Lightroom Intro From Aperture Notes:

If you’re making the switch from Aperture to Lightroom, as many are now due to Apple unfortunately discontinuing support and version updates for Aperture, there is a learning curve, but you’re not working entirely from scratch, most of the functionality is mirrored between the two programs with mostly subtle differences in approach and convention. In general the skills and tools you learned in Aperture will be an asset in quickly getting up to speed on Lightroom, however there are some fundamental differences that can become liabilities when you come to Lightroom with expectations shaped by how Aperture worked. In my own process of making the switch I had occasional hangups associated with expectations from Aperture that others I know who only worked in Lightroom never ran into.

One of the important central differences that is important to learn right away is how Lightroom handles files and folders. Many Aperture users took advantage of the self managed library system by which you would organize images in projects and libraries in the Aperture user interface, but Aperture handled all the actual files in the background under a central unified library file. Images could only exist in one “project”, but however many albums you wanted, and albums could be freely moved in and out of projects. Some Aperture users used what it called references to have more control over where files lived on your computers file system and hard drive(s), and if that’s how you managed your Aperture library it’s a little closer to how Lightroom works.

Lightroom’s conventions and workflow on how files are organized onto your hard drive, and how they are displayed and managed in the application’s user interface differ from the typical Aperture approach. There is no equivalent self managed file structure for the library, or what Lightroom calls your catalog, and Lightroom separates file organization into functionally seperate panels in your primary sidebar on the left of the interface. If you're used to the way Aperture organzies folders, projects, albums, and everything all in one panel, with the ability to nest albums in projects however you like, the Lightroom approach requires a little rethinking.

In order of appearance down the left sidebar, underneath "Navigator" (which controls zoom levels with a small image preview that can be used to drag zoom focus), are:
Catalog
Folders
Collections
Publish Services

Catalog gives options to view all photographs in the current catalog, and contains a few special "collections" (functionally equivlient to albums in Aperture), like All Photographs (for every single image in your catalog database, equivlent to Aperture libraries) "Previous Import" for all images in your last import operation, the similar "Previous Export" and missing photos. There is also a special "Quick Collection" used for temporary gathering of images to be organized or have batch operations applied

Aperture vs. LR differences of convention

File structure on harddrive(s) mirrored in Folders tab on LR, and completely separate within the UI from collections which are like Ap albums.

Collections are like Albums, and can be gathered in collection set folders, but are organized completely outside the Folders tab file structure, unlike Aperture which allows albums and other special set types to be mixed with “projects” folders.

Filmstrip seems like it should function similarly to grid view, but in Lightroom there is an important key difference, selecting multiple items and applying pasted adjustments or changing meta data, effects all selected images. In the film strip, multiple items can be selected, but changes apply only to the primary image currently previewed unless the grid view is also active.

Modules:

Each functions separately, to a greater extent than Aperture, in that each often has it’s own separate keyboard commands, and certain functions can only be applied when in a particular module.

The core modules where you’ll probably spend nearly all your time are library and develop. Library is where you will preview your collection of photos, one at a time, in grid view (g), or side by side in compare (c) or survey (n),

Target Collection: [B] sets an image selection to the current target collection. By default the “quick collection” is the current target selection, a special collection that exists to function as a kind of temporary holding space for organizing images. If an image is already in the target selection, indicated by a solid gray circle in the grid view, pressing B will toggle the image out of the target collection.

The target collection set has a + symbol next to it’s name in the sidebar.

[Command(⌘) + B] changes your active collection to the current target collection.

Develop Module:

Where all the image editing and adjustments are made. There are certain keyboard keyboard comands that only function when in develop mode, and some keymands associated with development tools will automatically switch LR to develop mode.

Some of the frequent commands handy to know the keyboard commands fore Q: Spot retouch tool is a handy one Heal Vs. Clone

c[R]op -If you want to quickly switch to a vertical crop in a horizontal image or horizontal crop in a vertical image, tap [X] while the crop tool is active. There is no button or drag down menu option for this anywhere unlike in Aperture, it’s only accessible by the keyboard command so it took me a bit before I figured out how to do it, that feature should be made more intuitive in LR.

\ (backslash handles before & after edits post cropping)

Snapshots: Stores various edit versions to a single image

Virtual Copy

Library Module: Grid View Loupe: Preview of image, defaults to image sized to fit and can be zoomed in further with the Z key, with different zoom in and out levels defined in the navigator in the left sidebar view.

Publish Services:

A special type of image collections/albums that maintain an export location and export settings for easily maintaining consistency. A common example is publishing to a folder to be used for a website, where images added and published all export to consistent size and jpeg compression settings.