Printing photos what resolutions

[AndrewW]

I have been editing a number of photos together. To ensure I did not change the overall size of the finished piece I made all the changes on top of one of the pictures which I used as the background. When I tried to print the picture I was told the picture was too wide for 10 x 8(without cropping), but was fine for 12 x 8. The strange point was the photo which I used for a back ground printed perfectly alone on 8 x 10??

The resolution of the pictures was 3456 x 2304 (from and EOS 350D)
I also have a powers hot S70 which produces pictures of 3072 x 2304

My question if I’m creating/editing photos for print and merging a number of pictures what are the required resolutions and DPI for printing for the main sizes ?
6 x 4"
5 x 7"
6 x 8"
8 x 10"
8 x 12"

Thanks

Andrew

 

[ksmattfish]

The aspect ratio from 35mm film and APS-C and 35mm DSLRs is 2:3, meaning without cropping they make prints sized: 4x6, 5x7.5, 6x9, 8x12, 10x15, 12x18, 16x24, etc....

If you want to use a different aspect ratio when you are composing you need to consider that you will need to crop some of the image.

http://en.wikipedia.org/wiki/Aspect_ratio

The "standard print sizes" of 4x6, 5x7, 8x10, and 11x14 are all completely different aspect ratios. Who knows what genius came up with that; I suspect it's a hold over from the days before enlarging when only contact prints were made. I don't know why we can't get it changed since 35mm film has dominated for the last 40 years. Whenever I have the opportunity I let my local frame sellers (from Target to small shops) that it's 2008, and until they start stocking 2:3 aspect ratio frames I'll be ordering on the internet.

Here's where I try to educate my clients on aspect ratio. http://www.mattneedham.com/faq.html#aspect_ratio

 

[davebmck]

If you are having your pictures printed by an outside source, they usually suggest (or require) that your picture resolution is 300 PPI. If you are printing on an inkjet printer you can get away with 240 PPI. Personally, I keep my resolution at 300 PPI. The only reason to go lower is if you want to print a fairly large print. The higher resolution is not needed there as most large prints are viewed from a longer distance than your standard 4x6.

 

[lvcrtrs]

This whole aspect ratio thing was a mystery to me. This was great to have it explained to simply. I just couldn't figure out why my new SLR had this 3:2. I thought it would be nice it you could pick which one you wanted. The D90 will let you change a pic to 4:3 after you take it. Seems like you do have to remember to figure that cropping into taking the original picture and leave some extra space around your subject.