jpeg format changed by a MAC so they can't be opened by non-apple hardware or software

Sorry but your post is inaccurate

1 - the Mac does not ever "take it on itself" to do anything and certainly never deletes anything on its own - any such action is defined and approved by the user

2 - and secondly the Mac JPEG is the same as any other

3 - to get help you need to post fewer RANTs and opinions and give more facts like what OS is on the Mac and exactly how the potos were moved o the Mac

If they were imported into either iPhoto or Photos then all that has to be done is to select them on the Mac and export as the original file which for both packages is copies bit for bit during import and can be exported bit of orbit giving you an exact bit for bit copy of the original image

and note that we are users like yourself so threatening not to purchase a Mac makes no difference at all - we are happy to help but to help you have to do your part

LN

Never had a problem with any of my Macs, and they generally do not (by default)

erase camera memory cards after downloading; that's likely an owner preference.

{However I manually move image files into dated folders, and use image editor

software to make changes; mostly minor, as I'm a photographer who uses camera

F-stop & Shutter speed settings, not photoshop; & learned on transparency film.}

You may be able to try a free running recovery utility (multiple platform) to get image

files from the camera memory card. It can be configured to search for file types.

•PhotoRec - Digital Picture and File Recovery:

http://www.cgsecurity.org/wiki/PhotoRec

•TestDisk - Partition Recovery and File Undelete - can help recover file systems

http://www.cgsecurity.org/wiki/TestDisk

The above is not a modern 'app kind of software' and is not simple; but it can be thorough.

It is cross-platform and works with a reverse method of thinking; it can be configured, too.

Usually if the memory card is put back into a camera or its native device and the file system

is not correct, the device will re-format the memory card; & your files are as good as gone.

Or, I should say they would be much harder to attempt to recover; layered overwritten content

is harder to recover and a professional service may be required. At some cost to you, then.

There are several newer things that users of recent OS X (10.10.4) should know about

the way certain camera memory cards may be seen, automatically, and a way to make

each card to it isn't automatically read in a default way, is on the user to know. I'm not

using Photos or iPhoto at this point, in the latest OS X systems. I prefer an image editor

that does a fairly good job, & works at my discretion for minor edits. I don't paint them.

Hopefully you can recover the images by file type & learn how to use the mentioned free software.

Good luck & happy computing! 🙂

Check the way the filename extensions are written on the JPEGs.

The Mac usually uses lower case filename extensions "IMG1234.jpg" and on a PC I frequently are seeing uppercase extensions. "IMG1234.JPG"

Perhaps simply renaming the files might make them readable.

Another possibility is that you tried to open the files staring with a full stop: i.e.: .123.jpg instead of its corresponding file 123.jpg. Such files are hidden on the Mac, but not so on the PC.

Is it possible to post one of these non-openable (if such word exists) files on a server (e.g. dropbox) and give us a link, so that we can download and analyse? Now - I must admit - I have only Mac so if the file opens normally on a Mac... But as far as I know, a JPG is a JPG and can be opened on any platform.

Clearly the MAC has done something to the format when the photos were uploaded. Please can somebody tell me what it is and how to open these files on a windows computer?

What are the filenames you are seeing on your Windows PC?

we need to know the format of the files that you transferred. What do you see as the file information?