File size suggestion

In Gigapixel, I would like to cap the size of the file even when set to the highest quality is set. Ie. I can only upload no larger than 28MB Jpegs so I would like to be able to set that size. I usually get a file size of 39+MB

I understand I can set the quality to high but then it gives me a file size half my original file. I can’t see any real difference between the 39MB and the 7MB even though they are the same dimensions. I would like to know how much I might be losing by going from Max Qual to High Qual? (What are the diminishing returns for Max versus High)

It would be better is there was a sliding scale for Jpg and it showed the file size when adjusted (30 - 100).

[quote=“Jeff-Foliage, post:1, topic:9894, full:true”]
[…] I would like to know how much I might be losing by going from Max Qual to High Qual? (What are the diminishing returns for Max versus High)[/quote]


JPEG compression is lossy, that’s how it can create much smaller filesizes. But the amount of compression also depends on image structure and amount of detail (or noise). The more detail, the less compression.

The lower the quality settings, the more aggressive information will be discarded before doing another compression step. The first to go is color accuracy in fine detail, and then ultimately also luminosity will start to suffer. It’s a gradual deterioration, while attempting to first discard information that human vision is less sensitive to notice.

It’s not really possible to predict that amount of compression accurately without actually doing it. So for each quality setting the program would have to actually compress the image in order to report it’s size. That would take time and result in a not very responsive updating of file size values.

So for the quality, one would ideally have a preview at 100% or larger to allow a before/after comparison, where one could select a region of interest with lots of fine color detail, or also smooth gradients which may start developing posterization artifacts.

For an update of expected file size, one could have an option for more accurate calcuation, based on an actual compression without really saving it yet, and doing it again when actually saving it.

For a desired maximum file size one could have an option, to have a slow under-the-hood kind of trial and error for a given target file size.


P.S. For those seeking to maximize filesize reduction without visual degradation, Google (amongst others) have developed a utility called Guetzli, that will analyze the image extensively, replaces some high detail areas with slightly better to compress detail, reduces color accuracy within the limits of getting too obvious, tries different compression rates, and finally produces a significantly reduced output size JPEG that’s visually hard to distinguish from a 100% quality JPEG. It also discards meta data.

Starting with a (recommended) 100% quality JPEG as input, it can often reduce the file size to between 10 to 30% of the original size (depending on image content). But it takes many minutes to do so, and larger sized images can take a very very long time.

Thanks Bart, I understood some of that but the gist of it, is that is it would significantly slow the processing down. I work in Lightroom as my main software to edit and catalog my images. I will edit in Topaz and then I’m back in LR to export and done.
The problem with the newer Topaz programs is that I have to export and work on them in gigapixel or sharpen AI and then take them back into LR. I will get my images processed and then take them into GP and on max quality settings it creates a file of 33MB to 40MB and the site where I upload my art to only allows 25MB.
When I just use the image quality set to high setting it creates a smaller file size than the 8-15MB file size. (5-10MB) and I have looked hard at 100% and above but the high and max setting seem to provide a really nice image quality wise. But I wanted to know what I might be doing to my image… Thanks…

But if down the road if the designer’s care at all it means more to me to keep all my programs working from inside LR and not creating more difficult work flows… Unless you think you will take over all the features of LR… I really want everything inside LR… Just my 2 cents.

Oh! I like that one!!!