1 person found this helpful
In the Develop module, you use the crop function to change the shape and contents of the image frame. While LR can show you the pixel size of the resulting crop, this info may or may not be helpful to you. (I like to see it.)
When you export to a file, you have controls over the various sizings:
You can control the pixel dimensions by using the resize options. If you pick 4000x4000 pixels, LR will scale your image down to fit into that square while maintaining the correct shape (no stretching). If your image is smaller than your limitation, you can keep it that size (the common option) by selecting "don't enlarge".
The size of the file is based on the pixel dimensions and the amount of JPG compression used. Here you can pick the compression level, or you can pick the desired kilobytes size where LR will adjust the compression to create a file no bigger than your limit.
In your example of 4000x4000 pixels and 1500 kb, I would just input those numbers. For the other site that wants different limits, just input those limits and export again.
Note: the resolution number is meaningless unless you are trying to describe the image dimensions in inches or cm when you should be using pixels in the first place.
Joe..... Thank you.
I read your message a day or so after you sent it, but I have been forgetting to search for the "pixel size" referencing of the crop itself. I just looked, and I have not found that anywhere. ............ any hints?
Most everything else you provided, I was already aware of, but also, since your message, I have been doing some sample exporting with a controlled set of images, and I think I have a better understanding of the process. I am still having trouble keeping the results consistent, but my tests are showing that the "data" that makes up the size of the image is impacted by "what I am cropping in and what gets dropped out". Common sense, I suppose.
Here is the example of what I am dealing with. I guess I don't have a huge problem with it, .... except that I can't understand why it happens and I don't like having good control over my export sizes.
The first item on the list is the Full Size image (which is a cropped 5x7) and you can see the exported image size is 1783kb
As you look down the list, the numbers that follow "MM" show various "Limit File Sizes" for the exact same export. No other size restrictions were picked and you can see how the numbers start to change and "not" change.
Notice between 1750 and 1700 the file size drops 724kb and then that file size does not change again until the "Limit File Size" changes to 999 where it then drops another plus-30%.
This is the crux of my problem... I would like to keep a file size as close to the 1500 kb mark as I can, but it appears that the "Limit File Size" has no real control of the final outcome!
The file size is not a good indicator of JPG quality.
The "limit file size" is just another way to set the compression setting. You pick the max size you want, and LR figures out what compression setting gets you something "just" under that number.
One thing to note here is that while LR has a "quality" slider that goes from 1-100, in reality there are only about 12 actual compression levels. This means that your file size limits are a lot less granular than you think.
Some good reading:
When I export a file, based on the intended use, I pick the pixel dimensions and the compression setting. Based on this I will have a vague idea of the megabytes of the file size due to experience, but as long as it is in the reasonable expectations the actual MB don't matter. Now, obviously some sites do place a limit on the pixel sizes and/or megabytes of images they host or link to. In those cases, I do adjust my export settings accordingly.