Focal length "equivalence": a proposal

[jakeblu]

As Britain invented the steam engine, the steam turbine, the electric lightbulb, the telegraph, the telephone, television, the marine chronometer, radar, the glider, the jet engine, the tension-spoked wheel, the pneumatic tyre, the passenger railway, the rifled gun barrel, the military tank, the safety bicycle, the seed drill, the spinning frame, cement, the electric motor, the electronic programmable computer, the hovercraft, waterproof clothing, disc brakes, the electric vacuum cleaner and the photographic negative, to name but a few, all using 'imperial' weights and measures, it doesn't seem to have held us back too much, does it?!

I rather fancy many of those inventors used the metric system. Engineers and Scientist have been using metric for centuries.

 

[Terrywoodenpic]

Your new idea lenses might be marked with a field of view, but they wouldn't visually give the same field of view when fitted to a crop sensor and a full frame camera, would they? So we'd be back to square one again.

I know, let's just do away with crop sensor cameras and make everyone use a proper one (full frame) and then we'd know where we were! Joking aside, I think people soon get the hang of the current 35mm focal length equivalent system, so why reinvent the wheel? Unless of course it's for a tension-spoked one fitted with a pneumatic tyre and measured in inches, or parts thereof!

Fewer and fewer camera makers are providing lenses intended for, and that fit more than one sensor size. This has been the trend for some time now.
where there is doubt. as between the canon lenses that share a mount, there is already a need to differentiate between lenses of different coverage. It would make it clearer is the intended uses were added to the lens designation. eg. APS / FF. Field of view is essentially a more useful concept than focal length.

 

[snerkler]

Your new idea lenses might be marked with a field of view, but they wouldn't visually give the same field of view when fitted to a crop sensor and a full frame camera, would they? So we'd be back to square one again.

I know, let's just do away with crop sensor cameras and make everyone use a proper one (full frame) and then we'd know where we were! Joking aside, I think people soon get the hang of the current 35mm focal length equivalent system, so why reinvent the wheel? Unless of course it's for a tension-spoked one fitted with a pneumatic tyre and measured in inches, or parts thereof!

It works well for Nikon and m4/3 as they're easy numbers to multiply. It's blooming Canon who make it awkward with their 1.6x crop

 

[Terrywoodenpic]

I rather fancy many of those inventors used the metric system. Engineers and Scientist have been using metric for centuries.

Hardly Centuries...?????
It was first proposed in 1791 and was made compulsory in France in 1837.
Though there was much resistance to its use for many years after that.
America sill uses mainly Imperial derived units.

so at best "Some" people have used the metric system for some 171 years
We were not even taught SI units in my school days.

 

[Nostromo]

I'm the same, although with measurements, I drop in and out. Very small tends to be thought of in thou(sandths of an inch) up to a millimetre then millimetres take me up to an inch or so then a yard (on the golf course) or metre until we hit a mile, although when driving an LHD car, km slide in. Weights depend on which scales I'm using - I use imperial weights on the balance scales but tend to have the digital scales set to grammes. I'm about 18 stone and would have to look at the scales to see what that is in kg! Cider comes in pints (or cans - not sure how much they hold but it fits in a pint glass with a little room to spare.)

For lenses, surely the diagonal of the sensor is approximately the "standard" length and anything smaller is a wide angle and larger is a telephoto. Equivalence only really needs to come into the equation if the same lens is used on different bodies or a user uses 2 or more different sized sensors and needs to think about it.

If I'm working in small measures, I'll use mm, when I get to 13mm I start to use ½",1" etc, then 1' 2' and after that it's meters or yards. For me it's to do with visualisation, I know what 1mm' 2mm looks like but fraction me little to me.

 

[Mr Badger]

Fewer and fewer camera makers are providing lenses intended for, and that fit more than one sensor size. This has been the trend for some time now.
where there is doubt. as between the canon lenses that share a mount, there is already a need to differentiate between lenses of different coverage. It would make it clearer is the intended uses were added to the lens designation. eg. APS / FF. Field of view is essentially a more useful concept than focal length.

Canon do differentiate between the two systems, with EF-S lenses fitting crop-sensor cameras and the EF series lenses fitting every Canon EOS SLR camera made. If people can't get their heads round that then how would writing a field of view on them help? Also, would it be the 35mm field of view or the crop sensor field of view that got written on them (if so, which size of crop sensor) or would it be an arbitrary FOV based on something else that no-one really understood?

It works well for Nikon and m4/3 as they're easy numbers to multiply. It's blooming Canon who make it awkward with their 1.6x crop

Talking of confusing measurements, how can you have four thirds? Isn't that one and a third?

 

[Box Brownie]

The industry I spent more than 25 years had its roots in imperial measurement.

The unit we sold the material was "the inch unit" ~ this the linear inch based on a 24inch wide roll.......then the range of widths expanded to include 30inch wide........which was ok .........then for whatever reason combined metric width sold in linear inch units! Faster forward to the age of reason (for the industry) in the late 1990's / early 2000's [yes, as recently as that ] it went all metric i.e sold in SqM

The adoption took a little getting used to but once embedded only the oldies remembered the old units

So change is possible in photography, or should that be cameras, but would need to be universally brought in with all the magazines etc publishing conversion tables to re-enforce the 'method'.

 

[adrianday]

Is it the 1st of April again?

 

[jakeblu]

Hardly Centuries...?????
It was first proposed in 1791 and was made compulsory in France in 1837.
Though there was much resistance to its use for many years after that.
America sill uses mainly Imperial derived units.

so at best "Some" people have used the metric system for some 171 years
We were not even taught SI units in my school days.

British scientists were at the forefront of the push for a universal measurement system. Any scientists or engineers whose work was related to electricity would have been using the metric system since the mid 17th century.

 

[john.margetts]

British scientists were at the forefront of the push for a universal measurement system. Any scientists or engineers whose work was related to electricity would have been using the metric system since the mid 17th century.

They used the metric system over 100 years before the system was invented? Very clever!

 

[jakeblu]

They used the metric system over 100 years before the system was invented? Very clever!

Whoops hehe, I did of course mean the 18th 19th century.

 

[Mr Badger]

Whoops hehe, I did of course mean the 18th century.

See what happens when you work in base 100?

 

[jakeblu]

See what happens when you work in base 100?

Its even worse than that, I meant the 19th century

 

[LongLensPhotography]

I'm of the generation that's in-between ie I use both metric and imperial. Measurements I can talk in mm, cm, m, inches and feet but I get lost with yards. Weight I generally talk kg but not with food, I'd order 1/4lb of bacon for example but don't ask me what that is in grams. Weight of people I still work in stones and pounds. Distance I talk miles for large distances but meters for shorter distances. There's really no hope for me

You see it is very possible for someone like me to memorise all these countless and inconvenient units. Time is (h, min) is certainly one of them. The trouble is it all gets confusing: US gallon vs UK gallon, mile vs nautical mile and so on. Worse still is doing the maths with the numbers. Computers may make it all more trivial but on a personal level I really don't fancy remembering what and lb or oz is and then dividing that by another number and so on... Pint has the advantage of being a single pint or half a pint in a worst case, and it just relates to a few sips over a 0.5L. When it comes to 3 3/8 inch it just becomes painful. Inch to yard conversion and surface area measurements take it to next level still. Metric system keeps it all very simple along the way, and only because it is a true and complete decimal system.

 

[john.margetts]

The trouble is it all gets confusing: US gallon vs UK gallon, mile vs nautical mile and so on. Worse still is doing the maths with the numbers.

When I was first working in the early 1970s I worked for a Canadian firm called Magsep. I worked in the assay lab and one of our jobs was to calculate monthly production. Being of a scientific bent, we did this in metric tonnes (1000 kg or 2204 lbs). Our manager wanted that in Imperial tons (2240 lbs). The smelters wanted weights in long tons (2200 lbs) and head office wanted the figures in short tons (2000 lbs)

 

[Mr Badger]

I rather fancy many of those inventors used the metric system. Engineers and Scientist have been using metric for centuries.

Wrong, it would be done in 'imperial' weights and measures... particularly anything that needed nuts and bolts, because that's another thing Britain invented, the standardisation of bolt and nut sizes, which was done by Joseph Whitworth in 1841... and if you have a tripod you'll still be using a Whitworth 'imperial' sized screw thread to attach it to your camera, and let that be a constant reminder to you of the wonders of British imperial measures.

 

[LongLensPhotography]

When I was first working in the early 1970s I worked for a Canadian firm called Magsep. I worked in the assay lab and one of our jobs was to calculate monthly production. Being of a scientific bent, we did this in metric tonnes (1000 kg or 2204 lbs). Our manager wanted that in Imperial tons (2240 lbs). The smelters wanted weights in long tons (2200 lbs) and head office wanted the figures in short tons (2000 lbs)

Good job the departments weren't also translating English and French back and forth, or were they?

 

[LongLensPhotography]

Wrong, it would be done in 'imperial' weights and measures... particularly anything that needed nuts and bolts, because that's another thing Britain invented, the standardisation of bolt and nut sizes, which was done by Joseph Whitworth in 1841... and if you have a tripod you'll still be using a Whitworth 'imperial' sized screw thread to attach it to your camera, and let that be a constant reminder to you of the wonders of British imperial measures.

1. You don't need to relate the numbers or do the math in this case, only just match them up for each application. There is very little if any hassle for the end user.

2. The imperial units do not cleanly translate to metric which really slowed or stopped the transition. The soviets tried it when they looted car factories from East Germany after WWII. As you all know the end results weren't spectacular for that [and many many other] reasons

 

[john.margetts]

... and if you have a tripod you'll still be using a Whitworth 'imperial' sized screw thread to attach it to your camera, and let that be a constant reminder to you of the wonders of British imperial measures.

Nowadays, tripod screws are 1/4 inch UNC grade one. The difference is miniscule but ISO were not happy with antiquated Whitworth.

 

[Mr Badger]

Nowadays, tripod screws are 1/4 inch UNC grade one. The difference is miniscule but ISO were not happy with antiquated Whitworth.

Perhaps a case for the application of the measurement term 1/2 Whit? Banter aside, at least Whitworth saw the need for standardisation, and chose to pioneer the cause.

 

[jakeblu]

Wrong, it would be done in 'imperial' weights and measures... particularly anything that needed nuts and bolts, because that's another thing Britain invented, the standardisation of bolt and nut sizes, which was done by Joseph Whitworth in 1841... and if you have a tripod you'll still be using a Whitworth 'imperial' sized screw thread to attach it to your camera, and let that be a constant reminder to you of the wonders of British imperial measures.

But, engineers and scientist would have been using the CGS system of measurement, implemented int eh 19th century, which is a variation of the metric system, eventually replaced by the SI system, another metric system. Those screwing the nuts and fixing the bolts into place may very well have been using imperial, but those designing them would have been using metric.

 

[Mr Badger]

But, engineers and scientist would have been using the CGS system of measurement, implemented int eh 19th century, which is a variation of the metric system, eventually replaced by the SI system, another metric system. Those screwing the nuts and fixing the bolts into place may very well have been using imperial, but those designing them would have been using metric.

In the UK in the mid 1800s (the 19th Century) they were working in inches, and fractions thereof. Joseph Whitworth is attributed with introducing the 'thou' (1/1000 of an inch) measurement and accuracy to engineering... so are you trying to tell me he'd have designed his lathes and precision flat surfaces in metric then converted those measurements and produced them in 'imperial'?

Basically, it was Whitworth that pioneered 'precision measurement' in engineering, making a precision flat plane and measuring screw that had an accuracy of 1 millionth of an inch, not bad for 1840! He is also credited with the quote: "You can only make as well as you can measure", and those measurements were very much made in 'imperial' in his day.

 

[Cagey75]

I can't decide whether this is a serious post or not?

^^

 

[jakeblu]

In the UK in the mid 1800s (the 19th Century) they were working in inches, and fractions thereof. Joseph Whitworth is attributed with introducing the 'thou' (1/1000 of an inch) measurement and accuracy to engineering... so are you trying to tell me he'd have designed his lathes and precision flat surfaces in metric then converted those measurements and produced them in 'imperial'?

Basically, it was Whitworth that pioneered 'precision measurement' in engineering, making a precision flat plane and measuring screw that had an accuracy of 1 millionth of an inch, not bad for 1840! He is also credited with the quote: "You can only make as well as you can measure", and those measurements were very much made in 'imperial' in his day.

Your missing my point, scientists and engineers in the 19th century were crying out for a standardisation of measurement and they weren't asking for it to be imperial. It seems those engineers scientists and inventors you quoted managed to build and invent those amazing things, despite imperial, not because of it.

 

[frod]

I don't really care by what metric we compare focal length

as long as we put a stop to the abuse of f stop as a measurement and comparison of depth of field. Stop it!

 

[Mr Badger]

Your missing my point, scientists and engineers in the 19th century were crying out for a standardisation of measurement and they weren't asking for it to be imperial. It seems those engineers scientists and inventors you quoted managed to build and invent those amazing things, despite imperial, not because of it.

You're missing the point completely, to them 'imperial' wasn't an impediment, it was a measurement system they fully understood and that was accurate enough to enable them to make equipment to measure to one millionth of an inch accuracy by 1840.

'Imperial' was just as logical and familiar to those chaps as metric is to the modern generation, it's really just a rose by any other name. Joe Whitworth was right, you can only make as well as you can measure... and as long as the end job is right then it doesn't matter if we call that measurement metric, 'imperial', AF, UNC, BSW or sausages, as long as it's replicable to within the required tolerances.

 

[cj4now]

A mile is still a mile even if it's measured in Kilometres.

Excuse my ignorance on this, but why are all cameras not made with the same size of sensor anyway? Is it a cost thing?

 

[User.82148]

It creates and feeds this pointless and expensive process whereby so many people feel they need to "upgrade" to full frame, regardless of the fact that for the majority of them it won't have any practical impact on their photography

For me this was not a consideration to upgrade. Better low light performance, dof, IQ, lower noise etc were the main reasons. I do not bother to work out the lens equivalents between the various formats. Experience with the results from each format is enough for me.

No need to change the current system imo.

 

[john.margetts]

A mile is still a mile even if it's measured in Kilometres.

Excuse my ignorance on this, but why are all cameras not made with the same size of sensor anyway? Is it a cost thing?

If you put a 24 x 36 mm sensor inside a mobile phone, the end result would be enormous.

 

[redsnappa]

Measurements based on parts of the human body (oh er) such as thumbs, hands etc are older and would make more sense.

Sounds like a good plan until some one who has put their brain in gear realises that everyone's body parts are not exactly the same size. The big clue here I that shops sell clothes, shoes, hats and gloves in many different sizes.

 

[sirch]

Excuse my ignorance on this, but why are all cameras not made with the same size of sensor anyway? Is it a cost thing?

Various reasons, of which cost is one, making a bigger piece of silicon for the sensor is more expensive. Also things like lens size (diameter) are proportional to sensor size and people often want smaller cameras. Then again some people want bigger cameras...

 

[Bythesea]

Measurements based on parts of the human body (oh er) such as thumbs, hands etc ...

I'm sure that the mods measure one or two of the members on here by one of the parts of the body you haven't mentioned...

 

[Steve Smith]

It wasn't an issue until digital came along. Before that, everyone knew what the 'standard' lens was for 35mm, medium format, 5x4, etc. and worked it out from there.


Steve.

 

[snerkler]

If you put a 24 x 36 mm sensor inside a mobile phone, the end result would be enormous.

The whole back would have to be the lens

 

[LongLensPhotography]

If you put a 24 x 36 mm sensor inside a mobile phone, the end result would be enormous.

How about a 24 x 36 array of smaller micro-lenses / micro-sensors? That won't be big at all, and you could do some crazy stuff by combining the output with a powerful CPU. That's where the tech may go long term. The more area the better.

 

[onform]

Nah.