film Q User Guide

What is film Q?

film Q is a web app that batch-inverts film scans (including large files) without the need to install software.

How does it work?

At its core is a simple, time-proven method for inverting film negatives: histogram equalization. Histogram equalization does not affect the original colour balance; it simply removes the base fog¹ from the inverted film scans. The result is greater creative control and a better understanding of the medium.

☝️ I’ve been using this method and the initial versions of the film Q code to invert the negatives on Analog.Cafe for the past four years! However, you should know that histogram equalization does not always produce finished colour positives — you may need to do your own colour correction afterward.

Because film Q does not process files on your device — everything is done on Analog.Cafe servers — you can control it with anything that has a web browser, like a Mac, an Android phone, an iPad, or that vintage Windows 95 computer.

film Q is made for batch processing. As the name suggests, you can queue up dozens or hundreds of film scans in one go and just let the app do its thing.

Combined with Dropbox (a cloud file storage with desktop and mobile app integrations), film Q can be used as a plug-in solution to your secure film negative archive. Once the conversion is complete, the service places clearly labelled processed files right next to your originals and adapts to your organizational system. This way, your files are easy to find and organize.

Quick start guide.

film Q processes files in batches. It looks for folders named watch inside your Dropbox and queues up files found in those folders.

film Q does not use all of your Dropbox storage space. It only has access to the Dropbox/Apps/film Q/ directory.

To get started, create a folder and name it “watch” anywhere inside the “Dropbox/Apps/film Q/” directory.

For example, I’ve created my folder here: “Dropbox/Apps/film Q/Pentax K1000 -- Gold 200/watch” — but you can place yours anywhere as long as its inside “Dropbox/Apps/film Q/,” it’s named watch, and your film scans are inside that folder.

Once your film scans finish uploading (remember, you’re uploading them into your “watch” folder), they will appear in the film Q app under the “Intake Folders” list.

To start processing your files, hit the green button that says “invert” next to the Queue.

film Q processes your files in the cloud, which means you can close your tabs while it works — your processed files will be saved in Dropbox without needing your device.

film Q will process your files and place them in a folder named converted, which will be adjacent to your watch folder.

Click the folder and file names inside the film Q app for more info and help finding them in your Dropbox.

Removing folders.

If you want to remove a folder from the intake list, click the “Edit” button next to the “Intake Folders.” When film Q removes intake folders from the app it renames them from “watch” to “originals.”

You can add up to 20 intake (“watch”) folders, after which you’ll need to remove one or more to add another. Your Queue will add the first 100 of the files from the “watch” folders — once it processes those, you will be able to add more.

Archiving film scans with film Q and Dropbox.

If you use Dropbox to archive your film scans, you can move your archive to the Dropbox/Apps/film Q/ directory.

If you do that, the next time you scan your film, name your destination folder “watch” — film Q will automatically queue up the contents and place converted files in the adjacent folder.

This technique speeds up archiving in Dropbox as there are fewer files to upload.

Dropbox apps for Mac, Windows, iOS, and Android automatically sync your scans and film Q’s converted images. If you install this on your Mac or PC, you won’t need to upload or download anything through a web interface (everything will show up in your local folder).

How does film Q invert film negatives?

film Q connects to your Dropbox account and detects your film negatives by looking inside folders named “watch” for supported files. It then processes those files one by one and sends the results back to Dropbox.

While film Q processes your files, there’s no need to be online or have your device on. As long as it has received a signal and your files are in Dropbox, it will do everything on the Analog.Cafe servers. The files are kept on the servers only for a short period of time while processing and are deleted within minutes.

Once the file is on the server, film Q creates a downsized, cropped version of the image that excludes the frame borders for calculations. It then looks at the downsized image to determine the values for histogram equalization. The final step is applying those calculations to the original file, inverting the colours, and sending it back to Dropbox.

Removing base fog from positives.

Histogram equalization ensures that your images’ deepest blacks are represented by the darkest pixels on your monitor and vice-versa. When applied separately to each of the colour channels, this technique can fix inefficient contrast and colour shifts in positive images. This can be helpful when fixing old positives or slide film scans.

To apply histogram equalization to your photos without inverting them, click the Settings button to the right of the Queue and select the “Fix Base Fog” option. This option will be remembered on your device, so be sure to switch it back.

The drawbacks of histogram equalization.

If you try to process a photo of a clear blue sky with nothing in it using histogram equalization, it may appear oversaturated. This issue may also occur in other overwhelmingly invariable colour plans. However, it is rare and not unique to this method.

Histogram equalization does not produce a final colour image from colour negatives unless they have a clear base. Even darkroom prints need colour adjustments before an image is made. Modern software often tries to guess what the final colour should be, but that may cause issues and take away control from the photographer by hiding or distorting the film’s properties.

Lastly, this method works well with scans natively made in TIFF or JPEG and may have issues with camera RAW files converted to the above formats, unless they are read in a particular way.

Troubleshooting

“Error” next to a file in the Queue. This could mean a few things. Here’s what you can try to fix this:

If this is your new Dropbox account, please make sure you’ve verified your email with them. If you don’t verify your email with Dropbox, it will not allow film Q to download any files.

If you are over your monthly upload quota, you won’t be able to convert files, which will show “Error” next to the first attempted file in Queue.

Please make sure that your files are smaller than 300MiB and at least 1MiB. film Q can currently process TIFF, PNG, and JPEG files only.

It’s possible that the server may have had a hiccup and could not process your file for whatever reason. Try restarting your Queue or removing the file in question from the Queue so that it can process the remaining files. I regularly monitor and fix errors and would love for you to report your found bugs to [email protected]!

I’ve added files to my Dropbox, but they are not showing up infilm Q. It may take time for your files to upload to Dropbox and for Dropbox to get back to film Q; give it a few minutes or longer on slow internet connections. Please also ensure that you named your folders as instructed in the film Q app.

You can refresh your file list by tapping the purple “Live” button on the top right.

Service limits and quotas

As with any system, there are limits to how much data film Q can process:

100 files per queue. You can add more files than that into your “watch” folders, but the Queue will only process 100 at a time.

20 “watch” folders. You can add several folders as sources of film scans. You are limited to 20 to make the app easier to use.

300 MiB per file. I haven’t seen many scans larger than that, so that should be plenty. Larger files may be acceptable in the future if there’s demand.

12 GiB per month. Most photographers (Threads poll, Mastodon poll) work with files that are smaller than 50MiB, which would make the 12 GiB limit enough for typical use.

Known issues.

I would like to develop this project collaboratively with the folks who support Analog.Cafe. Several of you have already helped me by testing the app and giving feedback. This and the below sections should give you a clear idea of how this project is doing and how to contribute your bug reports and feature requests.

These are the most visible issues that need to be fixed before this app becomes available for public use:

#1 The web interface may not show that files are processing (while they are in the background). This can happen with large queues with many files.

#2 Queue files may appear crossed out when they should not be. They should be crossed out if deleted or not found, but they may appear crossed out even if they exist.

#3 Film negatives not scanned with a dedicated film scanner using neutral settings at 16 bits per channel may produce colours that are difficult or impossible to fix.

#4 film Q only accepts TIFF and JPEG images for conversion. It should also accept RAW camera files.

#5 If two people want to start processing their files simultaneously, the second person in line must wait to try again later.

#6 Users are asked periodically to sign in with Dropbox again.

Roadmap.

This is the most complex application I’ve built from start to finish in my twenty years as a software engineer. It will take time to get right.

My main objective is to build a reliable service, which is why I am focusing on the bugs first. However, I am also investigating future features, such as automatic queue triggers (files start converting as soon as you add them), custom output file formats, a contact sheet generator, and Dropbox file upload alternatives.

Feature requests.

Please email [email protected] — thank you!