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Is free software like Siril finally good enough to replace a paid Adobe Photoshop workflow for deep-sky imaging? I decided to carry out this Siril Photoshop test in order to find out. The results surprised me!
For years, the “standard” advice has been that you need Adobe Photoshop to get professional astrophotography results. I wanted to challenge that. I conducted a direct head-to-head experiment comparing a $0 Siril workflow against a classic $260/year Photoshop workflow.
⚡ Quick Verdict Based on My Findings
For 95% of astrophotographers, Siril (free) is the superior choice.
- Speed: The Siril workflow took 8 minutes vs. 40 minutes in Photoshop.
- Cost: $0 vs. ~$300/year (including plugins).
- Quality: The results are nearly indistinguishable, with Siril actually offering better automated color calibration.
📊 The Siril Photoshop Experiment: The Numbers
I processed the exact same raw data (The Sadr Region) using two distinct workflows to measure time, cost, and image quality.
| Feature | Siril Workflow (Free) | Photoshop Workflow (Paid) |
|---|---|---|
| Total Cost | $0.00 | ~$260/year(Sub + Plugins) |
| Time to Process | ~8 Minutes | 30–40 Minutes |
| Key Tools Used | Siril, GraXpert, Veralux | Photoshop, GradientXterminator |
| Background Extraction | Automated (5 seconds) | Manual (Multiple steps) |
| Star Removal | Integrated Starnet++ | Required external/plugin |
🔬 Deep Dive: The $0 Siril Workflow
Total Time: ~8 Minutes
The biggest surprise in this test was how modern scripts have revolutionized the free workflow. We aren’t just doing things cheaply; we are doing them automatically.
The Process:
- Preprocessing: I used the standard Siril OSC_Preprocessing script. It handles biases, flats, and darks automatically.
- Background Extraction: This is usually the hardest part. I used GraXpert (integrated directly into Siril). It uses AI to identify gradients. I didn’t place manual sample points; I just clicked “Run.” It took about 5 seconds.
- Color Calibration: I used Siril’s Photometric Color Calibration (PCC). This plate-solves the image and matches star colors to a database, ensuring 100% scientific color accuracy without guessing.
- Stretching: Using the Veralux script, the image was stretched to non-linear instantly, preserving star color.
- Star Removal: Siril has Starnet++ built-in. One click separated the stars from the nebula, allowing me to process the nebulosity without bloating the stars.
Why it wins: The integration of GraXpert and Starnet++ means you never leave the interface. It flows logically from one step to the next.
Here is the link to download Siril if you would like to try it for yourself.
🎨 Deep Dive: The Photoshop Workflow
Total Time: ~40 Minutes
The Photoshop workflow represents the “traditional” way of doing things. While powerful, it felt like fighting the software compared to Siril.
The Process:
- Initial Stretch: Stretching the histogram manually using Levels and Curves. This is an iterative process—stretch, reset black point, stretch again. It is easy to clip data here if you aren’t careful.
- Gradient Removal: I used the GradientXterminator plugin (a paid add-on). While effective, it requires manual selection of “background” areas. If you select a piece of faint nebulosity by mistake, you will delete your target.
- Star Removal: Photoshop does not have a native star removal tool for astrophotography. I had to run an external instance of Starnet++ or buy a plugin like StarXterminator.
- Color Balance: This was done by eye using “Levels” per channel. Unlike Siril’s PCC, this is subjective. You are guessing what “neutral background” looks like.
The Problem: In Photoshop, you are manually building every tool that Siril gives you automatically. You are paying for the privilege of working harder.
The Results: The Winner Is…
I think that A (Siril) the free option is best and gives a slightly better image in my opinion. With more time you can get a great result from Photoshop and we do need to bear in mind that PS is not designed for astrophotography but Siril is. For a beginner or someone on a budget the best choice is Siril. What do you think?
❓ Frequently Asked Questions
Does Siril replace Photoshop for astrophotography completely? For “Pre-processing” (stacking, calibration, initial stretch), yes. Siril is objectively better. However, Photoshop is still king for “finishing touches”—adding text, making composite mosaics, or very specific local brush adjustments.
Can I use GraXpert without Siril? Yes, GraXpert is a standalone application. However, using it inside Siril (as shown in my workflow) saves you from saving/exporting TIF files back and forth.
Why is the Photoshop workflow so much slower? Photoshop is a generalist photography tool, not an astrophotography tool. Every action (like removing light pollution) requires a workaround or a plugin because Adobe didn’t build the software for deep-sky imaging. Siril was built only for this.
Is the image quality actually the same in my blind test? Yes. The Photoshop version had perhaps slightly better manual noise control because I spent 20 minutes tweaking it. But was it 500% better (to justify the time difference)? Absolutely not. The Siril Photoshop comparison proves that free tools are fast closing the gap.
Astroimagery Guides to Siril and Photoshop
I’ve written a several guides about the two software choices for processing astrophotography images and the best way to use them. Check them out:
A step by step guide to installing and using Siril
