I recently got a friend to Photoshop an image for a friend. It was 7mb when I sent it but only 3.05mb when it came back, the dimensions are exactly the same, however (4928 x 3264).
Please can I ask if this means that the 'quality' is now less?
Thank you in advance.
Well if the file format and image size are identical, but the file size has reduced significantly then the file has less info in it so the image quality may be reduced somewhat. Question is will it be detectable to the human eye without blowing it up to poster dimensions.
If it's an issue ask the friend exactly what he did and if he can produce a Photo-shopped file without loss of data.
When saving a photo in photoshop you have the option to set the resolution. For printing this would normally be 300 PPI (Pixels Per Inch). For display on a monitor it would be 72 PPI. This as you can see 228 pixels less info in the resized image.
Will it be detectable to the human eye? probably not if it's a small photo, but will be very pixelated at a larger size. Once this info has been discarded it cannot be replaced, it can however be improved by resaving at an higher PPI and using such as the 'Bicubic Smoother' setting in Photoshop.
As Belatucadtus says contact the friend to see if he has the original high res image on his computer.
Smoothing won't bring back lost details.
Even just viewing and resaving a lossy image format will reduce the quality.
If you want to NOT affect it you must make sure you either do not resave it or st the attributes to READ ONLY.