JPG File Size

[dmward]

I have been shooting raw + JPG with a Fuji XT-1.
The JPG generated by the camera, using one image as an example, is 5.8MB.
When I export a JPG from Lightroom V5.6 at full size, i.e. same pixel dimensions, the file size is nearly 3 times as large.

The JPG setting in LR export are for 100% quality and no resizing.

I think I understand about JPG lossy compression and how its algorithm optimizes file size by reducing pixel by pixel information for areas that have same color and luminance. But that doesn't account for the different in file size.

The only explanation that comes to mind is that the camera is applying a "quality" reduction compression on top. Similar to the ability in Lightroom export module via the slider.

If so, is there a way to determine how much is being applied?

[Slobodan Blagojevic]

Probably depends on camera. While most, if not all cameras offer at least two jpeg qualities, e.g., fine and standard, some cameras (in my case Canon 60d) offers only one (fine) when RAW+jpeg is selected.   

[CatOne]

Well we'd have to guess. But JPEG quality 10 versus 12 could easily account for that much difference.

Lightroom uses a different scale than the JPEG "standard" scale (which is 1-12) but you could guess at it. Try 80 or 90 and see what you get.

Note JPEG's lossy compression means you can never get better than you started with. So if you bring in a 5.7 MB file and export a 15 MB file you're wasting space. Experiment with 80-90 and see what the file size on output is. Generally exporting at 80-90 will be invisible to the eye unless you save over and over 10 times.

[Alan Klein]

I just tried re-saving an opened file in LR5.  The original jpeg was 6.8mb.  When I saved it at  92%, the resultant file is 6.2mb, slightly smaller.  At 93% through 100%, the resultant files are 8.8mb. I don't know why it's bigger at 93% than the original.  I doubt if the resultant larger files have any more data so I would not go above 92%.  So my file increased by around a third but not the three times the size you got.  Which LR version are you using?

[Slobodan Blagojevic]

What I suspect the OP is talking about, are two different jpeg files, not the same one. The first one is the one coming from the RAW+jpeg combination. The second jpeg is the one he himself creates from the RAW file in the Lightroom. I might be wrong in my assumption, of course.

[Dan Glynhampton]

Jeffrey Friedl has an interesting write up about Lightroom's JPEG quality settings in his blog:

http://regex.info/blog/lightroom-goodies/jpeg-quality

[Alan Klein]

 

I just tried re-saving an opened file in LR5.  The original jpeg was 6.8mb.  When I saved it at  92%, the resultant file is 6.2mb, slightly smaller.  At 93% through 100%, the resultant files are 8.8mb. I don't know why it's bigger at 93% than the original.  I doubt if the resultant larger files have any more data so I would not go above 92%.  So my file increased by around a third but not the three times the size you got.  Which LR version are you using?

I get similar larger sizes with Irfanview's editing program above 95% quality.  I suppose this is something most editing programs do.  The question is why?

[Alan Klein]

This reminds me of a question whose answer escapes me at this time. 

Is it better to save a jpeg file with all the pixels but less quality or a jpeg file with less pixels and more quality assuming the final file size of both are equal? 

When I transmit a file to be posted, I always reduce it to the pixel size first then save it at 100% quality before uploading it.  What to do folks do?

[Slobodan Blagojevic]

I remember seeing some tests that quality difference above 75% is unperceptable, so I keep it at that, especially for web. The only time I go for 100% is when I send it for printing large.

[Robert55]

Strange. I don't have camera JPG's from the Fuji but I just did an export at original size / 100% and the resulting file is 5.98 MB

[dmward]

As noted. Two different files.
One from camera.
Other generated by Lightroom.

[Steve House]

I remember seeing some tests that quality difference above 75% is unperceptable, so I keep it at that, especially for web. The only time I go for 100% is when I send it for printing large.

75% may well be imperceptible ... once.  But each cycle of open, edit, close, re-open ... etc tosses away that 25% of each cycle's starting file, the effect is cumulative and quickly becomes a visible quality loss.  I suggest conversion to jpg ONLY after all editing is complete and saving the final distribution version, if at all.

[Robert55]

As noted. Two different files.
One from camera.
Other generated by Lightroom.

I guess it is something in your Lr export settings then

[Simon Garrett]

Lightroom uses a different scale than the JPEG "standard" scale (which is 1-12) but you could guess at it. Try 80 or 90 and see what you get.

Trouble is everyone uses different scales.  Photoshop uses 0-12, Lightroom uses 0-100, some use 0-10...  The jpeg standard doesn't specify a scale like that.  Further: for a given quality level, one jpeg encoding software may produce a file size of 3Mbit (for example) but another might produce a file of 5Mbit.  The file size for a given quality is partly down to the ingenuity of that software writer, and how much processing they choose to use.  More modern encoders tend to produce better quality files for a given file size (as they generally assume more powerful processors). 

All you can say is that, for any particular encoder, the lower down the "quality" scale the smaller ther file size and the more quality loss. 

[Alan Klein]

Quality selection, I believe, also should depend on the original picture.  If it's complex, higher compression  selection (lower quality) won't matter.  If it's less complex, such as huge areas of blue skies, higher compression could lead to banding or at least less tonal steps especially noticeable in larger size prints.  I would side  with less compression and more quality unless you're sending an email or posting on the internet.