Why doesn’t 25mm on Micro Four Thirds look “normal” through the viewfinder?
Asked 6/5/2014
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On my Olympus PEN E-PL1 with the VF-2 electronic viewfinder, I expected 25mm to look like a “normal” 50mm lens because Micro Four Thirds has a 2x crop factor. But when I look with both eyes open, the EVF image looks smaller than what my other eye sees. To get the two views to match in apparent size, I have to zoom to roughly 35–42mm instead.
Why doesn’t 25mm give the same apparent view as a 50mm film camera? Is this caused by crop factor, the EVF magnification, or something else?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
12y ago
2 Answers
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The difference is that the crop factor doesn't apply to your eyes.
A 50mm lens on an SLR appears to have the same "focal length" as the human eye, because the lens combined with a typical optical viewfinder magnification results in an overall magnification factor of 1.0 x, hence if you look through the viewfinder with one and whilst keeping the other open, objects appear the same size with both eyes.
A 25mm lens will give a wider absolute view, which when used with a smaller sensor gives the same field of view as a 50mm lens on a 35mm SLR. However this doesn't matter to your eye which just sees the absolute field of view.
The VF-2 electronic viewfinder on your Olympus has a magnification of 1.15x, so the 50mm lens on your ME has effective 47.5mm, whereas the 25mm lens has effective 28.75mm
This is why you have to zoom your lens to 35mm (70mm equivalent) to get close to how your 50mm looks.
Originally by user1375. Source · Licensed CC BY-SA 4.0
user1375
12y ago
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Generated from our catalog & community — verify before relying on it.
Crop factor affects recorded field of view, not how large the scene appears to your eye in the viewfinder.
A 25mm lens on Micro Four Thirds gives about the same captured framing as a 50mm lens on 35mm/full-frame. But that does not mean it will look “life-size” when viewed through the finder.
What you’re noticing is viewfinder magnification. On your old Pentax, the 50mm lens plus the optical finder gave an overall view close to 1×, so with both eyes open the scene matched naturally. On the Olympus, the EVF has its own magnification behavior, and with a 25mm lens the displayed image appears smaller than life-size. That’s why you need a longer focal length before the EVF view matches your other eye.
So the issue is not that 25mm is the wrong equivalent focal length for framing. It’s that “normal perspective/field of view” and “1× finder magnification” are different things. A lens can be normal in framing on a given format without giving a life-size finder view.
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