You can use Negative Lab Pro to convert and edit multiple negatives at once.
To open Negative Lab Pro in batch mode:
How many conversions can I do at once?
In theory, you could do 1,000s, but this will be very slow because of how much memory the operation needs, and could crash. Therefore, I don’t recommend doing more than a 100 or so at once.
Is there a way to speed this up?
When you do Batch Conversions, Negative Lab Pro is analyzing and evaluating each negative independently. This can take a while, but only needs to be done once. If you want a faster workflow, one alternative is to convert only one image, and then use that conversion as the base for all other conversions via the “sync scene” option below. I do this a lot in my own workflow. Its great because the other images don’t even need to be converted yet (or white balanced) for this to work - it will just take everything over. You may find that some of the images via this method will need some major editing, but typically there is enough latitude in Negative Lab Pro to make the adjustments you need to individual images.
When you are in batch mode, you can also begin editing your images. But just note that only the “master” image will be updated with your new settings. This is both to save memory, but also to keep you from accidentally making unwanted changes to other images.
For instance, let’s say that all of your conversions were too bright. If you have all the images open, and start bringing down the brightness in NLP, only the “master” image will change brightness. If you want all the other images to change brightness as well, you will need to hit the “sync settings” button, to bring these specific NLP settings over to the rest of the images.
What if you want the EXACT same CONVERSION and EDIT across two or more images?
That’s where “Sync Scene” comes in handy. It copies both the image analysis and the NLP settings from your master image to your other selected images. This not only allows you to have the same exact conversion, but also to continue editing the negatives in the future using Negative Lab Pro’s controls.
Note: You may be tempted to use Lightroom's own Sync Settings tool, but this won't bring over the internal metadata that Negative Lab Pro needs to allow you to continue editing the file in the future.
Sync Settings copies the Negative Lab Pro Control Panel Settings across negatives. So for instance, if you prefer to use the “linear + gamma” tone profile as a starting point for editing, you can set that in your main negative, then copy it over to all the other selected negatives. Each Negative will still retain their own, unique image analysis.
In batch conversion mode, note that any further adjustments you make in Negative Lab Pro’s control panel will only be applied to the main image you have selected. If you would like to carry those settings across all the scans you have selected, you can hit the “Sync Settings” link at the bottom left of the Negative Lab Pro’s control panel.
Sometimes you may want to un-convert multiple images back into a negative (either to make adjustments, or try out different settings). You will need to do this un-conversion inside of Negative Lab Pro (hitting the “unconvert” link just below the “Convert” button.)
Just as you can batch convert negatives, you can also batch un-convert them, which is also useful in some situations.
You may find out of habit that you simply “reset” an image using Lightroom’s regular controls. If you do this, you’ll find that when you re-open Negative Lab Pro on the image, it will still think that the image should be converted, but it will look off because the underylying settings in LR have changed. In this case, you’ll need to properly unconvert it inside Negative Lab Pro, and then reconvert it.