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Author Topic: Sensor size v Lens size compromise - Your views  (Read 2795 times)

Eric Myrvaagnes

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Re: Sensor size v Lens size compromise - Your views
« Reply #20 on: June 01, 2017, 11:12:37 PM »

I recently upgraded my Sony RX10 to the RX10III, and my experience perfectly matches Terry's. I don't miss my Canon 5DII gear at all, and I don't miss having to clean the sensor after almost every photo shoot.
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hogloff

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Re: Sensor size v Lens size compromise - Your views
« Reply #21 on: June 02, 2017, 09:31:20 AM »

Lenses for full frame mirrorless, ie, Sony A7 camera, are the same size as lenses for full frame Nikon or Canon or any other brand.  Check out the weight, length of various camera/lens options at this site:   
http://camerasize.com
Brad

Depends on the lens. With a Sony system you can get a very nice compact kit if you want. For example the Sony 28 and 35 lenses are very compact as well as the 55. The Zeiss Batis line of lenses are relatively small and deliver exceptional quality. Sure the GM lenses are large, but if you want compact they are available.

I find it funny that every time people bring up the big and heavy GM lenses when making a point that Sony lenses are no smaller than DSLR lenses and totally ignore the ones that are smaller.
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Paul Roark

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Re: Sensor size v Lens size compromise - Your views
« Reply #22 on: June 02, 2017, 12:50:20 PM »

The combo I'm finding most rewarding in terms of quality v. size/weight is the Sony a7r, Kolarivision Ultra Thin cover glass replacement, and Leica M-Mount optics.  The widest, most symmetrical M-mount optics are still unduly affected by the cover glass, as they are on the M9.  However, some, like the Voigtlander 35mm Ultron are amazingly good -- better than the OEM Sony with the thicker cover glass.  The Voigtlander VM-E adapter can be used to precisely set the infinity stop, which is important to me for fast, hand held, dual-focus landscape shots.  Note that the infinity stop is somewhat unique to each lens (or ray angle) where there is a cover glass, but the VM-E is easy to put a calibration system/scale on so that I just adjust it to the indicated mark when a lens is changed.

Paul
www.PaulRoark.com
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Mosccol

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Re: Sensor size v Lens size compromise - Your views
« Reply #23 on: June 02, 2017, 01:25:52 PM »

Lenses for full frame mirrorless, ie, Sony A7 camera, are the same size as lenses for full frame Nikon or Canon or any other brand.  Check out the weight, length of various camera/lens options at this site:   
http://camerasize.com
Brad

What a great site!  :)
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Mosccol

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Re: Sensor size v Lens size compromise - Your views
« Reply #24 on: June 02, 2017, 01:54:45 PM »

Take a moment to consider the 1" sensor cameras. The Sony RX10iii has excellent Zeiss glass, is a 24-600mm equivalent at f/2.4-4. The DR is as good as any Olympus or Panasonic M4/3 and you never need to change lenses. I carry it around all day on my shoulder and in hand and never think twice. DoF at f/5.6 is the same as f/15 on FF, so even hand holding is much easier.

Almost everything I've shot in the last year has been with it, so have a look at my Flickr page to see what's possible. And they print to 13x19, no problem.

More on the Sony experience here, too.

Thanks Terry. Great LuLa article too
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Jack Hogan

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Re: Sensor size v Lens size compromise - Your views
« Reply #25 on: June 02, 2017, 03:23:17 PM »

Jim,
true IF that very shallow DOF is a goal, rather than just an unfortunate side effect of the need for adequate shutter speed with the far more limited ISO speeds of the film era — which I suspect was the most common reason for using such bulky lenses back then!

Another way to say what Jim said is that equivalent images could be produced with the Sony lens having a minimum aperture of f/5.6.  How small would that lens be?  It turns out that it could be about the same size as the 4:3 lens.

As a matter of fact if one compares a larger format to a smaller one the main difference is that the larger format is not necessarily better but it gives the photographer more options, and many of us like to have options (e.g. to have an equivalent f/5.6 lens, or if we wish to have an equivalent f/1.4 lens).  If you don't need options then stick with the minimum that will do what you need.

Jack
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BJL

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Re: Sensor size v Lens size compromise - Your views
« Reply #26 on: June 02, 2017, 04:03:38 PM »

Another way to say what Jim said is that equivalent images could be produced with the Sony lens having a minimum aperture of f/5.6.
Indeed: perhaps you missed my second paragraph, where indeed I said "a more relevant comparison might be 35-100/2.8 vs 70-200/5.6". But:
How small would that lens be?  It turns out that it could be about the same size as the 4:3 lens.
These "equivalent" lenses (with the same effective aperture diameter, a.k.a. entrance pupil size) are similar in front element size, but typically somewhat longer due to the greater focal length, and as I said there is also likely to be a more expensive body, so it hardly seems the best way to achieve a given DOF goal. The differences become more extreme when one can get the job done in the smaller format with a lens in the sweet spot for good, flexible lens design, like f/2.8-4 or constant f/4 zoom lenses, because then there are often no "equivalent" lenses for the larger format, so one instead is forced to using larger, heavier lenses that are "overkill" for the task.

Add to this the observation of Guillermo Luijk in the post after mine that this "equivalence at equal effective aperture diameter" breaks down in low light situations, due to the generally greater total internally generated noise in a larger sensor. Very rough modeling of electronic noise sources suggests that in terms of low-light (high ISO speed) SNR, the equivalence is about a one stop gain in usable ISO speed per doubling of linear sensor size, so f/2.8 in Four Thirds roughly matches f/4 at twice the focal length in 35mm format, and so with 1.4x larger effective aperture diameter ND twice the effective aperture area. Note that this means that equalizing SNR goes with somewhat shallower DOF in larger format.

Let me float an idea for discussion: for the sake of low DOF and high shutter speed/low light needs, there is value to using a larger format when the smaller format is falling short even with moderately fast lenses like f/2.8 or f/2.8-4 zooms and f/1.4 or faster primes. (Resolution and dynamic range are other factors of course; the ones most relevant to choosing larger formats in the film era.)
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Peter_DL

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Re: Sensor size v Lens size compromise - Your views
« Reply #27 on: June 03, 2017, 05:53:04 PM »

I guess the first decision I need to make is sensor v lens bulk.

Or, you may want to decide first about the range of focal lengths being of interest.
The balance of sensor size vs. bulk shifts considerable when long focal lengths are required.

Peter
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Jack Hogan

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Re: Sensor size v Lens size compromise - Your views
« Reply #28 on: June 04, 2017, 05:15:46 AM »

Indeed: perhaps you missed my second paragraph, where indeed I said "a more relevant comparison might be 35-100/2.8 vs 70-200/5.6". But:These "equivalent" lenses (with the same effective aperture diameter, a.k.a. entrance pupil size) are similar in front element size, but typically somewhat longer due to the greater focal length, and as I said there is also likely to be a more expensive body, so it hardly seems the best way to achieve a given DOF goal. The differences become more extreme when one can get the job done in the smaller format with a lens in the sweet spot for good, flexible lens design, like f/2.8-4 or constant f/4 zoom lenses, because then there are often no "equivalent" lenses for the larger format, so one instead is forced to using larger, heavier lenses that are "overkill" for the task.

Sure Bill, lens availability at either end of the usability spectrum depends on manufacturer's marketing focus.  However most folks who do this type of thought experiment do not realize how much marketing has to do with it.  If you bring equivalence into the picture at the design stage you get more options to make larger format lenses smaller and lighter than one would guess. One can easily trade off f-number for focal length as demonstrated by the addition of, for instance, a 1.4 teleconverer which transforms a 300mm f/4 lens into 420mm f/5.6 in just 20mm.  That's with an outside adaptor, imagine what could be done by a good optics engineer.

Add to this the observation of Guillermo Luijk in the post after mine that this "equivalence at equal effective aperture diameter" breaks down in low light situations, due to the generally greater total internally generated noise in a larger sensor. Very rough modeling of electronic noise sources suggests that in terms of low-light (high ISO speed) SNR, the equivalence is about a one stop gain in usable ISO speed per doubling of linear sensor size, so f/2.8 in Four Thirds roughly matches f/4 at twice the focal length in 35mm format, and so with 1.4x larger effective aperture diameter ND twice the effective aperture area. Note that this means that equalizing SNR goes with somewhat shallower DOF in larger format.

Guillermo's demo, though interesting for what it is, has too many hidden assumptions to be a good reference for this kind of discussion.  I do not understand what he means by in that case, noise statistics dictate that the M4/3 sensor will double the SNR over the FF sensor: that's not what I know, all other things equal.  What I know is that, in general, if two cameras of different formats are set up equivalently in theory the signal in photoelectrons out of both is pretty well the same, as shown below.  Forget the Aspect Ratio (AR) and lens transmittance (q*) terms for now, if the signal out of both sensors is the same, they both have the same number of pixels and read noise is the same, why would the SNR be different?



Jack
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Guillermo Luijk

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Re: Sensor size v Lens size compromise - Your views
« Reply #29 on: June 04, 2017, 10:17:59 AM »

Guillermo's demo, though interesting for what it is, has too many hidden assumptions to be a good reference for this kind of discussion.  I do not understand what he means by in that case, noise statistics dictate that the M4/3 sensor will double the SNR over the FF sensor:

My demo just demonstrates how noise statistics make invalid the FF vs M4/3 equivalence just giving the M4/3 a lens with two extra stops of max aperture. It's a counter example.

For the case you cited: same amount of collected light and same DOF, the smaller sensor provides better SNR than the FF sensor.

Just think of two sensors with the same photosite size (or any sensor vs a crop of irself):

- Two extra stops of light multiply per-pixel SNR in the shadows of the M4/3 sensor by 4.
- The four times extra surface of the FF sensor, once rescaled to the same final pixelcount of the M4/3 just doubles the SNR.

The result is that the M4/3 sensor still doubles the SNR of the FF sensor for the same collected light and DOF.

In a real case like my demo smaller sensors usually have smaller photosites so the advantage is less than one whole stop, but still remains some advantage.

In low light conditions with a minimum DOF requirement, smaller sensors (or crops from a bigger sensor) perform better in SNR at the cost of pixelcount.

I tried to explain it here without much success:

http://forum.luminous-landscape.com/index.php?PHPSESSID=badlu6vmb2c0gv55njahfbanj5&topic=102356.0

Regards
« Last Edit: June 04, 2017, 10:23:43 AM by Guillermo Luijk »
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Jack Hogan

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Re: Sensor size v Lens size compromise - Your views
« Reply #30 on: June 04, 2017, 12:23:35 PM »

My demo just demonstrates how noise statistics make invalid the FF vs M4/3 equivalence just giving the M4/3 a lens with two extra stops of max aperture. It's a counter example.

For the case you cited: same amount of collected light and same DOF, the smaller sensor provides better SNR than the FF sensor.

Hi Guillermo,

I did not cite a specific case, I made a general statement: With an Equivalent setup - leaving aside differences in lens transmission, effective QE and sensor aspect ratio for simplicity - two sensors of different formats will produce exactly the same signal in units of photoelectrons.  Therefore, if the Signal is the same and assuming similar read Noise performance, normalized SNR out of the two will be about the same.

Just think of two sensors with the same photosite size (or any sensor vs a crop of irself):

- Two extra stops of light multiply per-pixel SNR in the shadows of the M4/3 sensor by 4.
- The four times extra surface of the FF sensor, once rescaled to the same final pixelcount of the M4/3 just doubles the SNR.

In my opinion it is easier to start by assuming that both sensors are made up of the same number of pixels.  All else being equivalent/equal, the FF and mFT pixels will see/collect more or less the same number of photons/e-, as shown in the link in the earlier post.  Does that make sense?  If so the rest, including situations where the number of pixels is different, follows from there.

Jack
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Guillermo Luijk

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Re: Sensor size v Lens size compromise - Your views
« Reply #31 on: June 04, 2017, 04:31:32 PM »

In my opinion it is easier to start by assuming that both sensors are made up of the same number of pixels.  All else being equivalent/equal, the FF and mFT pixels will see/collect more or less the same number of photons/e-, as shown in the link in the earlier post.  Does that make sense?  If so the rest, including situations where the number of pixels is different, follows from there.

Hi Jack, I think the opposite because the effect of different photosite sizes is much more complex to model than just changing the pixelcount, which is pure resize noise statistics.

For instance the Canon 7D II is a perfect APS crop of the 5DS. If one looks at DxOMark DR and SNR figures for both cameras will find that noise advantage of the FF sensor is just 2/3EV, not 1+1/3EV which is the difference needed in aperture to match DOF.

4dB in SNR (2/3EV eq.):


2/3EV in DR:



My personal cameras (16Mpx E-P5 and 24Mpx A7 II) fall in between the equal photosites and equal pixelcount cases, being closer to your preferred situation, equal pixelcount. Still the M4/3 beats the A7 II in SNR for equal amount of collected photons. A photosite collecting four photons is better than four photosites collecting one photon each.

Regards
« Last Edit: June 04, 2017, 04:45:38 PM by Guillermo Luijk »
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Jack Hogan

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Re: Sensor size v Lens size compromise - Your views
« Reply #32 on: June 04, 2017, 04:51:37 PM »

Here are two cameras with roughly 20MP, roughly Equivalently setup, roughly same number of photons on the image, roughly the same FOV, roughly exposed for same DOF (cheating here, but it works for SNR*): from the second cc24 gray square from left, Em1-II SNR 10.8, D5 SNR = 10.2, compatible with many small differences and non idealities.



Similar story and same Exposure with two older cameras with different pixel counts (16 vs 24MP), normalized to the same size by the 'comp' button:



Where is this SNR doubling?

Jack
* These are captures from DPR's dim sudio scene, you can see them there.  The Em1s were shot at 1/10s f/5.6, which for SNR purposes is equivalent to 1/40s f/2.8.

« Last Edit: June 04, 2017, 05:06:15 PM by Jack Hogan »
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Guillermo Luijk

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Re: Sensor size v Lens size compromise - Your views
« Reply #33 on: June 04, 2017, 05:29:24 PM »

The SNR doubling is always there when photosites are the same technology, it is dictated by simple statistics. This counterexample alone makes false the argument that "a FF sensor is equivalent to a M4/3 sensor with a lens two stops faster".

Regarding your examples, mixing technologies you'll find all possible comparisons (D5 is the King of high ISO at the cost of base ISO DR). Even M4/3 Sony sensors with better DR than Canon FF sensors. But again this makes false that "a FF sensor is equivalent to a M4/3 sensor with a lens two stops faster".



Regards
« Last Edit: June 04, 2017, 05:33:35 PM by Guillermo Luijk »
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JoachimStrobel

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Re: Sensor size v Lens size compromise - Your views
« Reply #34 on: June 04, 2017, 05:38:33 PM »

I will probably attract a lot of criticism and other comments: But is there not more to this question then DOF, equivalent this and that? I always admired the 120 roll film photos being taken with cheap cameras in the 60s. They had this special appearance I never got with 35 mm. And I did admire Polaroids because they all had this big-format feeling. There is more to large vs small format then just the numbers that have been cited here. It is the "Anmut" of these Images. Same as comparing these tiny Iphone photos to FF and eventually M43. This might all be imagination and not backed up by hard data, or is it not?
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Jack Hogan

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Re: Sensor size v Lens size compromise - Your views
« Reply #35 on: June 05, 2017, 03:02:30 PM »

The SNR doubling is always there when photosites are the same technology, it is dictated by simple statistics. This counterexample alone makes false the argument that "a FF sensor is equivalent to a M4/3 sensor with a lens two stops faster".

Regarding your examples, mixing technologies you'll find all possible comparisons (D5 is the King of high ISO at the cost of base ISO DR). Even M4/3 Sony sensors with better DR than Canon FF sensors. But again this makes false that "a FF sensor is equivalent to a M4/3 sensor with a lens two stops faster".

I have no idea what you mean by this Guillermo, my post was in reference to your comment "in that case, noise statistics dictate that the M4/3 sensor will double the SNR over the FF sensor", that case referring to equal total collected photons and DOF for two different formats.  I cannot see where this SNR doubling comes from all else being equal/equivalent.  Can you take a look at the physics in the link in my earlier post?  Unless you can point to an error there, it says that they would be about the same and that's my experience as also shown by the images in my previous post.

Jack
« Last Edit: June 05, 2017, 03:06:35 PM by Jack Hogan »
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BJL

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Sensor size v Lens size compromise - TC equivalence, broken by read noise
« Reply #36 on: June 05, 2017, 05:19:31 PM »

One can easily trade off f-number for focal length as demonstrated by the addition of, for instance, a 1.4 teleconverer which transforms a 300mm f/4 lens into 420mm f/5.6 in just 20mm.  That's with an outside adaptor, imagine what could be done by a good optics engineer.
Yes; in fact I have advocated the "teleconverter equivalence" idea, as far as FOV, DOF and photon shot noise go–if one ignores read noise.  The idea is that an "equivalent" 70-200/5.6 for 35mm format could be created from a 35-100/2.8 for Four thirds by adding a 2x TC.  Then the size difference need not be nearly as much as comparing to a 70-200/2.8, but the TC would add some bulk.  And this is somewhat close to how telephoto lens designs work: by definition, a true "telephoto" lens (any that is physically shorter than its focal length) consists of a shorter, brighter lens design at the front with a diverging group ("integrated TC") at the back.  Something like "50–140/4 + 1.4TC = 70–200/5.6".

Hence my "somewhat bulkier" comment.

if the signal out of both sensors is the same, they both have the same number of pixels and read noise is the same, why would the SNR be different?
Your formulas indeed show "teleconverter equivalence" if the only noise is photon shot noise, or if there is an equal amount of noise from other sources. But Guillermo's point and mine is that it is unreasonable to assume equal read noise: instead, the greater size of the larger sensor and its electron wells, transistors, ADC units and so on increases electronic noise, and this theoretical observation is supported by Guillermo's experimental result, as well as other "equivalent exposure in different formats" comparisons that I have seen.
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Guillermo Luijk

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Re: Sensor size v Lens size compromise - Your views
« Reply #37 on: June 05, 2017, 06:23:14 PM »

In fact in my opinion the importance of photon noise is overestimated. No picture gets ruined because of photon noise, everytime noise is a problem there is a read noise problem.

That is why I consider irrelevant the fact that SNR increases by sqrt(2) per exposure stop in well exposed areas where photon noise is dominant, because noise is not a problem for the photographer there. The game is played in read noise dominant areas where SNR improves by a factor of 2 everytime exposure is increased by one stop. That is why four times more surface (SNR differs by a factor of 2) can't compensate for the loss of two stops in aperture (SNR differs by a factor of 4).

Regards
« Last Edit: June 05, 2017, 06:30:05 PM by Guillermo Luijk »
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Jack Hogan

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Your formulas indeed show "teleconverter equivalence" if the only noise is photon shot noise, or if there is an equal amount of noise from other sources. But Guillermo's point and mine is that it is unreasonable to assume equal read noise: instead, the greater size of the larger sensor and its electron wells, transistors, ADC units and so on increases electronic noise, and this theoretical observation is supported by Guillermo's experimental result, as well as other "equivalent exposure in different formats" comparisons that I have seen.

I see, so we all agree that in an equivalent setup (with same FOV, number of photons collected, DOF, number of pixels etc.) as far as SNR is concerned in the end it mostly boils down to read noise in e- and other non idealities (like differences in eQE, lens transmission etc.).  And we also all agree that "The SNR doubling is always there when photosites are the same technology, it is dictated by simple statistics" or that "same amount of collected light and same DOF, the smaller sensor provides better SNR than the FF sensor" makes no sense when different formats are compared with everything else including read noise equal/equivalent.

Once read noise and the non idealities are accounted for, I can see small deviations from equivalent theory and practice in typical mFT vs FF SNR comparisons (examples shown above) but nowhere near approaching 2x with same grade kit of the same generation.

Jack
« Last Edit: June 06, 2017, 10:43:58 AM by Jack Hogan »
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Jack Hogan

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Read Noise and Practical Photography SNR
« Reply #39 on: June 06, 2017, 05:35:49 AM »

In fact in my opinion the importance of photon noise is overestimated. No picture gets ruined because of photon noise, everytime noise is a problem there is a read noise problem.

Ok, it may have been worth mentioning in your demo and previous posts as quoted to Bill that you were referring specifically and only to read noise differences in a disaster scenario when you suggested "For the same amount of total collected light and DOF, a M4/3 sensor needs two extra aperture stops over a FF sensor, that is right. But in that case, noise statistics dictate that the M4/3 sensor will double the SNR over the FF sensor".  That was not obvious to me.  And of course it's not true when all else is equal/equivalent - in fact in practice it is mostly not true at all :)

In practice the impact of read noise in this type of comparison is limited for the typical photographer.  For instance Bill Claff has a neat way of defining the ratio of maximum to minimum useful/acceptable signal in typical photography.  He calls it Photographic Dynamic Range and has calculated this value and much more for a large number of cameras at his site http://www.photonstophotos.net/.  That clever metric is based on Bill's realization that most photographers will find image data below a certain SNR unacceptable when viewed in typical conditions.  If interested in the subject I encourage folks to read up on its details there.

Using the earlier example of two cameras from roughly the same generation and number of pixels to guide us through this, PDR says that image data with an SNR below 5 would be unacceptable for photographers with 16MP cameras like the EM-1.  His fine site also indicates that at ISO 3200 the EM-1 has a read noise of 1.4e- and the D610 at ISO12800 of 2.4e-*.  The Signal at which the normalized D610 would hit a SNR of 5 is about 29.7e-, this is the minimum acceptable Signal.  As a result of its lower read noise, theory says that at that Signal the EM-1 would instead produce a SNR of 5.28, not substantially different from the D610's.

Theory is confirmed by looking at actual images and measuring SNR off them, as I did in the earlier post**.  The EM-1 at ISO3200 1/40s f/5.6 below received two stops more Exposure than the D610 at ISO12800 1/10s f/5.6:





Even in a disaster scenario, with the D610 limited to an SNR of 1, the EM-1 would have an SNR of 1.33 - the difference wholly accounted for by the EM-1's lower read noise and still very, very far from 2x.  I would also like to point out that all formats are fast converging to the current read noise limit of just over 1e- per pixel in 'dark' ISOs (see FF cameras released over the last year or so), therefore it's unlikely we are going to see such big differences in disaster scenarios in the future.

Jack
*Normalized to 16mp, but normalization is not a determining factor for this calculation.
** From DPR dim studio scene, 'comp' button pressed, many non idealities and provisos apply.
« Last Edit: June 06, 2017, 10:28:28 AM by Jack Hogan »
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