Newbie question - photo size by pixel

Hi, all

I'm going to be submitting some photographs to a web page that has the
following size requirement:

"Photos must be at least 2.5MP (2.5 Million Pixels). To determine the
amount of pixels in a photo, multiply the width by the length. For
example: a photo which is 1700x1500 adds up to a total of 2.55 million
pixels -"

And I don't understand what this means. Why don't they just say, photo
must be 4 inches by 6 inches, or whatever?

I use a Kodak EasyShare DX7590, set at 4.4 resolution. The photos are
huge so I resize them in PhotoImpression to 400 X 600, whatever that
means...it works out to a 4 X 6 print.

Anyway, sorry to sound dumb, but if someone can explain this to me.
When I look at the site itself the photos all look like they're 3 X 5,
but I don't know if they've been shrunk down from the size they were
submitted at...

Oh, where to start.

To start with, your screen is about 72 pixels per inch but for good
quality printing, you need a LOT more than that. But in general, 300
dpi (dots per inch) is about where you want to be. Some printers will
go higher than that, but it is arguable if most people can tell the
difference.

If the site wants 1700x1500, that's about 5.5 inches by 5 inches, at
300 dpi. Argueably, you can print down into the 180 dpi range, but it
starts to show. So, they might go bigger, but figure they are looking
for a good quality print of that size. But the same token, the same
picture will look fine on a website at 400 x 600 at about 5 inches by
about 8 inches -- with with a the top of the browser, the stuff at the
bottom of the page, a little border around it, it will reasonable fill
a screen and look good.

Most photo sites have you post big files and the "resample" them down
to a smaller size or a thumbnail as convenience and to get more
pictures per page.

So as you work on photos, work on as full size files. For many things,
the order you do them in doesn't matter, but the second to the last
step ever do is use "sharpen". The last step is to reduce (or
downsample) the image for your screen. Also, when you reduce the size,
make absolutely sure you keep a full size version because if you email
a picture to your Aunt Minnie and she wants you to print it, you'll
need the full size image.

Good luck and have fun taking pictures. I hope this helps.

Thanks to both of you for your responses.

Very helpful!


Barbara

wrote:
Hi, all

I'm going to be submitting some photographs to a web page that has the
following size requirement:

"Photos must be at least 2.5MP (2.5 Million Pixels). To determine the
amount of pixels in a photo, multiply the width by the length. For
example: a photo which is 1700x1500 adds up to a total of 2.55 million
pixels -"

The reason they don't say "4x6" or "5x7" is that it gives no guidance
for the number of pixels that make up the image; you could have a 4 x6
picture that has but a few thousand pixels, and would look horrible even
at screen resolutions of ca. 100 ppi (it used to be 72; old monitors
still are), or it could be a huge file of several thousands of pixels
per edge (giving several dozens of megabytes to store).

So, rather than have you calculate out that a 8 x 10" image at 300 ppi
would give them more than they want, they just tell you the number of
pixels; the ppi doesn't matter until they size it up to their specs.

--
John McWilliams

In article .com,
wrote:

Hi, all

I'm going to be submitting some photographs to a web page that has the
following size requirement:

"Photos must be at least 2.5MP (2.5 Million Pixels). To determine the
amount of pixels in a photo, multiply the width by the length. For
example: a photo which is 1700x1500 adds up to a total of 2.55 million
pixels -"

And I don't understand what this means. Why don't they just say, photo
must be 4 inches by 6 inches, or whatever?

Doesn't the company that operates that web site have an email address of
phone number to use for asking tech support questions? If so, I suggest
you contact the company to see what they say.

On 6 May 2006 17:00:37 -0700, wrote:
Hi, all

I'm going to be submitting some photographs to a web page that has the
following size requirement:

"Photos must be at least 2.5MP (2.5 Million Pixels). To determine the
amount of pixels in a photo, multiply the width by the length. For
example: a photo which is 1700x1500 adds up to a total of 2.55 million
pixels -"

And I don't understand what this means. Why don't they just say, photo
must be 4 inches by 6 inches, or whatever?

I use a Kodak EasyShare DX7590, set at 4.4 resolution. The photos are
huge so I resize them in PhotoImpression to 400 X 600, whatever that
means...it works out to a 4 X 6 print.

Short answer: Don't resize the photos that come out of the camera, and
you'll be fine.

Other people have already posted the longer explanation.

-dms

Shawn Hirn wrote:
In article .com,
wrote:

Hi, all

I'm going to be submitting some photographs to a web page that has the
following size requirement:

"Photos must be at least 2.5MP (2.5 Million Pixels). To determine the
amount of pixels in a photo, multiply the width by the length. For
example: a photo which is 1700x1500 adds up to a total of 2.55 million
pixels -"

And I don't understand what this means. Why don't they just say, photo
must be 4 inches by 6 inches, or whatever?

Doesn't the company that operates that web site have an email address of
phone number to use for asking tech support questions? If so, I suggest
you contact the company to see what they say.

This is not really a technical support question in many ways, and I
believe the OP got plenty of correct info.

--
john mcwilliams

On 6 May 2006 17:00:37 -0700, wrote:

I use a Kodak EasyShare DX7590, set at 4.4 resolution. The photos are
huge so I resize them in PhotoImpression to 400 X 600, whatever that
means...it works out to a 4 X 6 print.

The photos may appear huge on your computer's monitor, but even
without resizing them, they'll fit on a 4 x 6 print, minus a small
amount lost due to the DX7690's 4.4 mp images not having exactly the
same aspect ratio as the 4 x 6 print paper.

If you mean that the resized images have a 400 pixel by 600 pixel
dimension, then your 4 x 6 prints are probably much less sharp than
they could be. By reducing the original 4.4 megapixel images to
only 1/4 megapixels (400 x 600 == 240,000), you've thrown away 94%
of what the DX7590's sensor captured. You may have selected 400 x
600 because it matches the 4:6 aspect ratio of the 4" x 6" print
size. You could also resize your images to 800 x 1200, 1200 x 1800
or 1600 x 2400 pixels, and they'd all have the same 4:6 aspect ratio
but they'd save as larger files, containing more image data. Try
reprinting one of your previous shots, this time after resizing the
image to 1200 x 1800. It should be quite a bit sharper, but if the
difference doesn't seem that great (and it may not, since the 4 x 6
print is fairly small), compare the two prints with a small
magnifier. If you do, you'll probably be amazed at how poor the
print made from the 400 x 600 pixel images appears. I hope that you
saved the original images, and didn't replace them with the smaller
resized versions. If you ever make larger prints such as 5" x 7"
or 8" x 10", you'll easily see the drastically lower quality that
you'll get from 400 x 600 pixel images.