dpi, res & print size confusion

mrfizzed

I have read, and read and read all over the internet so many things about dpi, resolution, print sizes etc, but bottom line is it seems they all contradict each other. using smugmug's ;abls (ezprints etc), what exactly do i need for ppi (dpi) and what size will yield quality prints. For example, what dpi and res do i needd for a 16x20...some sites say 150ppi, others say 300dpi. I am confused. Please advise.

Thanks!!

The Mechanic

Hi mrfizzed,

Yes, there is a lot of confusion around dpi and ppi. DPI or dots per inch is often used in the printing world. This was referring to how many dot per inch were laid down when printing an image. Now PPI or Pixels Per Inch is most often used to determine how an image displays on a screen. The most common being the web, which is most often at 72ppi, now that is changing but that is a whole different story.

In either case, the actual image data does not change, you still have the only the data you have collected or the pixel count. Dimension X by dimension Y. So if you have an image that is 3600px x 3600px that is how much image data you have captured. This is much more important than the DPI or PPI of an image. Aside from resampling an image, the DPI and PPI never change the image, they are just a field of data that is filled in telling some device how to display or print the image.

Long story short, if you do not resample (change size and create new pixels) the image, the DPI and PPI will have little to no affect. You can for example set the export PPI in Adobe Lightroom to 300. This will not affect your upload or printing of your images from your SmugMug Account. You can see a bit more here: http://help.smugmug.com/customer/portal/articles/93359-are-there-resolution-requirements-for-printing-through-smugmug- . Again the most important numbers to keep an eye on is the actual pixel count, dimensions X by Y.

In regards to your example, you would need an image of at least 1024x1280 pixels. No matter how you set the ppi or dpi you still need at least 1024x1280 pixels to get a quality print.

I hope this makes a bit of logical sense. There are tons of long drawn out explanations of how these work, when they were used, how some are not important anymore and so forth found out on the web.

The Most important part here to remember, if using Adobe Photoshop or similar, Do not resample unless you intend to create or alter the pixels of your original image this can make major changes to your image!

mrfizzed

thanks for the info!!!! so you are saying that i can get a 16x2 with a pixel coiunt of only 1024x1280 for pixel X x Y dimension sides? Seems low res to me....

mrfizzed

adding to this...are you saying that if i export in lightroom at say even 3000 pixels on long side for a client and a dpi of say 240, i should be more than ok for almost all prints? also, what aboutu quality in lightroom, its default is 100, can i scale that down to say, 70, 80 and still have high quality photos but save time and space?

rainforest1155

The 1024x1280 pixel is the minimum we would print a photo in 16x20 size. It'll give you good quality, but not great quality. For great quality, we recommend that you upload the original sized photo as it comes out of your camera. The DPI setting does not matter at all - you can ignore it.
If you wish to keep the file size down, check out the file preparation guide.

EntropicTendencies

mrfizzed wrote: »

adding to this...are you saying that if i export in lightroom at say even 3000 pixels on long side for a client and a dpi of say 240, i should be more than ok for almost all prints? also, what aboutu quality in lightroom, its default is 100, can i scale that down to say, 70, 80 and still have high quality photos but save time and space?

Remember, the Lightroom DPI setting is just sets a number to act as a scale - it doesn't affect the image data unless you resize/resample (and more importantly specify physical dimensions). It's the 3000 pixels which count (that's nearly 3x our minimum resolution for a 16" print) - you really need to decide based on what image sizes you want to sell. Or use Proof Delay to replace images when/if they are purchased.

Image sharpness is more important than resolution for large prints (there are still a lot of large prints made from older cameras). A small print might mask some blur or missed focus, but a large print will make it pretty obvious.

You definitely don't need a JPEG quality setting of 100. I normally upload at 75% for online display, but if the gallery was for high quality or large prints I'd probably just be lazy and set it to 85%.

I suspect that few would spot the difference between an image generated at 80% and 100% and if they do, they've spent far too long looking at the pixels and have forgotten the subject of the image

Barrie
Smugmug Support Hero