having considered layout, what goes here and there etc. The size is a bit
larger than A4, like a typical glossy magazine found everywhere.

I can't wait until the print publishing industry is long dead and gone,
hopefully before the trees and the rain forests have dissappeared!

Michael

Thanks but I don't understand. I know my pixels but not my pixels
p/inch.
In fact, I have a 15' monitor which is 1024x768 pixels. But of course,
the
image file doesn't change if viewed on another screen or system, which
may
have a different resolution. I use The Gimp, which is like Photoshop. I
do
not see any option you mention, such as "setting the PPI to produce the
image physical you want". All I know are my number of pixels for which I
simply need to know if the number is large enough for this image size
requirements I just received from someone from the world of printing.

Perhaps there some convertors, such as web based tools, where I can
simply
upload an image and it will identify and tell me its "dpi" value?

Thanks for any additional tips.

Toxedo

You'll need to find a program which allows you to set the PPI value, so
that you can lie to the printer! Work out what size you expect your image
to be printed, and then how many pixels per inch will meet that
requirement. 10 inches, 3000 pixels. if your image doesn't have enough
pixels, interpolate (i.e. resize). Then set the PPI. Perhaps the
IrfanView program will allow that?

It's a real pain, I know, and we know how many pixels makes an image of
the quality we want. But on the printed page it's the pixels (or dots)
per inch which distinguishes the quality between a newspaper image, a
magazine image, and a fine-art book image.

Cheers,
David

"Tuxedo" wrote in message
...
Hi,

I've been asked to send high-res images in minimum 300 dpi to a print
publication. But I'm only familiar with the pixels concept. For example, I
have a set of images which are 1000x1500 pixels and another which are
3300x2200 pixels. Approximately, what dpi are these respective set of
images?

Thanks,
Tuxedo

1000/300 = 3.33 inches
1500/300 = 5 inches
So, at 300 dpi, the largest size you can have is 5 x 3.33 inches

3300/300 = 11 inches
2200/300 = 7.33 inches
So, at 300 dpi, the largest size you can have is 11 x 7.33 inches

MG

On 12/3/10 PDT 3:35 AM, MG wrote:
wrote in message
...
Hi,

I've been asked to send high-res images in minimum 300 dpi to a print
publication. But I'm only familiar with the pixels concept. For example, I
have a set of images which are 1000x1500 pixels and another which are
3300x2200 pixels. Approximately, what dpi are these respective set of
images?

Thanks,
Tuxedo

1000/300 = 3.33 inches
1500/300 = 5 inches
So, at 300 dpi, the largest size you can have is 5 x 3.33 inches

3300/300 = 11 inches
2200/300 = 7.33 inches
So, at 300 dpi, the largest size you can have is 11 x 7.33 inches

For DPI in all instances on this page, substitute PPI. The original
request was stated in wrong terms, not uncommon even among the literate
in photography groups.

--
John McWilliams