[mdbrown]

Partly it's a matter of language. Crap.factor is not self-descriptive in Anglish. In German the term is format-faktor which indicates that the FORMAT is what controls the FOV. And then we have focal-length-modifier, which is the b!tch-kitty term that leads to lens-morphing confusion. Aaarghhh...

[/me omits rant about the shortcomings of Anglish]

Agreed. When I first hear about crop factor I understood what it was and what it meant. Then I heard focal length modifier and that's when I got confused and thought that the focal length actually changed... then again I didn't stop to consider how the physical focal length could changed just because it's a DX format as opposed to FX...

[Jodokast96]

So you want to stop basing things on a format that's been around for nearly a century, and still being used, for a format that's been around for just over a decade?

[mdbrown]

So you want to stop basing things on a format that's been around for nearly a century, and still being used, for a format that's been around for just over a decade?

Not necessarily as I stated in the previous message. Consider though that 35mm might have longevity but it is going away... sooner rather than later I would guess. I don't think it matters though as this industry seems to hold on to obsolete terminology long after it's necessary or relevant. Case in point, sensor size: 1/2.33"... as I understand it that format is a carryover from long gone video sensors of some kind. APS... a dead film format that wasn't even that popular to begin with. Micro 4/3???

Matters not, things will continue as they are. I just fail to see the logic.

[RioRico]

I just fail to see the logic.

Usage trumps logic. That's why we still have units of measurement based on barleycorns.

[keithlester]

Maybe I should clarify myself. I know the focal length doesn't change but the original poster was saying why don't we adopt using APS-C to name it. On the APS-C a 100mm lens would have a FOV of 150mm. I was just trying to point out if APS-C became the new standard. And we through out the original naming, we'd just run into the same problem again when everything went FF or m4/3.

I hope that helps to understand my points earlier.

Still wrong, not a true statement at all.
A 100mm lens on APS-C will have the FOV of a 100mm lens. FOV does not change from one 100mm lens to another 100mm lens, it changes between bodies, if they are of different formats.

[Cambo]

This applies both to the sensor and the lenses. With the lenses such as the Pentax DA line or the Nikon DX line, both are designed for aps-c sensors. So, if you have say a 100mm DA/DX lens... why not just call it a 150mm lens? This would seem to reduce possible confusion. Same for the sensor, why call it aps when that format doesn't even exist anymore?? Seems to me it's like describing the size of a car as 1.2 or 1.5 wg (wagon lengths as per distance between axles of a covered wagon).

Is there something here I'm missing? As far as I know, focal length is determined based on 35mm camera size and distance from the back of the lens to the film to clear the mirror. If there are large changes because of the move to digital, it seems to me that it would make sense to make a DSLR the standard and base your measurements and such on that rather than hanging on to 35mm film which is nearly gone...

Ok... fire away

like this F* 300 which is now an F* 450 f=4.5 (at f8):



I rest my case.

Cheers,
Cameron

[RioRico]

A 100mm lens on APS-C will have the FOV of a 100mm lens. FOV does not change from one 100mm lens to another 100mm lens, it changes between bodies, if they are of different formats.

Indeed. Focal length changeth not; different frames crop different amounts of an image, is all. FOV depends on focal length AND frame size together. No lens has an inherent FOV, any more than a guitar string has an inherent pitch. And guess what? FOV can change with the SAME prime lens on the SAME camera! Notice what happens to FOV when you change focus, eh? Uh oh, another can of worms...

Oh, FOV *might* differ (VERY slightly) amongst various 100mm lenses on the same body, the same format. But that will be due to slight variations in their build. You'll see slight variances depending on how close your eyeball is to the VF, or even which eyeball you use. None of this is above the 5% level however; it's trivial.

But again: FOV IS NOT A PROPERTY OF A LENS!! Labeling a lens as such is meaningless and useless.

Usage trumps logic. That's why we still have units of measurement based on barleycorns.

Nobody questions this? Here we go: The grain, basis of English (non-metric) weight systems, was the weight of a barleycorn. The inch, basic of English length measurements, is the length of three barleycorns. USA and (old) English shoe sizes increment by... the length of a barleycorn. Many of us still weigh with grain-based ounces and pounds, still measure with grain-based inches and shoe sizes. The nice thing about this basis is that it can also be used to make beer. Cheers!

Grains and inches have been used for most of a millennium. I'll say that 135-based standards are good for at least a century, eh?

Hay Cambo: Nice parrot!

---

Last edited by RioRico; 07-11-2011 at 04:06 PM.

[Blue]

Just to throw the curve ball in there, not all aps-c sensors are exactly the same size, especially between different manufactures. As I pointed out before, Pentax is ~ 1.5 (as is Nikon and Sony), Canon is ~ 1.6 and Sigma around 1.7. That means the field of view for a Sigma 105mm EX DG macro lens will differ on Pentax, Canon and Sigma aps-c bodies.

[newarts]

All of that makes perfect sense. My point is why hang on to a standard based on something that is completely obsolete? At some point it makes sense to move the standard to something more current. HP in car engines is a good example... ......

Your point is very logical.

Unfortunately that's not the way language evolves. I think the reason that language evolves using slightly changed meanings of old words is that's the only way that people can hope to keep up with changes.

Very few people know what a horsepower actually is; even if they look it up they still don't *really* know what it is. But they do know that 200 is more than 100 and they know what is implied regarding acceleration.

You ask "My point is why hang on to a standard based on something that is completely obsolete?" I ask why not? (except for an occasional mars lander shooting off into space because of a meters vs feet error.)

[mdbrown]

Your point is very logical.

Unfortunately that's not the way language evolves. I think the reason that language evolves using slightly changed meanings of old words is that's the only way that people can hope to keep up with changes.

Very few people know what a horsepower actually is; even if they look it up they still don't *really* know what it is. But they do know that 200 is more than 100 and they know what is implied regarding acceleration.

You ask "My point is why hang on to a standard based on something that is completely obsolete?" I ask why not? (except for an occasional mars lander shooting off into space because of a meters vs feet error.)

In the case of sensors it is, at best, imprecise. For starters, APS is a format that failed in the first place and is long gone in the second. Sensors in digital SLRs vary in size... 23.6x15.7, 22.2x14.8, 28.7x19... as a matter of accuracy it's just not correct. Why not just use the diagonal measurement of the sensor. Same applies to compact digital cameras as well I mean come on... 1/1.7" or 1/2.33"??

I know it won't change but really, it should in this case. Sometimes hanging on to something like that might make sense but I don't see it here.

[dadipentak]

I was just trying to point out if APS-C became the new standard. And we through out the original naming, we'd just run into the same problem again when everything went FF or m4/3.

Right: since there are constant attributes associated with FL and format is a variable, it makes sense to stick with naming based on the constants.

[newarts]

In the case of sensors it is, at best, imprecise. For starters, APS is a format that failed in the first place and is long gone in the second. Sensors in digital SLRs vary in size... 23.6x15.7, 22.2x14.8, 28.7x19... as a matter of accuracy it's just not correct. Why not just use the diagonal measurement of the sensor. Same applies to compact digital cameras as well I mean come on... 1/1/7" or 1/2.33"??

I know it won't change but really, it should in this case. Sometimes hanging on to something like that might make sense but I don't see it here.

Oh I agree completely! Diagonal and ratio are all that's needed to completely specify a format. But as you say it probably won't happen regardless of the sense it makes.

I glean that you are not yet a WISE OLD PERSON. Wait 40-50 years and you too will understand (or at least have given up trying to understand.)

Q. Why don't we call a Giraffe a Tallhorse?
A. Because it looks like a Giraffe.

[mdbrown]

Oh I agree completely! Diagonal and ratio are all that's needed to completely specify a format. But as you say it probably won't happen regardless of the sense it makes.

I glean that you are not yet a WISE OLD PERSON. Wait 40-50 years and you too will understand (or at least have given up trying to understand.)

Q. Why don't we call a Giraffe a Tallhorse?
A. Because it looks like a Giraffe.

Not sure what constitutes wise old, I turn 50 this year... can't say that I'm wise though. In this case, I have been away from any kind of real photography since the late 80's. I come back and start again and so I'm looking at this like a newbie and so I'm at a point where I don't have the familiarity anymore with 35mm so it is of little use to me as a point of reference.

I've been carrying around a super-zoom point and shoot up until late so this is all somewhat new to me now. I guess I got annoyed when focal length modifier confused me...

[RioRico]

In the case of sensors it is, at best, imprecise. For starters, APS is a format that failed in the first place and is long gone in the second. Sensors in digital SLRs vary in size... 23.6x15.7, 22.2x14.8, 28.7x19... as a matter of accuracy it's just not correct. Why not just use the diagonal measurement of the sensor. Same applies to compact digital cameras as well I mean come on... 1/1.7" or 1/2.33"??

I didn't say I *like* the nomenclature, just that I grok why it persists. Even if I don't always grok what is meant. Fractional-inch sensor sizes? Meta-barleycorns, actually. Gimme a break! But the metrics are even worse. I keep a couple tables in my data spreadsheet to tell me just which dimension is what. Those are almost as much fun as tracking the sizes of film frames. Hint: 8mm and 16mm and 36mm and 70mm films can be (and have been) structured in many many ways. The lenses projecting light upon those frames have known focal lengths. The frames themselves keep shifting. As we said in my electronics days, "What's nice about standards is that there are so many of them!"

I don't know why APS is still a base standard (sorta -- my K20D's sensor is NOT official APS-C size). I know why it WAS a standard. Film cams were made to that standard, and then digicams, and by the time APS film failed, APS digital was quite entrenched. And nobody established a new, better standard. I'll say that again: NOBODY SET A BETTER STANDARD! Maybe it's because all sensors are grown by just a few firms who are all in cahoots. Yes, that's it, IT'S A CONSPIRACY!

So here's what to do: Build or buy a sensor fab. Make new-standard sensors. Give them new-sensor names: 456 for a 4x5x6mm chip, etc. No, that makes too much sense. Give them arbitrary names, like Euro paper sizes: A35, E10, B52... BINGO!! Then we can have confusion without tradition.

I do my bit. I refer to 135/HF (half-frame) size sensors, where APS-C is pretty close. Well, most APS-C's are pretty close. 110-film frame size is about the same as m4/3, so call those 110's. The 1/2.33" Q sensor? That's about the same as Super-8. Yeah, Olympus makes Instamatics and Pentax will make Super-8. It all just cycles around, with different names. [/me head explodes]

[Marc Sabatella]

In the case of sensors it is, at best, imprecise. For starters, APS is a format that failed in the first place and is long gone in the second. Sensors in digital SLRs vary in size... 23.6x15.7, 22.2x14.8, 28.7x19... as a matter of accuracy it's just not correct. Why not just use the diagonal measurement of the sensor. Same applies to compact digital cameras as well I mean come on... 1/1.7" or 1/2.33"??

Same reason most auto companies out names rather than numbers on cars, or that we refer to each other by name and not by, oh, some sort of DNA code designation. People find names easier to deal with in most cases. There's really nothing more to it than that, and it's not new or unique to photography. I mean, we use numbers when there are an ininifte number of possibilites and we need to be precise, but for lumping things onto a handful of standardized categories, names will almost always trump numbers.