[Andi Lo]

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No, because you expose like a 1.8 lens, not like a 2.8 lens.

So, like it was said earlier, equivalence is for DOF and FL, not for exposure.

You're right but bear in mind that FF usually have one stop high iso advantage, so it evens out. If you're buying 18-35mm/1.8 because you want the lowlight capability and dont need APSC advantages, consider FF since 28-75/2.8 can be had for $250 used, and it's lighter!

I keep thinking to buy the 18-35 (to run dual body with D600/85mm) but I remind myself that I might as well save up a bit longer and buy another D600.

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Last edited by Andi Lo; 10-10-2014 at 07:02 AM.

[jsherman999]

"Of course, you could just shoot with one format, too - the D810 - and just stop down 1.2. and then 2 stops to match the K-r and m43 DOF, and about match the noise and DR."

But, of course, then you would be 1.2 and 2 stops underexposed, we have already established that (with great pain) about equivalence ...

Of course - and you would in that case increase image brightness by bumping ISO. Once you stop down, you match the smaller formats in FOV, DOF and noise as well.

This is why aps-c (and m43) is a subset of FF. Equivalence explains it all

[normhead]

I would like to respond to what you are saying Normhead but you are not making any sense at all. if you want to enage with the discussion then dicuss the points raised. I don't know why you are calling Northrup a liar, I suspect you haven't seen the video or don't understand it.

I'll simplify for you...
1.The amount of light captured is relevant to noise. Not to exposure. Mixing up the the term of noise with the term used of exposure is nonsense. Northrup knows better, he's making a point. Why doesn't Northrup use the proper noise units? Because in many cases they are insignificant. Where as saying the are "more than one stop" makes them sound huge.

2.Aperture relates tot he intensity of light hitting the light sensitive material. Not DoF. DoF can be measured in inches or mm or meters to whatever. There is no reason to measure in Stops. Tha's not what ƒ-stops are.

3. The big square on his comparative sensor size chart should be a 5x7 scanning back. Then an MF then an FF. By using an FF instead of the largest digital format available he implies that FF is some kind of standard to be emulated. That everything should be compared to FF, when in fact there are 2 or 3 larger formats.. Again, very manipulative. IN fact through out his whole video he implies that everything should be rated by it's noise performance, and light gathering performance compared to FF. That's just FF propaganda.

4. He claims that ISO is "obsolete" because it's an old standard. The funny thing about that is, it still does exactly what it was designed to do. And is still very useful in that regard. His ideas threaten the simplicity and ability to understand what ISO does and what its for.

5. His claim that Aperture should be used to define DoF is equally confusing and unnecessary.

SO why is he doing this?
First of all, he's not a high resolution guy. Or he'd be using a 645 or Scanning back. He's not a "use the most light for your image" guy or he'd be using a scanning back or a 645. He's a guy who defines the whole world in terms of FF format cameras.

To the point where he argues that the Full Frame DoF values are the "normal" values, and every other format needs to be converted to it.

The man is a sophisticated propagandist. I can understand how it would be possible to get sucked in. But he isn't any more than that.

Why does he talk in terms of stops...not the actual values? Only one reason, photographers recognize stops and think they know what they mean. If he just said, at 8 mm the DoF @ ƒ2.8 of a 50mm FF will be about 6 mm and a 35mm APS-c will be about 12... see the difference? Now it's not FF is the standard and APS_c is somehow inferior. It's do I want the 6mm of DoF or the 12mm. Now you have informed debate. Now you know what you're talking about. If you want your whole subject in focus you can say "well. my subject is 6mm deep, the FF should be perfect." Or you could also say My subject is 12 mm deep, APS-c would be better."

Don't check my math, these are examples to illustrate a point. Not real world examples. (There's nothing worse than when I put up an example and someone says "your math is not right." I really don't owe it to anyone to go to the DoF tables and figure out a real example. I'm not being paid for this.)

You see the difference? One is knowledge of the two lenses and formats giving you real information on how to attack a technical situation. And you won't always choose the Full Frame. The "what is the DoF ƒ-stop or how much light does the sensor collect tells you next to nothing. One is technical information. One is technical gobbledy goop. And that's because he's applying terms with strict definitions to functions, noise and DoF, to which they do not apply.

The only measure of DoF is inches/feet or mm/meters. (Not Aperture)
Noise is usually measured as an RMS (root mean square) voltage. (Not ISO)

Using those measures gives you a clear understanding of the effect of those elements on your image. Talking about stops with respect to either DoF or ISO does not.

I hope that's a little clearer for you.

[marcusBMG]

You - and Tony - are mostly correct. I say 'mostly' because putting the equivalent aperture right on the lens barrel or camera face does three slightly negative things in addition to the positive things -

Thanks for the post jshermann999 - clarity

However I should apologise for my OP - it was carelessly thrown in and I didn't understand the distinction between total light and light density (intensity) This is now clear to me. My analogy with eg TC's is incorrect.

I have been scrutinising the Northrup videos. At ~8mins in the long one he says (discussing ISO, SNR)

" ISO basically amplifies the amount of light to achieve a particular level of brightness"

Then at ~ 10mins he says:

"..ISO has a co-dependent relationship with the sensor size. The small sensor is not gathering enough light so ISO over there is, like, 'don't worry I'll just crank it up I'll amplify everything'. And that does allow us to use the same settings, but not to take the same pictures."

All very muddy with hindsight. I just want to say that it is at this point IMO he should be clear and say.:

"of course I am not saying this affects the exposure, exposure doesn't depend on this but on the light intensity, which depends upon the real aperture not any equivalent/calculated aperture..."

Like it does in the dpreview article.

He does not do so, and in fact he does not say this at any point in any of his videos. He is cognisant of this point, he mentions it in responses to comments. I do not know whether this is merely careless on his part, or perhaps an unfortunate consequence of trying to keep things simple.

[jsherman999]

Assuming you are shooting at f5.6, iso 100 and 1/180 second with studio lights, do you honestly think, Jay, that you could tell the difference between the formats? I couldn't in that situation, even if technically full frame is still "one stop better," it is pretty meaningless in this situation.

The original example implied that you would need "f/5.6" to get correct exposure no matter what format you were using - and that's it, nothing more needs to be considered.

I was pointing out that f/5.6 would still give you different images on the three formats (m43, aps-c, FF) even if exposure was the same. This is the major point people seem to continually miss.

Assuming that all anyone ever cares about is exposure (and not noise, DR, DOF) is a conceptual mistake.

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---------- Post added 10-10-14 at 08:27 AM ----------

What I hate is the rigid, limited thinking it brings. What I hate are the assumptions pushed onto me,

I don't get how an open discussion in which you willingly participate about simple photographic formula are 'pushing assumptions on to you.'

Do you have an iphone app that's feeding these threads to you that you can't turn off? Is your forum reader software trapped in this forum?

What I hate is the crazy assumption that rejecting "equivalence" means rejecting knowledge itself.

Rejecting it's relevance to you or your style of shooting is perfectly fine, especially if you only shoot one format. Rejecting it's validity is indeed rejecting knowledge itself - and is in fact extremely rigid.

.

[ChristianRock]

You're right but bear in mind that FF usually have one stop high iso advantage, so it evens out.!

But when you throw a term like "usually" then you no longer have true equivalence - equivalence has to be based on constants, not variables. What if sensor technology allows noise levels in APS-C to be the same as 135mm? And what if it gets to have only half the difference?

The only thing that is constant is the ISO setting, the noise isn't.

[jsherman999]

I've read a first couple of posts in this thread and said to myself 'nah, this's been chewed over'. Here we are 100 posts later. Most. Successful. Troll. Ever.

It has been chewed over. (Did this thread get moved here from another forum, I see a lot of newbies to the discussion )

[Andi Lo]

But when you throw a term like "usually" then you no longer have true equivalence - equivalence has to be based on constants, not variables. What if sensor technology allows noise levels in APS-C to be the same as 135mm? And what if it gets to have only half the difference?

The only thing that is constant is the ISO setting, the noise isn't.

Yes you're right, but that caveat applies to everything when comparing new gear. If you buy Canon 5D classic of course you won't get any high ISO advantage vs current gen APSC. Even within APSC ISO performance isn't constant. I suspect K-3 will still outperform the new Canon 7Dii, even though the 7Dii is newer. Back in the K-7 days, upgrading to K-7 from K20 actually sets you backward in high ISO

http://www.dxomark.com/Cameras/Compare/Side-by-side/Pentax-K-3-versus-Canon-EOS-70D___914_895

Everyone just need to do their own research and see what works best for them.

tl;dr, If you're getting Sigma 18-35 solely to get better high ISO performance, consider a used D600
http://www.ebay.ca/itm/NIKON-D600-24-3MP-FULL-FRAME-DIGITAL-SLR-CAMERA-BODY-...item4629132c6b

[wombat2go]

I am sorry, really tried to follow some of the pseudo-science here about DOF, energy levels, noise figures, sensors etc etc here.
Some posts led me to ponder that if true, I can focus a lens from an inferior format camera back to back
with a lens from the hallowed 35mm, I will get more light out than went in.
Thus, there would be a solution to the global warming etc and allowing me to make my toast for free,
so I don't have to eat day old Tim Hortons nut sprinkled do-nuts.

[Vitalii]

It's obvious when you think about it.

Put a 1.5x tc on a lens and you take it for granted that you are going to lose slightly more than a stop. Put extension tubes on to magnify another 1.5x - same. Crop factor is no different - there is no free lunch. If you think your classic 70-200 f2.8 is giving you 105-300mm and f2.8, you too have been successfully ...... what word should I use here, brainwashed? gulled? confused? led astray... you decide! by camera and lens marketings smoke and mirrors. You can't multiply the focal length by the crop factor and NOT multiply the aperture by the crop factor . As Tony Northrup says in his video "it breaks the math".
Your 70-200 f2.8 equates to 105-300 f4.2!!!

Sorry.

Light strength isn´t same as DOF. Its not like the light can choose how bright to schine on full frame and how for aps-c. Sure it would be nice to say - I paid much more money, from now on, the sun will shine brighter on me...)))
You have a 1.5xDOF at the SAME exposure. So you need LESS LIGHT to shoot SHARPER photos. If it is a disadvantage or not, is up to you.
If you shoot macros I think you would preffer a µFT sensor intead of focus peaking with full frame.

SO you were just misleaded by yourself. yourself and math, yes, math is always bad.

[jsherman999]

As I remember, this thread started under the statement that "aps-c costs more than one stop relative to full frame"

So, why now you are supporting this argument based on something totally different. "one stop" refers to EXPOSURE, and based on it, the OP based his arguments on EXPOSURE. Now things have changed. Your answer is: " Same exposure but totally different light = different images"....

'Stop' doesn't just refer to exposure, though. The vernacular includes other usage like "One stop DOF," or "one stop noise." Even if you don't like that usage, you should know what it's referring to: the effect on those things that changing f-stop causes.

.

The ones that succeed were the ones that reached the "second nature" state. That is when you simply think, understand and speak the new language without even caring for its meaning or translation to the old one.

In learning any second language, you need to start with a translation mechanism - a way to map meanings. Car = Coche. Equivalence simply provides this translation mechanism for learning your photographic second language

And indeed after you learn it it's second nature... until you have to fire up the translation mechanism again to learn a third language (1'' sensor?) .

[Rondec]

I'll simplify for you...
1.The amount of light captured is relevant to noise. Not to exposure. Mixing up the the term of noise with the term used of exposure is nonsense. Northrup knows better, he's making a point. Why doesn't Northrup use the proper noise units? Because in many cases they are insignificant. Where as saying the are "more than one stop" makes them sound huge.

2.Aperture relates tot he intensity of light hitting the light sensitive material. Not DoF. DoF can be measured in inches or mm or meters to whatever. There is no reason to measure in Stops. Tha's not what ƒ-stops are.

3. The big square on his comparative sensor size chart should be a 5x7 scanning back. Then an MF then an FF. By using an FF instead of the largest digital format available he implies that FF is some kind of standard to be emulated. That everything should be compared to FF, when in fact there are 2 or 3 larger formats.. Again, very manipulative. IN fact through out his whole video he implies that everything should be rated by it's noise performance, and light gathering performance compared to FF. That's just FF propaganda.

4. He claims that ISO is "obsolete" because it's an old standard. The funny thing about that is, it still does exactly what it was designed to do. And is still very useful in that regard. His ideas threaten the simplicity and ability to understand what ISO does and what its for.

5. His claim that Aperture should be used to define DoF is equally confusing and unnecessary.

SO why is he doing this?
First of all, he's not a high resolution guy. Or he'd be using a 645 or Scanning back. He's not a "use the most light for your image" guy or he'd be using a scanning back or a 645. He's a guy who defines the whole world in terms of FF format cameras.

To the point where he argues that the Full Frame DoF values are the "normal" values, and every other format needs to be converted to it.

The man is a sophisticated propagandist. I can understand how it would be possible to get sucked in. But he isn't any more than that.

Why does he talk in terms of stops...not the actual values? Only one reason, photographers recognize stops and think they know what they mean. If he just said, at 8 mm the DoF @ ƒ2.8 of a 50mm FF will be about 6 mm and a 35mm APS-c will be about 12... see the difference? Now it's not FF is the standard and APS_c is somehow inferior. It's do I want the 6mm of DoF or the 12mm. Now you have informed debate. Now you know what you're talking about. If you want your whole subject in focus you can say "well. my subject is 6mm deep, the FF should be perfect." Or you could also say My subject is 12 mm deep, APS-c would be better."

Don't check my math, these are examples to illustrate a point. Not real world examples. (There's nothing worse than when I put up an example and someone says "your math is not right." I really don't owe it to anyone to go to the DoF tables and figure out a real example. I'm not being paid for this.)

You see the difference? One is knowledge of the two lenses and formats giving you real information on how to attack a technical situation. And you won't always choose the Full Frame. The "what is the DoF ƒ-stop or how much light does the sensor collect tells you next to nothing. One is technical information. One is technical gobbledy goop. And that's because he's applying terms with strict definitions to functions, noise and DoF, to which they do not apply.

The only measure of DoF is inches/feet or mm/meters. (Not Aperture)
Noise is usually measured as an RMS (root mean square) voltage. (Not ISO)

Using those measures gives you a clear understanding of the effect of those elements on your image. Talking about stops with respect to either DoF or ISO does not.

I hope that's a little clearer for you.

Depth of field is a weird thing that always seems to come up in these discussions as though it was the goal of photography. Depth of field is dependent of focal length, aperture, and distance to subject. Using a term like "one stop" more depth of field is pretty confusing. When I say it, I mean (I guess) whatever increase I would get going from 55mm f2.8 to 55mm f4, but it certainly isn't going to be clear for most people how much that really is.

[normhead]

'Stop' doesn't just refer to exposure, though. The vernacular includes other usage like "One stop DOF," or "one stop noise." Even if you don't like that usage, you should know what it's referring to: the effect on those things that changing f-stop causes.

.




In learning any second language, you need to start with a translation mechanism - a way to map meanings. Car = Coche. Equivalence simply provides this translation mechanism for learning your photographic second language

And indeed after you learn it it's second nature... until you have to fire up the translation mechanism again to learn a third language (1'' sensor?) .

As in almost any vernacular translation, the technical meaning is lost in the vernacular term. They are used by the ignorant who don't know any better, and not by those who actually need a technical understanding. The simple reality of that situation is, as soon as you stop talking technically it becomes impossible to clearly define any situation. All of the confusion relating to these issues is caused by the lack of a technical approach.

One stop of noise between 100-200 DB leads to much less deterioration in IQ than does a stop between 6400 ISO and 12800 ISO. One stop of noise where the difference is not visible is not an issue. Noise is also affected by the construction of sensors. The size of the actual area used for collection of photons on a pixel can change depending on the manufacture of the sensor and sensitivity or the materials used. You can over-simplify a process, until it actually tells you nothing useful.

I'd argue that's what has happened with the vernacular use of technical terms.

If people would use DB or some other noise to signal ratio to define noise, and mm/inches to define DoF... people could see exactly what they were gaining or losing changing from one format to another. But even those theoretical postulations would only be validated by testing...and measurements showing they were in the ball park. You can say a Full Frame camera "should" have better Dynamic Range than an APS-c. But the K-5 ended that. There are technical innovations being applied all the time that affect the final image created and create situations where camera performance falls outside the parameters of narrowly defined technical limitations.

The constructs of basic optical physics to applied modern technology.. is like driving a screw with a hammer. You can do the job, but you won't make best use of the technology and it won't give you the best results.. To do that you have examine all aspects of what a photographic system does and how it does it. The more complex the system is, the less use, the basic physics is. If were were using single elements, with all lenses using the same basic design, film cameras that all used the same emulsion, these "vernacular" constructs might be of some use.

As it is, they are pretty much useless.

When you underexpose a properly exposed photo -1EV one stop, it's one stop underexposed.
When you go from ISO 200 to ISO 100 is your image one stop under-exposed?
Can you see the one stop of noise like you can see the one stop of exposure?

People seem to be so in love with the simplicity of these concepts, have to realize, just because it's simple, and in the vernacular, doesn't make it useful. At some point, you should probably just buckle down and do the work using the math that was designed to do the job, and then doing actual tests to show they've applied their knowledge correctly.. instead of taking shortcuts with inappropriate terms, which leads to confusion, mis-information and endless debate.

Remember one simple change in technology, like backlit sensors can change how much use the sensor makes of available light. A sensor using a newer tech can be just as efficient collecting light and therefore in reducing noise as a larger older type of sensor, and there is no one I know that rates sensor light to digital efficiency of various sensor. Without that information all speculation on what "format" will produce the best noise to signal ratio is hogwash. You have to go camera by camera. And all of these "simple" assertions, are made without that information. You have to assume that all sensors are equal in their light gathering capacity, and that any difference is based on the size of the pixel area. That simply isn't true.

The best way to evaluate ISO noise performance... if to go to Imagine Resources and check out the swatches.In the end, it doesn't matter what some internet expert says the is possible, it only matter what the camera makers can actually achieve. (and why so many of the "internet experts" hate Imaging Resources.)

Repeating what some guy said on the internet isn't science.

[redrockcoulee]

I'd say only people who grew up with digital only and still need to preview their shots. No way I'd ever haul around a DSLR for a light meter. Totally lame, really.

People do, especially when they first start out and do not have a light meter. I have a light meter in my MF bag and another in my LF bag but one of the reasons I use a K-r and small primes is the ease of taking them with me if a am going off with one of the larger formats they add neither much bulk or weight. The light meters in an iPod or iPhone would be more convient than a dslr as well. I also read of some one claiming to backpack with a Fuji GX680 so anything is possible.

There is also the sunny 16 rule and now I need to get an app to translate it between the various formats I have.

[Kunzite]

I don't get how an open discussion in which you willingly participate about simple photographic formula are 'pushing asumptions on to you.'

Do you have an iphone app that's feeding these threads to you that you can't turn off? Is your forum reader software trapped in this forum?

What's that, trying to clean up the forums from "infidels"? Only your camp should be allowed to post?

FTR, you did that "pushing assumptions" yourself, several times. Others did it too, should I remember (again!) the recent moon shooting example?

Rejecting it's relevance to you or your style of shooting is perfectly fine, especially if you only shoot one format. Rejecting it's validity is indeed rejecting knowledge itself - and is in fact extremely rigid.

Thank you for illustrating - once again - what I said. You, indeed, cannot differentiate between "equivalence" and knowledge.
But please don't get mad at me just because I can, and I am able to see that its only novelty is this very specific way of comparison between formats, and a quite peculiar set of assumptions being made.
And I'm rejecting "equivalence" precisely because those assumptions are wrong. I can do that precisely because - gasp! - I have the knowledge to do that, and an open mind required to see beyond a rigid formula.

P.S. I'd really like to know what makes anyone think that, when switching formats:
- the shutter speed should stay constant
- aperture will be selected exclusively to obtain a specific DOF
- there are no other reasons which might dwarf wide-aperture DOF in importance