# how do I relate image size to photo size

Discussion in 'Australia Photography' started by Troy Piggins, Jan 29, 2008.

1. ### Troy PigginsGuest

I don't get many photos printed, but there are a couple I would
like to get printed out now. I think Harvey Norman prices are
reasonable. Not sure how they compare quality-wise, but I'm not
printing commercial type photos so I think they'll be good enough
for little ol' me.

So if my original image size is 3504x2336, what max size photo
could that print without being "pixely"?

And what size would a 1280x853 image print with comparable
quality?

What sort of DPI do photos print at so I can calculate myself?

Troy Piggins, Jan 29, 2008

2. ### Colin_DGuest

The generally accepted standard for good prints is 300 ppi (not dpi)

So if you divide the pixel count by 300 you will get the size in inches:

3504/300 = 11.68 inches by 2336/300 = 7.79 inches without interpolating

You can work out the 1280*853 yourself.

Note: Images are always expressed as pixels per inch - ppi. Printers
print dots of ink, so the resolution of a printer is so many dpi. My
Canon i9950 prints at 4800*2400 dpi. When fed with a 300 ppi image, it
will use 16 ink dots to make one image pixel (4800/300 - 16)
horizontally, and 8 dots vertically (2400/300). So one image pixel is
made up of 16*8 = 128 individual ink dots.

Colin D.

Colin_D, Jan 29, 2008

3. ### Mike WarrenGuest

If you allow 150 to 200 pixels per inch or greater you'll get
reasonable results.

Mike Warren, Jan 29, 2008
4. ### Troy PigginsGuest

* Mike Warren is quoted & my replies are inline below :
OK thanks.

Troy Piggins, Jan 29, 2008
5. ### Mr.TGuest

And 250-300 PPI for good results.
Any more than that and they will usually be resampled before printing
anyway.

MrT.

Mr.T, Jan 29, 2008
6. ### Rob.Guest

But don't depend on that as I have 3000x2000 images printed at 1 x 1.5
mtrs (with excellent results), which is dependent on the printers raster
program.

I suggest you have a look at a crop at 6x4 or 8x10 and you will have a
better idea just how far you can push the pixels.

You may find several conspiracies on the subject especially from that
1001 person whoever they are now

r

Rob., Jan 29, 2008
7. ### Troy PigginsGuest

* Colin_D is quoted & my replies are inline below :
Thanks for the detailed explanation Colin.

Troy Piggins, Jan 30, 2008
8. ### Mike WarrenGuest

Hi Colin,

I notice your message didn't show up for quite some time. I had the
same problem with Terranews but have now solved it. Email me (remove
the spam trap) if you want to know how.

-Mike

Mike Warren, Jan 31, 2008
9. ### Mr.TGuest

What does "straight from the camera" mean here? Many camera's including
DSLR's, can't even manage an 8*10" print at 300PPI, let alone anything
bigger! Most would be far more than that for 6*4" prints, but offers little
advantage at that small size anyway.
Post processing will usually improve the result over that "straight from the
camera", unless the person is incompetent. Remember not everyone is silly
enough to shoot JPEGS! (I assume you are indicating processing and resaving
may reduce the quality of an already compressed print)
Of course it also depends on your definition of "normal viewing distance".
This will usually be different for a 4*6" print than for a 1*1.5 metre
print, and I'm talking actual viewing angle here, not just measured
distance. It is "usual" IME to view a big print at a relatively closer
distance than a small one, regardless of theory. It's easy to examine
smaller details on big prints and sometimes difficult to get far enough away
to compare with a small print, (assuming anyone would actualy want to do
that) which cannot be critically examined by most people without a
magnifying glass in any case.

And there is often a good reason to blow prints up, you often WANT to see
the fine detail not readily apparent on a small print.

MrT.

Mr.T, Feb 2, 2008
10. ### kGuest

| Mike Warren wrote:
|
| > Troy Piggins wrote:
| >
| >
| >>I don't get many photos printed, but there are a couple I would
| >>like to get printed out now. I think Harvey Norman prices are
| >>reasonable. Not sure how they compare quality-wise, but I'm not
| >>printing commercial type photos so I think they'll be good enough
| >>for little ol' me.
| >>
| >>So if my original image size is 3504x2336, what max size photo
| >>could that print without being "pixely"?
| >>
| >>And what size would a 1280x853 image print with comparable
| >>quality?

(1280/300 = 4.27 inch) x (853/300 = 2.84 inch)

| >>What sort of DPI do photos print at so I can calculate myself?

straight from the camera, 300 ppi (not DPI)

| > If you allow 150 to 200 pixels per inch or greater you'll get
| > reasonable results.

| But don't depend on that as I have 3000x2000 images printed at 1 x 1.5
| mtrs (with excellent results), which is dependent on the printers raster
| program.

yup, the printer RIP has a lot to do with the final image and as a general
rule 300 PPI is what you can safely aim for straight from the camera, for a
print to be viewed at the 'normal' viewing distance.

of course it depends on ones eyesight and a 150 ppi image may look wonderful
to a person with poor eyesight, and for someone like my good wife who's
legally blind without her coke-bottles, 50 ppi would probably suffice

karl

k, Feb 2, 2008