How to Convert HEIF back to JPEG

yzi2424 wrote: …all the photos that were taken in original form, jpeg,

jpeg is not an "original form." As taken, a 24 megapixel image would require a massive 72 megabytes of storage, even though most pictures are largely just empty space. jpeg, heic, gif, tiff, and others are methods of compressing all that data into a file of reasonable size through compression. HEIC is just the most efficient way to do that. Using jpeg or heic, it's common to squeeze pretty much all the information in a normal photo down 1/50th the "taken" size, or less.

incompatible formats,

Incompatible with what? The format of the file has nothing to do with the loss of quality of the image sent through a text.

how much better the jpeg versions are, I'd love to get them back to the original jpeg format to get back the information for each file.

To save bandwidth, most message apps and email systems reduce the size and quality of a transmitted image, since looking at a picture in a text message, for instance, doesn't require too much detail. These apps also often strip personal information that might be stored in the metadata of the image. There is no suggestion that an image transmitted by text or by email will have the same quality as the original.

You can't return information to a file that has been reduced in quality to save space or bandwidth.

photos to be taken and shared in original format - jpeg.

Again, that's not "original." And jpeg is not special; it's just older. Sharing pictures can be done in a number of ways. For iCloud Photos, for instance, we can use shared albums, but those are lower quality so they don't use up our precious storage. Or we can use iCloud Links that let friends download original quality images. Dropbox, Google, One Drive, etc., offer systems that allow people to access full quality pictures.

I'm confused,

Me too. Surely if the pictures are important to you, then you have kept them, and you have them in backups.

if this is the standard for most unknowing users, what is the point of having a high photo or video quality if once it's shared the quality ultimately gets destroyed anyway?

That's why we keep the our pictures safe in backups rather than depending on a text preserving them. I doubt there is any computer user anywhere who has not heard that they should keep backups in case they mess up, an accident happens, or they just didn't understand the way it worked.

yzi2424 wrote:

Converting that way does not recover the original quality of the image.

I did not say it would. The OP just said "original form, jpeg" which I took to mean the file format, not the bit-by-bit original data.

Usually the unvoiced objective with this kind of question is the person wants a more widely friendly file format since HEIC is a bit like the photo equivalent of ALAC. Yes, a few more things can open HEIC these days, but just about everything can open jpeg.

yzi2424 wrote: … jpeg is the original photo format and therefore more compatible.

No.

Again when you compress a jpeg into HEIF you lose information

No. Generally jpeg reduces the information-- it is a lossy compression, but the amount of loss is controllable. In Photos export on a Mac or in Lightroom you can choose different levels of loss, or "quality." Exactly the same is true for heic. The difference is that for the same quality, heic takes less storage, because the compression is more efficient.

The information loss that you seem to be concerned about is not connected at all to format or compression scheme, but rather that you're comparing images before and after being sent by text. It's the sending by text that is the problem, not the format.

Please take time to understand how that works before suggesting an option you might not be familiar with.

Huh?

Here's an example from an Export dialog from Lightroom Classic:

It allows the user to adjust the "Quality" of a jpeg from 0 to 100. I usually choose 100 which is nearly, but not absolutely, lossless. Admittedly, I haven't tried 0…

Here's the part of Mac Photos export dialog:

The "quality" is not continuously variable, but you see you can choose the amount of loss in the jpeg export.

This is from GraphicConverter's jpeg Save As… dialog:

And this is from GraphicConverter's HEIC Save As… dialog:

Perhaps you can see that it has just the same range in quality as jpeg. The big difference is that HEIC, for the same choice of quality, does a better job of compression, making a smaller file with the same information.

Choosing a 20 on the jpeg scale produces a smaller file with less information than choosing an 80 on the HEIC scale, and vice-versa.

Actually, HEIC (not HEIF) is already basically a JPEG. It's just a newer format that has been tucked into a container.

What's different about it?

1) You have no control over the quality level. It's fixed at what on a JPEG would be about an 8 (on a scale from 1 (worst) to 12). So, pretty lossy.

2) The color depth can be 16, or 10 bit. A straight .jpg can only be 8 bit.

3) It uses a newer compression scheme to make the image smaller than a comparable JPEG.

4) As it's fairly new, some image editing apps still can't open an HEIC file.

I've tested this by setting up my iPhone 14 Pro on a tripod and taken the same image as HEIC and DMG. Then took the uncompressed DMG and saved a copy as a JPEG, using different compression levels until I got one that matched the lossy compression of HEIC.

If quality is your goal, HEIC is not a good choice.

Kurt Lang wrote:

1) You have no control over the quality level. It's fixed at what on a JPEG would be about an 8 (on a scale from 1 (worst) to 12). So, pretty lossy.

2) The color depth can be 16, or 10 bit. A straight .jpg can only be 8 bit.

GraphicConverter 12.4.3 offers these .heic options (tested on Monterey):

Original .jpg exported with HEIF quality 1-80-100. Quality 1 clearly loses detail but is not too bad at least with this sample image.

Ah! There it is. I've noted in other topics that an HEIC image is just a JPEG container. To double check before my previous post, I tried looking up such information again, but everything insisted it wasn't. So then I wasn't sure.

That quality slider says just what I thought. While it isn't a JPEG (the tell-tale 8x8 blocks aren't there), it is compressing the heck out of the image.

The sites that said they were 16 bit is also wrong. Just as I thought, HEIC is 10 bit to give the image slightly more color range. Should've known that anyway. An image editor I was testing didn't know what to do with an HEIC file, complaining mainly about the 10 bit color depth.

Anywho, I just now took a shot of a wall in my house.

An as is, small section of a 48MP image, uncompressed DMG saved to a lossless TIFF:

An easy way to see compression is to open an image and max out the saturation. Here's the same image, only with fully saturated color. No compression artifacts. Actually, darn nice for an iPhone shot.

Now the same shot of the wall, only as HEIC. Looks fine until you pop out the compression. This is how much detail is lost using the iPhone's unadjustable, default compression:

yzi2424 wrote:

Maybe this will help: Lossy HEIF provides a balance between excellent visual quality and efficient storage, making it ideal for everyday photography. However, lossy compression means quality is permanently reduced, a process that can worsen with repeated saving. 

JPEG also uses lossy compression. Storing a picture in JPEG format typically means that quality is permanently reduced, a process that can worsen with repeated saving.

This is easily done on a Mac (just do a web search for how) but you say you have an iPhone which may require dedicated special software.