"Equivalence" demonstrated: Canon 5D and Panasonic GX1

Started Apr 27, 2013 | Discussions
walkaround Senior Member • Posts: 2,551
"Equivalence" demonstrated: Canon 5D and Panasonic GX1
14

There has been a lot of talk by a few people here about "total light", and how an f/1.4 lens on a m4/3 camera supposedly acts like an f/2.8 in regards to "light on the sensor", etc. No examples have been given in those threads, so I thought I would post some test shots I just did.

Panasonic GX1 with Canon FD 50mm f1.4

Canon 5D with EF 100mm f2.0

Both photos were taken at ISO 160, 1/250, f/2.0
I have not edited the out of camera jpegs in any way. Other than slight differences in the magnification of the two lenses, WB, and the obvious DOF difference, the exposures are equivalent. They are the same. When I print both photos on 4x6, they look the same. "Total light on the sensor" is a meaningless concept. Exposure and density is not.

Canon EOS 5D Panasonic Lumix DMC-GX1
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ethern1ty Regular Member • Posts: 338
Re: "Equivalence" demonstrated: Canon 5D and Panasonic GX1
2

What about the same comparison with ISO > 800 ?

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OP walkaround Senior Member • Posts: 2,551
Re: "Equivalence" demonstrated: Canon 5D and Panasonic GX1
8

Here is another example.

Panasonic GX1 with Canon FD 50mm 1.4

Canon 5D with EF 100mm 2.0

Again, both taken with the exact same camera settings.

The summary: an f/1.4 lens on a m4/3 camera acts like an f/2.8 lens on a 35mm camera for the purposes of framing and depth of field only. For exposure and "final brightness", "total light", prints or any other visual idea you want to throw in there, it acts like what it is: an f/1.4 lens.

NOTE: the exif in dpreview for the GX1 is showing the lens as a "Tokina 28mm". I don't own a Tokina lens, there is some kind of software glitch. The lens used was an old manual Canon FD, with a Novoflex adapter. This is why there is no aperture shown.

PhotographicPhil Regular Member • Posts: 320
Re: "Equivalence" demonstrated: Canon 5D and Panasonic GX1
3

I agree with you. I also think you have explained it very clearly and concisely. I hope you realise though that this thread will now max out with all sorts of irrational and overly complex "explanations"! The can of worms has been opened once more!

Macx Senior Member • Posts: 1,433
Re: "Equivalence" demonstrated: Canon 5D and Panasonic GX1
1

Some more examples (not my website): http://www.pieterderaedt.net/Tutorial-EStests.htm

And the theory behind: http://www.pieterderaedt.net/Tutorial-AA.htm

baxters Veteran Member • Posts: 5,156
Re: "Equivalence" demonstrated: Canon 5D and Panasonic GX1
3

If you ever printed in a darkroom, you knew this. It's like saying exposure depends on the size of the paper, which would blow the use of test strips out of the water.

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Peng Bian
Peng Bian Contributing Member • Posts: 608
Re: "Equivalence" demonstrated: Canon 5D and Panasonic GX1
3

PhotographicPhil wrote:

I agree with you. I also think you have explained it very clearly and concisely. I hope you realise though that this thread will now max out with all sorts of irrational and overly complex "explanations"! The can of worms has been opened once more!

I think people are getting tired of arguing.

Equilvance with respect to light gathering over sensor surface area and SNR versus practical equivalence with respect to shutter speed.

Who cares, go out and shoot!

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jrtrent Veteran Member • Posts: 4,783
Re: "Equivalence" demonstrated: Canon 5D and Panasonic GX1

walkaround wrote:

There has been a lot of talk by a few people here about "total light", and how an f/1.4 lens on a m4/3 camera supposedly acts like an f/2.8 in regards to "light on the sensor", etc. No examples have been given in those threads, so I thought I would post some test shots I just did.

Both photos were taken at ISO 160, 1/250, f/2.0
I have not edited the out of camera jpegs in any way. Other than slight differences in the magnification of the two lenses, WB, and the obvious DOF difference, the exposures are equivalent. They are the same. When I print both photos on 4x6, they look the same. "Total light on the sensor" is a meaningless concept. Exposure and density is not.

I'm a little confused by the comparison.  From past threads, wouldn't "equivalent" pictures have meant:

GX1:  50mm, F/2, 1/250, ISO 160

5D:  100mm, F/4, 1/250, ISO 640

I don't know that "total light on the sensor" is a useful concept for me in understanding or using cameras, but the "obvious DOF difference" might not exist--that is, the pictures might look even more the same--if the 5D's lens had been closed down a couple of stops.

Lost in Time Regular Member • Posts: 207
Re: "Equivalence" demonstrated: Canon 5D and Panasonic GX1
5

The summary: an f/1.4 lens on a m4/3 camera acts like an f/2.8 lens on a 35mm camera for the purposes of framing and depth of field only. For exposure and "final brightness", "total light", prints or any other visual idea you want to throw in there, it acts like what it is: an f/1.4 lens.

Of course it does. If I take two difference formats and set the same framing, subject/lighting, f-stop and ISO, I will get exactly the same shutter speed.

However, this is precisely because this is how ISO is defined. The FF camera really does receive 4x the light of the u4/3 camera, each pixel being 4x larger and hence gathering 4x the light, and hence having 4x the signal/noise. What this means is that although the settings are the same, the FF camera will show less noise than the u4/3 camera, just as the u4/3 camera shows less noise than a P&S at the same ISO. I don't think anyone here would claim that the noise level on u4/3 is the same as a FF camera at the same ISO, just as no one would claim that the u4/3 noise is the same as a P&S at the same ISO.

The curious thing is that this means that if you stop-down the FF lens to give the same DOF as u4/3, and boost the ISO to maintain the same shutter speed, you end up an identical image in terms of DOF and image noise. This is what is meant by 'equivalence': there is no magical advantage to either FF systems if the cameras are correctly set so that the resulting images would be truly identical.

In reality, none of this matters: you choose the format and lens for the subject you want (and hopefully something more interesting than the pink mess at the start of this thread, which completely misunderstands the entire concept of equivalence as the images have obviously different DOF...).

JosephScha Veteran Member • Posts: 5,290
What you have demonstrated is not what they mean by equivalence

I spent a considerable amount of time reading several long posts here and one huge web page on this topic, last night. I am not up to explaining it in one short post. But I can give you some ways that it differs from what you are thinking - which is exactly the way I was thinking.

1. Equivalence means what they say it means. What is equivalent is perspective (you got that right), framing, depth of field, shutter speed and displayed size. Nothing more.
2. It is not about equivalent exposure (light per unit area), it is about total light reaching the sensor. The goal is to measure efficiency of different sensors.

In your pictures you made exposure the same, and (therefore) depth of field was different. That is meaningful, maybe even more intuitive, but it is not what the people you are aiming at mean by equivalence. Once I understood that I was more happy to let them mean whatever they want. I am not yet convinced that thinking that way will be very useful, but it's not totally bogus. They just defined equivalence as they wanted to serve that particular purpose.

While I'm writing:
3. Exposure only means total light hitting the sensor. Everything after that is "brightening". I a really like that, the only problem is general usage. Even the top slider in ACR is labelled "exposure" when it's clearly iso adjust, or brightening.
4. 4/3 needs two stops more open than FF to have same total light on the sensor.

I'd better stop here. There is tons more to read, some of it quite mathematical, to see where the definition they use for "equivalence" came from and how it can be useful. My intent here is just to ask you to allow them their definition, and if it's not what you care about that is OK.
--
js

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Great Bustard Forum Pro • Posts: 41,330
Are you kidding me?!
3

walkaround wrote:

There has been a lot of talk by a few people here about "total light", and how an f/1.4 lens on a m4/3 camera supposedly acts like an f/2.8 in regards to "light on the sensor", etc. No examples have been given in those threads, so I thought I would post some test shots I just did.

Panasonic GX1 with Canon FD 50mm f1.4

Canon 5D with EF 100mm f2.0

Both photos were taken at ISO 160, 1/250, f/2.0
I have not edited the out of camera jpegs in any way. Other than slight differences in the magnification of the two lenses, WB, and the obvious DOF difference, the exposures are equivalent. They are the same. When I print both photos on 4x6, they look the same. "Total light on the sensor" is a meaningless concept. Exposure and density is not.

All you've demonstrated is that the GX1 has a more efficient sensor than the 5D, and that the predictions of Equilvance are exactly as stated.

So, that's an epic fail on your part.

jrtrent Veteran Member • Posts: 4,783
Re: What you have demonstrated is not what they mean by equivalence

JosephScha wrote:

In your pictures you made exposure the same, and (therefore) depth of field was different. That is meaningful, maybe even more intuitive, but it is not what the people you are aiming at mean by equivalence. Once I understood that I was more happy to let them mean whatever they want. . . My intent here is just to ask you to allow them their definition, and if it's not what you care about that is OK

That sounds reasonable.  Words can have more than one meaning, and even dictionary definitions of words change as popular usage changes.

While I'm writing:
3. Exposure only means total light hitting the sensor. Everything after that is "brightening". I a really like that, the only problem is general usage. Even the top slider in ACR is labelled "exposure" when it's clearly iso adjust, or brightening.

I'm probably stuck in traditionalism, but "brightening" really sticks in my craw.  Then again, I don't use ACR and want to avoid post-processing as much as possible.  I choose an exposure (shutter speed/aperture combination) according to how I want the image to look, but that choice is also determined by the intensity of the light falling on the scene as well as by the sensitivity (or sensitivity setting) of the material, whether film or digital sensor, that I'm exposing the light to.  With a digital camera, shutter speed, aperture, and ISO can all be changed at will, and all affect the brightness of the image I get out of my camera, so the "exposure triangle" concept is quite workable and has helped many make better sense of how their exposure choices, including ISO setting, affect their final result.  Some in the "equivalence" camp seem intent on eradicating the exposure triangle concept, but they also should be willing to allow others their own definitions and ways of working with their equipment.

Great Bustard Forum Pro • Posts: 41,330
Almost, but not quite.
3

JosephScha wrote:

I spent a considerable amount of time reading several long posts here and one huge web page on this topic, last night. I am not up to explaining it in one short post. But I can give you some ways that it differs from what you are thinking - which is exactly the way I was thinking.

1. Equivalence means what they say it means. What is equivalent is perspective (you got that right), framing, depth of field, shutter speed and displayed size. Nothing more.
2. It is not about equivalent exposure (light per unit area), it is about total light reaching the sensor. The goal is to measure efficiency of different sensors.

In your pictures you made exposure the same, and (therefore) depth of field was different. That is meaningful, maybe even more intuitive, but it is not what the people you are aiming at mean by equivalence. Once I understood that I was more happy to let them mean whatever they want. I am not yet convinced that thinking that way will be very useful, but it's not totally bogus. They just defined equivalence as they wanted to serve that particular purpose.

While I'm writing:
3. Exposure only means total light hitting the sensor.

No -- exposure is the density of the light hitting the sensor.  The total light hitting the sensor is the product of the exposure and sensor area:

Total Light = Exposure x Sensor Area

The reason the noise in the two photos is essentially the same even though the 5D is collecting 4x as much total light for a given exposure than the GX1 is because the GX1 has a significantly more efficient sensor at those ISOs, which makes the noise about the same.

Everything after that is "brightening". I a really like that, the only problem is general usage. Even the top slider in ACR is labelled "exposure" when it's clearly iso adjust, or brightening.
4. 4/3 needs two stops more open than FF to have same total light on the sensor.

I'd better stop here. There is tons more to read, some of it quite mathematical, to see where the definition they use for "equivalence" came from and how it can be useful. My intent here is just to ask you to allow them their definition, and if it's not what you care about that is OK.

On the quick, the GX1 has a QE of about double the 5D, which means even though 4x as much light falls on the 5D sensor for a given exposure, it only records 2x as much light.  Furthermore, the read noise on the GX1 is about half that of the 5D at the ISO the photos were taken at, so that, in combination with the higher QE, effectively nullifies the noise differential in the shadows.

JosephScha Veteran Member • Posts: 5,290
Re: Almost, but not quite.

JosephScha wrote:

I spent a considerable amount of time reading several long posts here and one huge web page on this topic, last night. I am not up to explaining it in one short post. But I can give you some ways that it differs from what you are thinking - which is exactly the way I was thinking.

1. Equivalence means what they say it means. What is equivalent is perspective (you got that right), framing, depth of field, shutter speed and displayed size. Nothing more.
2. It is not about equivalent exposure (light per unit area), it is about total light reaching the sensor. The goal is to measure efficiency of different sensors.

In your pictures you made exposure the same, and (therefore) depth of field was different. That is meaningful, maybe even more intuitive, but it is not what the people you are aiming at mean by equivalence. Once I understood that I was more happy to let them mean whatever they want. I am not yet convinced that thinking that way will be very useful, but it's not totally bogus. They just defined equivalence as they wanted to serve that particular purpose.

While I'm writing:
3. Exposure only means total light hitting the sensor.

No -- exposure is the density of the light hitting the sensor.  The total light hitting the sensor is the product of the exposure and sensor area:

Total Light = Exposure x Sensor Area

The reason the noise in the two photos is essentially the same even though the 5D is collecting 4x as much total light for a given exposure than the GX1 is because the GX1 has a significantly more efficient sensor at those ISOs, which makes the noise about the same.

Everything after that is "brightening". I a really like that, the only problem is general usage. Even the top slider in ACR is labelled "exposure" when it's clearly iso adjust, or brightening.
4. 4/3 needs two stops more open than FF to have same total light on the sensor.

I'd better stop here. There is tons more to read, some of it quite mathematical, to see where the definition they use for "equivalence" came from and how it can be useful. My intent here is just to ask you to allow them their definition, and if it's not what you care about that is OK.

On the quick, the GX1 has a QE of about double the 5D, which means even though 4x as much light falls on the 5D sensor for a given exposure, it only records 2x as much light.  Furthermore, the read noise on the GX1 is about half that of the 5D at the ISO the photos were taken at, so that, in combination with the higher QE, effectively nullifies the noise differential in the shadows.

Right. Damn, I knew that. Careless wording on my part. My point was that what's called exposure occurs only on the sensor.
--
js

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Olymore
Olymore Senior Member • Posts: 1,744
Re: Almost, but not quite.

GB, a question.....

Noise is always mentioned as an advantage of 4x light on a FF sensor over an identical except for smaller sized M43 sensor. And the amount of extra noise that an M43 sensor would produce for the final image viewed at the same size etc etc. can be calculated mathematically.

But what about the other aspects of the sensor  like DR for instance or colour depth ?

Would a FF frame sensor, given the above scenario, always have 2 more stops of DR and can this be calculated or is the gain from these other components of IQ harder to define scientifically ?

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Macx Senior Member • Posts: 1,433
Re: Almost, but not quite.
2

Olymore wrote:

GB, a question.....

Noise is always mentioned as an advantage of 4x light on a FF sensor over an identical except for smaller sized M43 sensor. And the amount of extra noise that an M43 sensor would produce for the final image viewed at the same size etc etc. can be calculated mathematically.

Yes, it is always mentioned, but this advantage only manifests itself if you shoot with an equal exposure, which is sort of meaningless. If you shoot with an equivalent exposure you gain no noise advantage by shooting 135 over 4:3.

The 135 advantage exists qua the lenses with large (virtual) apertures made for this system.

But what about the other aspects of the sensor  like DR for instance or colour depth ?

This isn't dependant on sensor size, as far as I know.

sean000 Veteran Member • Posts: 7,356
Re: "Equivalence" demonstrated: Canon 5D and Panasonic GX1
1

Lost in Time wrote:

The summary: an f/1.4 lens on a m4/3 camera acts like an f/2.8 lens on a 35mm camera for the purposes of framing and depth of field only. For exposure and "final brightness", "total light", prints or any other visual idea you want to throw in there, it acts like what it is: an f/1.4 lens.

Of course it does. If I take two difference formats and set the same framing, subject/lighting, f-stop and ISO, I will get exactly the same shutter speed.

However, this is precisely because this is how ISO is defined. The FF camera really does receive 4x the light of the u4/3 camera, each pixel being 4x larger and hence gathering 4x the light, and hence having 4x the signal/noise. What this means is that although the settings are the same, the FF camera will show less noise than the u4/3 camera, just as the u4/3 camera shows less noise than a P&S at the same ISO. I don't think anyone here would claim that the noise level on u4/3 is the same as a FF camera at the same ISO, just as no one would claim that the u4/3 noise is the same as a P&S at the same ISO

I would add that you also have to consider the age of the sensor since technology improves over time. My E-M5 produces images with less noise at high ISO than my 8-year-old Nikon D200, even though the the D200 gathers more light. Of course an old sensor isn't as efficient as a newer one and APS-C and FF sensors have improved a lot since then, but the advantage of a larger sensor (at least in terms of noise, detail, dynamic range) is not as big as it was a few years ago. Over time the advantages of a larger sensor will be little to nothing for most photographs. Many would argue that is already true. of course depth of field will still be different, but it won't be too long before Lytro-type technology will be in many cameras... Allowing us to select depth fielded, background blur, and bokeh characteristics using software.

The curious thing is that this means that if you stop-down the FF lens to give the same DOF as u4/3, and boost the ISO to maintain the same shutter speed, you end up an identical image in terms of DOF and image noise. This is what is meant by 'equivalence': there is no magical advantage to either FF systems if the cameras are correctly set so that the resulting images would be truly identical.

In reality, none of this matters: you choose the format and lens for the subject you want (and hopefully something more interesting than the pink mess at the start of this thread, which completely misunderstands the entire concept of equivalence as the images have obviously different DOF...).

Agree and excellent post.

Sean

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Olymore
Olymore Senior Member • Posts: 1,744
Re: Almost, but not quite.

Sorry, I should have said equal exposure.

Noise is rrelevant to me as I nearly always shoot at base ISO and for my tastes modern sensors are good enough with noise. Though I do realise that it is the lack of light that makes a photgraph noisy, so perhaps I should say 'I nearly always shoot in reasonably good light'.

I was curious whether an identical in every way sensor for FF, apart from size, would always have an x improvement in some other aspects of IQ and whether this could be quantified.

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OP walkaround Senior Member • Posts: 2,551
Re: Are you kidding me?!
3

Great Bustard wrote:

All you've demonstrated is that the GX1 has a more efficient sensor than the 5D, and that the predictions of Equilvance are exactly as stated.

So, that's an epic fail on your part.

The problem mr bustard is that you pick a definition of "equivalent" for two photographs that incredibly does not include exposure which is the basis of photography. From your website essay:

"Equivalent photos are photos of a given scene that share the following five parameters:

•  Perspective •  Framing •  DOF •  Shutter Speed •  Display Dimensions

Equivalent images on different formats, by definition, will not have the same exposure, and this is the source of most all resistance to the concept."

(my emphasis)

You should have wrote "by my definition", because I can't imagine there are very many people outside of this forum who believe that two photos two stops apart in exposure are in any way "equivalent", and you choosing to define it such just makes your definition irrelevant. The resistance to your "concept" that you note is because it doesn't make sense. I can write an article on cooking and state that the definition of good cooking does not include "taste", but who cares and who would want to read it?

Now this is all ok if you're just chatting with mom in the basement, but we now have threads here where people say "I'm going to buy the new Voigtlander f/0.95 because having an f/2.0 lens will still be fast enough for me." Sheesh.

I wouldn't expect someone with 15000 posts to ever say "you're right", but hopefully others will see that they can go out and buy that f0.95 lens and it will in fact still be an f0.95 lens when they get home and stick it on their m4/3 camera.

And if you are now claiming that the GX1 sensor is 4x more efficient than the 5D, please post a source for that information because I think it's nonsense.

Yohan Pamudji Senior Member • Posts: 2,874
Re: Are you kidding me?!
5

walkaround wrote:

Great Bustard wrote:

All you've demonstrated is that the GX1 has a more efficient sensor than the 5D, and that the predictions of Equilvance are exactly as stated.

So, that's an epic fail on your part.

The problem mr bustard is that you pick a definition of "equivalent" for two photographs that incredibly does not include exposure which is the basis of photography. From your website essay:

"Equivalent photos are photos of a given scene that share the following five parameters:

•  Perspective •  Framing •  DOF •  Shutter Speed •  Display Dimensions

Equivalent images on different formats, by definition, will not have the same exposure, and this is the source of most all resistance to the concept."

(my emphasis)

You should have wrote "by my definition", because I can't imagine there are very many people outside of this forum who believe that two photos two stops apart in exposure are in any way "equivalent", and you choosing to define it such just makes your definition irrelevant. The resistance to your "concept" that you note is because it doesn't make sense.

...

And if you are now claiming that the GX1 sensor is 4x more efficient than the 5D, please post a source for that information because I think it's nonsense.

Your definition of equivalent image makes no sense at all.  The DOF is completely different in the 2 images you took.  How can they be equivalent?  Isn't the point of photography to produce an image with particular characteristics, namely composition, angle of view, DOF, and blur (or lack thereof)?  How can 2 images be equivalent if they have different DOF?  That's a fundamental trait of a photo and altering it results in a different image.

Also, why would you compare a very old FF sensor against a much newer m4/3 sensor?  That's as far away from apples to apples as you can possibly get.  I promise you that if I compared my E-M5 to my 5DIII at ISO 3200, the 5DIII would be obviously cleaner.  Flawed experiment resulting from a flawed understanding of equivalence.  You don't have to like equivalence, but if you're going to argue about it at least make sure you understand it.

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