procedure for ‘lowres’ megapixel digital photo => high-res print?

AM
Posted By
Alia_Michaels
Feb 5, 2007
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441
Replies
9
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Closed
I have Photoshop 7 on a upgraded Mac G4 system. I’ve done web-related adjustments working with <100 dpi images, but I offered to help design a photo collage that needs to be printed professionally. The print shop has asked for all images be at 300 dpi.

Now the problem is that I’m receiving photos from different sources at all different resolutions. Most of the images I’ve received are less than 300 dpi (ranging from 72 to 180 dpi), but they’re all large megapixel .JPG files. Therefore, I have to ‘upsample’ if that’s the correct terminology, instead of downsampling like I’m used to doing.

If I change the resolutions to be consistent and in that process clear the Resample images box, the images are all different sizes AND I can’t change the size in the Image Size dialog box. To change the print size of the photo, I can scale it by dragging.

Question 1: Is this the correct procedure to use to adjust the photos to 300 dpi and keep a good-quality printed image? Basically, will the photos print correctly if I change the resolution to 300 dpi without resampling and scale the images individually by dragging?

Question 2: If this isn’t the best procedure to follw, what’s the correct/best procedure to use to get all the digital photos to 300dpi for printing AND scale each to the correct size for the collage?

Thanks,
Alia

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DR
Donald_Reese
Feb 6, 2007
Well, if you are starting with 72ppi images, it would depend what size they are to start. if you have a 3×4 at 72ppi,you are in trouble,but if you have a 20×30 at 72ppi,then you are in better shape.

If you need to upsize them,then you would need to resample them higher, with resample checked. remember when you resample,you are basically adding fake pixels and not really gaining detail, but it can appear to help sometimes.

I cant tell you the difference between dragging an image larger and resampling but i would lean toward resampling.
AM
Alia_Michaels
Feb 6, 2007
Thanks, Donald.

The original print size of each photo is larger than I need for the collage. (It’s going to be the back cover of a book.) So the final print size for all the photos will be SMALLER the original size; while the final resolution in each will be INCREASED.

Alia
DR
Donald_Reese
Feb 6, 2007
Okay, i seem to have missed that point originally. when you say the resolution will be increased, do you mean you are okay by just changing the numbers and leaving resample unchecked?
B
Buko
Feb 6, 2007
Alia. uncheck resample. change the ppi to 300. Is the picture big enough for that resolution?
AM
Alia_Michaels
Feb 6, 2007
When I change the resolution by unchecking Resample, the images are larger than needed for the collage. That’s why I then have to scale them them down by dragging. But I’m concerned that I’m screwing up the quality of the image by doing this.

When I was searching through the Adobe site and elsewhere on the Web about this issue, all the recommendations say to not have Resample checked.

I’m used to using the Image size dialog box with Resampling selected so I change the resolution and the size separately but at the same time. That’s why this is so perplexing to me. But in that case I’m always downsampling to <100 dpi for Web work.

Most likely there’s something basic here that I don’t understand… about working with low-res images and adjusting the resolution upwards, but mostly what I found in searches are responses about working with Web images — not for high-quality print.

thanks,
Alia
DR
Donald_Reese
Feb 6, 2007
Instead of dragging the images, just do your ppi change without resample checked. you are just reworking the same numbers. you can see that if you take your 72 ppi images and change them to 300 without resampling, the only thing that changes are your print dimensions. now with resample checked, just enter the size of the print you want in the image size and it will be ready to place in.
AM
Alia_Michaels
Feb 6, 2007
Thanks, Donald…
Just to make sure I have this clear:

1. Adjust the resolution of the images in the Image Size dialog box with the Resampling OFF and save the image.

2. Then open the Image Size dialog box again and with Resampling ON adjust the print size of the image.

Is that what you’re suggesting?

That’s what will best preserve the image quality?

Alia
B
Bernie
Feb 6, 2007
Is that what you’re suggesting?

Yes (though you don’t need to save the image between steps)

That’s what will best preserve the image quality?

No, since if you reduce the size and keep the resolution at 300 ppi, you now have less pixels than before. But this reduction in quality should not matter since it reflects (in a way) the quality of the final printed piece.

So work on a copy of the files so your originals remain intact.
AM
Alia_Michaels
Feb 6, 2007
OK. Since I have to covert the files from JPG to TIF anyway… I just did that in the interim ‘saving’ step so the originals are pristine. Then I did the size adjustment on the TIF file.

Thanks for all the help!

Alia

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