Lightroom JPG file size?

Hi, I shoot RAW with a Canon 5D III and just wanted to ask you guys about the expected size of full quality JPG exports coming out of lightroom.

Reason being is that when I want to export a max quality JPG, I end up with a file between 20-30MB. Thats the size of the original RAW!!!

What is going on here?

I set lightroom to NOT resize and put the quality at 100. I have never changed the PPI away from its default 240PPI.

Advice please?

Quality 100 is unnecessary, placebo territory, almost uncompressed. Q35 works fine for web use, Q70 is great for prints. I bet if you did 12" prints at Q10 - Q100 in steps of 10 you'd have trouble telling Q30 and above apart. I give customers Q9 or Q10 images, which is probably around 70%.

So basically Q100 is essentially JPG with no compression?

Want to stay away from that pointless setting then....

Yep. Read this.

The link Tim posted is practically required reading for Lightroom users.

Also, prior to exporting your jpeg, think long and hard about how that exported photo will be used. If it's just for web use, you may as well scale it down to a reasonable size, because the browser is going to scale it down anyway. I usually scale down to 1024px on the long edge, it's a nice size for most monitors and is (er, was) the standard size for embedded images here on POTN.

In my opinion, there's rarely a good reason to export a full-sized jpeg. Only if I need to send it to someone who's going to crop or chop it up for further refining, such as incorporating a portion of one of my images into a graphic design such as a flyer or poster.

My background in computer science does make me inclined to encourage people to read and understand how the jpg compression algorithm works, and try programming your own. However, that is the point where most photographers's eyes are going to glaze over and I get weird looks. If you are actually geeky enough to like poking around with math and such, then heading over to https://www.youtube.co​m/user/Computerphile and looking up their videos on jpg and images may be an entertaining way to spend some time.

A more realistic approach is to just acknowledge that different levels of compression will affect different photos in different ways, and that there is really no one size fits all setting that will be used in all cases, even if the Lightroom default level is going to cover the vast majority of them.

My advice is: Process and inspect. If you're not familiar with what is going on, then export at a few different settings and just look at what the results are. Pick out which option actually meets your needs, and then roll with that one. Experiment and explore.

The jpg compression algorithm was designed with the idea that things tend to change fairly rapidly within a photo, but not with a hard solid line of contrast. This is why highly textured elements, such as the Reed Window Shades in the link Tim posted above do so well, but then images such as text tend to break down and look weird, especially if you re-encode through the jpg method multiple times.

It does not however deal all that well with very fine and smooth gradients over large areas. The Sunset and Bird image on that link shows very noticeable banding effects on my macbook at the 39-46 slider, which fades to a faint 'sort of splotchiness' for the 70-84 options, and a faint but visible shift when switching between the last two.


As for which to use? I agree with nathancarter's comment on it depending on what you are going to use it for, but disagree with downsampling too far on export before uploading to the web in many cases. If you have a larger selection of data to work with initially, then you have more graceful options on the processing side to do more with it. For example, going with 2048 long side uploads to a website will allow the auto processing to handle things in a more graceful manner when it resamples the image to generate various sized images server side, especially when dealing with arbitrary level conversions that would result in 'splitting a pixel'.

I also encourage anyone dealing with digital imaging to read a short paper "A pixel is not a little square". Very interesting read for anyone who geeks in that direction, but not a paper for everyone.

Luckless wrote in post #17762411
My background in computer science does make me inclined to encourage people to read and understand how the jpg compression algorithm works, and try programming your own. However, that is the point where most photographers's eyes are going to glaze over and I get weird looks. If you are actually geeky enough to like poking around with math and such, then heading over to https://www.youtube.co​m/user/Computerphile and looking up their videos on jpg and images may be an entertaining way to spend some time.

A more realistic approach is to just acknowledge that different levels of compression will affect different photos in different ways, and that there is really no one size fits all setting that will be used in all cases, even if the Lightroom default level is going to cover the vast majority of them.

My advice is: Process and inspect. If you're not familiar with what is going on, then export at a few different settings and just look at what the results are. Pick out which option actually meets your needs, and then roll with that one. Experiment and explore.

The jpg compression algorithm was designed with the idea that things tend to change fairly rapidly within a photo, but not with a hard solid line of contrast. This is why highly textured elements, such as the Reed Window Shades in the link Tim posted above do so well, but then images such as text tend to break down and look weird, especially if you re-encode through the jpg method multiple times.

It does not however deal all that well with very fine and smooth gradients over large areas. The Sunset and Bird image on that link shows very noticeable banding effects on my macbook at the 39-46 slider, which fades to a faint 'sort of splotchiness' for the 70-84 options, and a faint but visible shift when switching between the last two.


As for which to use? I agree with nathancarter's comment on it depending on what you are going to use it for, but disagree with downsampling too far on export before uploading to the web in many cases. If you have a larger selection of data to work with initially, then you have more graceful options on the processing side to do more with it. For example, going with 2048 long side uploads to a website will allow the auto processing to handle things in a more graceful manner when it resamples the image to generate various sized images server side, especially when dealing with arbitrary level conversions that would result in 'splitting a pixel'.

I also encourage anyone dealing with digital imaging to read a short paper "A pixel is not a little square". Very interesting read for anyone who geeks in that direction, but not a paper for everyone.

Sounds interesting, but you're right, most photographers aren't going to want to look into this. Luckily I'm an IT infrastructure architect so have a pretty good grasp on storage technologies, not so much compression algorithms though!

For my flickr exports and such I usually export a 50% resolution JPG with the quality set to 70%. Watermarked of course.

tomstephens89 wrote in post #17762217
Hi, I shoot RAW with a Canon 5D III and just wanted to ask you guys about the expected size of full quality JPG exports coming out of lightroom.

Reason being is that when I want to export a max quality JPG, I end up with a file between 20-30MB. Thats the size of the original RAW!!!

What is going on here?

I set lightroom to NOT resize and put the quality at 100. I have never changed the PPI away from its default 240PPI.

Advice please?

With quality at 100 (minimum compression) the compression ratio can be as low as 1:2 or as high as 1:5, depending on content, but usually is in the range 3 to 4. A 5D3 8 bit RGB image is around 66 MB (the Raw is compressed 14 bit single channel) so a 22 MB jpg is 1:3.

Luckless wrote in post #17762411
but disagree with downsampling too far on export before uploading to the web in many cases. If you have a larger selection of data to work with initially, then you have more graceful options on the processing side to do more with it. For example, going with 2048 long side uploads to a website will allow the auto processing to handle things in a more graceful manner when it resamples the image to generate various sized images server side, especially when dealing with arbitrary level conversions that would result in 'splitting a pixel'.

This is a good point, and maybe one that I need to research more.

Specific example: I had a minor issue with an image that I posted on Flickr and shared here. I let Lightroom's export/publish dialog resize the whole batch based on the short edge; but when I chose to link an even smaller size to embed in the post, Flickr's slightly-scaled-down one looked oversharpened in the POTN thread.

Perhaps a larger one on Flickr wouldn't have had the same issue.

https://photography-on-the.net …showthread.php?​p=17718175

Yes, sadly image sharing still isn't as smooth and seamless as we could hope at this stage, and image data is kind of a science all in itself. Ideally you would keep control over everything, and be able to know what is going on at each stage of the process, but sadly putting stuff 'out in the wild' often involves giving up a lot of control to automated and sometimes heavy handed processes. Which in turn means falling back to 'trial and error' fairly frequently.

So export, review, upload, review, post, and review. If the reviews fail, then fall back and try to change things a bit for your next export and see if you can't get any improvements at your target display.

Going 'over target size' usually works by nature of giving an automate system more info to work with, but it is far from a guarantee of avoiding all problems.