Problems with resizing of images to smaller size

[HabmalneFrage]

Hello, I am new here and I have a question with regards to the batch resizing function.

I have some 200 pictures in various sizes, ranging from 40 kb to about 6 MB and I would like to make the really big images smaller to
a size about 1 MB or a little less. I have already used the software 2 or 3 weeks ago and everything worked nicely, I got my resized pictures, no problem.

Just recently now I have started to encounter a really strange problem which I don't understand. I try my best to explain it as it is really slightly weird. Anyway, I wanted to do the usual, i.e. resizing some really large pictures and decided to resize about 20 of them in one go. I didn't really care that some of them were 3 MB and some were 5 MB as it is not so important to me if the outcome is exactly the same smaller size for all of them - if only they are smaller.

I then opened the advanced options and checked "resize", and where it says "set new size as percentage of original" I typed in 40 %, I can't remember. Anyway, it was obviously a smaller ratio.

But when the conversion started I could see to my total confusion that all of a sudden the software resizes half of the pics to a smaller size (just as I wanted) but the other half was resized quite to the opposite to really large. And I mean really large. A picture that was only 2 MB right from the start suddenly went up to 4 MB size ?!?!?

I have no idea what went wrong. I have used the exact settings as I did a couple of weeks ago with another batch of pictures. And I don't see any difference in the "sort" of pictures (they are average jpeg format images).

I also deinstalled the software and set it up again just to see - but nothing changed. I can't use it at all right now because it has become totally unreliable. It seems to enlarge pictures randomly (although without qualitly loss - which is even more astounding). But I have no use for this. I need smaller pictures.

If anybody has any idea what could possibly be the problem I would be highly grateful. This is not a joke post, although it might sound like one. At least this strange phenonemon sounds like a joke to me.

Thanks for you help!! Highly appreciated !

[Bhikkhu Pesala]

I then opened the advanced options and checked "resize", and where it says "set new size as percentage of original" I typed in 40 %, I can't remember. Anyway, it was obviously a smaller ratio.

If you're not sure what you typed then its not at all obvious that its a smaller ratio. Try again, and this time make sure you know what you're doing.

[HabmalneFrage]

Well maybe my English, which is not my mother tongue, might have not been quite clear here. I did of course type in a smaller ratio. What I meant by "I can't remember" was that I do not remember if it was e.g. 40% or 50% or 60%. But it was definitely smaller ;-)

[Mij]

The size of the file depends on your JPG Save settings. The quality at which the original was saved and at which the reduction is saved are particularly important.

For example I took a typical 10MP image (without EXIF data) that had been saved at quality 50 - considerably lower than I would normally save at. The image size was 1.15MB.

I opened that file, resized it to 50% and saved with quality set to 100, with quality set to 50 and finally with the "Try to save with original quality" option set.
The results were as follows;
Saved at quality 100; Size 1.96MB - Bigger than original
Saved at quality 50: Size 358KB - considerably smaller than original (as expected)
Saved as "original" quality: Size 358KB - same as saving at original quality (50)

So, unless you know the quality at which your image was originally saved, my advice would always be to use that "Save with original quality" option, which is new to the latest Irfanview version 4.32

[HabmalneFrage]

Oh cool thanks ! I think I am getting the picture :-) I will try this ! Thanks very much - have a nice day!