Calibration Flow exports to the

.acv

format of Adobe Photoshop. This format was designed for Photoshop and is read natively only by it. Lightroom — even though it's published by the same company — doesn't read it. Capture One, GIMP, Affinity Photo, Darktable, Krita don't either.

This asymmetry is old. Adobe never opened

.acv

to Lightroom, and the situation doesn't seem to be changing. If Photoshop isn't in your workflow, you have to find a workaround. Three are possible, each with its limits — none is as simple as opening it directly.

#The three workarounds

#First — Photoshop preset triggered from Lightroom Classic

If you have both Lightroom Classic (the desktop version) and Photoshop in your Creative Cloud subscription, this is the cleanest option.

In Photoshop, you save your

.acv

file as a curve preset (the Curves palette offers "Save preset"). You then create a Photoshop action that opens an image and applies this preset. You convert this action into a droplet (File → Automate → Create Droplet). The droplet becomes a small executable program that you place in

Adobe/Presets/CalibrationFlow/

In Lightroom Classic, you point to this droplet via Edit → Preferences → External Editing. From then on, you can right-click a photo in Lightroom → Edit in → Calibration Flow Cyanotype (or whatever name you gave the droplet). Lightroom opens the image in Photoshop, applies the droplet (which loads your curve), saves, and sends the processed image back into Lightroom.

It's laborious to set up the first time, but after that it's one click.

#Second — Manual entry in Lightroom's Tone Curve module

Lightroom Classic and Lightroom Cloud both have a "Tone Curve" module. You can manually place up to 14 points there (Lightroom's limit). Your Calibration Flow curve contains up to 16 points in the

.acv

— you can get close by selecting the 14 most representative ones.

To get the coordinates, read them directly off the graph in Calibration Flow (the 25 sampling points give you landmarks) and enter them one by one in Lightroom. The precision is degraded (about 1% deviation), but visible only on very smooth gradients.

It's the option for whoever has no Photoshop at all. Count five to ten minutes per curve the first time, two minutes after.

#Third — Intermediate TIFF

You export your image from Lightroom as a high-quality TIFF into a temporary folder. You open this TIFF in Calibration Flow, which knows how to apply its own curve to any imported image. You export the corrected TIFF. You re-import it into Lightroom as a new file.

It's the fastest method to set up. The downside: you break Lightroom's non-destructive workflow. The processed image loses its link to its original RAW file. If you want to re-edit the image, you start again from the RAW in Lightroom and redo the pass through Calibration Flow.

#Why these workarounds exist

Because many alt-process photographers don't have Photoshop. The Creative Cloud Photo subscription (Photoshop + Lightroom) costs 11.99 €/month minimum. The "Lightroom only" subscriptions are cheaper and many practitioners have them. Without a workaround, they couldn't exploit a Calibration Flow calibration.

Because Capture One and Darktable have their own curve modules that don't read

.acv

either. Manual entry is the universal option that works everywhere.

Because multi-tool workflows are the norm in professional practice. Nobody does everything in a single app — you calibrate in Calibration Flow, you develop in Lightroom, you retouch in Photoshop, you archive in Lightroom. The workarounds make this chain possible.

#When it's not enough

If you want maximum precision. Stay on Photoshop with the direct

.acv

import. You keep the full 16 points of the curve. Lightroom caps at 14, and manual entry always introduces a few errors.

If you work entirely on mobile. Lightroom mobile has neither a Photoshop droplet nor an easy TIFF export. You only have manual entry of the 14 points in the mobile Tone Curve, or a pass through Calibration Flow iOS followed by a re-import via Photos.

If your flow requires batch consistency across a hundred images. None of the three workarounds is fast for batch. For that, Photoshop with an action loaded in batch via Adobe Bridge remains the mature solution.

#Worth remembering

Workaround	Tools needed	Effort	Precision
Photoshop preset + droplet	Lightroom Classic + Photoshop	Medium (initial setup)	Maximum
Manual entry	Lightroom only	High (per curve)	Reduced (14 points out of 16)
Intermediate TIFF	Calibration Flow + Lightroom	Low (but broken workflow)	Maximum

#The test

Choose the workaround that matches your tools. Set it up for your first curve (count 30 minutes for the Photoshop droplet, 10 minutes for manual entry, 5 minutes for the intermediate TIFF). Apply the curve to an image. Compare the render with the one obtained by loading the

.acv

directly into Photoshop (if you can do it elsewhere). For options 1 and 3, the renders should be identical. For option 2, expect tiny deviations visible only on very smooth gradients.