JPEG mystery

[treecreeper]

Can anyone explain this? My compact camera takes pictures (JPEG) with too many pixels for WAB, so I reduce them to 1600x1200 (still JPEG) using a free program called Paint.Net. After this they are still sometimes over the 1.0Mb limit, in which case I had been trimming off the edges using Adobe Photodeluxe, again exporting the cropped photo as a JPEG. I noticed the reduction in filesize was much bigger than the cropping could account for so I tried exporting the photo unchanged, i.e. read JPEG - do nothing - export JPEG (still at 1600x1200). To my surprise I was still getting a 45% - 65% filesize reduction every time. The pre- and post- photos look identical. Weird....

[Lancashire Lad]

Hi Treecreeper,

Have you checked the default "save" settings in Photodeluxe?

It might be that whenever you import/export a .jpg file, the software could be compressing it to a lesser level of quality, albeit that it may not be noticable when viewed on screen. (perhaps you could try importing & exporting the same pic. several times to see what eventually happens to the image quality and file size).

I don't use that particular software so can't check, but I would assume that it is this, or something similar that accounts for the large decrease in filesize you speak of.

Regards
Mike.

[Meta menardi]

It sounds as if the software is compressing it, that is what JPG files do. They two pics may look indentical, but the smaller one will have had data discarded. Our eyes are too clever (or not clever enough) at seeing what we want to see, so they make up for deficiencies in the picture. For this reason, I always use save as and a new name when resaving a JPG, or save as an uncompressed format such as TIFF. Don't throw away the detail you have paid for in buying the camera.

[Lancashire Lad]

I agree with everything you say Mm, as .jpg is a "lossy" filetype.

However, I suspect in this case there is more going on.

There would be a very small loss in quality, (and consequently file size), each time an individual .jpg is saved, even without using compression options.

But to lose between 45% and 65% of a file's size, in one import/export "save without editing" operation, means that there is definitely something within this software's settings that needs to be looked at.

Regards
Mike.

[treecreeper]

Hi Mike,
The Photodeluxe program is quite old. It came free with a scanner I bought a few years ago. I've been through the menus and I can't find any options relating to save/export. I did your recursive export experiment. The original filesize was 1203kb and with successive saves it went 517kb, 512kb, 512kb, 512kb, 512kb.

TC

[Lancashire Lad]

Originally Posted by treecreeper

Hi Mike,
The Photodeluxe program is quite old. It came free with a scanner I bought a few years ago. I've been through the menus and I can't find any options relating to save/export. I did your recursive export experiment. The original filesize was 1203kb and with successive saves it went 517kb, 512kb, 512kb, 512kb, 512kb.

TC

That seems very odd indeed.

I am assuming that you didn't do any editing/cropping at all, and just imported the image into the Photodeluxe software, and then exported it again, saving the resultant file.

What I can't understand now though, is the fact that on the first import/export the file lost over half it's size, whilst on subsequent import/export it lost very little. (Unless the software is programmed to "throw away" what it considers to be all the superfluous information during the first import/export procedure).

This may not be a problem for viewing on screen, but if you are in effect throwing away half of the data in your photo's, it could certainly have a visible effect on any that were subsequently printed.

If it were me, I'd be very tempted to only use that software as may be necessary for the scanner, and use something else for resizing & cropping etc.

I personally use Paintshop Pro, but several people on WAB swear by GIMP, which has had numerous good reviews. It has lots of very good tutorials on-line, and, since it is shareware, is readily available as a free download.

Regards
Mike.

[treecreeper]

Thanks Mike, I think it's time to treat myself to some new software. More so, as I've been reading about POD printing (Printing on Demand) which allows you to publish a book for no outlay at all by doing all the typesetting yourself. Very tempting. POD services require all photos to be uploaded in a lossless format like TIFF. Now I think I can see why!

Computer Shopper magazine regularly does comparisons of image editing software. Their current favourite is Photoshop Elements 7. In the most recent comparison the previous version (6) narrowly beat Paint Shop Pro Photo X2. They didn't like Paint Shop Pro's lack of wizards. GIMP didn't do very well - complicated interface and uneven performance.

TC

[Geoff F]

A 'proper' editing programme will certainly give you the option to be in full control of resizing settings. To get the best from these options there are a few technical tips to be mastered, but not difficult, and I feel sure that you will be amazed by the result.

Personally, I like the Serif Photo Plus software; currently using X2. But the first thing I do is to disable most of the auto editing options and work in full manual control. Yes, it does take a bit of learning but definitely worth the trouble.

In my opinion, don't worry about having Wizards; and magazines like Computer Shopper (which I consult from time to time) tend to review photo products based on what is easiest for the first time 'point and shoot' user rather than what can be achieved after a little bit of learning. So also read some of the Photography Magazines and specialist photo forums before buying.

[eeyore]

imo photoshop elements is the best of the "cheap" photo editing programmes - however before you spend money note that both GIMP (from gnu soft) and irfanview (from irfansoft) are free and very nearly as good.

[treecreeper]

....if anyone's interested, Computer Shopper's favourite budget DSLR is the Canon EOS 1000D with the Sony Alpha DSLR-A200K taking the 'budget budget' award. Their preferred Ultra-Zoom is the Panasonic Lumix DMC-FZ28