Question about digital printing

[Luciano]

I have an image I want to print. These are the specs.

TIF file

Pixel dimensions: 34.7 mgs
Width 3023
Height 2002

Document size

Width 10.093
Height 6.673

Resolution 300.

When I send my work to my stock agency, they have me plug in the number 5128 into the dimensions, depending on whether the image is vertical or horizontal. (I'm assuming this is calliner inpoliation?)

In this case the image is horizontal. After plugging in the numbers these are the specs I get.

TIF file

Pixel dimensions: 99.5 mgs
Width 5128
Height 3390

Document size

Width 17.093
Height 11.301

Resolution 300.


These are my questions. If I want to make a large 20 x 24 print, which file should I send? Will I get more detail in one or the other? Does it make a difference in smaller prints? Does it make a difference in even larger prints? What is the biggest I could print and not lose detail.

Thank you for the help. I've shot conventional film most of my life and I'm still feeling my way around a little bit when it comes to digital printing.

Luciano

[milleniummuppet]

I have actually been wondering the same questions myself.
I have digital photos etc that are about the same:
300 res
but about 40cm x 25cm - ish in doc size.
Yea just wondering how big I could really print these without compromising reso?

[Colin Southern]

Hi all,

I'll give you a quick "primer" on print resolutions ...

First concept to understand is viewing distance. Viewing distance follows one of two rules; If you're a photographer then the minimum viewing distance is limited only by the length of your nose - for everybody else, it's pretty much at whatever distance they can see THE ENTIRE image comfortably at. (OK, slightly tongue-in-cheek, but only slightly).

So (for normal people - ie "non-photographers") the viewing distance increases with the size of the print, and of course, the further away you are, the less detail your eyes can resolve - so to a large degree the drop in quality from the lower resolution of a large print is pretty much nulled out by the increase in viewing distance.

For some reason, this is a concept that although photographers understand, they none the less find it difficult to accept. I'm forever reading that you need resolutions in the order of 300 to 360 DPI for optimum quality - but "it just ain't so". Lets look at some simple maths - and lets work in millimeters (easier to visualise). 360 dots in 1 inch x 360 dots in the other direction is the same as 14 dots x 14 dots for every millimeter - or put another way - could your eyes resolve 196 tone changes in a single square millimeter? AT ANY DISTANCE? EVEN WITH A MAGNIFYING GLASS? ... mine neither.

My personal belief is that there's little to be gained (for closeup work) in going over 180 dpi - for bigger works that are viewed from further away you can go even lower (I print most of my commercial canvases at 100 dpi, although the texture of canvas means you can get away with it a bit).

At the end of the day, 100% of the information you have in a file is contained in whatever pixel dimensions the image contains. Sure, you can up-sample the image which might help smooth things out if trying to view a large image upclose - but there's no way any program can enhance an images to produce information that wasn't there in the first place.

So to address Luciano's specific image ...

First up, your current image is 2023 x 2002 pixels - that's close to a 1:1.5 aspect ratio - if you want a 20 x 24" print you'll have to do some cropping - otherwise you're looking at a 16 x 24" print.

2023 pixels divided by 20" gives 101 ppi - which from normal viewing distances will look just fine. You could up res it to 300 DPI - but it won't create any new new information - it'll only do a linear interpolation of what already there - none of which bears any resemblence to the actual resolution printers use anyway. In summary - at normal viewing distances - you're unlikely notice any difference.

Weather or not your print lab can handle something that's not upsampled to 300 dpi is another question - in theory it's simple to do if they really need it, but in practice many don't seem to have a clue what they're doing. Also, you might like to make sure that your image is 8 bit and sRGB colourspace before sending it to them as many can't handle 16 bit and/or other colourspaces like adobe RGB / LAB etc.

Millenium ...

"Yea just wondering how big I could really print these without compromising reso? "

It's one of those "impossible to answer" questions - you can't "compromise resolution" per sec - it simply gets lower the bigger you print - then again, as I mentioned above - viewing distances then increase (for non-photographers!) and it all evens out. If you're asking "what's the lowest resolution I can go to before the image starts to degrade visually when viewed upclose" then that's a bit different - and the answer is "it depends". With a magnifying glass you could see the difference between 240ppi and 300ppi if you were looking for it - normally you won't notice anything amiss even at 180 dpi. Once you start going below 100 then things can start to look a bit rough - and by about 70dpi it's starting to look pretty raggety (but still fine at a distance).

Upsampling isn't a majic bullet - if you go grab a 4kb file from a website - upsample it to 1GB - and print it 10 feet wide and 6 feet high, it's still going to look bad. Then again, if you take Luciano's print and print it out 50 miles wide by 30 miles high - with pixels that are 30 feet square, it'll still look good viewed from space (even with binoculars!).

Next time your passing a bill board take a good look at the image from a distance - then take another look up close - it'll look very raggety up close - but - that's not how they're designed to be viewed. Same with our photographs.

Hope this helps,

Cheers

PS: Millenium ... send me a PM and I'll print you an image for free up to 2 feet wide / long as you like - and I'll show you what I mean.