Collage and Size

[Omaha41418]

Hello,
I am currently new to Photoshop and have been using it primarily for creating Collages for my own personal use. I was wondering if there is a specific rule of thumb I should use when Downloading pictures and their size to use in the collage? Example: A picture with a size of 400 x 400 as opposed to one that is higher. I'm not completely clear regarding size and how it affects the overall collage when printed. All the collages I make are 8 x 10 and I print them with a resolution of 300 ppi. I made one collage and used a picture that was 1200 x 783 and the subjects in the collage came out with a pretty bad resolution. So in a nutshell, what size photos when downloading will give me the best quality or does it matter and what ppi should I be printing at to get the best quality? Any info is greatly appreciated.

Thanks

 

[IamSam]

Hello and welcome.

The rule of thumb is to use the highest resolution images you can. Hi res images tend to be larger in size. Convert them to a smart objects and resize them to fit the area designated for it in the collage.

 

[thebestcpu]

Here are some rules of thumb which may help with determining the minimum resolution you need.
The average viewing distance for a print is typically about the same as the diagonal of the print. For an 8x10 print that is about 12 inches.
At a distance of 12 inches of viewing a print, the average human eye cannot resolve more than about 240 dpi. At 24 inches the eye can resolve about 120 ppi and at 6 inches it can resolve 480 ppi.
So for an 8x10 just rounding up using 300 dpi is a fine choice.
For an element in your collage its best that each element has the same or better 300 ppi. So a 400x400 pixels element would have 300 ppi at 1.33 inch or a portion of your 8x10 (400 pixels / 300 ppi).
The 1200 x 783 should have been good for a 4 inch x 2.6 inch piece of your collage on your 8x10 using the same math.

Note that independent of the ppi, any image may have other issues that reduce its quality including the original focus, or blur from camera movement, bad contrast, etc, etc.

The approach that @IamSam mentions will be the easiest way to keep whatever quality the original images have. Subsequent downsizing and then upsizing (or vice versa) can introduce degradation where using Smart Objects will not have cumulative degradation with multiple resizing.
Hope these incremental tidbits are helpful
John Wheeler

 

[Omaha41418]

Thank You IamSam and John. Much appreciated!