Is my thinking about equivalence right?

Started 5 months ago | Questions
Muster Mark Contributing Member • Posts: 588
Is my thinking about equivalence right?
7

Hi all, I realize this is NOT the topic everyone loves to discuss and I totally understand. I hope no-one feels annoyed by this post. That said, after some investigation I have come to the conclusion that "traditional" equivalence math is only useful as a rough heuristic to get a sense of what DOF will be and NOT a reasonable way to compare individual lenses or judge cost/performance of lenses in different systems. I wanted to see what other geeky 4/3 sensor users think and if I am missing something in my calculations. I should add I fully understand the traditional argument that total light is 4x on FF camera (for example) at the same aperture since we need to multiply (integrate, actually) brightness by the sensor size to calculate S/N. This idea only works if you have an IDEAL lens and an ideal sensor. Lenses are never ideal though, so I wanted to dig deeper.

For the sake of simplicity let's limit ourselves to looking at "normal" lenses: e.g. fov roughly 1 radian. This FoV tends to "favor" larger formats as far as I can tell especially if the goal is to maximize bokeh-ball size/$. Furthermore, to limit permutations I only looked at examples of lenses for m43 and Sony E mount, specifically trying to find an "equivalent" lens to the M.Zuiko 25mm f1.2

My analysis boils down to 2 points:

1: No two lenses are actually "equivalent". This seems obvious. There is more to evaluating a lens than pupil diameter and FoV. People seem to forget this when comparing between systems.

2: Talking about "total light" without accounting for vingetting is either lazy or disingenuous. I am guessing this is 100% laziness as calculus is annoying. However FF lenses have much worse vingetting than m43 lenses for obvious reasons. Is this a hugely important aspect to image quality? No not really, IMHO, it's pretty easy to correct in post if you have the lens profile, but you are losing some of the signal to noise ratio advantage in the process. How much? that's what I wanted to figure out. By my calculation (of course it depends on lens a huge deal) FF lenses at 50mm lose about half a stop of light to vingetting MORE than the 25 f1.2. Specifically, the Sony GM 50mm 1.2 at 1.2 gathers about 2.9x the total light gathered by the olympus 25mm 1.2 (at 1.2). Is this a huge deal? No probably not, but it's not quite as impressive as the 4x factor everyone is repeating is it? I just thought it was interesting, mainly.

Calculating total light (for point 2): This is pretty handwavey, but after squinting at the data on lenstip.com, and specifically the level curves for brightness I thought it looked remarkably parabolic. Thus I approximated the brightness function of a lens wide open as a decreasing parabaloid -(x^2+y^2)K, where K is a constant that depends on the specific lens (I compared contour plots of these functions to the level curves provided by lens tip and they are remarkably close). When comparing between lenses of different aperture, there is a shift applied: e.g. approximating 1.4 as half a stop slower than 1.2, we would shift by -1/2. We then exponentiate and integrate over the frame. For these calculations I am assuming Fstop equals Tstop. Which is not correct, though lenses with similar numbers of elements will not have much difference in T stop I don't think (am no expert!). I couldn't find information on T stops for a lot of lenses which is why I left it out of consideration. I also couldn't find information on how it's measured (are they integrating total lite or measuring intensity at the center of the frame?) which further complicated trying to incorporate it.

Comparing lenses holistically: When more is taken into account than just pupil diameter, it seems to me at least, m43 lenses are not overpriced. For example the 25mm1.2 is optically pretty amazing when it comes to corner to corner sharpness, longitudinal CA correction (which is hard to correct in post, if my understanding is correct) and bokeh quality (not size).

For half the price one could use the Sony 50mm 2.5. This amounts to being about half a stop dimmer due to vingetting, the bokeh while the same size is much busier. Longitudinal CA is only a smidge worse though. Oh and yeah if you want a sharp full frame you need to stop down to f4 (the 50mm 1.8 by sony is not really worth looking at if optical performance is something you care about).

The Sony GM 50mm 1.2 lens performs very well when stopped down (and is pretty good wide open), but now we are back to being much heavier and costlier than the olympus. I am NOT saying it's a rip off, but I also don't think the lens needs defending as no one seems to doubt it.

The Zeiss 55mm 1.8 has lovely bokeh, but bad Long. CA and needs to be stopped down to 2.8 to be sharp.

Sigma ART lenses start to really shine honestly. Generally very well corrected optically, much less vingetting on FF than other lenses when wide open, and even slightly cheaper priced to the olympus. They are significantly bigger though (the 50mm 1.4 is 815g, versus 410g for the oly).

So what do we make of all this? My take away is that there is no free lunch. All lenses are compromises and on a system-wide level nobody is scamming anyone. If size of the bokeh balls is not your biggest concern, and you care about system size/weight and optical performance, m43 makes a lot of sense. I guess you already know that

I personally am shopping around at the moment (trying to decide if I want to adapt old 4/3 glass to m4/3 bodies, or buy new lenses and potentially change systems or buy new m4/3 lenses) and thus did this analysis to try to compare systems more accurately. Hopefully it was moderately interesting?

If there is anything I should be accounting for that I am not (and you know how I might, e.g. t stops) I'd be curious to hear.
--
Cheers,
-Ian

 Muster Mark's gear list:Muster Mark's gear list
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ANSWER:
miketala Regular Member • Posts: 350
Re: Is my thinking about equivalence right?
29

Buy new glass for your existing m43 and be satisfied. Some of the most beloved and iconic photos in the world were taken with worse systems (old film, whatever).

skill crushes system choice every time.   Develop your skills.   M43 is mature enough to get what you want unless you’re shooting fast sports.

RobBobW Contributing Member • Posts: 957
Re: Is my thinking about equivalence right?
19

Hi Ian,  you did a huge amount of analysis on this issue.  Here are a few observations and opinions of mine after shooting Canon FF and Olympus m43 for a decade.

- worrying about the size of boca(sic) balls is a waste of time in the real world.  
-  having a larger depth of focus is of more value overall.

-  the argument about total light is pointless as what is important is light density.  Yes FF will bring in 4 times the light, but FF also has 4 times the surface area of sensor to illuminate, so it is a wash.  Faster lenses bring in more light per unit area, period.

- my Olympus lenses consistently give me sharper images than my Canon “L” pro lenses.  
-  having a small and light system is fantastic.  I really enjoy carrying around a system that is  one half to one third the weight of a FF system.

-  equivalence, in my opinion, should only be considered in terms of focal length.  Any more is just intellectual diddling.

-  there are many folks who have very strong and different opinions than I do.  That is fine.  Live and let live.

All the best in your deliberations.  I know you will enjoy whatever camera system you select.  Now got have some fun taking pictures!

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OP Muster Mark Contributing Member • Posts: 588
Re: Is my thinking about equivalence right?
1

miketala wrote:

Buy new glass for your existing m43 and be satisfied. Some of the most beloved and iconic photos in the world were taken with worse systems (old film, whatever).

I have the 4/3 lenses (and E3) already.

skill crushes system choice every time. Develop your skills. M43 is mature enough to get what you want unless you’re shooting fast sports.

I agree. I had read a lot of opinions that 4/3 was dead when I began looking back into camera tech (hadn't really paid attention until I noticed focus issues on my e3). I concluded that unless I was missing something people badgering about equivalence were simply not accurate.

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Cheers,
-

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RSTP14 Veteran Member • Posts: 5,095
Re: Is my thinking about equivalence right?
29

I understand equivalency, but I just don't see the purpose if all you got is one system.

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Roger

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rovingtim Veteran Member • Posts: 8,861
Re: Is my thinking about equivalence right?
2

rogerstpierre wrote:

I understand equivalency, but I just don't see the purpose if all you got is one system.

How else would we measure our ?icks?

JosephScha Veteran Member • Posts: 6,662
Re: Is my thinking about equivalence right?
6

The idea of equivalence is to have the same angle of view, and the same depth of field and the same time of exposure so that the pictures are as indistinguishable as they could possibly be.  Any difference, therefore, is attributed to the efficiency of the sensor ... now that is the point I think you are arguing, and you have a point.  If the lenses are not both really the same then equivalence may not really work.

Anyway, let's assume Micro Four Thirds has the 25mm f/1.4 at f/1.4.   A full frame camera would have to have a 50mm at f/2.8.  Now no one actually SAID anything about the same amount of light, it's the same depth of field that makes FF use f/2.8.  And you probably noticed, in order to have the same time of exposure when two f stops reduced, the FF camera would have to use a higher ISO.  So the FF really is capturing the same amount of light, and spreading it out over a larger sensor.

Now, a good question might be, what does this prove?  It is supposed to compare the efficiency of the sensors.  If they are both the same, both will have the same amount of noise.   If one is more noisy than the other, then this test may have proved something about the cameras being compared.

That's all that equivalence is about.

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js

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SrMi
SrMi Senior Member • Posts: 2,397
Re: Is my thinking about equivalence right?

TL;DR

FWIW, a good explanation of equivalency can be found here.

ivan bayu Regular Member • Posts: 205
Re: Is my thinking about equivalence right?

Muster Mark wrote:

Hi all, I realize this is NOT the topic everyone loves to discuss and I totally understand. I hope no-one feels annoyed by this post. That said, after some investigation I have come to the conclusion that "traditional" equivalence math is only useful as a rough heuristic to get a sense of what DOF will be and NOT a reasonable way to compare individual lenses or judge cost/performance of lenses in different systems. I wanted to see what other geeky 4/3 sensor users think and if I am missing something in my calculations. I should add I fully understand the traditional argument that total light is 4x on FF camera (for example) at the same aperture since we need to multiply (integrate, actually) brightness by the sensor size to calculate S/N. This idea only works if you have an IDEAL lens and an ideal sensor. Lenses are never ideal though, so I wanted to dig deeper.

For the sake of simplicity let's limit ourselves to looking at "normal" lenses: e.g. fov roughly 1 radian. This FoV tends to "favor" larger formats as far as I can tell especially if the goal is to maximize bokeh-ball size/$. Furthermore, to limit permutations I only looked at examples of lenses for m43 and Sony E mount, specifically trying to find an "equivalent" lens to the M.Zuiko 25mm f1.2

My analysis boils down to 2 points:

1: No two lenses are actually "equivalent". This seems obvious. There is more to evaluating a lens than pupil diameter and FoV. People seem to forget this when comparing between systems.

from what i know, so far, you could match any equivalent for any system... but there's many obstacles to realise it ('enginering', size, price, ect) and it is nearly impossible to attain an exact looks...

2: Talking about "total light" without accounting for vingetting is either lazy or disingenuous. I am guessing this is 100% laziness as calculus is annoying. However FF lenses have much worse vingetting than m43 lenses for obvious reasons. Is this a hugely important aspect to image quality? No not really, IMHO, it's pretty easy to correct in post if you have the lens profile, but you are losing some of the signal to noise ratio advantage in the process. How much? that's what I wanted to figure out. By my calculation (of course it depends on lens a huge deal) FF lenses at 50mm lose about half a stop of light to vingetting MORE than the 25 f1.2. Specifically, the Sony GM 50mm 1.2 at 1.2 gathers about 2.9x the total light gathered by the olympus 25mm 1.2 (at 1.2). Is this a huge deal? No probably not, but it's not quite as impressive as the 4x factor everyone is repeating is it? I just thought it was interesting, mainly.

well, for light gather, afaik, even any lens that marked f1.2, the light that pasing through it will differ for one to another (dunno whether it will differ by every each one of them even from the same serie, but sure it is different by the maker). the only thing i will accept for such a thing is 't stop'. and for 50mm f1.2 that lost light most (as you said) so far i only know is the canon l, just take a look at the cine version of it, t1.3 if i'm not mistaken.

so far, many photographer i know, opted for any fast lens such f1.2 or f1.4 is for the dof. even if the raw is beaten to pulp by vignetting as long as is sharp at wide open.

for photography, i don't care about optical correction regarding vignetting, but another story for abberations and distortion (or pincushion). for video, it depends.

alas, i've never use any f1.2 besides canon's, konica's, pentax's, fujica's, sigma's, and minolta's. but according to this one, that particular f1.2 from sony is impressive.

Calculating total light (for point 2): This is pretty handwavey, but after squinting at the data on lenstip.com, and specifically the level curves for brightness I thought it looked remarkably parabolic. Thus I approximated the brightness function of a lens wide open as a decreasing parabaloid -(x^2+y^2)K, where K is a constant that depends on the specific lens (I compared contour plots of these functions to the level curves provided by lens tip and they are remarkably close). When comparing between lenses of different aperture, there is a shift applied: e.g. approximating 1.4 as half a stop slower than 1.2, we would shift by -1/2. We then exponentiate and integrate over the frame. For these calculations I am assuming Fstop equals Tstop. Which is not correct, though lenses with similar numbers of elements will not have much difference in T stop I don't think (am no expert!). I couldn't find information on T stops for a lot of lenses which is why I left it out of consideration. I also couldn't find information on how it's measured (are they integrating total lite or measuring intensity at the center of the frame?) which further complicated trying to incorporate it.

please don't assume. even i personally never heard any lens that its f stop and t stop are equal...

Comparing lenses holistically: When more is taken into account than just pupil diameter, it seems to me at least, m43 lenses are not overpriced. For example the 25mm1.2 is optically pretty amazing when it comes to corner to corner sharpness, longitudinal CA correction (which is hard to correct in post, if my understanding is correct) and bokeh quality (not size).

well i've never tried that oly, but the same site said that this lens suffer from some abberations and astigmatism

For half the price one could use the Sony 50mm 2.5. This amounts to being about half a stop dimmer due to vingetting, the bokeh while the same size is much busier. Longitudinal CA is only a smidge worse though. Oh and yeah if you want a sharp full frame you need to stop down to f4 (the 50mm 1.8 by sony is not really worth looking at if optical performance is something you care about).

The Sony GM 50mm 1.2 lens performs very well when stopped down (and is pretty good wide open), but now we are back to being much heavier and costlier than the olympus. I am NOT saying it's a rip off, but I also don't think the lens needs defending as no one seems to doubt it.

what do you expect from 50mm f1.2 of ff? lighter and smaller than nikon 50mm f1.8e?

The Zeiss 55mm 1.8 has lovely bokeh, but bad Long. CA and needs to be stopped down to 2.8 to be sharp.

Sigma ART lenses start to really shine honestly. Generally very well corrected optically, much less vingetting on FF than other lenses when wide open, and even slightly cheaper priced to the olympus. They are significantly bigger though (the 50mm 1.4 is 815g, versus 410g for the oly).

well, have you ever use that sigma art 50mm f1.4 before?

So what do we make of all this? My take away is that there is no free lunch. All lenses are compromises and on a system-wide level nobody is scamming anyone. If size of the bokeh balls is not your biggest concern, and you care about system size/weight and optical performance, m43 makes a lot of sense. I guess you already know that

er... that monstrous slower 100-400?

for me, just buy what suits your needs most, but yes, there'll be some compromises and sacrifices. just utilised your gear to its maximum potential...

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kcdogger Veteran Member • Posts: 3,439
Re: Is my thinking about equivalence right?
4

Muster Mark wrote:

Hi all, I realize this is NOT the topic everyone loves to discuss and I totally understand. I hope no-one feels annoyed by this post. That said, after some investigation I have come to the conclusion that "traditional" equivalence math is only useful as a rough heuristic to get a sense of what DOF will be and NOT a reasonable way to compare individual lenses or judge cost/performance of lenses in different systems. I wanted to see what other geeky 4/3 sensor users think and if I am missing something in my calculations. I should add I fully understand the traditional argument that total light is 4x on FF camera (for example) at the same aperture since we need to multiply (integrate, actually) brightness by the sensor size to calculate S/N. This idea only works if you have an IDEAL lens and an ideal sensor. Lenses are never ideal though, so I wanted to dig deeper.

For the sake of simplicity let's limit ourselves to looking at "normal" lenses: e.g. fov roughly 1 radian. This FoV tends to "favor" larger formats as far as I can tell especially if the goal is to maximize bokeh-ball size/$. Furthermore, to limit permutations I only looked at examples of lenses for m43 and Sony E mount, specifically trying to find an "equivalent" lens to the M.Zuiko 25mm f1.2

My analysis boils down to 2 points:

1: No two lenses are actually "equivalent". This seems obvious. There is more to evaluating a lens than pupil diameter and FoV. People seem to forget this when comparing between systems.

2: Talking about "total light" without accounting for vingetting is either lazy or disingenuous. I am guessing this is 100% laziness as calculus is annoying. However FF lenses have much worse vingetting than m43 lenses for obvious reasons. Is this a hugely important aspect to image quality? No not really, IMHO, it's pretty easy to correct in post if you have the lens profile, but you are losing some of the signal to noise ratio advantage in the process. How much? that's what I wanted to figure out. By my calculation (of course it depends on lens a huge deal) FF lenses at 50mm lose about half a stop of light to vingetting MORE than the 25 f1.2. Specifically, the Sony GM 50mm 1.2 at 1.2 gathers about 2.9x the total light gathered by the olympus 25mm 1.2 (at 1.2). Is this a huge deal? No probably not, but it's not quite as impressive as the 4x factor everyone is repeating is it? I just thought it was interesting, mainly.

Calculating total light (for point 2): This is pretty handwavey, but after squinting at the data on lenstip.com, and specifically the level curves for brightness I thought it looked remarkably parabolic. Thus I approximated the brightness function of a lens wide open as a decreasing parabaloid -(x^2+y^2)K, where K is a constant that depends on the specific lens (I compared contour plots of these functions to the level curves provided by lens tip and they are remarkably close). When comparing between lenses of different aperture, there is a shift applied: e.g. approximating 1.4 as half a stop slower than 1.2, we would shift by -1/2. We then exponentiate and integrate over the frame. For these calculations I am assuming Fstop equals Tstop. Which is not correct, though lenses with similar numbers of elements will not have much difference in T stop I don't think (am no expert!). I couldn't find information on T stops for a lot of lenses which is why I left it out of consideration. I also couldn't find information on how it's measured (are they integrating total lite or measuring intensity at the center of the frame?) which further complicated trying to incorporate it.

Comparing lenses holistically: When more is taken into account than just pupil diameter, it seems to me at least, m43 lenses are not overpriced. For example the 25mm1.2 is optically pretty amazing when it comes to corner to corner sharpness, longitudinal CA correction (which is hard to correct in post, if my understanding is correct) and bokeh quality (not size).

For half the price one could use the Sony 50mm 2.5. This amounts to being about half a stop dimmer due to vingetting, the bokeh while the same size is much busier. Longitudinal CA is only a smidge worse though. Oh and yeah if you want a sharp full frame you need to stop down to f4 (the 50mm 1.8 by sony is not really worth looking at if optical performance is something you care about).

The Sony GM 50mm 1.2 lens performs very well when stopped down (and is pretty good wide open), but now we are back to being much heavier and costlier than the olympus. I am NOT saying it's a rip off, but I also don't think the lens needs defending as no one seems to doubt it.

The Zeiss 55mm 1.8 has lovely bokeh, but bad Long. CA and needs to be stopped down to 2.8 to be sharp.

Sigma ART lenses start to really shine honestly. Generally very well corrected optically, much less vingetting on FF than other lenses when wide open, and even slightly cheaper priced to the olympus. They are significantly bigger though (the 50mm 1.4 is 815g, versus 410g for the oly).

So what do we make of all this? My take away is that there is no free lunch. All lenses are compromises and on a system-wide level nobody is scamming anyone. If size of the bokeh balls is not your biggest concern, and you care about system size/weight and optical performance, m43 makes a lot of sense. I guess you already know that

I personally am shopping around at the moment (trying to decide if I want to adapt old 4/3 glass to m4/3 bodies, or buy new lenses and potentially change systems or buy new m4/3 lenses) and thus did this analysis to try to compare systems more accurately. Hopefully it was moderately interesting?

If there is anything I should be accounting for that I am not (and you know how I might, e.g. t stops) I'd be curious to hear.
--
Cheers,
-Ian

Pass the popcorn and bring me another beer.

John

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WileEC_ID
WileEC_ID Senior Member • Posts: 1,122
Coming from top tier FF, transitioning to MFT
8

People like to discuss the theory of this stuff  ad nauseam. I do think there are some practical sides of it IF - ONLY IF - you are shooting multiple systems AND using fast lenses on the larger sensor systems.

I have been shooting fast long and shorter primes, so used to more light, faster shutter speeds at those focal lengths - for what I shoot, it is a practical issue. For example, shooting FF 300mm f/2.8 or 400mm f/2.8 - I wish there were lenses even remotely close - there are not.

Also, at a practical level I can shoot equivalent focal lengths at the same with lenses that start at the same aperture, and in decent light, the images (especially with some distance to the subject) are fairly comparable. I don't feel I'm giving up anything shooting MFT. This I have affirmed through several different subjects shot side by side - two cameras and lenses on same subject, same light. When I do this in lower light, I can really see the difference in light, as my shutter speeds on FF system are typically a stop or more faster.

With closer subjects, it can be an issue in terms of DOF flexibility. That said, if all one shoots is MFT, then they will not know any better. That said, there is a reason I invested in MFT f/1.8 and f/1.2 primes to give me the flexibility I want at those focal lengths.

Honestly, it is my opinion that people over think this stuff. Know your gear. Understand its edges and develop the skill to shoot it well. If you need faster primes or zooms, then invest in them, but only if you know you need them for what you shoot. More often than not many people buy the more expensive stuff because they can, not because they need it, or know how to shoot it well. I have observed this across all platforms - not trying to pick on MFT shooters.

At the end of the day, each platform has its pros and cons - there is no one perfect system. Mastery of what you use trumps just about anything else - so invest more time shooting than debating about stuff.

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Messier Object Forum Pro • Posts: 11,004
Re: Sigma 50mm F1.4 Art

Sigma ART lenses start to really shine honestly. Generally very well corrected optically, much less vingetting on FF than other lenses when wide open, and even slightly cheaper priced to the olympus. They are significantly bigger though (the 50mm 1.4 is 815g, versus 410g for the oly).

well, have you ever use that sigma art 50mm f1.4 before?

I’m curious about why you asked that question

Peter

Mark Ransom
Mark Ransom Veteran Member • Posts: 7,672
Re: Is my thinking about equivalence right?
31

RobBobW wrote:

- the argument about total light is pointless as what is important is light density. Yes FF will bring in 4 times the light, but FF also has 4 times the surface area of sensor to illuminate, so it is a wash. Faster lenses bring in more light per unit area, period.

This is simply false.  The reason apertures are measured by F-stops is because this equalizes the light density per unit area between lenses of different characteristics.  A lens at F/1.2 will produce the same light density, no matter the focal length of the lens or the size of the sensor behind it.  This means that a sensor with 4x the area really will collect 4x the light, when measured over the whole image, as long as the F-stops/T-stops of the lenses are the same.

The reason this matters is the nature of noise.  The majority of noise in today's cameras is from photon shot noise, which is a property of the light itself and not of the lens or sensor or any other camera electronics.  The only way to reduce shot noise is to collect more light.  Whether you do this with a larger sensor, a larger aperture, or a slower shutter speed is immaterial.

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OP Muster Mark Contributing Member • Posts: 588
Re: Is my thinking about equivalence right?

JosephScha wrote:

The idea of equivalence is to have the same angle of view, and the same depth of field and the same time of exposure so that the pictures are as indistinguishable as they could possibly be. Any difference, therefore, is attributed to the efficiency of the sensor ... now that is the point I think you are arguing, and you have a point. If the lenses are not both really the same then equivalence may not really work.

Anyway, let's assume Micro Four Thirds has the 25mm f/1.4 at f/1.4. A full frame camera would have to have a 50mm at f/2.8. Now no one actually SAID anything about the same amount of light, it's the same depth of field that makes FF use f/2.8. And you probably noticed, in order to have the same time of exposure when two f stops reduced, the FF camera would have to use a higher ISO. So the FF really is capturing the same amount of light, and spreading it out over a larger sensor.

Now, a good question might be, what does this prove? It is supposed to compare the efficiency of the sensors. If they are both the same, both will have the same amount of noise. If one is more noisy than the other, then this test may have proved something about the cameras being compared.

That's all that equivalence is about.

That's a good point. It can be useful to compare sensors, but then there is no need to talk about lenses. Sensor performance should be proportional to area.

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Cheers,
-Ian

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OP Muster Mark Contributing Member • Posts: 588
Re: Is my thinking about equivalence right?

Mark Ransom wrote:

RobBobW wrote:

- the argument about total light is pointless as what is important is light density. Yes FF will bring in 4 times the light, but FF also has 4 times the surface area of sensor to illuminate, so it is a wash. Faster lenses bring in more light per unit area, period.

This is simply false. The reason apertures are measured by F-stops is because this equalizes the light density per unit area between lenses of different characteristics. A lens at F/1.2 will produce the same light density, no matter the focal length of the lens or the size of the sensor behind it. This means that a sensor with 4x the area really will collect 4x the light, when measured over the whole image, as long as the F-stops/T-stops of the lenses are the same.

Only if illumination is even, which it is not. Now, it gathers MORE light for sure, but what inspired this post was that vingetting affects total light to the degree that 4x turns into more like 2.8x depending on lenses being considered. This might seem like technical hairsplitting, but to dig into technicalities was the point of the post.

The reason this matters is the nature of noise. The majority of noise in today's cameras is from photon shot noise, which is a property of the light itself and not of the lens or sensor or any other camera electronics. The only way to reduce shot noise is to collect more light. Whether you do this with a larger sensor, a larger aperture, or a slower shutter speed is immaterial.

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Cheers,
-Ian

 Muster Mark's gear list:Muster Mark's gear list
Olympus E-3 Olympus Zuiko Digital ED 50mm 1:2.0 Macro Olympus Zuiko Digital ED 12-60mm 1:2.8-4.0 SWD Olympus Zuiko Digital ED 50-200mm 1:2.8-3.5 SWD
OP Muster Mark Contributing Member • Posts: 588
Re: Is my thinking about equivalence right?
1

A lot of words there to say "multiply focal length and aperture by same constant" as far as I can tell. Which I get. My reason for making this post is that no one seems to be interested in doing these calculations correctly (i.e. integrating illumination over the frame) and instead assume lenses are ideal and have no vignetting, which should be part of the total light calculation (instead of saying pupil area x sensor size).

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Cheers,
-Ian

 Muster Mark's gear list:Muster Mark's gear list
Olympus E-3 Olympus Zuiko Digital ED 50mm 1:2.0 Macro Olympus Zuiko Digital ED 12-60mm 1:2.8-4.0 SWD Olympus Zuiko Digital ED 50-200mm 1:2.8-3.5 SWD
OP Muster Mark Contributing Member • Posts: 588
Re: Is my thinking about equivalence right?

ivan bayu wrote:

please don't assume. even i personally never heard any lens that its f stop and t stop are equal...

It seemed like a much more reasonable assumption than assuming ideal lenses that have no vignetting.

for me, just buy what suits your needs most, but yes, there'll be some compromises and sacrifices. just utilised your gear to its maximum potential...

Yep! I agree, this post was about technical hairsplitting for people that enjoy thinking about the engineering/physics of it.

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Cheers,
-Ian

 Muster Mark's gear list:Muster Mark's gear list
Olympus E-3 Olympus Zuiko Digital ED 50mm 1:2.0 Macro Olympus Zuiko Digital ED 12-60mm 1:2.8-4.0 SWD Olympus Zuiko Digital ED 50-200mm 1:2.8-3.5 SWD
jalywol
jalywol Forum Pro • Posts: 11,179
Re: Is my thinking about equivalence right?
3

Muster Mark wrote:

I personally am shopping around at the moment (trying to decide if I want to adapt old 4/3 glass to m4/3 bodies, or buy new lenses and potentially change systems or buy new m4/3 lenses) and thus did this analysis to try to compare systems more accurately. Hopefully it was moderately interesting?

If there is anything I should be accounting for that I am not (and you know how I might, e.g. t stops) I'd be curious to hear.

Here's the thing: There is a lot of really wonderful glass in M43. I would not, at this point, go with adapting, as it's a pain in the rear, and the adapters are only available as third party new or Oly used. And the M43 lens lineup is really nicely extensive in terms of focal lengths, price, speed, and sizes, so it wins there, too.

A lot of the answers to your questions can be found in what you like to shoot.

For instance: If you like to go long but don't like to carry heavy glass, then M43 is ideal. FF gets big in a hurry if you want to cover distances via lens optics. On the other hand, if you are doing most of your shooting in lower light, a bigger sensor is going manage high ISO noise better than M43.

Do you shoot a lot of macro? It's easier with M43. On the other hand, do you shoot images where you like to have lots of DOF control? FF is a lot easier to work with there.

I personally do an eye roll and inward groan when equivalence arguments crank up. For me, each format has strengths and weaknesses, and each has its place. Trying to shoehorn each one into a written equivalence comparison is fairly pointless, as it also doesn't take into account strengths and weaknesses of each individual camera or camera/lens combination, but, instead, makes broad generalizations about each system type that may or may not be entirely applicable to individual systems.

So, for me, I use my M43 for long work (birds, long lens insect macro) mostly, and have FF for wide to normal, or when I want to work in lower light without a noise penalty. I really like the output of the FF I have, but, when I take a good shot, it doesn't seem to matter what camera it came from; people react to the photo, not the technology that created it. So, I will continue to use both systems when each is the best fit, and, I would suggest that figuring out what the best fit FOR YOU is, is the path you might want to follow also.

-J

ivan bayu Regular Member • Posts: 205
Re: Sigma 50mm F1.4 Art

Messier Object wrote:

Sigma ART lenses start to really shine honestly. Generally very well corrected optically, much less vingetting on FF than other lenses when wide open, and even slightly cheaper priced to the olympus. They are significantly bigger though (the 50mm 1.4 is 815g, versus 410g for the oly).

well, have you ever use that sigma art 50mm f1.4 before?

I’m curious about why you asked that question

Peter

well, have you tried it? how's the vingetting? of cource on the uncorrected raw... that simple

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Messier Object Forum Pro • Posts: 11,004
Re: Sigma 50mm F1.4 Art
1

ivan bayu wrote:

Messier Object wrote:

Sigma ART lenses start to really shine honestly. Generally very well corrected optically, much less vingetting on FF than other lenses when wide open, and even slightly cheaper priced to the olympus. They are significantly bigger though (the 50mm 1.4 is 815g, versus 410g for the oly).

well, have you ever use that sigma art 50mm f1.4 before?

I’m curious about why you asked that question

Peter

well, have you tried it? how's the vingetting? of cource on the uncorrected raw... that simple

now you're asking me the question - or you've mistaken me for the OP

Are you asking to learn about the lens, or are you already familiar with it and you're trying to make some point about how poorly or otherwise it performs ? - that simple

If you really do want to learn about the lens then there are plenty of reviews out there. Here's one by Ken Rockwell Sigma 50mm Art

and this is what it says about vignetting . . .

and this from photographylife.com

Is that what you wanted to know ?

Peter

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