best resolution ???

[thegeeze]

Hi Folks,
I've been lurking around here for a few days and I have to say, "I'm impressed with all the bright / talented people on this site".

I have a favorite image of my wife that was taken in 640x480 @ 72ppi. Being a newbie at retouching and trying to figure out what all the tools do in PS-5.5 ... I have found it difficult to work on this image at this resolution. (i.e. selection tools) Suddenly, I had what is probably a "brain fart".

I took the original image/ opened the image size dialog box/ changed the reolution to 180ppi/ checked-constrain proportions/ checked-resample image "bicubic"...

End result: 1600x1200 @ 180ppi., which seems to allow more accuracy using selection tools.

Have I done wrong? Pros/Cons?

thx
Alan

[Jakaleena]

Welcome to RP Alan!

Your solution is not necessarily wrong, but usually not desirable. It depends on whether you like the end result or not...

I'm not the best at explaining the technical stuff, but here's basically what happens:

Increasing the image size like that adds information that wasn't there to begin with. The addition is done by interpolation, which is basically a "best guess" as to what needs to be added. PS reads the nearest pixels and then adds more pixels based on that information in order to increase the size. What you can end up with is a pixellated image with artifacts.

Have you tried printing it? How does your image look when printed? Have you tried taking the file to a photo lab and having it printed? Is it still clear and unpixellated?

In the end, whatever makes you happy with the image is what's ok. There are no hard, fast rules really - everything is subjective.

Generally speaking, if you are shooting with a digital camera, it's usually best to set it at the highest resolution so that you don't have to increase the size later.

[thegeeze]

thx Jak,
The image was taken digitally by a friend who is a memory miser and I guess he never really planned to print anything larger than a 5x7. My printer is on the fritz and I'm far from ready to send it out for developing, so I can't say how it will lok at print resolution.

Is what you mean by "pixillated"... that you can very easily distinguish between individual pixels? or, the image will look mottled?
This has me thinking and I decided to do a little experimentation.

Here are my examples: examples

Correct me if I'm wrong.
center image - original @72ppi (pixillated?)
left image - resampled bicubic @180ppi (very sharp)
right image - resamoled bilinear @180ppi (less sharp)


thx,
Alan