Photoshop: Image resizing vs image resampling

[santoro80]

When should check or uncheck the "resampling" option in image size dialog box? If I'm chaning the document size for the print I should uncheck the resampling option, right?

[John Wheeler]

If you want the number of pixels per edge to change, you have to check the resample option. If you want to just change the DPI around with the same number of pixels, do not check the resample box. Hope that makes sense.

[santoro80]

It makes sense. If I understand it correctly... lets say I want to decrease document size for print... when the resampling is checked, then the pixel resolution decreases too and the quality of the printed image would be lower than the quality of printed image with resampling unchecked (and pixel resolution unchanged)?

[John Wheeler]

Hi Santoro80

I think you got it.

If you are using the Image Size dialog to change size for print here is one approach

- With resample unchecked, set the dpi to what you want on final print. The dimensions should now be larger than your final print if you have enough pixels to downsample
- With resample checked, now change to the final print dimensions that you want. This will keep the dpi the same and adjust the pixels appropriately.

If my main focus is achieving a specific file size, I typically use FIle > Save for Web and Devices. It gives me all the options I need on one screen including jpg compression quality with previews of the results. (It's not just for Web and Devices Hope that helps.
-

[Doug Nelson]

If you want to dig deeper into this, we did a show with Andrew Rodney on resolution.

[santoro80]

Thanks for help. I have a last question. When I'm priting image on a photo paper, the only thing I know is the size of the paper. How do I know what resolution (dpi) I need?

[andrewrodney]

Originally Posted by santoro80

Thanks for help. I have a last question. When I'm priting image on a photo paper, the only thing I know is the size of the paper. How do I know what resolution (dpi) I need?

What kind of printer?

[santoro80]

Inkjet printer. Canon MP520.

[andrewrodney]

Originally Posted by santoro80

Inkjet printer. Canon MP520.

Set the resolution between a low of 180ppi and a high of 480ppi at the size you desire. IOW, go into Image Size. Turn resample off. Set the size you want for the print output. IF the resolution falls anywhere between 180-480, you’re set to go.

[santoro80]

Ok. Thanks.