Can you tell me what the difference is between the save as jpeg and the export as jpg functions. If I perform both actions on the same tiff/psd file, the jpeg is around 10mb and the jpg is around 2mb. What info am I losing through the export function?
I'm using Photoshop CC.
[year "2016" added to subject line for clarity by moderator]
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Export As > JPEG is the update for Save for Web which replaces ImageReady. You can preview the image and make changes.
Before any of these three newer options were available, Save as > JPEG was still there. I remember saving with a couple of choices and deleting the ones I didn't like.
To change the file size, change the Quality and other options. A quality of "100%" or "12" or "Maximum" will be largest.
In addition to what Jane has said, the reason for the difference in file size, assuming you have used the same quality setting in both cases, is due to the presence of metadata in the Save As version, but not the Export As version.
If you look at Jane's graphic you'll see the Metadata radio button 'none' is selected which tells the program to remove it. As you work in Photoshop on a PSD or other file types, the program records a history of all the things you do and stores them. This can result in a very large amount of effectively junk data getting recorded and the file size even of a PSD can really expand dramatically as the junk doesn't seem to be stored compressed. The longer you work on the document the more raw metadata accumulates. You can see this happening in Photoshop by selecting File Info
If you look on the Raw Data tab you see everything stored in an XML format. It doesn't mean much unless your an expert but I imagine someone finds it useful.
When Export As is used all that data is stripped out, reducing the file size. You can see that by taking a Jpeg exported that way and calling File Info again. What confuses some people is that data is still there when it shouldn't be, that occurs because the act of opening the file is recorded and dumped into raw data. It isn't really there in your file unless you save the file subsequently.
Hope that helps
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A regular Save As just saves the file as-is, about all you can do is set the jpeg compression level.
The Export function gives you several options to reduce file size while giving you a live preview of the result.
Unfortunately, the Export module still has several shortcomings compared to the old Save For Web module. Notably, the preview is not color managed, a deal-breaker for everyone with a wide gamut monitor, and there is no way to embed the icc profile (a mere 3 kB BTW). For this reason I still use Save For Web.
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To everybody who has replied so nicely: all correct, but still... ..there's a lot more.
I've worked with photoshop since version 1, and back then, there were some real limitations you had to work around.
At about cs2, it became apparent that photographers and other professionals working with images wanted to be able to save more information about their files than the standard PSD offered. HISTORY states was the first attempt to meet those needs halfway, as photographers had wanted to be able to go back several steps during work, undoing a whole set of steps. Originally, the PSD file format was supposed to expand to include the history states, but implementation proved to be too much work. Instead, other options were explored. Grouping, and even multiple compositions in photoshop are now possible. But these only allowed you to build your layers and quickly copy them for multiple attempts and adjustments, without retaining information on the values used in those steps. Enter the SMART OBJECT. This single function allowed the user to place multiple adjustments onto a single layer, then go back and check the values and make adjustments.
The export function was intially designed as a way to output only the final image data to file formats that were not supported in the save function, using the most compatible part of the data possible. The save for web function was designed to save files in common internet image formats with as little data storage as possible, so the images could be kept small in file size, to be handled by the web programming rather than using excess data to define how to handle it. This has become less necessary due to cheaper storage, and the growing need for copyright respect. The more recent version of the export dialog respects this, and the save as uses the more recent xml styles that web servers use to find out how to handle the images.
History states are now exportable to text files. but ultimately they still leave out the values utilized in each step. They are useful for teaching the major steps of different techniques, and can even help you set up instructional videos before shooting. SMART OBJECTS are still the best way to go as you work, though they do add more memory use.
The excess data that was stored in a JPEG has gone through several revisions. XML has become the standard because it is easily handled and read in almost any programming language, allowing programmers to make use of the information in various ways. Saving without that excess data invites people to steal your work. Most that I work with use a special container format on their webserver, and save a version for that, with another version saved for downloading that has all the data. Thus, the case for both methods is still strong.