Is it time to do away with quoting lens MM?

rjbell

rjbell

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In the new world we live in with cameras in our phones and countless sensor sizes using the lenses mm has become much less relevant. We currently making calculations to work out 35mm equiv which means knowing the crop factor of the sensor, it just seem a bit stupid, with the majority of the population no doubt completely baffled by all these numbers.

Is it time for everyone to use a different measurement? Surely a FOV degrees measurement or something similar would be much more useful? I think gopro do this, what does everyone think?
 
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If everyone just quoted 35mm equivalent we'd all be fine. The majority of the population are not so much baffled as disinterested nobody I know who isn't into photography cares!
 
I tend to think in 35mm film "Full Frame" terms, so my Nikon lenses are what they say they are, and I mentally convert my Fuji lenses.
But yes. It would appear to be more logical to state the field of view in degrees, since that is really what we want to know.
 
Um, that's the point Bob.

To find a common reference irrespective of sensor size.
 
DemiLion said:
Um, that's the point Bob.

To find a common reference irrespective of sensor size.
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I agree but FOV wouldn't be a common reference point.

I have a directors viewfinder which has a rotating collar that is used to select the various formats of sensor (aspect ratio) and a separate selection for focal length. I suppose lenses could have a similar collar that could be positioned with respect to the sensor in use and display AoV, Aspect ratio or some other variable.

Bob
 
DemiLion said:
To find a common reference irrespective of sensor size.
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A common reference to what? What do you put on the box/barrel of a lens that fits cameras of more than one sensor size? - e.g. Canon which has the same mount for three different sensor sizes.

rjbell said:
We currently making calculations to work out 35mm equiv
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How many really do that in practice that rather than know from experience what an image from a 35/50/85mm lens is going to look like using their camera or cameras?
 
I still tend to think in terms of 35mm (or 135 format if you prefer) film terms since that's what I grew up using. After a few years using a 1.5x crop (D70) and then FF and now a combination of the 2, I'm quite happy converting from one to t'other and at lest it's relatively easy doing it with Nikon (and Fuji) since 1.5 is far easier than 1.6 (unless of course you do a lot of conversion from miles to kilometres and back!) Using zooms rather than primes form most things, it's quite easy to know which to grab, especially with the Fujis since I have some overlap (10-24, 18-135 and 100-400) so wide, standard, long! As long as the user knows what field of view they're going to get, the actual measurement is relatively unimportant Besides, I have a feeling that some (if not most) zooms (and probably primes) aren't exactly what they're marked as and also vary with focus distance.
 
Fov might be ok on a fixed lens camera like a gopro, but I'm happy with mm.
 
Alastair said:
How many really do that in practice that rather than know from experience what an image from a 35/50/85mm lens is going to look like using their camera or cameras?
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I think it applies when considering purchasing a different camera/system more than when using them. I have no idea what the focal length range is for my compact, but I know it's roughly equivalent to 28mm in 35mm film terms at the wide end and 200mm at the long end.
 
Alastair said:
How many really do that in practice that rather than know from experience what an image from a 35/50/85mm lens is going to look like using their camera or cameras?
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Me for one. If I'm sitting at a fixed point, I need to know which body to mount (FF, APS-C or APS-H) on a fixed focal length lens.
Pick the wrong body and I can end up either under or over lensed.
 
DemiLion said:
Me for one. If I'm sitting at a fixed point, I need to know which body to mount (FF, APS-C or APS-H) on a fixed focal length lens.
Pick the wrong body and I can end up either under or over lensed.
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FOV isn't going to help though is it? Because you still have to figure out which figure quoted is relevant to the body in-hand.
 
Which means that we are back to 35mm equiv - hence the OP looking for an alternative.
 
rjbell said:
In the new world we live in with cameras in our phones and countless sensor sizes using the lenses mm has become much less relevant. We currently making calculations to work out 35mm equiv which means knowing the crop factor of the sensor, it just seem a bit stupid, with the majority of the population no doubt completely baffled by all these numbers.

Is it time for everyone to use a different measurement? Surely a FOV degrees measurement or something similar would be much more useful? I think gopro do this, what does everyone think?
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I think you're trying to solve an issue that's not really an issue.
 
odd jim said:
I think you're trying to solve an issue that's not really an issue.
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I use 120 half frame, 35mm film, APS-C digital and my pocket camera. Four different sensor sizes and I pay no attention to lens focal length. On each camera, I know which lens does what and that is all I need to know.
 
You only need to know the standard focal length for your particular camera. Those lenses with a longer focal length than that will be tele,
and those shorter wide angle.
On a 5x4 it is 150mm or so
on a 6x9 camera that is about 100 to 110mm
on 2 1/4 75 to 80
35mm about 42 to 50 mm
if you know the FF crop factor there is no problem anyway

if you know your sensor size in mm a standard lens would be equivalent to the diagonal, which is easy to work out.

a minimum wide angle or street lens is about 2/3rd of this
a portrat lens near double a standard.
and a moderate tele anything over 3 times

none of us use so many cameras as to make this difficult. It is just a case of knowing stuff.

many fixed lens compacts put the 35mm equivalent on their zooms.
 
It's just a reference point, there's got to be one, why not 35mm?
 
Cagey75 said:
It's just a reference point, there's got to be one, why not 35mm?
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Why has there? Until the advent of AS-C digital we managed with no reference point and had many more sensor sizes (aka film formats) in use without confusion.
 
rjbell said:
ant. We currently making calculations to work out 35mm equiv which means knowing the crop factor of the sensor, it just seem a bit stupid, with the majority of the population no doubt completely baffled by all these numbers.
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mm has worked for donkeys years....change it to another method and there'll still be masses of the population baffled, me included probably!!

Why change a system that has always worked, continues to work and is practically foolproof.......

Perhaps we could do to change aperture settings / numbers whilst we're at it as that can be, ( for a beginner) just as confusing, if not more so than calculating 35mm equivalents!
 
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I always go with 35mm, its what I know and I'm happy with it!
 
The focal length is a fundamental property of the lens. Field of view is relative to the format used, so not much use if you have a full-frame lens and put it on an APS-C camera, or even a 4/3rds with an adapter :)
 
Asha said:
mm has worked for donkeys years....change it to another method and there'll still be masses of the population baffled, me included probably!!

Why change a system that has always worked, continues to work and is practically foolproof.......

Perhaps we could do to change aperture settings / numbers whilst we're at it as that can be, ( for a beginner) just as confusing, if not more so than calculating 25mm equivalents!
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Aperture numbers were changed from the original US system to f/ numbers giving us two separate f/ number sequences, one of which was later abandoned. Same with shutter speed sequences. While DIN speeds have remained constant, the ASA definition was changed in 1960(ish) to be more relevant. DIN 21 stayed DIN 21 but ASA 40 (aka DIN 21) became ASA 100 (aka DIN21). We coped.

When the old system becomes irrelevant or awkward it is time to change it.
 
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The other consideration is that the mm measurement informs the perspective and depth of field of the lens irrespective of sensor/film size crop factor. A 35mm 2.8 lens on e.g. Nikon 1.5x crop will give quite a different perspectival/DoF appearance than will a 50mm 2.8 on FF, despite the different in field of view being negligible (2.5mm).
 
I get really tired of reading posts where people have to also put the crop equivalent. I get the impression they dont really have much to say so use that as an excuse to look like they are offering advice. Of course the difference is true but it doesn't need to be said over and over again. To me when a lens states a certain mm i know how its going to look on my camera. If i put it on a FF i know what to expect, same goes for a crop. For me them is only an indication of what im getting.


Maybe im being grumpy but i think its over used and pointless most of the time.
 
LWSC said:
The other consideration is that the mm measurement informs the perspective and depth of field of the lens irrespective of sensor/film size crop factor. A 35mm 2.8 lens on e.g. Nikon 1.5x crop will give quite a different perspectival/DoF appearance than will a 50mm 2.8 on FF, despite the different in field of view being negligible (2.5mm).
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For an equivalence conversion of field of view and DoF, both focal length and f/number should be multiplied by the crop factor. Perspective is a function of shooting distance, quite independent of the lens.

dave_bass5 said:
I get really tired of reading posts where people have to also put the crop equivalent. I get the impression they dont really have much to say so use that as an excuse to look like they are offering advice. Of course the difference is true but it doesn't need to be said over and over again. To me when a lens states a certain mm i know how its going to look on my camera. If i put it on a FF i know what to expect, same goes for a crop. For me them is only an indication of what im getting.

Maybe im being grumpy but i think its over used and pointless most of the time.
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No maybe about it ;)

The fact is that we now use the same lenses across multiple formats, and that changes pretty much every aspect of performance so it needs to be mentioned. There is no easy answer, but the one that's been most widely adopted is to relate both focal length and depth of field to full-frame. I can't think of a better way, and most people - certainly those coming from 35mm film - can relate to it.
 
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I often quote the EFL as well as the actual FL I used, particularly when playing with long telephotos and OIS where the old rule of thumb for hand holding (1/focal length = shutter speed) relates to 35mm.
 
Mentioning the crop factor is one thing, but stating the FF equivalent is what i have an issue with in some threads

If someone has never used a full frame camera how is knowing what the FL is on that format going to help someone with a crop camera?

Ive seen loads of threads when someone is upgrading a kit or low end lens to something better, but within the focal range they already have. Then someone posts its not actually that FL on their camera. Why on earth do that? Do they think the poster is so stupid that they will think its one thing and get another, even though they can already shoot at that FL?
I can understand telling someone the 35mm (for example) is not really true 35mm on their crop camera, but if they already have a lens that covers that then what's the point of telling them something they already know, other than to look smart?

Like i said, im not against people being told, but some use it as a standard reply without seemingly even reading the thread or understanding what the person asking has or wants to achieve.

Mr Gumpy out.....for now :-)
 
Just remembered a real example.
A few years ago on dpreview someone was asking about changing from a 24-105L to a 85mm prime as he had been doing portrait work with the 24-105L and wanted a more narrow DOF.
As the thread went on some clever spark pointed out that on his 7D the 85mm lens wouldn't actually be 85mm, and of course quoted the FF equivalent. Then there was the usual thread derailment about FOV's etc.
This is the sort of thing im moaning about. No posting relevant info, but posting this rubbish when its not relevant,.

EDIT: Sorry, i forgot to add, the OP had mentioned he liked the idea of the 85mm prime, as it was a FL he uses a lot with his 24-105L.
 
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john.margetts said:
Why has there? Until the advent of AS-C digital we managed with no reference point and had many more sensor sizes (aka film formats) in use without confusion.
Click to expand...


Um, people have been using it since the early film days actually.
 
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