Why a 50 mm lens (or an equivalent) makes pictures look so good

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I bought a used Panasonic Leica 25 mm f/1.4 lens recently. This is a micro four thirds lens with the 50 mm full frame equivalent field of view and a wide aperture. Even if I previously owned the Panasonic 20 mm f/1.7 lens (40 mm full frame equivalent), it never enthused me as much as the 25 mm. One thing is that the 25 has faster autofocus and a slightly wider aperture, but it is also twice as long as the 20 and with the lens hood thrice as long, and it weighs a bit more, so there are both advantages and disadvantages of one over the other. Some seem to think there is some sort of Leica magic in the colour reproduction of this lens since it is designed by Leica and made by Panasonic. Maybe that also adds to my enthusiasm. If so, it is probably very subtle. What enthused me the most wasn’t these niceties, but that somehow pictures just looked so much better with the 25 than the 20. When people test these lenses, both get good reviews for their image quality, so it is probably not related to that either. And I am not alone. 50 mm equivalents are often praised for making pictures look good. There is some sort of indefinable quality that the nifty fifty and its equivalents (25 mm on micro four thirds and 33,3 or 32 on APSC) brings that other lenses do not.

First, I thought it had to do with the field of view. The 50 mm equivalent field of view means that it is a bit easier to get a less cluttered composition with just a main subject and a little bit of environment around it. The picture below is a landscape taken with my 25 mm (= 50 full frame) where you can see that the field of view limits the number of houses I get into the frame and the sunset and the colours that reflects from it on the road becomes the centre of attention. Especially at close distances to the subject, the 50 mm field of view eliminates clutter. On the other hand, if I take a step backwards, what I get into the frame becomes similar with the 25 as with the 20. Add a few steps more backwards and what is in the frame is similar to when I use my 14. The nifty fifty is versatile in that it is long enough to be used to isolate a subject and leave the clutter outside the frame, while at the same time it is also short enough that it is possible to get quite a lot of a scene into the frame if you have room to take a step or three back. This makes a 50 mm good for portraits, environmental portraits, faux macro if you are really close, landscapes and architecture, which is nice, but the same can be said of a 43, 40 or 35 mm full frame (or equivalents), although, the wider the lens, the less good it becomes at portraits and macro because the longer depth of field you get at the same aperture. So the field of view is not really the determining factor.

Postveien

Then I thought it had to do with the longer focal length making it easier to isolate the subject with use of shallow depth of field. Shallow depth of field is determined by four factors: Aperture, focal length, distance to subject, and distance from subject to background. So a slightly longer lens means a slightly shorter depth of field at the same aperture. This is the reason why a 25 mm on a micro four thirds camera has double the depth of field at a given aperture than a 50 mm on full frame at the same aperture. (The f-stop isn’t a measure of depth of field, but of how much light per square mm hits the sensor through the lens, so the f-stop values given are right.) Of course, the same logic applies between full frame and medium format since the medium format lenses with similar field of view are longer than on full frame. Hence, you should get some fast primes if you shoot APSC or MFT (APSC is very close to MFT in sensor size with a crop factor of 1.5 or 1.6 compared to the 0.4 or 0.5 times smaller MFT sensors with a crop factor of 2.)

However, when I compare the depth of field of the 20 mm f/1.7 and the 25 mm f/1.4 there is a difference, but not enough that I cannot use depth of field to isolate my subject with the 20. Both lenses have enough of this expressive tool that I am able to use it if I want to. And again, if I want shorter depth of field with the 20, I have three other factors in addition to the aperture that I can change, so the difference between f/1.4 and f/1.7 isn’t all that important. And of course, there are other lenses that have even more of the advantage when it comes to depth of field, like the 85 mms (and their 42.5 mm MFT equivalents). With the same aperture, they have an even shallower depth of field. So the depth of field is not what makes the nifty fifty or its equivalents make pictures that look “just right” either.

The other day while I was out walking, I had the 25 mm on my camera and shot some faux macro shots first (the photo below is the best of them) and then some landscapes. At one point, I wanted to get a bit more of the width of the landscape into the frame, so I switched to a 14 mm (= 28 mm full frame). I tried to compose my shot to get the things into the frame that I wanted. When I had gotten the things I wanted into the frame, I still wasn’t happy. I realised that the background had “moved” further away and that one of the elements in the background that I wanted to keep placed at one of my thirds had become miniscule in all dimensions (maybe except time). I probably should have understood this a long time ago, but I think what makes the nifty fifty or my 25 mm equivalent produce pictures that look “just right” is the amount of compression that focal length produces.

The field of view is one thing, but as we move around, how much we actually see of our surroundings can be changed by getting closer or further away. We can also vary the aperture and where our subject is placed to either use a shallow or a long depth of field. The only factor that really stays the same in the pictures we take when we use a specific focal length is the compression. So a fifty will always have a specific look that you can’t get on a 35, even if you get the same things into the frame and use depth of field in a similar way. Whether you use zooms or primes, the look of a specific focal length is actually the look of the compression you get with that focal length.

Flower

What makes the look of any fifty lens so pleasant is the amount of compression. (The compression is the same on equivalent lenses, since the ratio of the size of the sensor to the length of the lens is the same. So my 25 mm has the same compression as a 50 mm on full frame, as well as the same field of view.) With wider lenses, the background is too far away and everything that isn’t really close to the lens seems small and distant. The picture below is the picture I took with the 14 mm the day I was out walking. Notice how the lighthouse seems really far away. When I looked at it without looking through the camera, it was much larger and closer. The things close to wide angle lenses seem comparably large and since the compression sort of makes further away objects even further away, if a nose comes close to the lens, it seems much larger, while the rest of the face is pushed back and looks smaller. This can be used to exaggerate features of a person’s face if they are very close to the lens, to create separation with distance between a subject and its surroundings or to put people into context in their environment if they are a bit further away.

(Travel photographers and many street photographers seems to use full frame equivalents to 28 mm, 30 mm or 35 mm a lot. Maybe this is because of the separation you get between the subject and the background with these focal lengths through the compression and that you can create separation without using depth of field. Using a small depth of field to separate the subject and its surroundings is impractical if you want to use a lens at a smaller aperture with everything in focus and prefocused to the hyperfocal distance so you can shoot fast without thinking of anything else than the composition. Many street photographers and travel photographers use this technique. Creating separation with contrasting colours is another option, but you cannot know that your subjects will contrast with the background in advance when shooting on the street, so that is also impractical.)

Stone beach and Lista lighthouse

With longer lenses, the background seems to come closer to us because of the compression. This is nice if you want the image to look flat and two dimensional, and it is of course useful when we want to capture things far away or want really small subjects to look really large. It also is nice for portraits where the point isn’t to show how people actually look, but rather to flatten their features out and squeeze them into the frame in the most flattering way possible. In the picture below, I have used the compression of my Panasonic 14-140 mm at 140 mm (= 280 mm full frame) to make the hazy mountains in the distance look closer to each other and the foreground. In contrast, with the fifty, the background seems proportional to the foreground in a very natural way. (See the first picture in this post.) The compression doesn’t make the background unnaturally close, but it neither makes everything in the background seem extremely distant. It can be used for portraits without making people into caricatures and it can be used for landscapes without the background seeming neither too close nor too far. It just looks really good.

Hazy mountains with windmills by the fjord

When we walk around, our eyes focus on a slightly narrow field of view and then additional, less in focus information from the sides is added, and our brains compose a large 3D panorama from this information. (We probably have the out of focus areas on the sides to be able to see movement from predators (or electric cars) that we are unable to hear before they come into the in-focus areas in the middle of our vision to avoid getting killed when out and about.) The slightly narrow area we actually see with our eyes is close to a fifty in full frame terms, or at least that is what people say. Maybe the 43 mm diagonal of full frame sensors and 22 mm diagonal on micro four thirds is what would make the camera see the same as us in terms of field of view. So maybe fifty is actually slightly too long to be absolutely neutral when it comes to compression.

Our brains see what they want to see. If we focus on something far away, it becomes larger or at least more prominent in our brains, even if our eyes do not change the focal length between the lens and the “photocites” (the neurons that actually register the wavelength of the different colours and their intensity.) If we want to see a whole scene, we can, even if our eyes can’t. So maybe having a little bit more compression in our images than what we really see might give us more or less the effect that we sometimes make ourselves in the brain when we bring the background into focus and closer? Maybe this is the allure of the nifty fifty?

It might also be that this perception is cultural. Since many of the iconic images of the 20th century were shot using a 50 mm standard lens, we might have developed an unconscious idea that pictures taken with a 50 mm (or equivalents) just look better. We certainly have developed other unconscious ideas that are similar as part of our culture, like for instance how people seem to think that music played in equal temperament with A=440 or A=442 is more in tune than music played in other temperaments at other pitches (even if most temperaments have some intervals that are closer to the intervals in the nature-given overtone-series than what equal temperament has and there is no way of determining a natural reference note) or how people often prefer films shot at 24 fps with shutter speeds long enough to get a bit of motion blur over more natural looking films shot at 30, 50 or 60 fps which necessitates shorter shutter speeds and actually has less motion blur.

Maybe it is all just a question of cultural bias? Are we just “brainwashed” into feeling that pictures look better with a 50? I don’t think so, since the compression of a 50 mm (or its equivalents) makes the background seem not too small and distant, but neither too large and cluttered. I think the compression we get with a 50 gives the picture a look that just feels quite natural (maybe with the background slightly larger than what is natural, but not too much), and I think we like that look instinctively since it is close to how we perceive the world. What do you think? Feel free to leave me a comment…

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