Two weeks ago, in the post Lightroom 3.2 RC I wrote “they haven’t tackled any of those things I find most annoying – like ‘Export’ giving lousy soft and over-large file size small jpegs.”
I met bahi a couple of months back at one of the monthly London meetings of Photo-Forum – well worth attending if you are in London on the 2nd Thursday of the month – it takes place in Jacobs Pro Lounge in the basement of their New Oxford St shop, from 6-8pm and afterwards we enjoy free food at a nearby pub paid for by a raffle during the meeting – the prizes are usually prints donated by the photographers who present work that evening.
Bahi is from Shoot Raw, an organisation that delivers support and training for photographers in digital photography, including Lightroom training and in a comment to that earlier piece gives a useful link to Jeffrey Friedl’s analysis of file size vs quality for Lightroom JPEG export, and also asks me to go into more detail about the problem I mention.
When I read his comment I’d just been going through some of the pictures I took at Notting Hill yesterday and so decided to use the picture I’d just developed in Lightroom 3.2RC(on PC) as a fairly random example.
This is the full image – scaled down from the original D700 raw file taken at ISO 800 from 42656×2832 px to 600×399 px (and displayed here at 450x299px.)
Not one of my greatest images!
First I tried using File Export to produce this file – here are the settings I used :
At 70% quality the file size for the 600-399px was 312kB.
At 30% quality the file size for the 600-399px was 254kB.
I tried to get File Export to produce a file using a file size limit of 150 and200Kb, but both times it reported it was unable to do so.
I selected the file and went to the web module in Lightroom, outputting a web site containing this file. I used the same 70% quality setting as before. The file produced was 118kB.
Here are some 300% details from the three Lightroom jpegs – as you can see, despite the huge file size differences the two 70% files are very similar.
300% view of detail: File Export, Quality 30, 254 kB file
300% view of detail: File Export, Quality 70, 312 kB file
300% view of detail: Web Output, Quality 70, 118 kB file
[These files were created by viewing the files at 300% in ACDSee Pro, capturing with PrintScreen and pasting into Photoshop and cropping.]
70% is the setting I currently use for My London Diary, generally giving file sizes that are reasonable for broadband users – even on a page with a dozen pictures. Back in the old days of slow dial-up I used greater compression (and some special software that could actually use different compression levels on different areas of the same image) to trim file sizes to the bone, but this is no longer needed. Before switching to Lightroom I had moved on to batch processing from full-size images with ACDSee Pro, which typically seemed to produce comparable quality with file sizes a little smaller than Lightroom. It isn’t possible to simply select an equivalent quality setting, but files slightly under 100kB from ACDSee seemed comparable to the Lightroom 70% file.
I’ve not investigated this Lightroom problem in great detail, butI get the impression it gives the largest files from those images I’ve worked on most with the tools such as the adjustment brush.
Friedl in his piece at the link given above points out that despite having quality settings labelled 0-100 actually only implements 13 quality levels – just like Photoshop. I think you also get those same 13 quality levels if you use the checkbox to limit file size, but the file sizes can be different. Using quality 92 (or rather 85-92) on the above image gave a file size of 3748 kB, while limiting the file size to 5000 kB produced a visually identical file of 3550 kB.
Long, long ago when I produced jpegs using a DOS command line program I there were at least two parameters which had to be specified. One was a 1-100 setting for the quality of the match required between cells which would be replaced by the same cell, and the second was some kind of smoothing function. I don’t know that we need that kind of control, but perhaps we could be offered a little more than we have at present.