Photographs to web and print resolution

[OWhatAThrill]

Hello all,
New to Gimp using 2.10.10. I have 25 photographs taken on my iPhone that I need to take and produce a set of files to be used on the web and then another set to be used for print on a home/office printer.  I understand I may be saving 25 files two times but as for actually resizing the files, I'm at a loss. Appreciate any guidance whatsoever!

[Blighty]

Digital images have a sizes in pixels. Best to think in pixels.

For example, if you want to print an image 6"x"' at 300dpi then you an image size of
(6x300)x(4x300) = 1800x1200 pixels.
Scale the image to that size.

Web pictures have sizes in pixels. Determine this size and then scale to suit.

Also consider aspect ratio.
A 6"x4" print has an aspect ratio of 6:4 or 3:2. Other aspect ratios can be 4:3, 16:9, .......
Determine the required aspect ratio. Your original image will probably have to be cropped to suit. Probably first crop, then scale.

Keep an original untouched copy of your photos.

[rich2005]

to add to Blighty's post

First a caveat, I do no "social media" whatsoever and not too keen on phones either.

Images are formed of pixels and the image size referred to in megapixels (MP) A quick search came up with this which seems a reasonable summary

https://www.cameracompany.com/blog/how-l...ne-photos/

I would not worry about printing, choose the paper size you are using, set the printer to fit on paper, and let the printer do the scaling.

If you want to check the optimum size in Gimp use Image -> Print size Set the X and Y resolution to 300, choose the units you use (inches / cms ...) and that shows the size for a quality print.  If you do any editing, export the image as a png or a jpeg. Gimp is not the best application in Windows for printing, Windows Image Viewer works.

   

Scaling for web depends on which part of the web you use. I assume these are valid. https://buffer.com/library/ideal-image-s...edia-posts

In Gimp, use Image -> Scale Image Set the width and height in pixels, and if you want the X & Y although for Gimp 2.10 this should already be 300 ppi.
Set the Quality to NoHalo. Hit the scale button. Export as a jpeg.

   

[OWhatAThrill]

Thank you both for your replies! I have always heard about DPI and how a good DPI for print is around 300 but all you need for web photos is 72 DPI and I knew that knowing absolutely nothing about the connection to the size of each photo at each resolution.

I'm going to have to wrap my head around thinking of DPI is sizes instead of DPI.

I am trying to follow some examples I have but in terms of how you have described it, I can't figure it out. A photographer from our local newspaper sent me some photo's she took and she sent the RAW files, printable files and WEB files. I'm comparing all files trying to copy the process of what she's done so I can get the same.

RAW 51.347" x 30.222" 72 DPI 5.59MB
WEB 12" x 7" 72 DPI 166KB ***goal - small file size
Printable 12.323" x 7.253" 300 DPI 5.62MB

When I use "Scale Image", if I change the Printable one to 300 DPI, it goes from the size of the RAW one to the size of the Printable one.

I have been trying to change the file size using the "Print Size" option and if I changed the X and Y, it changed the W and H or vice versa. My ultimate goal is to produce photographs that are optimized for either the web or print on a home office printer. My original files are 4-5MB, and as I'm trying to upload the photographs to an online photo album, I have to get the pictures down below 1MB if possible so there is no lag when visitors view the photos.

You both have helped me and I will use the "Scale Image" option but I have a whole LOT of reading to do before I totally understand the correlation between DPI and print size and how they now factor into social media because that's a whole different ballgame it seems from the links provided that I need to understand. Just a note, I have some issue in my brain that slows comprehension but once I get it, I "usually" understand it but I think a ways to go for me yet. Thank you for your replies again!

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Oh, and off to understand what "Interpolation" and "Hihalo" and Lohalo" mean...

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Hmmm, that would be "nohalo" and lohalo"...

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Now I'm really confused because I took my first image down from 56"x 42" inches down to 12" x 9" but my file size increase from 4.8 to 5.0 so what would get the photographer's file size to go to 166KB? Appreciate any guidance.

[OWhatAThrill]

I take that back. When I reduce the file size to the smaller print size, leaving it as 72 DPI because that's what it already was, when I export it out as a JPG, it reduces to 250KB. Thank you both!