The Three DOF Factors
Before we compare, let's recap the three main factors that control depth of field:
- Aperture — Wider (f/1.8) = shallower DOF; Narrower (f/11) = deeper DOF
- Subject Distance — Closer = shallower DOF; Farther = deeper DOF
- Focal Length — Longer (85mm) = shallower DOF; Shorter (24mm) = deeper DOF
All three factors play a role, but their impact is not equal. Let's find out which one dominates.
Test 1: Aperture Change
Let's see what happens when we change only the aperture, keeping everything else constant.
📷 Settings: 85mm lens, 3 meter distance, Full-frame
Going from f/1.8 to f/16 (a change of about 6 stops) increased DOF by 9x. That's significant!
Test 2: Distance Change
Now let's change only the subject distance.
📷 Settings: 85mm lens, f/4, Full-frame
Moving from 1 meter to 10 meters increased DOF by over 100x! That's an enormous change.
🏆 Key Finding
Subject distance has a far greater impact on depth of field than aperture. Doubling your distance roughly quadruples your DOF. Changing aperture by the same factor only doubles it.
Test 3: Focal Length Change
Finally, let's test focal length. This one's tricky because changing focal length changes your framing.
📷 Settings: f/4, 3 meter distance, Full-frame
Going from 24mm to 135mm reduced DOF by about 50x. Focal length has a huge impact too!
The Verdict: Which Matters Most?
🥇 Distance
Biggest impact
🥈 Focal Length
Major impact
🥈 Focal Length
Major impact
🥉 Aperture
Moderate impact
The ranking is:
- Subject Distance — Has the greatest impact by far
- Focal Length — Very significant effect
- Aperture — Important, but less dramatic than the others
Why This Matters for Your Photography
For Shallow DOF (Portraits, Subject Isolation)
If you want the creamiest background blur, prioritize in this order:
- Get closer to your subject — This has the biggest impact
- Use a longer focal length — An 85mm will blur backgrounds more than a 35mm
- Open your aperture — f/1.8 helps, but it's the cherry on top, not the main factor
For Deep DOF (Landscapes, Architecture)
If you want everything sharp:
- Step back if possible — Distance is your friend
- Use a wider lens — 16-24mm gives much more DOF than a 50mm
- Stop down to f/8–f/11 — But don't go beyond f/16 (diffraction)
💡 Practical Takeaways
- Struggling to blur the background? Move closer before opening your aperture wider
- Can't get the foreground sharp in a landscape? Try a wider lens before stopping down
- At close distances (macro), even f/16 gives paper-thin DOF—distance dominates
- Telephoto compression isn't just about perspective—it dramatically reduces DOF too
- Subject-to-background distance matters as much as camera-to-subject distance for blur
Real-World Comparison Table
Here's a comprehensive comparison showing how each factor affects DOF independently:
| Change Made | DOF Before | DOF After | Change |
|---|---|---|---|
| Aperture: f/2 → f/8 | 10 cm | 40 cm | 4x deeper |
| Aperture: f/2 → f/16 | 10 cm | 82 cm | 8x deeper |
| Distance: 2m → 4m | 10 cm | 40 cm | 4x deeper |
| Distance: 2m → 8m | 10 cm | 164 cm | 16x deeper |
| Focal: 85mm → 50mm | 10 cm | 29 cm | 3x deeper |
| Focal: 85mm → 35mm | 10 cm | 59 cm | 6x deeper |
Notice how doubling the distance (highlighted rows) has a more dramatic effect than extreme aperture changes.
🔬 Run Your Own Tests
Try different combinations in our calculator and see the DOF changes in real-time.
Open DOF CalculatorThe Bottom Line
Many photographers obsess over aperture when trying to control depth of field. While aperture matters, distance and focal length often have a bigger impact.
Next time you want more or less DOF, consider all three factors:
- Can you move closer or farther?
- Can you use a different focal length?
- And then, what aperture makes sense?
Thinking this way will give you much more creative control over your images than just reaching for the aperture dial.