Another Resolution Question

[Diella]

Hi All,

Sorry if the question has already asked. (another basic question)

I want to print my images taken from digital camera. When I download it, the resolution was 72 pixels/inch. I took them to photo lab (for testing) and print few of them with standard size (4R), and the result was not that good.

I want to use photoshop to fix my images resolution. I did in this way.

I open file with 640 pixels x 480 pixels (original size)
Resolution 72 pixels/inch.
I copied the image and paste it to new higher resolution layer. (I use 200 pixels/inch)
Then I re-size the image to 1181 pixels x 886 pixels (or 15 cm x 11.25 cm for photo size)
I printed with hp psc 2110 printer and the image and it looks fine.
(But I don?t know if I take them to photo lab, the result will be the same or becomes dull as previously)

The question is,

Did I do the right step for change the resolution? Or is there any other way to do it?
I have heard to have the good resolution, we need to print the image and re-scan it.
But concerning of a huge number of images, it takes time to do that.

Thanks in advance.

Diella

PS: Sorry for poor English ;\ feel free to correct it, I really appreciate it

 

[Erik]

640x480 means that the image is chopped up in 640 vertically, and 480 horizontally. Compare it to a mosaic.

On a monitor, 72 of these units (called picture elements, or pixels) go in every inch (some 2,56 cm).

For printing, when you only have 72 units per inch, you don't get a good quality: you need more. This can go 300 or even more. In print, the units aren't called "pixels" anymore, but dots because before computer days, screens were made out of dots. (this is a simplification).

So when you print, and you assign 72 pixels/dots, you will have a photograph of some 9 X 6,5 inch (22,5 x 17cm).

When you want a better quality, and you assign more pixels/dots per inch, you will have a photograph that is much smaller as you only have 640 x 480 inch at your disposal.

So, to get an acceptable size, you will have to sacrifice in quality. I suggest you change resolution to 120. That way you get a normal 15 x 10 cm photograph ( 5 x 4 inch)


The best way to do this is to go to the Image menu, and choose Image> Image Size. This opens a dialog menu. Here you uncheck Resample to stop Photoshop from creating new pixels by calculating, and then you change the resolution from 72 into 120.

Personally, I would try the result at 120 pixels/dots, and I would also try to let Photoshop recalculate. Save your photograph (save as)and add 120 to its name (save as tiff or psd). Then open the same Image>Image Size dialog, see that the Resample box is checked and set the resolution to 150. Save this one as (save as) and add 150 to its name.
Then print both, or have them printed (see that you can see which is which by adding some sign to them with a brush, or...) and compare both. That way you know which one is best, and what you can do in the future.


Sorry if this sound simplistic, but I intentionally avoid all theory and technical explanation. It is already complicated enough as it is.

 

[Diella]

Very Good explanation :}
Have you considered yourself as a very good trainer?? (or maybe you are! :\ )


Erik,
I do what you described.

My original file size is 640 x 480 pixels and resolution is 72 pixels/inch.

I made two files as you recommended.

The first file, I unchecked the resample image box and adjust the resolution to 120 pixels/inch. The image size now is 13.55 cm x 10.16 cm (the pixel still show 640 x 480 pixels, although the size now is smaller)

I printed this one, and it looks good.

The second file, I resize the image with resample image box checked. The size now changes to 1333 x 1000 pixels and the resolution is 150 pixels/inch.

The printing result is bigger size. I need to adjust the printing size to fit in to the paper, but still the sharpness is less comparing to the first one.

I like this !! Thanks so much for sharing it :} Now, at least I can do something with my 72 pixels/inch images.

Thanks a million!!


Diella