Why are classic focal lengths important?

[ionian]

I've just bought the 15mm f1.7, to add to my prime collection of 20mm, 30mm, 45mm and 60mm. Out of that lot, not a single lens (Well, maybe the O45 is damn close) is advertised as an equivalent of one of the classic 35mm focal lengths.

This seems to put off a significant number of people - i've read reviews giving the lenses a black mark just because the focal length doesn't fall into a 35mm category, and the furore (not on this site) about how the sigma 30mm is too long for one thing and too short for another is bordering on the evangelical.

I'm not saying that having a wide, standard and tele isn't important, I just don't get why 28mm, 35mm, 50mm and 85mm specifically are so special.

So what gives? Why are these focal lengths so important for anything except a legacy from a bygone age? Surely, especially in this day of excellent zooms, it's become nothing more than another number, and having decent coverage across a variety of focal lengths is more important than falling into some neat category from a system that belongs in the past?

Opinions welcome.

 

[Turbofrog]

Classic focal lengths have no importance whatsoever. No one can tell the difference between a 49mm, 50mm, and 51mm lens. In fact, many lenses that are listed as a given focal length and f-number are just rounded numbers.

They are just a useful shorthand for certain use cases. Everyone sees the world through their camera a little bit differently, so everyone's most comfortable with slightly different focal lengths.

Just pick the one that's good for you. With my zooms, I end up with a surprisingly number of shots clustered in the ~30-31-32mm range. Ain't no such thing as a 64mm SLR lens out there.

Not to mention, the way a focal length looks is highly dependent on the aspect ratio. An image shot with the same crop factor shot with any given focal length in 4:3, 3:2, 5:4, 1:1, or 16:9 is going to look different. Which makes it even sillier to try and inflict "classic" 3:2 focal lengths onto a 4:3 sensor.

That kind of dogma is silly, and you should just ignore it.

 

[barry]

Supposedly our eyes have a 'normal' fov somewhere between 35-50mm EQ...
The normal for a 35mm is around 42mm iirc, so about 21mm on mu-43.

Afaict, it was cheaper to make 50mm lenses for 35mm film, and then 35 and 28mm were the common wider lengths.
24mm was uncommon and quite expensive when they were available.

 

[Hendrik]

If you're saying do whatever works, I agree. But...

Having started with 2 1/4" square film and progressed later to 35mm, I do get how some might (might) have developed a comfort zone with given fields of view to the point of fetishism. In truth, I only ever shot 35mm with 50mm lenses, mostly. But to allow that to dictate that my lens purchases be made on considerations of field of view rather than quality or utility is a step too far for me. Even leaving zooms aside, with the advent of easy stitching software lens field of view becomes much less important.

It's a brave new world.

 

[oldracer]

The only classic range I think is significant is the portrait range, 85-105 or so. These give a pleasant perspective to portraits, with the shorter (85) more suitable for partial or full body shots and the longer (105) suitable for tighter head shots. Using a 50, for example, for a tight head shot makes the nose too prominent. Using a 200, flattens the face. With the 105 the face perspective looks similar to what we see with our eyes.

Re the 50 and "normal" eye FOV I have heard that and it makes sense. Personally, I have little or no use for that FOV and even in film days never owned a "50" except for my 55 micro-Nikkor.

 

[genesimmons]

yes i agree we are brainwashed to thinking certain focal lengths are required to achieve certain shots, i recently picked up a 75mm f1.8. i was very hesitant about it as to me 150mm is a very odd not common focal length and i was afraid i would hate it, turns out i love it for portraits, gets me far enough away from my subject and i can do half body or just head shots quite easy, and for bmx which i like to shoot it gets me far enough away, like mentioned numbers are numbers, shoot what u like for length

 

[SVQuant]

I learnt to shoot on a Rollei B35 and to me the 40mm focal length on 35mm film has an instinctual appeal. For several reasons (mostly affordability and availability), I shot a 50mm equivalent as my main prime for a long time. With m43, we are spoilt for choices in prime focal lengths and most of them are very affordable. Given that, there is no reason why you should not pick focal lengths which appeal to you, classic be damned.

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My only gripe is: Why don't we have a 22mm lens and maybe a 35-37mm as well?

 

[ionian]

I should be clear - I personally am a live and let live kinda guy, I just don't understand why someone would feel (for example as I read here, but it's not the only place) that 28mm equivalent is right and yet 30mm equivalent is weird. So weird that you couldn't recommend the lens.

 

[Turbofrog]

I learnt to shoot on a Rollei B35 and to me the 40mm focal length on 35mm film has an instinctual appeal. For several reasons (mostly affordability and availability), I shot a 50mm equivalent as my main prime for a long time. With m43, we are spoilt for choices in prime focal lengths and most of them are very affordable. Given that, there is no reason why you should not pick focal lengths which appeal to you, classic be damned.

From Four Thirds | Four Thirds | Micro Four Thirds | Chart(Lenses)
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My only gripe is: Why don't we have a 22mm lens and maybe a 35-37mm as well?

Haha, agreed, 22 (45 eq.) is a great focal length, too. I love the 90mm on my 6x7 MF camera, which has a 0.5x crop factor.

 

[oldracer]

I learnt to shoot on a Rollei ...

Yup. One of my first serious cameras was a Rollei, too:

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75mm "normal" lens

...there is no reason why you should not pick focal lengths which appeal to you, classic be damned.

Yes. This.

 

[TNcasual]

I should be clear - I personally am a live and let live kinda guy, I just don't understand why someone would feel (for example as I read here, but it's not the only place) that 28mm equivalent is right and yet 30mm equivalent is weird. So weird that you couldn't recommend the lens.

That's funny. My Leica Elmarit-R 28mm 2.8 lens is probably my favorite adapted lens. It is why I considered and eventually bought the Sigma 30 1.4. It is the closest equivalent lens in m4/3.

 

[Jonathan F/2]

Due to the more square'ish format of M43, I think being slightly wider from the traditional FLs make sense. 25mm actually feels really tight to me compared to the 20mm which feels like a better 50mm FOV equivalent, etc. I wish M43 would go just a tad wider on all the classic FLs.

 

[SVQuant]

I should be clear - I personally am a live and let live kinda guy, I just don't understand why someone would feel (for example as I read here, but it's not the only place) that 28mm equivalent is right and yet 30mm equivalent is weird. So weird that you couldn't recommend the lens.

Personally, I find both of them weird and wouldn't recommend either

I think that a lot of it comes down to appeal to authority where something is "right" because that's the way its been done and the masters did it that way. It takes more belief in yourself to recommend something more unusual. But if you are shooting m43 in world full of Canikon users, how much should you be appealing to authority anyways?

 

[Lcrunyon]

I only shoot fine art... 17.5mm black and white...

No wait... I don't shoot any of that.

 

[drd1135]

I've shot in equivalent terms from 47 to 60 for normal lenses. I did find 60 a bit long but otherwise made due just fine. It's almost like the standardization of sizes for certain produces at the grocery store. It just becomes an accepted standard that doesn't hurt enough to involve rebellion and changes.

 

[Rambling Sam]

I've no idea and don't think I've ever seen any definitive reason as to why lens designers decided to select the focal lengths they did - except in the case of 'standard' lenses, which was that these cover the AoV of human eyesight. 35mm film lenses evolved from those used by cine cameras, except cine cameras employ the diagonal format across the width, rather than the length of the frame, so the focal lengths of the lenses they employed are pretty much the same as those used on half-frame cameras.
I do have one possible suggestion and that when printing using film, with the paper held in an easel in the darkroom, the column of enlargers could only be so long, which causes problems if you are printing with the paper laid out 'Landscape' but you want to print with the easel turned 90 degrees to 'Portrait', but the because of the height available in most rooms, the column just isn't long enough, or it flexes etc.

Maybe, the longer 35mm lens designs were based on those already being manufactured for MF roll-film cameras? Maybe way back then, when producing distortion-free wide-angle lenses, things like barrel distortion set the limit at 35mm, based on what photographers deemed acceptable, but with telephoto lenses, this problem shows up less?

 

[Lcrunyon]

Whatever the reason they became standards, I agree with others on this post that the idea that one lens focal length 2mm off of another is somehow definitively better is rather silly -- especially considering how nominal focal lengths are not really exact, as well as how if you move a little bit forward or back you got the same thing. Sure, people can have their preferences; but that's on them, not the lens.

 

[T N Args]

I've just bought the 15mm f1.7, to add to my prime collection of 20mm, 30mm, 45mm and 60mm. Out of that lot, not a single lens (Well, maybe the O45 is damn close) is advertised as an equivalent of one of the classic 35mm focal lengths.....I just don't get why 28mm, 35mm, 50mm and 85mm specifically are so special.

If you are a lens maker, it makes sense to offer prime lenses with FL's consistent with past favourites. Because your target buyer, the experienced prime lens shooter, is skilled at pre-visualising the shot with lenses he/she has used for a long time. IMHO being comfortable that their learned pre-visualising skills will not be derailed is a factor for the target buyer. I don't think that the resultant images being any different is the driver here.

No doubt the manufacturers do their market research and get clear feedback from target buyers to stick to the familiar.

BTW your P20 is actually a classic FL.

 

[Andym72]

If you are a lens maker, it makes sense to offer prime lenses with FL's consistent with past favourites. Because your target buyer, the experienced prime lens shooter, is skilled at pre-visualising the shot with lenses he/she has used for a long time.

While I can see the sense in this, so much else about Four Thirds and Micro Four Thirds was about breaking with the past and with outdated orthodoxies (the sensor size, the sensor aspect ratio, telecentricity, fly-by-wire lenses, permanent Live View, disposing of the mirror box), I don't see why the standard had to keep to 25mm as being the "normal" focal length, when having 50mm as the normal on 135 film was just because of a readily available and easy to produce lens design for a 50mm prime lens which was easier to go with than designing a whole new 43mm lens.

When I've used software tools that graph my use of focal lengths from my library of images, the biggest peak is at 22mm, which is the nearest whole mm to the 4/3rd sensor diagonal (and it was imaging diagonal that the whole idea of a normal focal length is based on). And then the focal lengths of a series of primes, well at the very most, I would want the next longest prime to be about the same field of view as cropping to half the number of pixels, which means approx a √2 times bigger focal length, 1.414 times bigger.

This would give you a geometric series of focal length, each 1.414 bigger than the last. I like the idea of going a little wider because of the aspect ratio being closer to square, so I'd round 21.6mm down to 20mm, use that as the anchor point of the series and work from there (again, some of these numbers are rounded just like FL on most existing lens are):

10mm - 14mm - 20mm - 28mm - 40mm - 55mm - 80mm - 110mm - 160mm - 220mm - 320mm

 

[SVQuant]

10mm - 14mm - 20mm - 28mm - 40mm - 55mm - 80mm - 110mm - 160mm - 220mm - 320mm

And the OP seems to have put together a prime collection which is as close to this series as possible with the current lineup. In fact, this was something I noticed with the Panasonic prime focal lengths when I first moved into m43. I ended up going all Olympus for my prime collection, but I think that overall Panasonic's choice of focal lengths is actually more "native" to the system (though they seem to skipped the 28mm prime and replaced it with a longish 25mm). I would be interested to see if there will ever be a 100-110 f/2 prime from either vendor.