dpi adjustment to fit specific file size

AM
Posted By
Alan_Miyatake
Feb 4, 2009
Views
258
Replies
3
Status
Closed
Photoshop CS2 for Windows XP

When trying to attain a specific size for a JPEG image (60MB) I adjusted the image size by cropping the image to 8"x10", and changing the DPI to 450.

The image size window indicated that the file size was at 60 MB, which was the correct size that we wanted for the file.

After saving, the file size was way below the size indicated on the original image size (when the file was open). Upon reopening and looking at the file size, it indicated that it was still 60 MB.

I had done this same process with roughly 50 files and all of the sizes came up different (ranging from 6 MB-64 MB).

I also saved the images as PDFs after making some adjustments to the JPEG files, but the same problem of the file size changing still came up.

Does anyone know what would cause the image size to change so much? A reply would be greatly appreciated.

MacBook Pro 16” Mockups 🔥

– in 4 materials (clay versions included)

– 12 scenes

– 48 MacBook Pro 16″ mockups

– 6000 x 4500 px

RK
Rob_Keijzer
Feb 4, 2009
Alan,

When your document is open it shows the uncompressed size. When you save it as aa Jpeg file a compression takes place reducing the file size.

You say that you aim for a size of 60MB. Why? why does the file size outweigh other IMO more important properties like pixel dimensions.

Why must the file be 60 MB? or any MB for that matter?

Rob
DM
Don_McCahill
Feb 4, 2009
all of the sizes came up different (ranging from 6 MB-64 MB)

This is natural. JPG compression will be different for every picture, based on the content of the picture. As well, you can use different compression settings, that will determine how much quality you lose. (The more quality lost, the smaller the file size. Some quality loss and reduction in size occurs at all sizes available.)

And I agree with everything Rob told you.
B
Buko
Feb 5, 2009
Jpeg is what is known as a lossy format. A lossy format is one that throws away data every time you save. the higher the compression the more data lost with every save.

Also you should learn the difference between DPI and PPI please read the following link.

<http://www.adobeforums.com/webx/.3bb51427>

How to Master Sharpening in Photoshop

Give your photos a professional finish with sharpening in Photoshop. Learn to enhance details, create contrast, and prepare your images for print, web, and social media.

Related Discussion Topics

Nice and short text about related topics in discussion sections