Images reduce in size on export

Well....

Exporting has NOTHING to do with preview size and previews are JPGs anyway. There are two exporting functions in Aperture. The first is export master - this will do nothing to your original file but put a copy of it wherever you want. The second is export version - this will export a file of whatever format and size YOU specify using an included preset or one you make up yourself. This should be pretty self evident.

If you are still having issues maybe give us a little more detail about exactly what you are doing.

RB

What format were your originals? raw, tiff, jpeg, or something else?

Regards,
Calx

Yep, whenever I export to jpeg from a RAW master my file size is smaller.

Tony

Definitely worth checking that the presets are actually set to what you thought they were then.
Tony

I just conducted a test of JPEGs imported from a CD, and then exported from Aperture. The originals were saved with a compression setting of 10, and my Export preferences are set to Original size, compression 10. Comparison of the original on CD, with file size in the Metadata reading in Aperture, and the exported image showed them all to be the same.

Ernie

Hi, I have also been trying to figure out why versions exported from Aperture are reduced in size whether edited or not. As one person pointed out exporting original size with quality set to 10 reduces the size, quality set higher increases size. On the other hand the pixel count remains the same. Can anyone explain what exactly happens to the image and why. Example: Master is 3.4 MB 2448x3264 and is imported as referenced. When the version is exported it becomes 2.8 MB and remains 2448x3264 in dimension. In this case I am referring to a jpg imported and exported.
Thanks

Example: Master is 3.4 MB 2448x3264 and is imported as referenced. When the version is exported it becomes 2.8 MB and remains 2448x3264 in dimension. In this case I am referring to a jpg imported and exported.

You do realize that exporting a jpeg file as a new jpeg means re-compressing the same data a second time right? I'm not an expert on the subject but I think the small discrepancy could be due to the loss of information from the second pass. That's what compression does after all...

Thanks, I understand what you are saying but the issue is that the jpg or any other format is exported "original size" yet the size changes and this applies only to versions as exporting a master (jpg included) does not change the size. Also how come the MB changes but the dimension shows the same? Any thoughts?

You're confused about the term size.
+Original size+ in the Export dialog refers to dimensions not file size. That's why the other choices in the pop-up are all pixel related. It has nothing to do with bytes.

When you export a master the size doesn't change because you're simply creating a duplicate of your master file in another location, not producing an exported version with different attributes. Those are two very different things.

In the export dialog you control two things: how large the image will be (dimensions) and how much compression will be applied (which will affect file size). You'll notice that if you export as a TIFF file, you no longer have access to compression settings because TIFFS in Aperture are uncompressed. in that case your only control is dimension. Same goes for PSD.

Try this: export your 3.8 mb jpeg as an original size TIFF. Now look at the resulting file size and dimensions. You've now apparently added information to your picture 😉

Message was edited by: Jade Leary
Just noticed RB had explained this quite well before me. You should read his post again...

Well thanks, I think you might have answered many peoples question! Actually I did export the Jpeg as Tiff as a test and it was of course a very large file and the image was sharper but surely the information added is useless for Jpeg? I was only testing on jpeg since raw files are a different issue. However I also reimported the exported (unedited) version and exported it again and the file size did not change so how is this? Shouldn't it have compressed again?
Otherwise is it correct that whatever we do to a jpeg will change its size therefore if we need to edit for quality prints it would be best to use raw?
Coming from darkroom editing to digital I am fairly new to this, thanks

Glad it's starting to sink in.
however, you still need to understand some basic stuff regarding digital (which is normal at first!).

Otherwise is it correct that whatever we do to a jpeg will change its size therefore if we need to edit for quality prints it would be best to use raw?

JPEG is a lossy format, which means it's already been compressed - some information has been discarded by your camera to make the file smaller. The more compressed a file is, the more info you lose. When you work inside Aperture all the adjustments you make (without going to plugins or an external editor) are instructions that are applied on the fly by the software, so you're not actually affecting pixels but the way you see them. Only when you export that file are those adjustments then applied. If you export as a JPEG, you're applying compression again so in essence you're getting a degraded file. This may not be apparent but it's there. If you should re-import that degraded file and re-export it again, eventually you'd get something pretty useless. That's why we have lossless formats: a TIFF or PSD will not contain compression, allowing you to manipulate the picture without losing data.

Compression is a pretty complex beast and while you can shrink a file down a lot, eventually you reach a limit where compression becomes useless. There's just so much data that can be taken out. That's why zipping a TIFF will make a much bigger difference with the original than zipping a JPEG.

Otherwise is it correct that whatever we do to a jpeg will change its size therefore if we need to edit for quality prints it would be best to use raw?

It's not and it is. It's NOT correct that you should use RAW for printing. You can't print from RAW. RAW is just sensor data that always needs to be converted in order to be used, whether in print or digital format. The big advantage is in editing because it allows much greater manipulation of the camera's data after the picture has been taken and without loss or degradation.

But it IS correct that manipulating a JPEG file will result in data loss if you repeatedly export and import as JPEG. When editing JPEG you should either stay in Aperture or export to TIFF or PSD before editing in another app. You can get spectacular prints from a JPEG file as long as you watch your workflow.

There's a lot more to be said about this subject and I'm not sure if I'm being as clear as I could be. But hopefully this is shedding some light for you on the subject...

One more thing:

Actually I did export the Jpeg as Tiff as a test and it was of course a very large file and the image was sharper but surely the information added is useless for Jpeg?

I wasn't serious when I said there was suddenly more information because the file was bigger. The image can't be sharper because it's a TIFF. All you've done is keep the information that was already there. The larger file size is due to the fact that you've now created an uncompressed file (so it's actually now what it should be in the first place depending on dimension and content).

I feel like we've opened a can of worms!

Many thanks, your post is extremely helpful and has cleared some confusion so I can move on... as you say, there is a lot more on the subject and I will surely be back for more answers!

P.S. On the subject of raw: I did not express myself correctly - I meant raw being best for editing before converting to Tiff or other for best quality in print for all the reasons you mention.