Reducing question here

[bradleyheathhays]

First time caller here. I'm placing an add on craigslist selling of all things tires, and I have some really high res photos (jpegs) I'm trying to dumb down to a smaller sized file (while keeping the same size photo) so that they're better handled by anyone accessing my advertisement, but I don't have a photo management/editing program that will let me reduce an image's resolution without reducing it's size. Can you guys suggest a free downloadable program that will let me reduce my images resolution without reducing an image's size, and tell me how to do it? Embarrassed for the simplicity of my question on this advanced forum, but I'm in need. Thanks so much. I'm all ears.

 

[Dao]

You can use the free opensource software called GIMP and choose save for web option. (And adjust the compression level for jpeg format or color level for png format)

 

[Big Mike]

There are two thing to consider when talking about the size of a JPEG image. The first is the actual size of it....the number of pixels it has. Most cameras give you a good sized image, because that is what you need when you want to print it. A general rule of thumb is 300 pixels (linear) per inch of print. So for a 4x6 print, you might want 1200x1800.
But for viewing the image on a computer screen, you don't need that much resolution. A common number to use is 72 PPI (pixels per inch). So if you want you image to be 10x8 inches on a screen (that has it's resolution set to 72), you would only need 720x576 pixels. That is a much smaller size, and will be a smaller file size, so it will load faster.

The next thing is the compression / quality. JPEG is a compression format, so with most image software, when you 'save as' and choose JPEG, you can also choose the compression or quality level. As you dial down the quality (up the compression) the file size gets smaller. You can actually dial it down quite a bit, without it showing in the image.

So by doing those two things, you can make a jpeg image, a very small file, which will be easy & fast to load.

 

[The_Traveler]

Resizer.com

 

[KmH]

A common number to use is 72 PPI (pixels per inch). .

Pixels-per-inch is meaningless for electronic display, and it does not effect the file size of an image.

The only numbers that matter are the pixel dimensions.

File size is in large part a function of how much detail there is in an image. One of the ways you can reduce the file size is to blur the details in unimportant parts of an image.