[OldBull]

I noticed if I used the MS program Paint to open a photo (in .jpg format) and then tried to save it without any changes, the photo size shrank for 50-70% (i.e. to less than half of its original size). I compared the two photos but I couldn't see any differences. My questions are:

1> Is there any useful data lost in the photo file by the 'save'?
2> If the answer for 1> is No, should I use this way to save space for photos on my disk?

Thanks.

 

[elf]

You mean the dimensions of the image (heigh and width), or the size it occupies on the hard drive (in KiloBytes)?

 

[OldBull]

You mean the dimensions of the image (heigh and width), or the size it occupies on the hard drive (in KiloBytes)?

The size it occupies on the hard drive (in KiloBytes), i.e. the file size on disk. Thanks.

 

[elf]

jpg files are lower quality. You will lose some clarity, which is more visible if the image contains text. The upside to jpg's are the small file size.

It's kind of a toss up depending on what you want.
jpg = small file size, but poor quality
bmp, and png = larger file sizes but the image will retain the quality

 

[OldBull]

jpg files are lower quality. You will lose some clarity, which is more visible if the image contains text. The upside to jpg's are the small file size.

It's kind of a toss up depending on what you want.
jpg = small file size, but poor quality
bmp, and png = larger file sizes but the image will retain the quality

Thanks for your reply. But I'm still a little confused.

I didn't try to compare .jpg file to other formats, such
as .bmp, or .png. I only 're-saved' the original .jpg file
without changing anything in it. It's a .jpg file to .jpg file.

When the file size became less than half of its original size, I thought
something related to the original photo must be lost. But I don't
know what got lost. That's what I'm trying to find it out.

 

[elf]

That is strange...I wonder if someone took the original file and just changed the file extension. Where did these pictures come from? If you can get some pictures of text that is generally the best way to the see the image degredation when converting to jpg.

 

[OldBull]

I think you can download any photos from your digital camera to your PC. Remember a .jpg file size on your hard disk then use the Paint to open the file and hit the 'save' button without changing anything to the photo. You will see the file size get reduced. (If you like to do some comparison, just save the same photo with a different name. All in .jpg format)

 

[tosh9i]

Even if it's still the same format, the quality of the picture can still be reduced from 0%-100%.

MS Paint is a very old program. If I were you, I'd switch to something more up to date, such as Irfanview. It's basically one of the most popular image viewing programs available.

http://fileforum.betanews.com/detail/IrfanView/967963863/1

If you have a lot of pictures, you can use Irfanview to "batch convert" them. In other words, you can convert 100 pictures from a high quality jpg format to a lower, but acceptable quality jpg format.

I just opened a jpg picture and saved it using MS Paint. The original size was 72 kb but after I saved in using MS Paint, the size was 39 kb. As far as I can tell, the DPI (dots per inch) was reduced from 15.0 x 20.9 cm; 5.9 x 8.2 inches to 11.3 x 15.7 cm; 4.4 x 6.2 inches

 

[OldBull]

Thanks a lot elf and tosh9i. I'll give Irfanview a try soon.