Image resolution and quality

Backlight 4 & 5 Support
#1

I need help understanding how to get the appropriate image resolution and quality for photos and thumbnails. Currently I export my photos from photoshop with a resolution of roughly 2400 on the long side and a jpg quality level of 60% to a folder on my drive. I then publish the photos using backlight 5 to my albums with the image rendition settings in the album template set to 512x512 at 69% for the thumbnails and 2048x2048 at 69% for the photos. Am I doubling up on the quality settings so my images are being double reduced in quality? Also, are my size settings reasonable or too large?

Thanks in advance.

#2

I’d just export the images to the size required by your album template.and quality level of around 70%
With today’s hi-resolution monitors, the image size seems reasonable.

#3

I think you’re probably hurting yourself by exporting from your library at 60%.

I would export at 85-100%, then rely on Backlight to compress your images to final quality.

I also maintain that it is best to export images at either 1x or 2x the desired display size. This is especially true for the new Kookaburra, which actually uses the 2x renditions.

#4

Thank you for the response and suggestions. I am using the new Kookaburra. I would still like to understand if I am double reducing quality if I export from photoshop using less than 100% quality and then publish using backlight with the image rendition setting at less than 100% quality? Thanks.

#5

Yes, you’re doubt compressing.

Honestly, there’s not a huge different in the range of 85% - 100% on the initial export. So not really a problem when the rendition gets compressed again from Backlight generating renditions.

But at 60%, that’s a huge loss. We’re then compressing an image that’s already been significantly compressed.

For comparison, my own flow is this:

  • export from Capture One Pro: 2048px @ 95%
  • run images through JPEGmini for optimization
  • upload images to Backlight, for display at 1024px

I haven’t put a great deal of thought into that 95% value, but the rest of it is very intentional, and I am generally pleased with my file sizes and my image fidelity.

Also, if you have any feedback on Kookaburra, I’d love to hear it. Probably in a separate thread. Check out the Kookaburra Roadmap thread, if you haven’t already seen it.

#6

Thanks Matt. May I ask what your image rendition settings are in your album template?

#7

One consideration is that Backlight does not resize images for specific renditions if the dimensions of the uploaded image matches that required for the rendition.

It in doubt, I suggest trying different settings and seeing for yourself which settings work best for visual quality and file size.

#8

For Kookaburra, the defaults are set for what I’d likely use. The only thing I might adjust is the thumbnail size, increasing it if I think my grid might need it.

But I plan to keep the default 1024px for photos, while uploading 2048px images.

And in this case, the srcset attribute will use both the 1024 and 2048 size image, depending on the screen resolution of the viewer.

#9

Do you convert your jpg’s to be progressive at some point in your process or do you feel this is not necessary.

#10

No, never. I think the larger Web has pretty well left progressive JPGs in the past.

#11

I am still muddling over my workflow on this. In the Kookaburra image renditions there is a quality setting for both thumbnails and photos. The quality setting allows values between 47 and 84. I am assuming that this setting reflects the jpeg compression applied when publishing.

Currently I export my images from Photoshop setting the jpg resolution (2048 on the long side) and the jpg compression (75%). I then run the images through JPEGmini for optimization.

When publishing to Backlight 5 if this process does further jpg compression wouldn’t this degrade the image further and undo some of JPEGmini’s optimization?

#12

Ben has done good work on our compression settings to keep things nice. I personally haven’t had any issues with Backlight degrading images.

And, of course, Backlight does need to create its own renditions, else you wouldn’t be able to upload just a single image. You’d have to upload your all of your own renditions separately – various sizes of thumbnails and photos – which would be a nightmare.

And I think if your master images are of appropriate size – meaning Backlight uses 2048px images and you upload 2048px images – then it just uses the master file for that rendition. @Ben, correct me if that’s wrong.

FWIW, I typically export 2048px JPEGs at 95%, then run them through JPEGMini before upload.

#13

Hi @Matthew and @charles101, I can confirm that Backlight uses the master image as-is for the required rendition if the dimensions are identical, with the following exceptions:

  • The embedded metadata is altered slightly. In particular, copyright information is added into the generated rendition.
  • If you have configured Backlight to apply watermarks within Backlight’s publisher then a new rendition will be created from the master.

As for quality, when Backlight’s Publisher does resize images, it uses the fixed quality of 90%. JPEG creation uses the PHP ‘gd’ library, and this figure does not correspond to file size and visual quality with Lightroom’s quality settings as set in the album template settings. I had tested various percentages in GD to find a setting that produced high quality images without blowing out file sizes.