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Lens FAQ #2: Can A Bright Lens Really Make It Easier To See Through The Viewfinder?

This series is all about answering questions regarding cameras you thought you knew (but didn’t). In this article, I will explain why using a bright EF lens will make you want to take more pictures. (Reported by: Ryosuke Takahashi)


You’ll be impressed by how bright the image appears in the viewfinder

Viewfinder fitted with an f/1.4 lens

Viewfinder fitted with an f/4 lens


By comparing the viewfinder images from the EF24mm f/1.4L II USM & EF24-105mm f/4L IS USM, you can tell that the different f-numbers of the lenses are directly linked to the viewfinder’s brightness. Although the difference is relatively harder to see in bright scenes such as outdoor shoots, when shooting dark scenes, the smaller the f-number is, the more apparent this brightness will be in the viewfinder.

In cameras equipped with an optical viewfinder, light entering from the lens is reflected by the primary mirror etc. onto the viewfinder, allowing the image captured on the focusing screen to be viewed directly. As a result, when a bright lens (i.e. lens with a small minimum f-number) is used, the viewfinder image will naturally appear brighter as the amount of light entering the viewfinder increases proportionally.

This mechanism is unique to an optical viewfinder. In contrast, for an electronic viewfinder, the image captured by the image sensor is transferred to and then displayed on an LCD screen. Therefore, the brightness of the image in the electronic viewfinder does not vary with the lens brightness.

With a brighter view in the optical viewfinder, not only will it naturally be easier to see the subject’s details, you’ll also have a greater advantage when shooting in dark places.

Although a bright viewfinder will not have an adverse effect in Autofocus (AF) photography, it can make it hard for the eye to clearly check the peak focus when using Manual Focus (MF) for bright scenes. In this case, switch to a dedicated focusing screen (compatible models only) and customize it so that the peak focus can be easily checked.


A: Pentaprism or pentamirror
B: Viewfinder
C: Primary mirror

This is an illustration of what happens when you look at a subject with the viewfinder through the lens of a DSLR. As the light passing through the DSLR lens is determined by the lens aperture, the amount of light visible to the eye is dependent on the lens’ maximum aperture. If it is a bright lens, the viewfinder will appear bright as more light is available at any one time.

Ryosuke Takahashi


Born in Aichi in 1960, Takahashi started his freelance career in 1987 after working with an advertising photo studio and a publishing house. Photographing for major magazines, he has travelled to many parts of the world from his bases in Japan and China. Takahashi is a member of the Japan Professional Photographers Society (JPS).

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