[wallyb]

[lots of text]

And this still does nothing to explain real-world applications, and seems like just an exercise in mathematical wankitude. Marc, please note, I have no qualms with your calculations -- it's not something I don't understand the concept of. Your maths are sound now that I know you're not trying to say a lens takes in less light on smaller formats.

But it's just something that I don't know why anyone would care... how many times have you been in a situation where you knew if you just changed that aperture from f/8 to f/7.1, you'd have the perfect shot instead of a throw-away? Or if you had just shot at ISO 400 instead of ISO 200, man, that would've made all the difference in the world? I still defy anyone to be able to tell which shot is which with two pictures of separate scenes, taken at different but neighbouring apertures (i.e, a picture of a house at f/11 and a picture of a flower at f/10). And without that real-world application, this is just... so many posts over... nothing.

*All* of your benefits/analogies, like less noise, lower ISO, etc. that you gave for why you'd care about this hinge on one thing, and one thing only -- carrying over the same "level" of blurriness of OOF objects from one format to another. And again, I see no reason why anyone would need to care about that, and you still haven't provided an answer as to why you think so. You've given examples about what benefit it causes someone who already thinks this way, that it's important to recreate the same DOF between formats for some reason, but no benefit to someone who doesn't care about that.

[Marc Sabatella]

And this still does nothing to explain real-world applications, and seems like just an exercise in mathematical wankitude.

Then you clearly haven't understood a word I've written. If you can't see why someone already shooting at their maximum aperture and highest ISO on their camera in order to get a fast enough shutter speed (hint: some people shoot moving subjects in low light) would be interested in ways of getting a faster shutter speed for the same amount of noise, or less noise for the same shutter speed, then there is little else I can say. But I absolutely assure you, the desire for faster shutter speed or less noise is not "mathematical wankitude". It might not be something you have ever had had the occasion to care about it, but for a great many real world photographers in real world situations, it is as real a photographic concern as there is. Might not be your reality, but it is mine, and if the concern over high ISO performance or the desire expressed here for "fast" lenses is any indications, I'm hardly lone in this.

*All* of your benefits/analogies, like less noise, lower ISO, etc. that you gave for why you'd care about this hinge on one thing, and one thing only -- carrying over the same "level" of blurriness of OOF objects from one format to another.

No they don't. DOF has next to nothing to do with it - it's all about shutter speed and noise for me, with DOF playing a small role in deciding what price I'm willing to pay. Please try to actually read my previous responses rather than just post off-the-cuff replies without taking the time to understand what I've written.

[wallyb]

Then you clearly haven't understood a word I've written. If you can't see why someone already shooting at their maximum aperture and highest ISO on their camera in order to get a fast enough shutter speed (hint: some people shoot moving subjects in low light) would be interested in ways of getting a faster shutter speed for the same amount of noise, or less noise for the same shutter speed, then there is little else I can say. But I absolutely assure you, the desire for faster shutter speed or less noise is not "mathematical wankitude". It might not be something you have ever had had the occasion to care about it, but for a great many real world photographers in real world situations, it is as real a photographic concern as there is. Might not be your reality, but it is mine, and if the concern over high ISO performance or the desire expressed here for "fast" lenses is any indications, I'm hardly lone in this.

No they don't. DOF has next to nothing to do with it - it's all about shutter speed and noise for me, with DOF playing a small role in deciding what price I'm willing to pay. Please try to actually read my previous responses rather than just post off-the-cuff replies without taking the time to understand what I've written.

Oh, Marc, has it come to this? I have read all your posts. I guess I can't get away with writing concise replies and hoping you follow them, but must instead detail everything in excruciating minutiae.

If it's all about shutter speed and noise for you, then the idea of equivalence doesn't matter. Because using a 35mm f/2.0 lens on 135 at 200 ISO will put the same amount of light on the image plane as a 35mm f/2.0 lens on APS-C at 200 ISO will, which will yield the same shutter speed.

The only thing that the change of formats will have affected is the apparent focal length, which is just a crop (and upsizing, due to an assumed high megapixel count).

And that's what you said yourself:

And that's the point of "equivalence" - to tell us what focal length and aperture will give the same DOF/shutter/speed/noise characteristics between two different formats.

You really carry a film camera and a digital APS-C camera with you to each photo shoot, and restrict yourself to one ISO speed on the digital camera during the shoot, and take alternating pictures of each scene with each camera, using different lenses on each body? Because that's the only way equivalence would play any part in any real-world scenario. And the first paragraph of what I quoted above is just a melange of hypothetical ideals; a faster shutter speed for moving objects and better ISO performance -- who doesn't want that? But none of it has to do with:

And that's the point of "equivalence" - to tell us what focal length and aperture will give the same DOF/shutter/speed/noise characteristics between two different formats.

Still no concrete situation where it would matter, just ideals and meaningless phrases like "it's important to many real photographers" and "I assure you it's a real concern". So explain a real-world situation with it...

[brecklundin]

I blame it all on the silly season time of year...

[wallyb]

I blame it all on the silly season time of year...

You're off by two months, that's from a Treehouse of Horror episode (the season escapes me)

[brecklundin]

You're off by two months, that's from a Treehouse of Horror episode (the season escapes me)

hehehe...yeah, I know I think it was a number of years back now...hard to imagine that show is now one of the longest running shows ever.

Still I felt it worked better than this:

[Ben_Edict]

I might be a bit late to suggest this article. But I warn you: many would prefer to instead take photographs.

Thanks for THAT link!

I had a good laugh, this guy has logohroe!

He is not even able to use the numbers he gives correctly within a single sentence. And his "apparent aperture" is so nonsensical, that I simply cannot believe, how somebody can invest so much time (as this "essay" surely afforded) for that. What he says, in a short summary, is, that the "apparent aperture", which is simply the diameter of the entrance pupil (that is the usual term) varies with the focal length of a lens and its numerical aperture. Wow, he needs 40 pages to say that and in the course of that destroys any clarity. Especially the Introduction and the following Q&A section go to great length to make simple things hard to understand.

I cannot deny, he also writes some things, which are perfectly correct and true. Among them, what I tried to get through here for several postings: that the same numerical aperture (say f/2) leads to the same expsoure on any sensor or film format (given the ISO is the same, ofcourse).

This simple, basic truth, will be compromised, if we are introducing "equivalent apertures", as in some of the postings in this threads, because, the uninformed reader will automatically equal that much smaller "equicvalent aperture" with an accodingly smaller "light throughput".

The term of "equivalent apertures" does only one thing: it creates confusion, because it tackles only one photographic issue (DOIF), but compromises the clarity of another issue, namely exposure.

Ben

[Ben_Edict]

True - it's also the shutter speed determining factor for a given ISO setting. And this is the real beauty of "equivalence". If it was just about match DOF, I wouldn't care nearly as much, as I'm not one who often feels the need for shallwoer DOF than I can get already. But I do often find the need to great shutter speeds for a given level of noise.



True, but what is the *real world ramification" of this? As I said, the idea of equivalence isn't to say a 40/2.8 *actually becomes* a 60/4 or whatever. It is to say that is *behaves similarly* in certain important real world senses:

- same FOV
- same DOF (comparing f/2.8 on APS-C to f/4 on FF)
- same shutter speed for a given amount of noise (again, comparing f/2.8 to f/4)
- same noise for a given shutter speed

Are there other aspects of the picture taking experience that are *not* the same? Sure - but if I can't put those in to terms of FOV, DOF, shutter speed, or noise, then I am simply allowing them to be different. That is, I am saying I don't care if anything *else* varies for the purpose of making this comparison. I'm only making observations about FOV, DOF, shutter speed, and noise. There might be other things in the world worth worrying about, but that's simply not the point of equivalence.

Marc, if you find that concept helpful, than it is fine for you. But how you can now even mix "noise" into that equivalence is a complete mystery to me.

* Focal length and aperture (and entrance pupil) are physical properties of the lens.
* DOF is a convention, based on acceptable blurriness in final prints.
* Noise is a sensor property (unless you're talking about noise on the level where the law of uncertainty starts to be important).

So, if we mix up those very different technical or physiological aspects, it may by mere coincidence work for you now. But it won't work tomorrow, when other sensors with other noise behaviour will be available or not even today, for most other people, because you would need to redefine your equivalence for every possible comparisson pairing of FF and APS-C format cameras (not to talk about MF etc.)

I personally think, that this equivalence concept can be of some practical value only in two areas: to compare fields of view (or angles of view) and perhaps DOF. But as soon as properties as the aperture and the noise level get into play, that proposed equivalence gets so complicated and so highly individual, that it is completely worthless, because it would be a multitude of equivalences.

Ben

[ryan s]

One thing I've noticed about myself is that I don't really care about the "crop factor" anymore.

If I want a narrow DoF, throw on the 55/1.4 lens.

28mm isn't wide enough...time for the 16mm.

This doesn't mean I'm ignorant to the facts and theories...I'm ignorant to why I need to think, and contemplate, and do math when taking pictures.

On the other hand, I love the technical aspects of car audio. Frequency response graphs...impedance changes...Time Alignment settings...oh yeah. That gets me excited. Since I'm basically building my stereo myself, and I find I like the technical stuff behind it, I have educated myself.

I going to rebuild my sub's box for a ported 1.3 cubic foot net config, 25Hz tuning frequency, for an F3 of 25Hz ( ). Lowpassed at 63Hz actively, -18dB slope.

Anyone excited yet?

You need to hear about my front stage, that will be run off a 100 x 2 tube amp at 4 ohms, and I'm going to be high-passing the mids at 63Hz and low-passing them around 1,000Hz on a -12dB slope. Not to mention the 3" full rangers crossed to go from 450Hz all the way up to 20kHz! It's too bad those are 8 ohm drivers, so they'll only be getting about 30 RMS in the end. But with a .5mm Xmax and 12 RMS thermal handling, that should be a good start.

Now that's some numbers I like Shall I post some WinISD graphs?

If you glazed over my last few paragraphs...that's fine.

[GeneV]

On the other hand, I love the technical aspects of car audio. Frequency response graphs...impedance changes...Time Alignment settings...oh yeah. That gets me excited. Since I'm basically building my stereo myself, and I find I like the technical stuff behind it, I have educated myself.

I going to rebuild my sub's box for a ported 1.3 cubic foot net config, 25Hz tuning frequency, for an F3 of 25Hz ( ). Lowpassed at 63Hz actively, -18dB slope.

Anyone excited yet?

You need to hear about my front stage, that will be run off a 100 x 2 tube amp at 4 ohms, and I'm going to be high-passing the mids at 63Hz and low-passing them around 1,000Hz on a -12dB slope. Not to mention the 3" full rangers crossed to go from 450Hz all the way up to 20kHz! It's too bad those are 8 ohm drivers, so they'll only be getting about 30 RMS in the end. But with a .5mm Xmax and 12 RMS thermal handling, that should be a good start.

Now that's some numbers I like Shall I post some WinISD graphs?

If you glazed over my last few paragraphs...that's fine.

That's the most interesting thing that has been posted in the last page or so. I'd love to see your WinISD graphs.

With .5mm Xmas, you won't be getting much bass out of those babies, so I assume your subs cook.

[rparmar]

Then you clearly haven't understood a word I've written... Please try to actually read my previous responses rather than just post off-the-cuff replies without taking the time to understand what I've written.

Um, Marc, he's a troll. He understands nothing of what anyone else writes, fails to defend his own arguments and then accuses others of exactly what he is engaged in. And apparently his only satisfaction is in "winning". How sad! You've said all you can; any more is wasted energy.

[pardes]

I just ordered THIS MORNING the 50/1.4 for $414 from Amazon with expedited shipping to arrive tomorrow. Christmas present from me to me. Tonight, I checked the status and the price has dropped to $359. Sigh.

[Marc Sabatella]

I guess I can't get away with writing concise replies and hoping you follow them, but must instead detail everything in excruciating minutiae.

You could have cut right to a particular sentence or section of my post you took issue with and reply to that. As opposed to blowing off an entire post by saying "lots of text deleted", and then responding in a way that made it clear you didn't understand anything I wrote.

If it's all about shutter speed and noise for you, then the idea of equivalence doesn't matter. Because using a 35mm f/2.0 lens on 135 at 200 ISO will put the same amount of light on the image plane as a 35mm f/2.0 lens on APS-C at 200 ISO will, which will yield the same shutter speed.

Again, you appear to not bothered to read or understand what I've written. Yes, those two yield the same shutter speed - but different images in every other possible way. Different fields of view, different levels of noise, different DOF. There will be *nothing* in common about the two images except the effect of the shutter speed. What on earth would the point of such a comparison be? *This* is a comparison with no real world relevance.

You really carry a film camera and a digital APS-C camera with you to each photo shoot, and restrict yourself to one ISO speed on the digital camera during the shoot, and take alternating pictures of each scene with each camera, using different lenses on each body? Because that's the only way equivalence would play any part in any real-world scenario

Except the one I've patiently explained several times now - trying to understand what benefit buying a FF camera would have to me in terms of noise when shooting low light, and what lenses I'd need to realize that benefit. I can't think of a way to make that any clearer. This is a *very real* application to many people.

the first paragraph of what I quoted above is just a melange of hypothetical ideals; a faster shutter speed for moving objects and better ISO performance -- who doesn't want that?

Precisely. And that's why equivalence has real world relevance - because it tells you useful things about thing lots of people actually want.

So explain a real-world situation with it...

I have - several times now. The desire for lower noise levels in low light shooting is a real-world situation. Understanding equivalence is a key to learning how to *get* those lower noise levels.

[ryan s]

That's the most interesting thing that has been posted in the last page or so. I'd love to see your WinISD graphs.

With .5mm Xmas, you won't be getting much bass out of those babies, so I assume your subs cook.

Geeking out while other people could care less...

I'm going "tweeterless" with the 3" full range speakers (similar to computer drivers) so they don't have to move much. The way I'm designing their "pods" is so that I can swap in any ~3" speakers. The Fountek FR88s have a 3mm Xmax But their cone is aluminum. I'm going with an "all paper" front stage with the Bamboo/paper 3", and I'm going to try and squeeze 7" Usher paper/carbon fiber mids into the doors. 7mm Xmax on those...6.5lb total weight each

The sub will really only have to work from ~30-80Hz and it's already a low-end monster. My car's cabin gain gives me even more free output around 40Hz

Now for the techie stuff. Look at the "free" output just from porting the box:

Current sealed box, in orange


The bump in output is just where I need it...and I really don't think I'll be playing anything lower than my tuning frequency (25Hz).


My new toy, for the mids


Ok...enough geeking in this thread for me. I made a thread about thread jacking just yesterday Sorry...

[wallyb]

Um, Marc, he's a troll. He understands nothing of what anyone else writes, fails to defend his own arguments and then accuses others of exactly what he is engaged in. And apparently his only satisfaction is in "winning". How sad! You've said all you can; any more is wasted energy.

Debase the entire argument and the participants themselves, rather than give a defense

And you're calling me the troll?