Tools that claim to reduce jpg size with no quality loss

Question

Microsoft used to have an "image resizer" as part of their Mini Tool Pack in Win XP and today, there are many such tools for Windows 10, some free and some not.

Lots of them claim to reduce the size of the jpg by 80% with no quality loss like jpegMini does: https://www.jpegmini.com

My question is, this seems logical for screen view but what about in print? When printing a 80x30 cm' digital wedding album, will the 300dpi print quality be the same quality even after reducing the file by 80% with these tools?

Answer 1

Short answer: no, the quality won’t be the same, but that might not matter. You’d need to proof it though.

Tools like jpegmini make their big savings by removing or adjusting parts of the image that the human vision system is unlikely to detect. One example: In an image with a big blue sky, the sky area would likely be made up of lots of blobs of different blues, whites, and probably a handful of other colours. If you start by blurring that sky you remove a lot of that complexity which can make compressing the image a lot more effective - smaller file size.

The problem can be that what’s visible to the human eye on screen is different to what’s visible in print. The only way to tell is to get a printed proof and see if you are happy with the new result.

Answer 2

1) I always say this. Quality is a process, you do not "lose quality", you decide your quality parameters.

Sometimes "quality" means speed, on a website, you need to load your images fast, or the viewer will leave.

But on a printed project "speed" is not an issue. File size is not an issue.

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2) No. Any aditional compression to reduce file size lose information.

Sorry, this old webpage of mine is not translated in English but it is only to show you a method to analyze this information lose. There are different methods for JPG compression, which gives different results, some of them less file size, but some of them lose more info.

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If for some reason your "online provider" limits the size of the files you can upload, first check some other things.

Needed resolution. You probably do not need 300PPI, you probably need only 200PPI.

Color modes, you most likely do not need CMYK, send them in RGB.

You probably need to send the full page in vectors, not in raster format.

As a last resource, simply use PShop to resample a copy of the photos. Do not use any online website, which you do not know the sub settings used to compress your images.

You most likely want to deliver the maximum quality print you can. Do not risk it for smaller file size.

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On some more professional environments, you do not use JPG at all.

You start with a RAW image, save it as a 1 bit PSD file, which can be saved as a TIF lossless compression format to be printed.

On a normal everyday life project yes, you can use JPG. You take some photos saved on JPG format directly from the camera, and you can save JPG files using the correct parameters. As @Alex Magill said, some of these compressions are imperceptible to the human eye, (but potentially can cause some issues when printed) but you can still use them as JPG.

Answer 3

You can usually compress JPEG images in a lossless way, but you can achieve only(?) 5-10-20% compression depending on the source image. For example, digital cameras may not optimise the hell out of their JPEGs to conserve battery, other images might not have been saved with the best options, and this can be fixed. If you use a Mac, you can use Kornel.Lesiński's ImageOptim:

https://imageoptim.com/mac