Printable size advice please

michael23 said:
HI there, I have just received my daughters school photo in the form of a jpeg file on a cd.

The dimensions are

Resolution 1536 x 2304
Dpi is 72
File size is 496.5kb!

What would be the optimum max size I could print such a sall file too? The max print size they showed was 16"x12".
Click to expand...

A few things.

the file size of 496.5kb shows they have used a lot of compression (jpg quality 4!!! or around that has probably been used) - That is poor and really restricts the size because as you blow it up, the artefacts show up heavily.

ppi (not dpi) doesnt really matter in a digital image - you change the ppi yourself to get the print size you need. The main thing is the number of pixels.

So if you print at the standard 300ppi the file size would be 7.68" x 5.12"

At 200ppi - 11.52" x 7.68"

At 150ppi - 15.36" x 10.24"

Easily calculated
Same equation can be written three ways.

R = Px/Ps
Px = PsxR
Ps = Px/R

Ps = Print Size(per axis)
Px = Pixels (per axis)
R = Resolution

So if you want a 16x12 you do the calculation for each axis

R = Px/R
2304/16 = 144pi
1536/12 = 128ppi

if the crop ratio is different to the original image the figures will be different. Just means you need to crop a tad and print at the lower ppi value.

In this case the final image is a 4:3 ratio but the image you have is 6x4 ratio. So you would need to crop a little to get the ratio right and you could print this at 128ppi - It should still look fine - You are advised not to resample too much though because the compression they have used really restricts the image IQ.
 
Good photo quality print is 300dpi, and magazine quality is 150, iirc. So, working at 150dpi, you could reasonably get about 15 x 10 with those current dimensions. You could always try resizing in Photoshop or Elements and seeing what the quality is like at 100% size on your monitor...

EDIT: Jim's answer is obviously far more in-depth... I wasn't thinking about the jpeg compression they've used...
 
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michael23 said:
HI there, I have just received my daughters school photo in the form of a jpeg file on a cd.

The dimensions are

Resolution 1536 x 2304
Dpi is 72
File size is 496.5kb!

What would be the optimum max size I could print such a sall file too? The max print size they showed was 16"x12".
Click to expand...

i should have advised OPTIMIM QUALITY I would say would be printing the image at between 240 and 300 ppi so at 240ppi the image size is

2304/240 = 9.6"
1536/240 = 6.4"

So 9x6 really.
 
michael23 said:
Thanks very much! I got a shock when I saw the file size. I did a contrast boost and a slight sharpen and that took the file size to 1.7mb.
Click to expand...

You've not added any more detail doing that though.... In fact you have probably reduced the detail of the file more by saving the compressed file (unless you saved as a tif).

The reason they reduce compression to such a degree is so you can't print massive images (I've done that too with nursery images but not quite so much).
 
Catdaddy said:
Good photo quality print is 300dpi, and magazine quality is 150, iirc. So, working at 150dpi, you could reasonably get about 15 x 10 with those current dimensions. You could always try resizing in Photoshop or Elements and seeing what the quality is like at 100% size on your monitor...

EDIT: Jim's answer is obviously far more in-depth... I wasn't thinking about the jpeg compression they've used...
Click to expand...

300ppi is over used to be honest - you won't see any difference using 240ppi. Tried and tested on all sizes of image. In fact 150ppi produces a great quality print too but you may see a slight reduction in IQ if you look close up but at normal viewing distance should be perfectly acceptable.

Don't believe all the 300ppi thing. Yes it will probvide a great quality image but at 240ppi you will not see a difference.

Most labs prefer prints to equal their printer output (of 300dpi) that's why they like 300ppi images (one pixel = 1 dot of output).

dpi = printer resolution
ppi = image resolution

THey are different even although most mix this up.
 
No worries and good that it looks better.

Cheers
Jim
 
A couple of points....

The filesize may also reflect the fact that the photo is probably a photo with a white background - and a white shirt (or single colour). The filesize of a jpeg reflects the amount of detail in the image - in fact some people testing cameras photograph a given test subject and the bigger the jpeg the more detail recorded!

The company you've bought this file from will probably print their own prints - so the file will probably be balanced to print as you've got it. If, as the original posted says, he doesn't have photoshop, the odds are the screen is not colour profiled, so he'll probably do more damage "correcting" the file. Whilst you may think the file small, the photography company will have done tests to find the optimum file size to print the vast majority of prints ordered quickly - so the odds are the prints you make will be fine.

The printing will also have a huge issue - as if it's a shot with a white background - if printed on an automatic balance printer you might find its printed too dark.... blue background will print too yellow - and so on......

Why not pop down to a good local independant minilab with an owner operator - and get them to print the file without your tweeking (and perhaps one with too!!).
 
Sam may be able to offer an indication on size if you send to him :) His lab produces fine prints.
 
My wife got 1 of each printed earlier for me, have to say, only on a kodak instant kiosk thing, but at 8x6 it would give me an idea of how they compared. The original looked much better printed than it did on the screen of my laptop, but there was a clear lack of sharpness, the edit I did looked better, I might just have to balance the sharpness out if I print a little larger.

How much difference would there be if it were run through a lab rather than a kodak machine?
 
michael23 said:
My wife got 1 of each printed earlier for me, have to say, only on a kodak instant kiosk thing, but at 8x6 it would give me an idea of how they compared. The original looked much better printed than it did on the screen of my laptop, but there was a clear lack of sharpness, the edit I did looked better, I might just have to balance the sharpness out if I print a little larger.

How much difference would there be if it were run through a lab rather than a kodak machine?
Click to expand...

Sam may be able to answer that better.

THe lack of sharpness is down to the amount of compression the company have used when providing you the image (I've received the same images)!

My own images are very sharp and I was disappointed with the size and level of compression.
 
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