cropping loss of Mb

[cladav]

when cropping I lose approx 75% of the initial Mb's. I think this is something to do with old and new image or canvas size. I have photoshop and have tried many variations in the canvas and image size drop downs but have got nowhere. I am sure there is a simple solution and would love to know what it is.

[kcoppock]

...that's because you're cropping.

You're literally throwing away data, so of course your file size will go down. Am I misunderstanding this?

[cladav]

as experiment I cropped to same size i.e. maintaining exactly the same photo but after I saved, the file size had reduced by 75%

[kcoppock]

What file formats? If you're saving from RAW to JPG, then that's to be expected. If you're saving from TIFF to TIFF it shouldn't happen (unless you're going from uncompressed TIFF to compressed TIFF). If you're saving from JPG to JPG with different quality settings, there would be a large difference. Even at the SAME quality settings, you'll still have another layer of compression that will reduce it further.

[cladav]

sorry don't understand quality settings? - i take image from my archives put it in photoshop crop minimally (and as said no cropping as experiment) save and the new file has massivley been reduced

[cladav]

I am saving from jpeg to jpeg

[kcoppock]

JPEG is a compressed file format. Any time you save to JPEG you are losing quality, no matter whether you save at 12 (Maximum Quality) or 1 (Lowest Quality). Obviously, the lower your quality choice, the higher the compression, and the more image quality is lost. You should always keep your original file and save copies.

[cladav]

I was not aware there are options on saving quality - how do you access it?

[kcoppock]

When you save as JPEG from Photoshop, it will give you a slider that goes from 1 to 12. Alternately, save to PNG or TIFF to avoid any quality loss, but that will take up much more hard drive space, so that's the tradeoff.

[cladav]

sorry gave duff info I am not using photoshop, just checked and its jasc paintshop pro opened a file and saved but no options appeared, should i do something else instead of photography knitting possibly