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Pentaprism vs Pentamirror optical viewfinder

A digital single lens reflex camera consists of many mechanical and electronic parts working in parallel to produce a digital photograph. One such part is the viewfinder, which allows the human eye to view the scene and decide on composition and focusing. Taking into account the latest development in electronics, the viewfinder can be either electronic or optical. An optical viewfinder (also called as OVF), as the name suggests, shows an optical representation of what the scene looks like. The view offered by an optical viewfinder does not change when shutter speed, aperture or ISO is changed. If it is a dark environment (night photography), it will show darkness.  Let's talk a little bit about how light travels inside a digital camera.

To explain the path traveled by light rays inside a camera, I made a simple diagram to make it easy to understand. Skipping over other parts, let's look closer to what's happening just before the viewfinder. The light rays have to pass through a reflecting mechanism before entering the viewfinder. The role of this reflecting mechanism is to show a proper orientation view of what the scene looks like. Not upside down, not rotated to left or right. Based on the material used for this reflecting mechanism, two main types of optical viewfinders are pentaprism and pentamirror. They do the exact same work of sending the light rays into the viewfinder but are constructed in different ways. But how does this matter for photography and which one is better?

Optical viewfinder pentamirror vs pentaprism

What is the difference?
Pentamirror: A pentamirror optical viewfinder is made of separate small mirrors with air present at the center. This makes it lightweight and inexpensive to manufacture. 
Pentaprism: A pentaprism optical viewfinder is a solid dense piece of glass. This makes it relatively heavier and expensive to manufacture. There is no air gap present and only 2 air/light interfaces are involved. One where light enters the prism and one where it leaves the prism. 

Which one is better?
The only benefit offered by pentaprism viewfinder is being more bright than a pentamirror viewfinder. A brighter viewfinder helps with manual focus lenses when focusing and also in low light conditions focusing. It also helps with macro photography as it offers a brighter view to the photographer. If you find yourself taking photos in manual focus mode or you have a set of manual focus lenses, pentaprism is a good choice. Pentaprism viewfinder is generally found in higher-end professional grade DSLR cameras, while pentamirror is seen in the lower end ones. Between using a pentamirror or pentaprism based camera, image quality output is not impacted in any way as long as there is no photographer error involved.

Worth the extra cost?
The only small caveat with pentaprism based DSLR cameras is they tend to be more expensive, but there is a big exception to this called Pentax. Pentax is well known for providing pentaprism based viewfinder in almost all of its digital camera bodies. If you are a Canon or Nikon user, the list below will help you to select a camera based on your choice of the viewfinder. 

List of digital cameras with pentaprism viewfinder:
Nikon D7100
Nikon D7000
Nikon D7200
Nikon D750
NIkon D810
Nikon D850
Nikon D4
Nikon D800/D800E
Nikon D600
Nikon D7500
Nikon D90

Canon 30D
Canon 40D
Canon 50D
Canon 60D
Canon 70D
Canon 80D
Canon 7D
Canon 7D Mark II
Canon 6D
Canon 6D Mark II
Canon 5D
Canon 5D Mark II
Canon 5D Mark III
Canon 5D Mark IV
Canon EOS 1D-X
Canon EOS 1D
Canon 5DS
Canon 5DS R

Pentax KP
Pentax K10D
Pentax K-7
Pentax K-30
Pentax K-50
Pentax K-500
Pentax K-70
Pentax K-1s
Pentax K-3s

List of digital cameras with pentamirror viewfinder:

Nikon D3400
Nikon D3300
Nikon D3200
Nikon D3100
Nikon D5500
Nikon D5600
Nikon D70
Nikon D5200

Canon T5i/ EOS 700D
Canon T4i/ EOS 650 D
Canon T3i/EOS 600D
Canon T2i/EOS 550D
Canon T1i/EOS 500D
Canon T5/ EOS 1200D
Canon T3/ EOS 1100D
Canon T6/ EOS 1300D
Canon T6i/ EOS 750D
Canon T7/ EOS 2000D
Canon T7i/ EOS 800D
Canon 77D

A good bright viewfinder makes the camera usage experience more enjoyable but that shouldn't be the only deciding factor to upgrade or buy an expensive body. If you are upgrading to a new camera body in need of some other functionality and pentaprism comes with it, great. The whole purpose of buying a camera is to learn and improve your photography skills by practicing. Not so important choices like pentamirror or pentaprism shouldn't be a topic of worry for a beginner. Take photos, learn and then take more photos. Happy photography:)


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