Why You Can’t Use Any Lens on Any Camera

A simple guide to understanding lens compatibility, mounts, and adapters.

Have you ever wondered why you can’t just take any lens and put it on any camera body?
All lenses look similar — round glass in metal tubes — but underneath, the connection system between a lens and a camera is surprisingly complex. Let’s break it down step by step.

1. Every Camera Has Its Own “Mount”

The mount (sometimes called bayonet) is the metal ring where the lens attaches to the camera.
It’s like a lock-and-key system: every brand designs its own “key shape.”

Each mount has:

• Shape and size — determines how the lens physically fits
• Electronic contacts — let the lens and camera “talk” (for autofocus, aperture, etc.)
• Flange focal distance (FFD) — the distance from the lens mount to the camera’s sensor

If the lens doesn’t match the mount’s shape or its optical distance requirements, it simply won’t fit or focus correctly.

2. Major Camera Mount Families

Each mount type has its own set of compatible lenses.
For example, a Canon EF lens fits all Canon DSLRs — but not Nikon or Sony without special adapters.

3. What Are SLR and DSLR Cameras?

Before we get into compatibility, let’s clear up a common confusion — SLR and DSLR.

• SLR stands for Single-Lens Reflex. These are film cameras that use a mirror and prism system to let you see through the same lens that takes the photo. Classic examples include the Canon AE-1 and Nikon FM2.
• DSLR stands for Digital Single-Lens Reflex — the digital successor to SLRs. They work the same way but capture images with a digital sensor instead of film (Examples: Canon EOS 5D, Nikon D850, Pentax K-1).

Both SLR and DSLR cameras have longer flange distances because of the space needed for the mirror mechanism.
That’s why when manufacturers moved to mirrorless cameras, the lens mount became shorter — opening the door for better optical designs and easier adaptation of older lenses.

Full-Frame and Crop-Sensor DSLRs

Not all DSLRs have sensors of the same size. Some use full-frame sensors (the same size as 35 mm film), while others use smaller sensors, often called crop sensors or APS-C sensors.

APS-C stands for Advanced Photo System – type C (Classic) — a term that originated from a 1990s film format.
An APS-C sensor is smaller than a full-frame sensor, which means it “crops in” on the image. This gives a narrower field of view — about 1.5× on Nikon, Sony, Fujifilm or 1.6× on Canon cameras.

For example, a 50 mm lens behaves more like a 75–80 mm equivalent on an APS-C camera.
This makes crop DSLRs great for telephoto work and budget-friendly, since the smaller sensors allow for more compact and affordable bodies and lenses.

In short: both are DSLRs and share the same mount type, but their sensor size changes how much of the lens’s image they capture.

4. DSLR vs. Mirrorless: Why It Matters

DSLRs and mirrorless cameras have different internal designs:

• DSLRs have a mirror box, so the lens sits farther from the sensor.
• Mirrorless cameras remove the mirror, bringing the lens closer to the sensor.

This change affects the flange focal distance — and that’s the key to understanding compatibility.

Because mirrorless cameras have shorter distances, they can use adapters to mount older DSLR lenses.
But DSLR cameras can’t use mirrorless lenses — the lens would sit too close and lose focus.

5. Why You Can’t Mix Lenses Freely

Here are the three main barriers:

1. Mechanical Fit

The bayonet shape must match exactly. A Nikon F lens simply won’t click into a Canon EF mount because the notches and tabs are different.

2. Flange Distance

If the lens sits at the wrong distance from the sensor, it won’t focus to infinity.
Too far = can’t focus on distant objects.
Too close = can’t fit at all.

3. Electronics and Control

Modern lenses often rely on electronic communication for:

• Autofocus
• Aperture control
• Image stabilization

If the camera and lens don’t “speak the same language,” features may stop working — or the lens won’t function at all.

6. The Role of Adapters

Adapters act as “translators” between mounts.
They can be simple mechanical rings or smart adapters with electronic contacts.

• Simple adapters: work with manual lenses (you adjust focus and aperture yourself).
• Smart adapters: transmit autofocus and aperture signals (e.g. Canon EF → Sony E).

⚠️ Some combinations don’t work even with adapters — especially when trying to mount lenses from systems with shorter flange distances (like Canon RF or Sony E) onto DSLRs.

7. Compatibility by Camera Body

Here’s a simple table showing what lenses each popular camera body can use — natively, with adapters, and which ones are not compatible.

Tip:
If the adapter name includes the lens mount → camera mount (for example, EF–E), it means you’re adapting Canon EF lenses to Sony E cameras.
Mirrorless bodies (RF, Z, E, L, X, MFT) are the most flexible because their shorter flange distances make it easier to use older SLR or DSLR lenses with simple adapters.

8. The Good News: Mirrorless Cameras Are Very Adaptable

Mirrorless bodies (Sony E, Canon RF, Nikon Z, etc.) can use:

• Their native lenses (full compatibility)
• Older DSLR lenses (with adapters)
• Vintage manual lenses (with cheap metal adapters)
• Cinema lenses (with professional mounts like PL)

That’s why mirrorless cameras are now so popular — they let you experiment with almost any lens ever made.

9. Quick Examples

• Canon EF lens on Canon RF body: ✅ Works perfectly with Canon’s official adapter
• Nikon F lens on Nikon Z body: ✅ Works via FTZ adapter
• Canon EF lens on Sony E body: ✅ Works with smart adapter (Metabones, Sigma MC-11)
• Sony E lens on Canon DSLR: ❌ Not possible (flange distance too short)
• Minolta MD or M42 lens on mirrorless: ✅ Works great, manual focus only

10. Takeaways

• Lenses aren’t universal because mounts differ in shape, distance, and electronics.
• Mirrorless systems are more flexible thanks to their short flange distances.
• Adapters can solve many — but not all — compatibility problems.
• Always check mount type before buying a lens or body.

In short:
Every camera system has its own “language.” With the right adapter, many lenses can “learn a few words” — but not all can become fluent.

If you’re starting out, choose a camera system with a wide lens ecosystem and good adapter support, such as Sony E, Canon RF, or Nikon Z. These let you explore both modern and vintage lenses with minimal frustration.