[ElJamoquio]

As far as I can tell, equivalence says that DOF and noise are inextricably linked.

Absolutely correct (assuming a given sensor technology stays the same between different formats)

The only way to have less noise on any format is to shoot with less depth of field. Therefore, if you are talking about one aspect of the equation, you are talking about the others as well.

Yes, and yes (assuming the same shutterspeed, which is also a 'good' assumption).

[wilton]

Sorry... what? Are you upset because decades ago, people agreed to call a lens "normal" if its focal length is roughly the same as the frame's diagonal? And you'd like to silence me, the others who know this, and burn all the books that were written on the subject?

How could they do the math "based on one measurement"? The Mighty Crop Factor itself is computed using the format's diagonal, so you can't avoid finding out the normal in the process. It doesn't make any sense... sorry, but you're one of the people confused, not helped by "equivalence"

Two things, the first is that I don't want to silence you, just ask that you present something possible and useful, that is, for people who don't have the expertise to measure a sensor. The second thing is that I don't fully understand what you mean by "based on one measurement" all that one needs is a factor to work with and good science says we should apply that factor and test if it works, guess what? All the tests worked. You may argue that something was not accounted for, or there is a testing error but it's difficult to rationally argue with the results that came out

Rondec also states

But all equivalence does is tell you what lens has less depth of field on a given format. That's it.

I disagree with that. I have never shot the larger formats but, it seems to me that an aperture of 5.6 is pretty fast in those formats and 2.6 is pretty much a top lens (although I've read somewhere about a Tessar 45mm/1.9 MF lens). When the crop factor is applied to the aperture of those lens of a FF body then one understands that a similar look can be achieved.

I've read over and over that equivalence doesn't matter but photography is both artistic and technical. Both of these sides require reproduction of the look and feel of an image from time to time, whether for testing of equipment or for learning and growth or to correct a flaw or to measure oneself. I wonder how many Pentaxians have been to the Half Dome to "recreate" Adams famous piece? How many left their DSLR at home because they thought a cellphone would be sufficient for the job? The argument of just shoot doesn't really stand up sometimes. Trying for equivalence with every shot would be fool hardy but sometimes one needs to know how to get that particular "look" in a shot with different equipment and it's going to be trial and error or equivalence.

[Kunzite]

Please don't take it too seriously, it was of course a joke (I put an emoticon there!) Your "problem" seemed a bit funny to me, and it still does. Forgive my amusement!
Why would you need to expertly measure the sensor? Come on, all you need is a computer and Google: somebody else already did it for you! Like this: Glossary: Sensor Sizes: Digital Photography Review
And I'll ask again: if you are unable to find out the publicly available sensor diagonal (actually, a very rough approximation of - we were talking about normal lenses), how come you're able to find out the "crop factor"? You're very partial about what information you want to find, and what you don't

In order to precisely recreate Ansel Adams' works, I would not recommend a cellphone - but a photocopier
But if you're using him as an "example" on why "equivalence" is supposedly useful, please tell me, what are the 35mm-"equivalent" parameters for his Half Dome image?
And even if you get all those parameters "correct", including camera's position and orientation, is that enough?

What is needed is not "equivalence", but undistorted knowledge. Know your format, know what works and what doesn't, experiment, experiment more (it's "free" on digital!). Buy photography books, learn from them (not from the Internet, it's so full of pseudo-experts!) and experiment more.
And then, perhaps, you'll be able to take a photograph without attempting to photocopy another.

[Rondec]

Two things, the first is that I don't want to silence you, just ask that you present something possible and useful, that is, for people who don't have the expertise to measure a sensor. The second thing is that I don't fully understand what you mean by "based on one measurement" all that one needs is a factor to work with and good science says we should apply that factor and test if it works, guess what? All the tests worked. You may argue that something was not accounted for, or there is a testing error but it's difficult to rationally argue with the results that came out

Rondec also states I disagree with that. I have never shot the larger formats but, it seems to me that an aperture of 5.6 is pretty fast in those formats and 2.6 is pretty much a top lens (although I've read somewhere about a Tessar 45mm/1.9 MF lens). When the crop factor is applied to the aperture of those lens of a FF body then one understands that a similar look can be achieved.

I've read over and over that equivalence doesn't matter but photography is both artistic and technical. Both of these sides require reproduction of the look and feel of an image from time to time, whether for testing of equipment or for learning and growth or to correct a flaw or to measure oneself. I wonder how many Pentaxians have been to the Half Dome to "recreate" Adams famous piece? How many left their DSLR at home because they thought a cellphone would be sufficient for the job? The argument of just shoot doesn't really stand up sometimes. Trying for equivalence with every shot would be fool hardy but sometimes one needs to know how to get that particular "look" in a shot with different equipment and it's going to be trial and error or equivalence.

Ansel Adams' images aren't good examples, because he shot them on large format, on a tripod, stopped down as much as possible. An iphone could easily take those photos, although you would struggle with the lens on most phone cameras (not very high quality) and you couldn't print them very big. The shots that are hardest to recreate on smaller formats involve narrow depth of field and wider angle lens.

[Kunzite]

Please don't put words in anyone's mouth. No-one is saying you have 'nothing' if you don't use it, we're saying it's to your benefit to use it if you're considering adding another format or migrating between formats. That's all.

You said it yourself: "You can certainly go into these purchases completely blind instead". What's the meaning of this, if not ignoring there are other ways of making an informed decision?

I believe I'm better off not using it, beyond getting some AOV clues based on my APS-C experience (which, as repeatedly pointed out, is not "equivalence"). I would rather spend some time getting re-acquainted with and re-learning the new format, exploring it, seeing what works and what not - than trying to obtain the same thing as I have right now.

A few people really, really hate it because they think it:

1) Negates the need for other more hands-on system evaluation (it doesn't), and

2) "Proves" that larger formats are better than smaller (it doesn't,) and

3) Is "different" than what they're used to. I suspect that's because it suggests (to them) the removal of 'Exposure' from the throne of primary photographic concepts in favor of a strange usurper: Total Light. That's just not the way they were taught. It's an abomination.

Equivalentionists are spending a lot of time trying to "characterize" others, attempting to invent convenient "enemies" which can be "proved" wrong. Just sayin'.

You're really, really stretching now

Isn't it likely that our equivalence-acolyte has at least some exposure to one format - the one they're thinking of moving from or supplementing? Or are you imagining everyone is starting fresh, no camera in hand? I guess your objection works if it's always the latter.

Of course I'm not stretching anything. All assumptions should be made explicit, and I just enumerated one of them.
In our past discussion, I also explained how I migrated between formats, without having a baseline when deciding to buy new lenses. I never had "AOV-equivalents" for my DA Limiteds; yet I never bought lenses by guessing.

You fault equivalence for not being able to discern between sensor QE and read-noise, now, although you claim to have read JJ and Falk and would know that it can't and never made any such claims. Check.

No. That's not a "fault", that is a serious limitation - and I'm not talking about cvasi-abstract things like sensor QE and read-noise, but all the visual characteristics of an image which "equivalence" can't touch.
The fault is with the claim that you're getting "equivalent" images, then having to explain what you actually mean by equivalent - images that might not look similar (except for DOF and composition). The fault is with endlessly hyping up a tool which is barely useful.

I have a feeling that if I showed you how to use trigonometry and basic polygonal area equations to help you estimate how much it would cost to re-shingle your roof, you'd get angry and discount the equations involved because they don't encompass material cost or labor. It's those silly 'Trigonometrists', don't they know it's all a fool's errand and they should just give up their infernal maths!?!

Your feeling is in line with the mantra that "equivalentionists" are the Keepers of Knowledge and everyone who disagree the tiniest bit, usability of "equivalence" included, must be living in the dark ages. This is arrogant and rude.
When you actually have an issue with knowledgeable people who decided they'd better apply their knowledge in a different and more useful way.

[wilton]

Ansel Adams' images aren't good examples, because he shot them on large format, on a tripod, stopped down as much as possible. An iphone could easily take those photos, although you would struggle with the lens on most phone cameras (not very high quality) and you couldn't print them very big. The shots that are hardest to recreate on smaller formats involve narrow depth of field and wider angle lens.

I quite agree Kunzite, know the gear. part of that knowledge is understanding how it performs against other systems and whether a particular shot would start to fall apart on your system. The whole business of books and the net is to reduce experimentation and almost every book on photography invariable gets to crop factor (and by default equivalence) very early experimentation will not change that.
Rondec, I agree with you in full. I just want to query whether the iPhone's camera is inherently bad or is it a matter of being too cropped? . Could it be that the sensor is really not bad but too much algorithms has to be applied image due to it's size and the amount of light it receives? As with Rondec learning the gear seems to be what you are saying but it doesn't change the fact that equivalence is an important part of that knowledge.
I still would like some insight into why MF lens are fast at 5.6 but on a FF it is considered slow. Anyone?

[Kunzite]

Knowing how your system will perform is an obviously good idea. Knowing how it perform against other systems might be useful in particular circumstances. I know of no better way of knowing how it perform against other systems than building up experience with both your, and the other system.
I consider information restricted to angle of view and calculated DOF to be terribly incomplete.
I consider the assumption that you'd use two different formats in an "equivalent" manner dangerous; it must be challenged before proceeding.

I've got all the "size matters" issue clarified, without computing a single parameter, when I saw a projection of images - small format and medium format combined. Again, I strongly recommend seeing

MF lenses are not fast at f/5.6, who told you that? Pentax (Hassie, PhaseOne, Leica's) slowest lenses are f/5.6.
They don't reach f/2 for practical reasons: it's more difficult and expensive to make faster lenses covering a larger image circle.

[Andi Lo]

It only matters when you start hitting the limits of your system, which I frequently did with APSC. Can't get the DOF thin enough, cheap enough.

[ElJamoquio]

Know your format, know what works and what doesn't,

I only ever have to learn this once, and then I know it for every format.

[Kunzite]

No offense, but you're fooling yourself into thinking that you know. It's photography, not geometry.

[ElJamoquio]

No offense, but you're fooling yourself into thinking that you know.

I'm never offended when I'm correct!

It's photography, not geometry.

Of course. And I know exactly what settings to use on every camera made right now to get the picture I want, immediately, just by knowing one number.

[Kunzite]

So you would never want to take advantage of the amazing detail offered by the medium format to print larger? You would never use camera movements, if available? Or the extra "reach" of a high pixel density "cropped" format? You would use everything, from iPhone to the large format, in an "equivalent" way, based on a mere number? You're worse than DXOMark.

What I'm saying by "know your format, know what works and what doesn't, experiment, experiment more" can't be obtained by mere "equivalence".

[ElJamoquio]

So you would never want to take advantage of the amazing detail offered by the medium format to print larger?

I've used a medium format camera, only once though. If I'm spending your money I'd buy it again, sure. I know it doesn't offer any SNR because of equivalence, though, and I think 36x24 has 'good enough' detail.

You would never use camera movements, if available?

Of course. I'm in the middle of purchasing a TS lens right now.

Or the extra "reach" of a high pixel density "cropped" format?

extra reach, that's just funny. Plenty of pixels on almost every camera made today to crop quite a bit.

You would use everything, from iPhone to the large format, in an "equivalent" way, based on a mere number? You're worse than DXOMark.

You're reaching too much, and assuming things way outside the bounds of what I typed.

What I'm saying by "know your format, know what works and what doesn't, experiment, experiment more" can't be obtained by mere "equivalence".

And of course I'm saying that, of everything you have to learn, one of those things is DOF, another is SNR, and those parts you already know (or at least, I do) because of equivalence.

[Kunzite]

I've used a medium format camera, only once though. If I'm spending your money I'd buy it again, sure. I know it doesn't offer any SNR because of equivalence, though, and I think 36x24 has 'good enough' detail.

This is an EPIC FAIL and a perfect illustration of why the "equivalence" hype is dangerous.

Of course. I'm in the middle of purchasing a TS lens right now.

So you wouldn't even try before purchasing your TS and experimenting on the small format before. And after that you'd never surpass what the small format TS lens can do, if you somehow had access to a view camera.

extra reach, that's just funny. Plenty of pixels on almost every camera made today to crop quite a bit.

Crop capabilities are not included in the "equivalence" theory; so you, as a true believer in "equivalence", are not allowed to crop
By the way, current "full frame" cameras are ranging from 12 to 36MP; none of them can reach the same pixel density as a 24MP APS-C sensor. For most of them, the difference when cropped to APS-C would be easily visible.

You're reaching too much, and assuming things way outside the bounds of what I typed.

You posted in order to move the direction from my "know your format" to your "know equivalence".

And of course I'm saying that, of everything you have to learn, one of those things is DOF, another is SNR, and those parts you already know (or at least, I do) because of equivalence.

Since when is computing DOF and estimating shot noise (you're of course incorrect to assume to know SNR by mere multiplication with a "crop factor") is enough in photography?
Since when it is better than seeing with your own eyes?

[jsherman999]

I quite agree Kunzite, know the gear. part of that knowledge is understanding how it performs against other systems and whether a particular shot would start to fall apart on your system. The whole business of books and the net is to reduce experimentation and almost every book on photography invariable gets to crop factor (and by default equivalence) very early experimentation will not change that.

It's funny how someone could suggest books, yet discount equivalence in the same breath

I still would like some insight into why MF lens are fast at 5.6 but on a FF it is considered slow. Anyone?

Good question ^^, why is that?

By the way, if anyone's reaction to this whole subject is 'I understand, but it just doesn't matter to me,' that's perfectly valid. There are a few photographic concepts and sciences I understand but don't really care about, either. I think that's basically Kunzite's tack. I (we) just want to make sure the personal 'I don't care' messages get misconstrued as 'it doesn't matter to anyone', which would be a sad way to throw away an interesting and extremely useful tool and set of concepts. if you like your craft, you should understand it, I feel.

I've said it before and I'll say it again: in my view, (how can I put this succinctly...) I've bought/used hundreds of lenses on aps-c, I'm talking from direct experience... the differences between lenses on one format is generally overshadowed by the differences a format change brings, even when AOV is matched. Equivalence describes the differences mathematically and conceptually.

it can be used as a decision-making tool that works in conjunction with the minds-eye and other external sources of knowledge.

But again, what matters to you is your own decision - you don't need to bother with it at all, just like you don't need to read any books or forums on photography to jump right in and start shooting, just like you don't need to know anything about your car's engine to start driving, etc. Your choice.

And before this gets lost in thread-time, the reason this thread was resurrected: helping to bring it mainstream. (make sure you read page 2 especially.) I called for some such recognition by the 'major' players like dpreview in the first few pages of this thread, and my ask was answered.


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---------- Post added 07-28-14 at 12:37 PM ----------

Knowing how your system will perform is an obviously good idea. Knowing how it perform against other systems might be useful in particular circumstances. I know of no better way of knowing how it perform against other systems than building up experience with both your, and the other system..

See my comments on 'equipment churn.'

You can do yourself a favor by using equivalence as a jumping off point. Or you could just start buying stuff, I guess.

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