I have not one but two digicams now and I'm really getting into it as a hobby, and I'm doing quite well at organising the photos I work on, but the ones I don't work on are a bit of a mess and are taking up a lot of space. Some of them I want to keep intact for working on in the future, and the rest I want to save as smaller jpg files (for reference, memento etc) and delete the originals. A few of them I'm going to process by hand, but most of them could be batch processed.
Most of the originals are jpgs of (approx) either 3000x2000 and 1.5-3.5 MB, or 4200x3400 and 1.5 -5 MB. (I'm not doing anything with my RAW files yet.) I've tested quite a few and I've worked out that I'd like to make the files 1 MB but have them no smaller than 1000 pixels on the shorter side. This won't be a one-off job; I'll be doing this every time I shoot.
I'm trying very hard to satisfice here rather than optimise - these photos are rejects, after all (I mainly want to be able to see why I rejected them, refer to the EXIF data, and also to keep a chronology alongside the photos I am keeping). But the files vary in size quite a lot - and so if I use FastStone Image Viewer, for example, and set the shorter side at 1000 pixels, and set the jpg quality to give me an average file size of 1MB, I end up with quite a lot of files considerably smaller and larger than 1MB (and the setting would be different from batch to batch anyway).
Is there a smart way of doing this? Does anyone know of a program that will deliver a file 1000 pixels short-side at 100% quality, unless result is more than 1MB, in which case try 99%, unless result is more than 1MB, in which case try 98%, etc etc?
Alternatively, is there a program that will simply reduce the quality of the jpg to a given file size (1MB) without resizing? And can anyone tell me how different the result will be from a re-sized file (new dimensions) in terms of quality? I would have thought it would be much the same when viewed at the same size on the screen.
I'm aware, by the way, that if I were to use a percentage as the quality setting then the resultant files would have a neatly consistent relationship to their originals, but I don't want to go that route, even though it would be easier to manage. Firstly, the originals with smaller file sizes are the ones to benefit from not being over-compressed and the byte-rich files can afford it. Secondly, if I can get the files near to 1MB each it will make accounting for future file storage extremely easy.