Large File loses size

[eboggs_jkvl]

I have some JPEGs that are 10 -12 megs in size. When I load them into Pro X6, do my editing and save, the saved file is <2megs. I need to keep the file in the original size. The Corel auto preserve keeps the original at 10-12 megs but it is the original and is unedited.

How do I edit the large file and save it as the original size?



Elmer

[eboggs_jkvl]

I kept searching this site and finally found the answer. "File" "Save as" "options" and set compression to "1".

Back to my editing now.

Thanks

[df]

Corel's implementation of Save is downright stupid. It has a compression of 20 by default (1 being no compression, 100 but max). Use Save As, when the dialog opens click Options, set the compression to 1. Even then Corel in it's infinite wisdom doesn't think that you need to retain all that info and you'll still lose a tiny amount, but it is tiny.

[eboggs_jkvl]

It needs to be 0, not 1. I hate to lose perfectly good pixels!


Thanks,



Elmer

[Jan Shim]

Not only Compression Factor set to 1 but make sure Chroma Subsampling is set to 4x4 2x2 2x2 to better preserve your original IQ.

[eboggs_jkvl]

Not only Compression Factor set to 1 but make sure Chroma Subsampling is set to 4x4 2x2 2x2 to better preserve your original IQ.

Now that one helped a lot. I'm good now and the pictures are staying very close to the original.

Thanks.

Elmer

[Forriner]

JPG is by it's own definition a lossy compression type. If you want lossless, try TIFF and I believe PNG and PSPIMAGE for editing and JPG for exporting your finished product to print or whatever. Every time you save a JPG you lose a bit of quality. At the 1% compression that PSP offers it will take a few saves before you notice, but it will happen.

Speaking of lossy, here's an article on JPG subsampling from wsu.edu that you might want to read before going subsampling.

[pearson100]

Is there a way to change the default behavior of the "Save" command so that there is no compression? I see the option for "Save As" in its dialog box.

[df]

Not only Compression Factor set to 1 but make sure Chroma Subsampling is set to 4x4 2x2 2x2 to better preserve your original IQ.

I think you're right but isn't that backwards from what it's supposed to do? Odd.

[Forriner]

Not only Compression Factor set to 1 but make sure Chroma Subsampling is set to 4x4 2x2 2x2 to better preserve your original IQ.

I think you're right but isn't that backwards from what it's supposed to do? Odd.

Did you read the article? Subsampling is always lossy, does NOT preserve image quality, but according to the article it can be okay or even desirable for certain situations. But the information is lost forever if you don't retain the original.

If you're working on a JPG, saving it and reloading to edit another time, you might consider saving the first edit as a .pspimage or .tiff, which are lossless, big files but lossless. Then after the last edit you can save as lossy JPG and lossy subsample all you want.

[df]

I'm not arguing that jpeg is or isn't lossy. I think most people know that it is. But if you're starting with a jpeg, for whatever reason, it would be nice to not lose as much as possible. The loss of image quality is also not what it used to be.

[Forriner]

I'm not arguing that jpeg is or isn't lossy. I think most people know that it is. But if you're starting with a jpeg, for whatever reason, it would be nice to not lose as much as possible. The loss of image quality is also not what it used to be.

"
Hi df,

Jan Shim advised the original poster to apply the sturdiest chroma subsampling possible in PSP in order to "better preserve original image quality" and you thought he was right, odd but. All I did was say that he was wrong, and I linked to proof.

Then I offered a sort of work flow to make sure that you lose as little quality as possible when editing JPG images. Because each save of a JPG loses quality, period, while saving as pspimage or tiff doesn't. This was an answer to your "But if you're starting with a jpeg, for whatever reason, it would be nice to not lose as much as possible".

So in PSP, once you decide to save the .pspimage as JPG, you can set compression to 1 and don't do the subsampling, to maintain optimal quality. If, as the article states, subsampling is good for the use you're going to put it too, or if you just want to, by all means subsample, but know that you are losing information, so keep the original if possible. The loss is in the compression, same as it's always been, PSP's 1% is almost lossless but loss is cumulative over many saves, and subsampling just makes it worse. That's all.

[df]

I'm not arguing that jpeg is or isn't lossy. I think most people know that it is. But if you're starting with a jpeg, for whatever reason, it would be nice to not lose as much as possible. The loss of image quality is also not what it used to be.

"
Hi df,

Jan Shim advised the original poster to apply the sturdiest chroma subsampling possible in PSP in order to "better preserve original image quality" and you thought he was right, odd but. All I did was say that he was wrong, and I linked to proof.

Then I offered a sort of work flow to make sure that you lose as little quality as possible when editing JPG images. Because each save of a JPG loses quality, period, while saving as pspimage or tiff doesn't. This was an answer to your "But if you're starting with a jpeg, for whatever reason, it would be nice to not lose as much as possible".

So in PSP, once you decide to save the .pspimage as JPG, you can set compression to 1 and don't do the subsampling, to maintain optimal quality. If, as the article states, subsampling is good for the use you're going to put it too, or if you just want to, by all means subsample, but know that you are losing information, so keep the original if possible. The loss is in the compression, same as it's always been, PSP's 1% is almost lossless but loss is cumulative over many saves, and subsampling just makes it worse. That's all.

Are you saying that you get less compression when Subsampling is set to 1x1 1x1 1x1 as opposed to 4x4 2x2 2x2? Because I'm seeing the opposite, hence my comment on being backwards from what it's supposed to be. Do you understand what I'm saying? It's not that what you're presenting isn't what's supposed to happen, but PSP is being opposite of what it's supposed to do.

[Forriner]

Sorry, I'm having trouble being clear today When I started about the subsampling I wasn't concerned about compression but about image quality. The original poster wanted highest possible quality and was told to set compression to 1 for maximum quality, but s/he was then told to subsample. As s/he was concerned about quality, I decided to inform about what subsampling does, which IMHO reduces quality because it averages colours. The choice is the user's, with an explanation in the link.
I'm not an image file expert, so I don't know what the effect of subsampling is on file size. Seeing as you can open a jpg in any program, the compression parameters must be in the file, the subsampling parameters maybe too. Or just averaging colours can create more info than the original, I just don't know, sorry.

The other part, save as pspimage or tiff instead of jpg if you can't do all the edits in one sitting and want to continue tomorrow, for example. Saving as those formats is lossless and working on those tomorrow morning avoids the 1% compression at least one time, until you're ready. This is just to maximize the ultimate quality of the final JPG through multiple saves before editing is finished.

I hope this clarified something, though Sunday the 24th is never my day.

happy shooting.

[Jan Shim]

df and Forriner,

I came across a discussion in this forum where someone suggested that maybe COREL screwed up Chroma Subsampling in PSP X6. Compression 1 with Chroma Subsampling set to 1x1 1x1 1x1 is supposed to yield the highest JPEG quality like previous PSP versions. However he discovered that in the case of X6 it does the complete opposite with 4x4 2x2 2x2 yielding the largest file size while 1x1 1x1 1x1 reduces image size significantly. Can I say reduction in file size (without being technical) equals quality loss?

It would be interesting to see if this behaviour is carried over to PSP X7.


Jan