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Has the term focal length become obsolete?


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In analogue times, the world was still simple. If you disregard medium format cameras, which were only affordable for professional photographers these days, there were only 35mm format cameras available. All focal lengths were easy comparable. Nowadays, however, there are several formats available. Besides the 35mm format APS-C and Micro Four Thirds are available. Those cameras, are showing a different angle of view with the same focal length due to different sensor sizes. To make matters worse, the APS-C cameras also have slightly different sizes. With Canon, APS-C is 22.3 × 14.9 mm2 and Nikon has 23.5 × 15.6mm2. This sounds little but makes a difference in the recorded angle of view.

Olympus E-P7 in front of a phone

Since customers were used to the focal length specifications in 35mm format in analogue times, at the beginning of the digital age camera manufacturers converted the focal lengths of other sensor formats to 35mm using the so-called crop factor. This helped the user to understand which angle of view he could record with the lens. The approach certainly made sense. As at the beginning the entire target group of manufacturers were used to the focal length information from the analogue cameras. Therefore, easier to sell new products.

Nowadays this is no longer the case, as the younger generation did not grow up with the 35mm format. So I notice again and again that I look into questioning eyes when I talk about crop factor, when I try to explain that the lens with a focal length of 25mm in Micro Four Thirds format records the same angle of view as a 50mm lens in 35mm. After all, the lens says, mostly very prominently, 25mm and not 50mm.

Why don’t we use the angle of view instead of focal length?

In the specifications of the lenses, the manufacturers always specify the angle of view. Which is in case of a 25mm lens in Microfour Thirds it 47 ° the same as for a 50mm lens in 35mm format. In case the manufacturers would write the angle of view on the lenses instead of the focal length, a comparison would again be possible without any conversion. Even newcomers would understand that the two lenses can be used for the same purpose. For the experts among us, this might be hard in the beginning. Who has the angle of view for each lens in mind? But that is only a matter of time, especially if the corresponding angle of view is printed on each lens. It would soon be easy for us to have the angle of view ready.

image of a  micro four third lens with focal length of 8-25mm

Conclusion

I am aware that this is only a theoretical game of thought. Current practice is too deeply rooted for that. Manufacturers who use 35mm image sensors, in particular, have a strong interest in having this sensor size as a reference. This strengthens their position as the holy grail of image quality. Thought by the end-user, however, it makes perfect sense to use the angle of view. This would make all lenses directly comparable. A conversion of focal lengths would not be necessary. Yes, maybe not for those of you who are well versed, but for those of you who are new to photography and have no idea about all of this, it will be easier.

Your opinion is asked

I am looking forward to discussing the topic with you. So leave a comment with your perspective or opinion. I look forward to a factual discussion with you.

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