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Correct setting to export to JPEG without huge file size

kenwood

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I export to JPEGs with 100% quality, 3500 pixel on the long side and 300 dpi, and I notice that file size range from 15-20mb each. I found that to be huge, considering my 22MP raw file is only 30mb, and 3500 pixel works out to be 15MP. I also don't see the same quality to match what I see inside lightroom, when zoom in 100%. I m curious if I m missing a setting somewhere? I am hoping to keep jpeg below 15mb each with the same quality seen inside lightroom.
 

BarrySchwartz

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It depends on your intended use of the exported file, but the advice I've been given by people who beta and alpha test for Adobe is that for printing, there is no gain in quality at 100%, as you've seen, and that 80% is just fine - and will make a real difference in file-size. I've never had a client complain about the quality of my delivered files for printing. As for the web, 72ppi, sRGB, and 50% quality works fine with images at 2000 pixels on the long side, and I've gotten decent results at lower levels - it really depends on the final pixel dimensions, mostly.
 
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Of course, you can experiment as JF did in the above (quite excellent) review, just export the same photo repeatedly and the view at various sizes.

One thing to bear in mind is that JPG quality loss tends to accumulate as you edit, so try never to use JPG for images to be further edited, but somewhat less obvious is that if used on web sites and similar, those sites will almost always resize the image themselves, with some further loss (it is a sort of edit), so starting a bit better than you might be happy with will give a bit of headroom for photo display sites to mess up.

However, much as Barry mentioned, by and large most of us use a far higher quality setting than is really merited in most cases.
 
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there is no gain in quality at 100%, as you've seen, and that 80% i
The scale in LR compression is 1-100. It is not a percentage. Photoshop uses a scale 1-12. Lightroom and Photoshop use the same compression algorithm. So in reality, it does not matter whether you use 93 or 100 you still get minimum compression equal to a PS value of 12. A setting of 80 falls into the 3rd level of compression between 75 and 83.
 

kenwood

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When I reduce the size of the image from 3500 on the long size, to 32xx (all other settings the same), I found that the file size dropped significantly, from 15-20mb to 5-10mb. Also the image actually looks better when zoom in 100%. I tried this with a bunch of images, shot with a canon 5d3 at iso3200, indoor, with flash. I can't explain why but at least this is the workaround for now.
 

yngvar

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The scale in LR compression is 1-100. It is not a percentage. Photoshop uses a scale 1-12. Lightroom and Photoshop use the same compression algorithm. So in reality, it does not matter whether you use 93 or 100 you still get minimum compression equal to a PS value of 12. A setting of 80 falls into the 3rd level of compression between 75 and 83.
What do you mean by "it does not matter whether you use 93 or 100"?

I just exported the same file (CR2 raw file cropped to 6689x4480 pixels in Lightroom) with five different compression settings:
- Resize Long Edge to 3000 pixels quality 100 => file size 3,48 MB
- Resize Long Edge to 3000 pixels quality 95 => file size 1,63 MB
- Resize Long Edge to 3000 pixels quality 90 => file size 1,08 MB
- Resize Long Edge to 3000 pixels quality 85 => file size 866 KB
- Resize Long Edge to 3000 pixels quality 80 => file size 718 MB

To me it seems the compression increases at least every time i drop five in quality, and I see subtle degradation every 5% too.
 
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I have not retested this for a few years but the JPEG compression in Lightroom is in 12 equal steps just like Photoshop JPEG compression. In stead of a simple 0-12 the Lightroom Scale is 0-100 and every ~8 units on the LR scale corresponds to 1 unit on the Photoshop compression scale. So a PS setting of 12 will yield the same compression as a LR setting of 100 or 95. Having said this, I saved a RAW file to a JPEG using PS setting of 12 and then again in LR using a setting of 100 and 95. The 2 JPEGs from LR are the same size and the PS created JPEG was within a few bytes of being the size of the LR files.
 
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I just did an experiment and it's definitely quantized.

Export at 93, 95, 98, 100 = 6197 KB
Export at 85, 90 and 92 = 3610 KB
Export at 77, 80, 83, 84 = 2348 KB
Export at 75, 76 = 1592 KB

So it's definitely quantized. What's odd is I could not reproduce what @yngvar saw that 80 and 85 were different, for me they were the same (size), the change occured right between 84 and 85. I don't know if there are differences by resolution or LR version or.... ?

So if you look at the shifts it is 77, 85, 93 == about each 8, and 8 * 12 = 96 or about 100 to map, correlating with Cletus' memory. I suspect one could track this backwards now to 67, etc. +/-1.
 

yngvar

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What's odd is I could not reproduce what @yngvar saw that 80 and 85 were different, for me they were the same (size), the change occured right between 84 and 85. I don't know if there are differences by resolution or LR version or.... ?
I did one more experiment and I believe I might have found a solution to the coundrum:
  • When I export without resizing the image, it seems to shrink in size only in certain steps, 100%, 95% are same size, 90% and 85%, too, probably in 12 steps.
  • When I export and resize (shrink) the image, the size shrinks every time I lower the quality percentage, 100%, 95%, 90% and 85% are all i different sizes, gradually shrinking!
Do you think that might be the answer, @Ferguson and @clee01l ?
 
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Do you think that might be the answer, @Ferguson and @clee01l ?
Yes, this is probably the explanation. And it depends on the order of the operations. (1. Resize then compress Jpeg OR 2. Compress Jpeg , then resize)
 
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Interesting info. when I started using LR I set to 100% but was aghast at the file size and after a bit of reading around (10 years ago) I changed the setting to 70% which have used ever since.
 
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Always drease the image size first as low as possible ("how much" depends of the output and the usage of the image, of course), then apply a compression.
Decreasing the image size is much less degrading the image quality (as long as the new size fit the destination of the image) than the compression.
 
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Always drease the image size first as low as possible ("how much" depends of the output and the usage of the image, of course), then apply a compression.
Decreasing the image size is much less degrading the image quality (as long as the new size fit the destination of the image) than the compression.
Don't these occur at the same time when exporting?

--Ken
 
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Don't these occur at the same time when exporting?
When exporting, LR first resizes the image (if requested) then applies compression. It's whta I saw in my testing.
 

sty2586

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Just tested with LR 8.1
100% 2868 KB
93% 2868 KB
85% 2041 KB
.....
8% 254 KB
7% 232 KB
1% 232 KB
0% 232 KB

Franz
 
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This might well have been what I read all those years ago which resulted in my adopting a setting of 70. However, does it still apply to the latest LR versions ?
It is applicable to any JPEG file as all JPEGs have Lossy compression. AFAIK Adobe has not changed the JPEG compression algorithm which is the same and used for both LR and PS.
 
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Just tested with LR 8.1
100% 2868 KB
93% 2868 KB
85% 2041 KB
.....
8% 254 KB
7% 232 KB
1% 232 KB
0% 232 KB

Franz
The scale used by LR for JPEG compression is NOT a percentage. You only confuse others as well as your self by adding the "%" to the scale value. It is just a linear scale which Adobe reinterprets to fit their 12 step JPEG compression algorithm.
 
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On LRCC on my Iphone when I share a photo via say whatsapp, the only options that pop up are for Image Size; "Small - 2048px" or"Maximum available". Any idea what file format is sent and if Jpeg what compression is applied ?
 
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It's certainly Jpeg that is sent, but there seems to be a difference in terms of the Quality setting between LRCC desktop (around 90) and LRCC iOS (around 75). The latter is when using the "share/email" option, I assume the same quality setting would apply if sharing to a social media account.
 

sty2586

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The scale used by LR for JPEG compression is NOT a percentage. You only confuse others as well as your self by adding the "%" to the scale value. It is just a linear scale which Adobe reinterprets to fit their 12 step JPEG compression algorithm.
Sorry, if I was confusing but I assumes that "Quality" is somehow correlating to "File-size".

But for me any scale which goes from 0/1 to 100 is Percent (per centum = out of hundred).
I wanted only to show that this behaviour described by Jeffry Friedl is also in LR 8.
When you compare the file size with the "%" you can see that there are only steps in a width of 8 or 7 , not linear (50 gives approx. 25% of the file size.
In Photoshop (Vers. 20) you in Save as settings from 0 to 12 (13 steps), a drop down list with 4 possibilities and a slider which shows an analogue smooth behaviour.
And the funniest thing: If you "export" in Photoshop as JPG you can choose the Quality in 10 %-steps (really with the sign "%") and can also write in what you want.

So part of the confusing goes with Adobe

Season greetings
Franz
 
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But for me any scale which goes from 0/1 to 100 is Percent (per centum = out of hundred).
Back in the days when the federal government set the speed limit to 55mph, Auto Manufacturers started creating speedometers that no longer ranged 0-120 or 0-150 but 0-100mph The engines did not change (though some got smaller to improve gas mileage) 100% of the speed limit was still 55mph and you could still break the law and achieve speed above 100mph.
Centigrade temperature scales (centi = 100) is denominated a ˚C not %C.
Frankly I do not know why Adobe set the JPEG compression quality scale form 0-100 when they did not increase the granularity of the compression. A setting of 100% quality implies no compression, yet JPEGs are always lossy compressed to some degree even a the PS setting of 12 or the LR setting of 100.
 
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