[rparmar]

You're not even reading the posts being made, so there's no need to spend time formulating an argument until you do.

I had no idea I was this powerful. Apparently, once I develop sufficient reading skills you will magically realise sufficient powers of logic and argumentation to prove your point.

I only wish I had some way of using this to my advantage, say at the betting track or to snag some of those killer eBay lens deals I keep reading about. I mean, now the FA50 has become so expensive it's almost impossible to afford a decent lens.

But for those I do purchase, I use cheap eBay metal lens hoods, generally sticking with those labeled "wide angle" so I don't have to worry about occluded edges. The last batch came from an outfit in India. They were dead cheap but don't take too much abuse.

(I have no idea how many or which emoticons would make this message parse correctly, so I leave them all out and trust to the reader.)

[wallyb]

I had no idea I was this powerful. Apparently, once I develop sufficient reading skills you will magically realise sufficient powers of logic and argumentation to prove your point.

So instead of properly reading through the recent posts made, and making a logical argument, you'd rather give up, admit I'm right, and engage in ad-hominem attacks? I just want to make sure...

[brecklundin]

This gets my vote as the 'Greatest Thread of the Week'

I Learned, I fought, I laughed, I cried.. it don't get much better

[brecklundin]

This gets my vote as the 'Greatest Thread of the Week'

I Learned, I fought, I laughed, I cried.. it don't get much better

ab-so-freaking-lutely!!!

[Wheatfield]

Wheatfield. it isn't. The thing is: lens properties are physical, unchangeable properties, like focal length and aperture.

Depth of field is mere convention, because it depends which size of the circle of least confusion appears acceptable. This is wholly dependent on the size of the final image and all the given sizes you'll find in the literature (for example the 0.025 mm acceptable circle of least confusion diameter for 35mm film) are based on assumptions or conventions (size of print, viewing distance), not on simple optics.

My opinion is, that it is not helpful in the least to mix hard facts (aka physical lens properties) with assumptions.

ALSO, I can still see no valid explanation, why the aperture would be different between different film formats (as it is a hard physical property of the lens). At least all the numerical aperture values remain unchanged between film formats, there is simply no other way.

Ben

P.s.: a personal note: I just thought, I am getting as grumpy in my answers as you sometimes have been lately! Haha…

Ben, judging from you more recent posts, it is, I believe, safe to say that we are actually on the same page. I've always thought that the depth of field thing gets introduced as a red herring. The reality, for me at least, is that it matters not a whit that my depth of field is altered between the two formats.
There are certainly advantages to full frame cameras, no matter what the cropped format apologists would say, higher iso noise is lower with reasonable pixel count full frames, and having a real, full frame viewfinder is a real pleasure after using an APS-C sized viewfinder.

[Class A]

... higher iso noise is lower with reasonable pixel count full frames...

FF has no noise advantage (only a lens advantage, please see the "no noise benefit" thread I referenced a couple of times now) and pixel count (density) does not influence noise.

This is why letting angles dance on a pin sometimes is useful, in order to avoid misconceptions about technical questions.

We don't need to be all on the same page, but we should be tolerant of each other's strengths.

[PentaxForums-User]

I bought my FA 50mm 1.4 off here for $175 hand-delivered to me this summer in June 2009!

I wondered the same thing... that the prices are skyrocketing on many lenses!!!

[rparmar]

So instead of properly reading through the recent posts made, and making a logical argument, you'd rather give up, admit I'm right, and engage in ad-hominem attacks? I just want to make sure...

To be accurate I am:
a) giving up
b) admitting you are wrong, and
c) engaging in humorous asides.

So you got one of them right.

Typically you blame me for the very behaviour you exhibit. Or is continuously questioning my ability to read not an ad hominem?

On the contrary I know exactly what you wrote and have called you to defend it, which you cannot do. Some might admit they were wrong and learn from their mistakes, instead of lashing out randomly. Oh well, I hope you have better luck imposing your world view on others elsewhere.

[wallyb]

To be accurate I am:
a) giving up
b) admitting you are wrong, and
c) engaging in humorous asides.

So you got one of them right.

By giving up, you automatically declare me the winner, because you are unable to come up with any pertinent follow-up argument (actually, you weren't even able to read the posts leading up to your forfeiture).

You surrendered, and I'm fine with that

Typically you blame me for the very behaviour you exhibit. Or is continuously questioning my ability to read not an ad hominem?

On the contrary I know exactly what you wrote and have called you to defend it, which you cannot do. Some might admit they were wrong and learn from their mistakes, instead of lashing out randomly. Oh well, I hope you have better luck imposing your world view on others elsewhere.

No, you didn't "call out" anything. You made an irrelevant post and didn't understand that I never said comparing f/19 and f/22 was your point. For some reason, you implied that I said it was part of your argument (I'll quote you -- "Or not, since the f/19 and f/22 quoted was part of your argument, not mine." -- makes absolutely no sense), so clearly you were unable to read the posts I made. And "lashing out" when you were the only one to use ad-hominem attacks, and "imposing your world view on others"? Ouch. Now you're really trying too hard! Are there going to be any examples of Godwin's Law coming up from you as well?

[Wheatfield]

FF has no noise advantage (only a lens advantage, please see the "no noise benefit" thread I referenced a couple of times now) and pixel count (density) does not influence noise.

This is why letting angles dance on a pin sometimes is useful, in order to avoid misconceptions about technical questions.

We don't need to be all on the same page, but we should be tolerant of each other's strengths.

You are depending on the red herring of DOF to cloud reality.
Take away that parameter (and it is one easily taken away as it is a non sequiter) and your theory pretty much falls on it's face in a puddle of drool.
Let me give you an example of reality:
A friend brought me a file from a Nikon D3. It was shot at our local police academy, under horrid lighting conditions at ISO 1600. When I adjusted the levels to see how much noise was in the dark blue trousers that the cadets were wearing, I was surprised to see the nap of the fabric and the stitching in the seams.
What I did not see was noise.
I know that if I had done a similar picture with my cropped frame Pentax it would have been a noisy mess.

[Marc Sabatella]

The only problem is: why? Why would you want to think that?

Um, I think it pretty obvious. I would love to be able to take pictures where I can get less noise for a given shutter speed in low light - wouldn't most of us? So it is quite relevant for me to think about what equipment I could purchase that *might* accomplish that, and then consider what tradeoffs I'd have to make along the way in terms of cost, size, and DOF.

DOF is actually the least of these concerns, but I'm already painfully aware that DOF is uncomfortably shallow at, say, 100mm and f/2.8. So knowing that in order to get better shutter speed / noise performance comes at an additional penalty in DOF does give me pause.

it is simply a numbers game that I still don't see the practical use for.

I don't see how I could possibly explain it any more clearly. I want a given benefit (less noise for a given shutter speed) and want to know how I could spend my money to get that, and what tradeoffs this would require making along the way. Aren't these exactly the same things one thinks about when making *any* purchase?

[Marc Sabatella]

But Marc and Class A, aperture is more than just the DOF determining factor.

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.

And the simple , basic and all important function the diaphragm serves as controling the amount of ligh falling through the lens, gets not only lost in your argument, it will also be falsified! Because f/2.8 is f/2.8, completely independent of sensor or print format. The basic function of the aperture does very obviously not adhere to your calculations.

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. If you happen to care about some *other* photographic consequence of aperture, then the equivalence might or might not hold. But so far, you haven't really clearly identified what effect you might be talking about. Yes, it's true that as far as numbers and physical measurements go, 40/2.8 and 60/4 are very different. But we're talking about the *images* these lens produce.

So what I'm asking you is - what *difference* do you expect you'd be able to see in the *actual pictures taken* (between a 40mm lens at f/2.8 on APS-C and a 60mm lens at f/4 on FF)? I'm telling you - and this is not opinion, but easily calculatable fact - they'll have the same FOV, the same DOF, and the same level of noise for a given shutter speed (assume the same sensor technology). If there difference, it's going to have to lie somewhere else.

And the whole DOF discussion concentrated on the on sensor format is completely pointless. Because as we agree, the final output determines "visible" DOF. So, what about the typical screen printed ad poster at the next bus stop. How will you define DOF, when dealing with a print resolution of 10dpi?

You're making this needlessly complicated. I'm not interested in calculating precise DOF figures. I'm simply observing that *whatever* the DOF turns out to be in that print when shooting 40/2.8 on APS-C, the DOF will be *exactly the same* in that print when shooting 60/4 on FF. This is just a fact; there is no possibl counterargument to it any more than there is any possible counterargument to the simple fact that 2 + 2 = 4. If you want to know what DOF you will get shooting 40/2.8 on APS-C for a given print size, the answer is: "you will get exactly the same DOF at that print size that you would get shooting 60/4 on FF". this fact is not up for debate; it simply *is*.

[Marc Sabatella]

You are depending on the red herring of DOF to cloud reality.

Not really; it's just *one* of the things that will necessarily vary in order to get an improvement in noise. Chances are in many cases, it won't be the most field-relevant - size, weight, and price will.

Let me give you an example of reality:
A friend brought me a file from a Nikon D3. It was shot at our local police academy, under horrid lighting conditions at ISO 1600. When I adjusted the levels to see how much noise was in the dark blue trousers that the cadets were wearing, I was surprised to see the nap of the fabric and the stitching in the seams.
What I did not see was noise.
I know that if I had done a similar picture with my cropped frame Pentax it would have been a noisy mess.

Had you shot at the f-stop, ISO and shutter speed, the noise would have been one stop worse - at least, that's the difference made by the difference in *size* between the sensors. Who knows what difference is made by the sensor technology itself, or different NR algorithms, etc. But the "FF-ness" of the D3 was good for one stop.

The idea of equivalence is to allow you also consider what *else* had to change to get that advantage. In order to get the same FOV between the two cameras means you had to use a lens with 1.5X longer focal length. And in order to get the same f-stop on that longer lens means also larger glass elements. Basically you need a lens 1.5X times as large overall in order to realize that benefit. And depending on what focal length we are talking about, the lens might well be much *more* 1.5 times as expensive, too. Or it might not - some fields of view turn out to be wins on FF, others turn out to be wins on APS-C. the beauty of equivalence is that it gives us a way to figure out which is which.

If you're talking "normal" ranges, FF wins pretty handily. Say you were shooting a 35/2 on APS-C; all you'd need on FF to get that one stop win is a 50/2. Here, the lens required to give a win to FF is no larger, no heavier, and no more expensive than the APS-C lens. You get a shallow DOF at 50/2 on FF than at 35/2 on APS-C, but you are correct to observe that in many cases, this doesn't matter, or would indeed even be a good thing. Of course, there are cases where it *does* mater. We don't mention DOF to cloud the issue; we mention it because it is a necessary part of the equation mathematically, not because anyone assumes it is a term people would always care about. And for the times when DOF *does* matter, it's nice to know the equivalence covers that as well.

On the other hand, at the telephoto end, it is considerably less clear even without taking DOF into consideration. If you were shooting the APS-C camera at 135/2.8, you'd need a 200/2.8 to realize that one stop win in noise. If you were shooting the APS-C at 200/2.8, you'd need a 300/2.8 to realize that same win. I think you'll agree that in both cases, you're looking at a significantly larger, heavier, and more expensive lens, so that's what I mean abut paying a price for the improvement in noise. The fact you *also* pay a price in DOF is, as you observed, not normally the most important issue - and indeed, often, people *want* that shallower DOF. Equivalence isn't about making value judgements - it's about telling you which focal length / aperture combinations will produce the same results between APS-C and FF, and what focal length / aperture you'd need to get less noise, shallower DOF, deeper DOF, faster shutter speed, slower shutter, or whatever effect it is you want.

With equivalence, we can quickly see that a 200/4 on FF is "equivalent" to the 135/2.8 on APS-C - they will provide the same FOV, the same DOF at each click of the aperture ring, and - most importantly - the same amount of nosie for a given shutter speed. That is the fact that the 200/4 is a stop slower thn the 135/2.8 exactly nullifies the one stop advantage of FF in terms of noise. In order to get the same shutter speed out of the 200/4 on FF, you'd need to go one stop higher in ISO than you needed to with the 135/2.8. So if you shoot with a 200/4 - which is *already* a larger and heavier lens than the 135/2.8 - you don't get any benefit from FF at all - you are just needlessly carrying around a bigger and heavier camera and lens.

Conversely, equivalence lets us see that shooting a 135/2 on APS-C would give you the same DOF as the 200/2.8, but more importantly, that it *also* would nullify the noise advantage of FF, because the 135/2 would allow us to shoot the APS-C camera one stop lower in ISO.

Whether or not a 135/2 ends up being cheaper / smaller / lighter than a 200/2.8 is another matter. But that does help illustrate the basic point here. In order to realize a one stop advantage at the telephoto end over what you get with a given lens on APS-C, you need a lens 1.5X times as big. The interesting part is, *it doesn't matter if you also go to FF*. That is, you can *either* go to FF nd a larger 200/2.8, *or* you can stay with APS-C and simply upgrade the lens to 135/2. Either way you get the same one stop advantage over where you were before. The 200/2.8 on FF and 135/2 on APS-C are *equivalent* in this extremely important sense - the 200/2.8 on FF does *not* allow you to enjoy a one stop advantage in noise over the 135/2 on APS-C.

Obviously, getting the faster/larger lens for APS-C is not always a viable option, and that's why FF often makes the difference - because it makes it most feasible to actually get that bigger lens in many cases. But make no mistake - at the telephoto end, you don't get a win in noise from FF without a much bigger lens (and shallower DOF, for whatever that happens to be worth to you).

You are depending on the red herring of DOF to cloud reality.

This is the first thing in the last three pages I have understood enough to agree with...

"Cloud reality" is exactly what I want my DOF to do... The cloudier the better!!!!