JPG quality and file sizes

26 October 2009 00:00 | Comments: 0 | Categories:

When you Export from Lightroom and select the JPG quality it seems to use a different scale from other software.

Even setting it to 50 makes a very big file, which if I open and resave in Irfan reduces from 170 to 110 (quality 70%) (and 356 to 190). Not sure how safe it is to reduce the LR quality factor - or maybe it just generates big files.

I want a small file size because in my gallery, click on a single image and you get the large image on the screen. Smaller file sizes download faster.

No obvious answers - but see this for loads to flickr, which seems to resize anyway.

I'm going to do some tests with export a single image.

Export to 1024 pixels longest edge.

Chose an image which generated a file size which was very big because it has a lot of detail - leaves etc.  Even at 5 no obvious jpg artifacts.

LR JPG quality File size (Kbytes) Open in Irfan and save-for-web, quality 70, file size

100 1266 192

90 952 192

80 726 192

70 559 192

60 362 191

50 356 191

40 308 188

30 244171

20 196 138

10 167 117

05 158 111

Now another image

5 53 bad artifacts

10 55 bad artifacts

20 60 less artifacts

30 73 almost no artifacts

40 88 (LR image clean, Irfan makes artifacts)

50 101 56 (Irfan artifacts only visible when enlarging)

100 428 53 (Irfan artifacts only visible when enlarging)

I see the Lightroom Preset Export Option "Export for Email"uses quality of 50. Looking at the data above, I suspect you'd be safe with 40, but still will end up with bloated file sizes.

Alternatively, and a bit of an extra step, export at a highish quality (say 60), and then use Irfan to blast through and resize them (say 70).

 



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