Exporting as a JPG - what does the Quality slider do??

Tom Pinchenzo

Tom Pinchenzo

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It reduces the file size but what aspect of 'quality' does it reduce? Resolution? Its default is 95 - is that overkill? I've exported at a few different levels and can't really see the difference.
 
It defines the amount of image compression. If you’re exporting for web use, you can usually get away with around 80%.

The lower the quality, the higher the compression.
 
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You will notice very little difference down to 85% after that smaller pixel count images tend to show compression artifacts and softening.
 
Ben's link is still good, although I find some colours and parts of an image - blue skies especially - show banding very quickly with jpg compression. I've seen really bad banding in some of my images exported at 75, and where appearance matters I won't use less than 90. If I need to keep file sizes down & quality is less important then I'll try 75 initially, but nothing less than that unless the image quality doesn't matter at all.
 
why would you not use 100%?

If as i assume 95% will produce a file 5% smaller than if exported at 95% why would you want to reduce potential quality and not export at the 100%?
 
AgentOrange76 said:
why would you not use 100%?

If as i assume 95% will produce a file 5% smaller than if exported at 95% why would you want to reduce potential quality and not export at the 100%?
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The point of a JPG is to compress the image for use in various different ways. A 16mp JPG at 100% quality rocks in at around 12mb whereas at 80% it is more like 3mb, which gives you much more storage spaces for negligible drop in quality. Yes storage is cheap but try living somewhere with slow internet...
 
AgentOrange76 said:
why would you not use 100%?

If as i assume 95% will produce a file 5% smaller than if exported at 95% why would you want to reduce potential quality and not export at the 100%?
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If you are talking about Lightroom, there are two things to consider. First, the scale isn't linear in terms of image size - a file saved at 80% may be less than half the size of a file saved at 100%. Second, there probably aren't really 100 meaningfully different levels of compression available - I've seen it claimed that LR is really just using the 0-12 scale of Photoshop, which may mean that 95% and 100% will actually give the same result, corresponding to 12 on the Photoshop scale (I don't have Lightroom here, so I can't verify this - would anyone like to try it?).
 
Retune said:
I've seen it claimed that LR is really just using the 0-12 scale of Photoshop, which may mean that 95% and 100% will actually give the same result, corresponding to 12 on the Photoshop scale (I don't have Lightroom here, so I can't verify this - would anyone like to try it?).
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I don't have photoshop so can't help.
 
Retune said:
You can test this without PS, just by trying some different closely-spaced percentages in LR to see if they make a difference to file size. Here's a claimed mapping between LR and PS:

https://photographylife.com/jpeg-compression-levels-in-photoshop-and-lightroom

If this is correct, anything from 93-100% in LR should give you the same output.
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I use PSE rather than LR or PSCC and can't for the life of me think of any reason why dropping the quality sometimes makes the file size BIGGER! Only use it to resize for dropping straight into a post on here but sometimes find that a level 8 file is smaller than a level 7.
 
I think the best way to reduce the file size is reduce the definition according to the intended use.
 
AgentOrange76 said:
why would you not use 100%?
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Nawty said:
The point of a JPG is to compress the image for use in various different ways. A 16mp JPG at 100% quality rocks in at around 12mb whereas at 80% it is more like 3mb, which gives you much more storage spaces for negligible drop in quality. Yes storage is cheap but try living somewhere with slow internet...
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Another reason..

I supply newspapers who prefer a file to be 1mb to 1.5mb and 2500 pixels longest edge so i save all my work at 80%

the slider is there for a reason.. you just have to open your mind :)
 
ancient_mariner said:
It might help the op if you unpack that comment.
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I meant the best way to reduce significantly the file size is reduce the resolution. E.g.
800 pixels for a full page web
1920 px for TV screen
2400 px pour les impressions 8 "

In this case 90-95% compression ratio will be fine.
 
The one real issue with saving at below 90% is if you edit multiple times. This can start to build up JPEG artifacts, storing at 95-98% I've never had these noticable despite sometimes re-editing a file many times.
 
Petrochemist said:
The one real issue with saving at below 90% is if you edit multiple times. This can start to build up JPEG artifacts, storing at 95-98% I've never had these noticable despite sometimes re-editing a file many times.
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It's the open>save>open>save cycle that causes degradation fairly quickly, multiple edits without repeated saving and reopening shouldn't. I'm not a huge one for a lot of editing but when I do, I do it all in one sitting (if possible) and if that's not possible, I tend to save as a .psd or similar rather than risk the degradation. I always shoot in JPEG at the largest size and highest quality available and do as little PP as possible.
 
I once did a test. Open and saved the same file I think 10 times, visually I couldn't see much difference, not enough to be a problem at normal sizes. Obviously it's not a great idea, but I doubt in realy life a file would get that many saves/edits.
 
Petrochemist said:
The one real issue with saving at below 90% is if you edit multiple times. This can start to build up JPEG artifacts, storing at 95-98% I've never had these noticable despite sometimes re-editing a file many times.
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If I was editing JPEGs I would save at lossless/100% until I wanted to publish and then reduce the size/quality for the published version still keeping the original lossless version for possible future edits.
 
Nod said:
It's the open>save>open>save cycle that causes degradation fairly quickly, multiple edits without repeated saving and reopening shouldn't. I'm not a huge one for a lot of editing but when I do, I do it all in one sitting (if possible) and if that's not possible, I tend to save as a .psd or similar rather than risk the degradation. I always shoot in JPEG at the largest size and highest quality available and do as little PP as possible.
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Yes it's that cycle that's the killer, especially when the quality slider get moved down...
I too always shoot best JPEG, & do minimal processing. But I often find I've missed dust marks etc and have to re-edit.


sirch said:
If I was editing JPEGs I would save at lossless/100% until I wanted to publish and then reduce the size/quality for the published version still keeping the original lossless version for possible future edits.
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I typically save at 98% which has very little effect on quality, and only compress further after resizing for posting online.
Sometimes especially while at work the only version I have available is one I've uploaded to flickr or a forum (the original being archived at home). A few forums don't like BB code (ideal for direct linking from Flickr etc) and have tight limits on file uploads - I think one is 800pixels max.
 
Petrochemist said:
I too always shoot best JPEG, & do minimal processing. But I often find I've missed dust marks etc and have to re-edit.
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Glad I'm not the only one!

If I need to redo an edit, I usually go back to the original file and start again from scratch - if it's been a particularly long edit (very unusual - I have usually lost patience and binned the shot!), I'll generally have saved as a .psd so can go back to a decent restart point.
 
Tom Pinchenzo said:
It reduces the file size but what aspect of 'quality' does it reduce? Resolution? Its default is 95 - is that overkill? I've exported at a few different levels and can't really see the difference.
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No, it is not an overkill.

Thankfully you're not using 1.44MB floppy diskettes to save your JPEG images, because with modern technology, we can have anywhere between 32GB USB memory sticks to 8TB external HDDs at prices that would be considered to be up to something like between up to £500-£700. Back in the 1970s, there were adverts showing a 10MB hard drive for something like $3999. Today you can get far more storage space for lower price, and with a lot of storage, you can save all your JPEG files at 100% setting. (And that's not even counting the online storage you could use, thus more spaces for more big files!)

Back in the early 1990s with the World Wide Web becoming a household item, to cut down on file size so you could upload to a server or download from the Internet, it would be consider an overkill to go for the very lowest quality. A quality setting of 5% would make the image look almost like it came out of Minecraft. It was acceptable to try to limit it to something like a trade-off between file size and picture quality by lowering it as much as you dare, like down to 80% or thereabouts.

The quality is about how the image look. Higher setting makes the image look like a photograph print, but lower settings makes the image look like a 1990s photocopied image.

Like some of those examples: https://www.google.co.uk/search?hl=.....1..gws-wiz-img.....0..0j0i10i24.DBSr4jWMzoo
 
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