[Kerrowdown]

Why hang on to film carry overs??

I'm kinda hopeful that will will get FF back one day, for all my legacy glass.

Ducks as inbounds start heading my way.

[les3547]

If APS-C were all that had ever existed, we'd be used to the FOV a 100mm lens gave us while using it. And then if the 35mm format were subsequently developed, we'd be trying to get people used to the FOV a 100mm lens gave on the new sensor by expressing it in ASP-C terms. So the extrapolations are just communication devices to help people understand what they now have compared to the standard they were used to.

[GeneV]

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.

That would really be hanging on to film. You are comparing the lens to one with a similar FOV on 135. If we wanted to make comparisons easier, I suppose we could make more use of the diagonal angle of view figures.

[Blue]

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.

The trouble is, not all aps-c sensors are the same. Canon is different, Sigma is different while Nikon, Pentax and Sony are close. You end up with 1.5,1.6 and 1.7 factors for aps-c and those are just estimates. Then there are the 4/3 guys . . .

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Last edited by Blue; 07-09-2011 at 01:27 PM.

[Lowell Goudge]

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.

It seems you want to name a lens based , for some absurd reckoning that the lens definition should reflect the format it was designed for. Specifically te FOV

While this may offer some use when comparing different formats FOV is not a parameter that is unique to define the lens as it is related to the format of the sensor

I think the present naming is just fine focal length a d aperture define the main parameters of a lens and suffixes like DA define the intended sensor usage. Why reinvent the wheel( and make square in the process)

[mdbrown]

It seems you want to name a lens based , for some absurd reckoning that the lens definition should reflect the format it was designed for. Specifically te FOV

While this may offer some use when comparing different formats FOV is not a parameter that is unique to define the lens as it is related to the format of the sensor

I think the present naming is just fine focal length a d aperture define the main parameters of a lens and suffixes like DA define the intended sensor usage. Why reinvent the wheel( and make square in the process)

I would agree with this and say that focal length modifier and crop factor should be done away with. It's FUD in it's finest form. IMHO it makes a reasonably simple thing confusing...

[RioRico]

I think the present naming is just fine focal length a d aperture define the main parameters of a lens and suffixes like DA define the intended sensor usage. Why reinvent the wheel( and make square in the process)

Indeed! I was going to snidely suggest that those with such concerns could just calculate the FOV's of their lenses on their cameras and stick the numbers onto each lens. But that would just be a learning crutch. The goal is to know what each lens will do on each camera. I have some idea of what to expect with my FA50/1.4 or Kiron 42/2 or Zenitar 16/2.8 on my K20D vs my ZX-M. Oh, and I can cheat -- I can mount a lens and actually LOOK THROUGH IT and see it's FOV!!

[pacerr]

Oh, and I can cheat -- I can mount a lens and actually LOOK THROUGH IT and see it's FOV!!

Knock it off right now RR!

You're gonna invalidate this whole topic (again) if people learn to LOOK.

just calculate the FOV's of their lenses on their cameras and stick the numbers onto each lens

An' what if the original lens description had been FOV or AOV rather than FL in MM??

H2

[GeneV]

Oh, and I can cheat -- I can mount a lens and actually LOOK THROUGH IT and see it's FOV!!

And it's funny how that works, but after I do that once or twice, I pretty much know what the FOV is going to be.

[civiletti]

I would agree with this and say that focal length modifier and crop factor should be done away with. It's FUD in it's finest form. IMHO it makes a reasonably simple thing confusing...

How would you "do away with" crop factor? Make it illegal for people to mention it? Perhaps we should do away with the term "v8" because I drive an inline-4. People use terms they find useful. I sometimes mount a 165mm lens from the Pentax 6x7 system on the K-5. Crop factor is a useful metric in considering how this functions.

Focal length, maximum aperture, and image circle are the basic photo lens metrics. That's physics. Crop factor is a handy comparator of image size.

[RioRico]

How would you "do away with" crop factor? Make it illegal for people to mention it?

Just don't mention it during psychoanalysis.

I sometimes mount a 165mm lens from the Pentax 6x7 system on the K-5. Crop factor is a useful metric in considering how this functions.

I sometimes mount a 162mm EL on bellows on my K20D. I know that it's FOV will be about halfway between my 140mm EL and M42 180mm lens. Easy-peasy. But I still cheat...

Focal length, maximum aperture, and image circle are the basic photo lens metrics. That's physics. Crop factor is a handy comparator of image size.

Quite right. Those physical qualities, and the register (somewhat related to image circle) are primary, built-into the lens. Crap.factor is a function of the camera frame size vs other frame sizes, not a property of the lens. FOV is secondary, a function of focal length (lens) AND frame size (camera) and can't be assigned to an interchangeable lens by itself. FOV will even vary amongst dSLRs called APS-C but with slightly different sensor sizes.

The situation is rather like saying at a length of wire of 0.1in diameter is a high-E string. That depends on the instrument neck length, and how much you tighten it. It'll be different on standard guitar, mandolin, banjo, 3/4 guitar, etc. In this metaphor, the neck length is like camera frame size; the string diameter is like lens focal length; the pitch is like FOV. The string/lens qualities don't change. What they're used on, does change; that and how they're used determines the pitch/FOV. Something like that.

[Marc Sabatella]

My point exactly, if focal length is a product of lens design only then focal length multipliers and crop factors are fictional nonsense and should be dropped altogether.

It's not nonsense, although sone don't like the idea. Focal length itsrlf is not changed by cropping, but field of view is, and crop factor explains this perfectly. A 100mm lens doesn't become 150mm when mounted on APS-C, but a 100mm lens on APS-C does have the same FOV as a 150mm on 35mm film. That's useful for some people to know. Indeed, not useful at all for people without familiarity with film. But that doesn't make the concept nonsense - just misunderstood by many, and not all that relevant to most.

[Marc Sabatella]

I would agree with this and say that focal length modifier and crop factor should be done away with. It's FUD in it's finest form. IMHO it makes a reasonably simple thing confusing...

No, it does exactly what it is supposed to do, and does it well. You might as well argue we should do do away with conversion factors like 2.54 for tranlsating inches to centimetes. Sure, for most purposes, you just think in inches or in centimeters as appropriate. But for people used to one system, this conversion actor helps you understand how measurements in the unfamiliar system relate to units in the familiar.

[mdbrown]

No, it does exactly what it is supposed to do, and does it well. You might as well argue we should do do away with conversion factors like 2.54 for tranlsating inches to centimetes. Sure, for most purposes, you just think in inches or in centimeters as appropriate. But for people used to one system, this conversion actor helps you understand how measurements in the unfamiliar system relate to units in the familiar.

In retrospect, I would agree that crop factor makes sense but focal length modifier can be a confusing subject as it sounds like the focal length changes based on sensor format. Crop factor OTOH, is a more logical way of conversion... at least to me anyway.

Sensor terminology still seems to be stuck in bad spot. I would venture a guess that many, if not most people have no clue what APS film was (it is dead right?) or what a 1/2.33" or 1/1.7" format means in a practical sense. Seems to me that describing a sensor size by diagonal measurement or, better yet, like medium format makes more sense....

[RioRico]

In retrospect, I would agree that crop factor makes sense but focal length modifier can be a confusing subject as it sounds like the focal length changes based on sensor format. Crop factor OTOH, is a more logical way of conversion... at least to me anyway.

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]