On Sharpness, ISO and Shutter Speed

Started 9 months ago | Discussions
Jack Hogan
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On Sharpness, ISO and Shutter Speed
9 months ago

Some of this information has appeared in recent posts, but I thought it deserved its own thread.

DPR's improved technique in capturing images for its new Studio Scene includes focus bracketing and controlled lighting, resulting in one of the better databases of systematically collected raw files available for downlonad online. Nevertheless there have been reports of inconsistencies and unexpectedly blurry images which most people (including myself) have almost subconsciously ascribed to either faulty equipment or operator error. Given the vast number of variables, pieces of equipment and information collected there are bound to be some of those. On the other hand, if we take the information for good, we may be able to gain some interesting insights on our gadgets, their performance and testing at large. As some of you know I've been playing with MTF Mapper recently, so in this post I am going to concentrate on MTF50 as an imperfect but convenient indicator of Spatial Resolution quality in the captured information (aka sharpness).

I used the slanted edges in DPR's new Studio Scene's raw files to derive vertical and horizontal MTF50 readings at base ISO in order to get the cleanest reading possible. AFAIK the captures are taken on a tripod, mirror up (where there is one), delayed release, typically at a lens' sharpest aperture, at whatever shutter speed is appropriate for the desired Exposure. The few times that I checked ISOs just above base I saw a tendency for the MTF50 readings to creep up, which I assumed was increased noise messing with MTF Mapper's algorithms. Upon further inspection, it turns out I was wrong.

Here for instance is how the MTF50 readings vary with ISO on a Nikon DF whose sensor has a 'traditional' antialiasing filter:

It doesn't vary much. Here are two more with sensors by a different manufacturer (the D800 applies digital scaling after ISO1600)

Shutter Speeds Correspond to ISO 200-6400

And since we are at it here is a more recent camera with a sensor by the same manufacturer as the last two, Sony's A7

The vertical and horizontal readings in previous graphs were within what I think would be the expected accuracy of measurements from different setups (say +/-3% from the average), but obviously something is very different in this case compared to the previous ones - most likely the AA as explained by The_Suede here . It is also clear that MTF Mapper deals with the increasing noise with aplomb, so taking the data for good it is worth investigating some of the imperfections in it.

For instance the dip in performance of the EM5 at base ISO. There have been suggestions that some cameras suffer from obvious shutter shock. Could this be it? Let's take a look at its younger brother, which reportedly shows the issue more clearly

Shutter Speeds correspond to ISO 100-6400

Whoa. Looking at the relative images in the comparometer confirms these results: below 1/320th the EM1's images are definitely blurrier. Shutter Shock, changed lighting, changed positions, changed hardware, misfocus, operator error? And what do we make of that vertical/horizontal crossover?

Steen Bay wondered how the AAless Sony A7r would look next to the AAful A7 above, because the A7 has an electronic shutter while the A7r has a mechanical one.

Interesting. This confirms reports that the A7's images look sharper than the A7r's at some ISOs in the Studio Scene - I (probably incorrectly) thought the A7r's focus had not been peaked properly. And there's that dip again.

I also wondered how the D610 (mechanical shutter) would do against the A7, since its sensor is the same size, it is made by the same manufacturer and it has the same resolution.

The first set of ISOs come from the 'Dim' Studio Scene Setting. The seond from the 'Daylight' setting

Still interesting. The large difference in horizontal and vertical readings is similar to what it was in the A7 - but here we see the inconsistent 'dip' near base ISO and few subsequent stops, which is not there in the A7 with its electronic shutter. The slower shutter speeds are from 'dim light' Studio Scene raw files, to see whether a change in lighting/WB would make a difference. It apparently doesn't.

So I have two initial questions, assuming that the data is valid:

1) What are the practical implications for a photographer of the large spatial resolution differences in the V+H directions seen in the newer sensors measured here ? Will it make a difference whether we look at the final image in portrait vs landscape orientation?

2) Are the dips we see in MTF50 around 1/10th of a second to about 1/300th possibly due to shutter shock - or something else? What implications does this have for people choosing a high resolution camera today?

Everybody's thoughts are welcome.

Jack

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Steen Bay
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Re: On Sharpness, ISO and Shutter Speed
In reply to Jack Hogan, 9 months ago

Very interesting, thanks for posting. Wondering why the D800 resolution (or 'sharpness') is so relatively low (about the same as the 24mp A7)? Another mFT camera with a serious shutter shock issue (I assume) in the new comparison tool is the Panasonic G6. Seems to be even worse than on the E-M1. Could probably have been avoided if DPR had used the optional electronic shutter on G6. Olympus E-P5 and E-PL5 are affected too, but it doesn't seem to be a problem on the (also mirror less) Fuji X-E2 and X-Pro1. Can't spot any problems on Canon and Nikon DSLRs, except maybe a bit with the D5300.

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Austinian
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Re: On Sharpness, ISO and Shutter Speed
In reply to Steen Bay, 9 months ago

Steen Bay wrote:

Very interesting, thanks for posting. Wondering why the D800 resolution (or 'sharpness') is so relatively low (about the same as the 24mp A7)?

Seeing this data raises a number of questions in my mind; unfortunately I lack the technical background to even begin to answer them. I will be watching what you gentlemen and the other experts discover with great interest. There may be implications for everyone in this.

Another mFT camera with a serious shutter shock issue (I assume) in the new comparison tool is the Panasonic G6. Seems to be even worse than on the E-M1. Could probably have been avoided if DPR had used the optional electronic shutter on G6. Olympus E-P5 and E-PL5 are affected too, but it doesn't seem to be a problem on the (also mirror less) Fuji X-E2 and X-Pro1. Can't spot any problems on Canon and Nikon DSLRs, except maybe a bit with the D5300.

One thing that concerns me; if this is shutter shock vibrating the sensor, external damping (heavier tripod, draping the camera body on the tripod with weights, etc.) may not be of much help.

I do wonder; how could high-end camera manufacturers, with vast resources for testing, possibly miss an engineering problem like this with a potential for degrading the value of their premium products?

More data! 

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Anders W
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Re: On Sharpness, ISO and Shutter Speed
In reply to Austinian, 9 months ago

Austinian wrote:

Steen Bay wrote:

Very interesting, thanks for posting. Wondering why the D800 resolution (or 'sharpness') is so relatively low (about the same as the 24mp A7)?

Seeing this data raises a number of questions in my mind; unfortunately I lack the technical background to even begin to answer them. I will be watching what you gentlemen and the other experts discover with great interest. There may be implications for everyone in this.

Another mFT camera with a serious shutter shock issue (I assume) in the new comparison tool is the Panasonic G6. Seems to be even worse than on the E-M1. Could probably have been avoided if DPR had used the optional electronic shutter on G6. Olympus E-P5 and E-PL5 are affected too, but it doesn't seem to be a problem on the (also mirror less) Fuji X-E2 and X-Pro1. Can't spot any problems on Canon and Nikon DSLRs, except maybe a bit with the D5300.

One thing that concerns me; if this is shutter shock vibrating the sensor, external damping (heavier tripod, draping the camera body on the tripod with weights, etc.) may not be of much help.

External damping does help. Put the camera on a heavy and perfectly rigid surface (like for example a stone floor) and you won't see any sign of shutter shock even with lenses far more sensitive to the problem than a short tele. I have tried it with my Oly E-M5 and Pany 100-300 at 300 mm (600 mm EFL) and see no problem at all under those conditions. When shooting the same combo from a reasonably sturdy tripod, however, I can't get blur-free images in the critical range of shutter speeds (about 1/25 to 1/250 with the peak about 1/100 or slightly higher).

That said, I am surprised to see the problem appear (if that's what it is in DPR's studio samples; we don't know that yet) with what is supposedly a heavy studio tripod and a much shorter FL (about 100 mm EFL). I can't remember seeing any problems of this kind with the old DPR studio samples, which makes you wonder if they have some special problems with the support gear they are using for some or all cameras.

I do wonder; how could high-end camera manufacturers, with vast resources for testing, possibly miss an engineering problem like this with a potential for degrading the value of their premium products?

A so-called good question.

More data!

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Anders W
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Re: On Sharpness, ISO and Shutter Speed
In reply to Jack Hogan, 9 months ago

Jack Hogan wrote:

Some of this information has appeared in recent posts, but I thought it deserved its own thread.

DPR's improved technique in capturing images for its new Studio Scene includes focus bracketing and controlled lighting, resulting in one of the better databases of systematically collected raw files available for downlonad online. Nevertheless there have been reports of inconsistencies and unexpectedly blurry images which most people (including myself) have almost subconsciously ascribed to either faulty equipment or operator error. Given the vast number of variables, pieces of equipment and information collected there are bound to be some of those. On the other hand, if we take the information for good, we may be able to gain some interesting insights on our gadgets, their performance and testing at large. As some of you know I've been playing with MTF Mapper recently, so in this post I am going to concentrate on MTF50 as an imperfect but convenient indicator of Spatial Resolution quality in the captured information (aka sharpness).

I used the slanted edges in DPR's new Studio Scene's raw files to derive vertical and horizontal MTF50 readings at base ISO in order to get the cleanest reading possible. AFAIK the captures are taken on a tripod, mirror up (where there is one), delayed release, typically at a lens' sharpest aperture, at whatever shutter speed is appropriate for the desired Exposure. The few times that I checked ISOs just above base I saw a tendency for the MTF50 readings to creep up, which I assumed was increased noise messing with MTF Mapper's algorithms. Upon further inspection, it turns out I was wrong.

Here for instance is how the MTF50 readings vary with ISO on a Nikon DF whose sensor has a 'traditional' antialiasing filter:

It doesn't vary much. Here are two more with sensors by a different manufacturer (the D800 applies digital scaling after ISO1600)

Shutter Speeds Correspond to ISO 200-6400

And since we are at it here is a more recent camera with a sensor by the same manufacturer as the last two, Sony's A7

The vertical and horizontal readings in previous graphs were within what I think would be the expected accuracy of measurements from different setups (say +/-3% from the average), but obviously something is very different in this case compared to the previous ones - most likely the AA as explained by The_Suede here . It is also clear that MTF Mapper deals with the increasing noise with aplomb, so taking the data for good it is worth investigating some of the imperfections in it.

For instance the dip in performance of the EM5 at base ISO. There have been suggestions that some cameras suffer from obvious shutter shock. Could this be it? Let's take a look at its younger brother, which reportedly shows the issue more clearly

Shutter Speeds correspond to ISO 100-6400

Whoa. Looking at the relative images in the comparometer confirms these results: below 1/320th the EM1's images are definitely blurrier. Shutter Shock, changed lighting, changed positions, changed hardware, misfocus, operator error? And what do we make of that vertical/horizontal crossover?

Steen Bay wondered how the AAless Sony A7r would look next to the AAful A7 above, because the A7 has an electronic shutter while the A7r has a mechanical one.

Interesting. This confirms reports that the A7's images look sharper than the A7r's at some ISOs in the Studio Scene - I (probably incorrectly) thought the A7r's focus had not been peaked properly. And there's that dip again.

I also wondered how the D610 (mechanical shutter) would do against the A7, since its sensor is the same size, it is made by the same manufacturer and it has the same resolution.

The first set of ISOs come from the 'Dim' Studio Scene Setting. The seond from the 'Daylight' setting

Still interesting. The large difference in horizontal and vertical readings is similar to what it was in the A7 - but here we see the inconsistent 'dip' near base ISO and few subsequent stops, which is not there in the A7 with its electronic shutter. The slower shutter speeds are from 'dim light' Studio Scene raw files, to see whether a change in lighting/WB would make a difference. It apparently doesn't.

So I have two initial questions, assuming that the data is valid:

1) What are the practical implications for a photographer of the large spatial resolution differences in the V+H directions seen in the newer sensors measured here ? Will it make a difference whether we look at the final image in portrait vs landscape orientation?

Why would it make a difference if we look at it this way or that way? Blur is blur and to my knowledge, the human visual system isn't differently sensitive to blur in one dimension than in the other. Besides, we wouldn't normally want to look at something shot in landscape orientation in portrait mode or vice versa, for pretty obvious reasons.

2) Are the dips we see in MTF50 around 1/10th of a second to about 1/300th possibly due to shutter shock - or something else? What implications does this have for people choosing a high resolution camera today?

Hard to say without knowing more about what's going on in DPR's studio. But the shutter speed range affected and the fact that the blur is largely vertical makes shutter shock the likely culprit. The problem is known to occur in that range, with a peak at about 1/100 s or slightly higher. The point where the problem disappears at the upper end of the range may be related to the max sync speed of the camera (disappearing later the higher that speed is). At the lower end, it disappears more gradually, without much of a clear cut point.

That said, it surprises me to see the shutter-shock problem (if that's what it is) appear so clearly in the DPR studio scene samples. Presumably, they use a heavy studio tripod and the focal length is not all that long (about 100 mm EFL). Furthermore, one would at least have expected DPR to take the precaution of using anti-shock delay with Oly bodies and the electronic shutter option with Pany bodies. But I certainly wouldn't have expected any clear shutter-shock problems even if they didn't, provided that my assumption about good tripod support is correct.

Everybody's thoughts are welcome.

Jack

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Jack Hogan
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Re: On Sharpness, ISO and Shutter Speed
In reply to Anders W, 9 months ago

Anders W wrote:

Jack Hogan wrote:

So I have two initial questions, assuming that the data is valid:

1) What are the practical implications for a photographer of the large spatial resolution differences in the V+H directions seen in the newer sensors measured here ? Will it make a difference whether we look at the final image in portrait vs landscape orientation?

Why would it make a difference if we look at it this way or that way? Blur is blur and to my knowledge, the human visual system isn't differently sensitive to blur in one dimension than in the other. Besides, we wouldn't normally want to look at something shot in landscape orientation in portrait mode or vice versa, for pretty obvious reasons.

Yes, I saw that did not come out right but only after having used up my two corrections already.  Let me rephrase the question:

If in the A7 and D610  there is really such a large difference in horizontal vs vertical captured resolution, is that an issue in practice?  Or should we be preferring capturing in landscape vs portrait orientation to maximize, say, vertical detail in the center of an image?  Many of us spend thousands of dollars on better lenses to typically gain less than the 20% difference shown.

2) Are the dips we see in MTF50 around 1/10th of a second to about 1/300th possibly due to shutter shock - or something else? What implications does this have for people choosing a high resolution camera today?

Hard to say without knowing more about what's going on in DPR's studio. But the shutter speed range affected and the fact that the blur is largely vertical makes shutter shock the likely culprit. The problem is known to occur in that range, with a peak at about 1/100 s or slightly higher. The point where the problem disappears at the upper end of the range may be related to the max sync speed of the camera (disappearing later the higher that speed is). At the lower end, it disappears more gradually, without much of a clear cut point.

That said, it surprises me to see the shutter-shock problem (if that's what it is) appear so clearly in the DPR studio scene samples. Presumably, they use a heavy studio tripod and the focal length is not all that long (about 100 mm EFL). Furthermore, one would at least have expected DPR to take the precaution of using anti-shock delay with Oly bodies and the electronic shutter option with Pany bodies. But I certainly wouldn't have expected any clear shutter-shock problems even if they didn't, provided that my assumption about good tripod support is correct.

The A7r and the D610 show signs of dips around there as well, and they are the lighter of the four FF bodies shown.  Possibly some of this is surfacing now exactly because the better technique and smaller sensors are no longer hiding imperfections that before were below the 'noise' floor.  I wonder if anybody ever put a camera through such rigorous scrutiny 30 years ago

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Austinian
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Re: On Sharpness, ISO and Shutter Speed
In reply to Anders W, 9 months ago

Anders W wrote:

External damping does help. Put the camera on a heavy and perfectly rigid surface (like for example a stone floor) and you won't see any sign of shutter shock even with lenses far more sensitive to the problem than a short tele. I have tried it with my Oly E-M5 and Pany 100-300 at 300 mm (600 mm EFL) and see no problem at all under those conditions. When shooting the same combo from a reasonably sturdy tripod, however, I can't get blur-free images in the critical range of shutter speeds (about 1/25 to 1/250 with the peak about 1/100 or slightly higher).

Interesting. I'm guessing the camera isn't actually attached to the stone floor (as it would be for a tripod), so I wouldn't think it would provide much internal damping. Perhaps the vibrations really are causing whole-camera movement, rather than my original notion of sensor-only movement.

Your info opens up a good deal of speculation on my part; would the problem be minimized by hand-gripping the tripod and camera (with consequent damping), and/or by leaving the IBIS on even when using a tripod?

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Jack Hogan
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Re: On Sharpness, ISO and Shutter Speed
In reply to Steen Bay, 9 months ago

Steen Bay wrote:

Very interesting, thanks for posting. Wondering why the D800 resolution (or 'sharpness') is so relatively low (about the same as the 24mp A7)?

Yes, I wondered that too.  Could be AA strength (the D800 is the oldest model in this sample).  And/or the lens difference.

FWIW Figure 6 here  shows the D800+24-70 @50mm at 2161 lw/ph, so the figures are at least iin the ballpark.

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rubank
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Re: On Sharpness, ISO and Shutter Speed
In reply to Jack Hogan, 9 months ago

Jack Hogan wrote:


If in the A7 and D610 there is really such a large difference in horizontal vs vertical captured resolution, is that an issue in practice? Or should we be preferring capturing in landscape vs portrait orientation to maximize, say, vertical detail in the center of an image? Many of us spend thousands of dollars on better lenses to typically gain less than the 20% difference shown.

It´s interesting (and surprising) to see that the vertical and horisontal readings has swapped places between the two cameras. I wonder what´s with this?

And then a question: does MTFmapper take readings from the "raw" RAW files or from processed files. If the latter, how are they processed?

Side note: I once downloaded the D800 RAW file from DPR, and developed it with my preferred settings in ACR; the result was quite different vs the DPR conversion (i.e. mine was much better), so I wouldn´t make too much of the "weak" D800 performance in DPR's comparison. That is at it should be, maybe, but should be remembered regarding whatever camera is tested.

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rubank
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Re: On Sharpness, ISO and Shutter Speed
In reply to Jack Hogan, 9 months ago

Thanks for this.

Your analysis makes it clear that the studio tests must be taken with some grains of salt.

BTW, the sometimes much critisized IR test shots doesn´t show the same variations, AFAICT.
I´ve downloaded a vast number of IR's RAW files during the years and for more cameras than I can remember, but I haven´t seen this kind of difference between exposures (ISO's). Differences in focussing between cameras is a wellknown fact, but that is something else.

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exdeejjjaaaa
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Re: On Sharpness, ISO and Shutter Speed
In reply to Jack Hogan, 9 months ago

Jack Hogan wrote:

Shutter Speeds Correspond to ISO 200-6400


For instance the dip in performance of the EM5 at base ISO. There have been suggestions that some cameras suffer from obvious shutter shock. Could this be it? Let's take a look at its younger brother, which reportedly shows the issue more clearly

Shutter Speeds correspond to ISO 100-6400

Whoa. Looking at the relative images in the comparometer confirms these results: below 1/320th the EM1's images are definitely blurrier. Shutter Shock, changed lighting, changed positions, changed hardware, misfocus, operator error? And what do we make of that vertical/horizontal crossover?

E-M1 has faster x-sync than E-M5 - so shutter blades impact (higher speed) affects suspended sensor more... as as result I use only manual (non TTL) flashes @ 1/400 xsync now, that allows me to move futher away out of shutter shock prone exposure speeds...

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Ken Strain
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Re: On Sharpness, ISO and Shutter Speed
In reply to Jack Hogan, 9 months ago

These data are puzzling, two features disturb me most:

The spread between H and V gets to about 20% in several of the plots, including the points for the EM5 at 1/4000s. I am reluctant to accept that particular case as being due to shutter shock. If those data are bad, how can we tell which are good?

The EM1 plot is the only one that looks somewhat like I would expect if shutter shock were the main cause of the spread, but even here it appears that something else breaks the H-V symmetry with the opposite sign (such that there is roughly 6% discrepancy between the averaged H and V scopes of the 3 fastest speeds).

Ken

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Jack Hogan
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Re: On Sharpness, ISO and Shutter Speed
In reply to rubank, 9 months ago

rubank wrote:

Jack Hogan wrote:

If in the A7 and D610 there is really such a large difference in horizontal vs vertical captured resolution, is that an issue in practice? Or should we be preferring capturing in landscape vs portrait orientation to maximize, say, vertical detail in the center of an image? Many of us spend thousands of dollars on better lenses to typically gain less than the 20% difference shown.

It´s interesting (and surprising) to see that the vertical and horisontal readings has swapped places between the two cameras. I wonder what´s with this?

Perhaps in Sony cameras the AAs are laid down in one orientation, and in Nikon cameras in another 90 degrees off Sony's.

And then a question: does MTFmapper take readings from the "raw" RAW files or from processed files. If the latter, how are they processed?

I believe these are the least processed files used for this type of analysis on the net: the raw data is just clipped to black and white balanced.  That's it.

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Jack Hogan
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Re: On Sharpness, ISO and Shutter Speed
In reply to rubank, 9 months ago

rubank wrote:

Thanks for this.

Your analysis makes it clear that the studio tests must be taken with some grains of salt.

BTW, the sometimes much critisized IR test shots doesn´t show the same variations, AFAICT.
I´ve downloaded a vast number of IR's RAW files during the years and for more cameras than I can remember, but I haven´t seen this kind of difference between exposures (ISO's). Differences in focussing between cameras is a wellknown fact, but that is something else.

Imho IR is not a good source for this type of information: they admit that they do not have time to meet Imatest's focusing standards, so they do not focus peak properly.  The few images of theirs that I have tested (e.g. D800) confirm this.

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Jack Hogan
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Re: On Sharpness, ISO and Shutter Speed
In reply to Ken Strain, 9 months ago

Ken Strain wrote:

These data are puzzling, two features disturb me most:

The spread between H and V gets to about 20% in several of the plots, including the points for the EM5 at 1/4000s.

Yes. That is the EM5 at ISO 6400, where it is very, very noisy - the noisiest of the sample by a fair margin. I mentioned in the other thread that I believe the spread there is due to the data being too noisy for a reliable MTF50 reading. I included it for completeness in case someone saw something else in it, but otherwise I would be tempeted to ignore it as being outside of usable range. I should experiment a bit with noisy images to see if that is indeed the case.

The EM1 plot is the only one that looks somewhat like I would expect if shutter shock were the main cause of the spread, but even here it appears that something else breaks the H-V symmetry with the opposite sign (such that there is roughly 6% discrepancy between the averaged H and V scopes of the 3 fastest speeds)

Yes, I also wonder about that switch. The other camera that shows it is the A7r (but not the A7). Same problem?

I would be very interested to see a series of properly taken images form the EM1 and A7r at these same apertures with shutter speeds from a couple of seconds to 1/4000th every 1/2 stop or so to see whether I could pinpoint the issue.

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Jack Hogan
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Re: On Sharpness, ISO and Shutter Speed
In reply to Jack Hogan, 9 months ago

Jack Hogan wrote:  I would be very interested to see a series of properly taken images form the EM1 and A7r at these same apertures with shutter speeds from a couple of seconds to 1/4000th every 1/2 stop or so to see whether I could pinpoint the issue.

At base ISO, that is.

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rubank
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Re: On Sharpness, ISO and Shutter Speed
In reply to Jack Hogan, 9 months ago

Jack Hogan wrote:

rubank wrote:

Thanks for this.

Your analysis makes it clear that the studio tests must be taken with some grains of salt.

BTW, the sometimes much critisized IR test shots doesn´t show the same variations, AFAICT.
I´ve downloaded a vast number of IR's RAW files during the years and for more cameras than I can remember, but I haven´t seen this kind of difference between exposures (ISO's). Differences in focussing between cameras is a wellknown fact, but that is something else.

Imho IR is not a good source for this type of information: they admit that they do not have time to meet Imatest's focusing standards, so they do not focus peak properly. The few images of theirs that I have tested (e.g. D800) confirm this.

Yes, as I noted but as I also said that is something else. And at least some part of their studio scene tends to be in good focus....
They don´t show the vaying behavior with changing ISO (i.e. varying shutter speeds), which was my point.

But of course, would it turn out that the DPR setup is so good that it just reveals manufacturers shortcomings then we know who to blame

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Jack Hogan
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Re: On Sharpness, ISO and Shutter Speed
In reply to rubank, 9 months ago

rubank wrote:

But of course, would it turn out that the DPR setup is so good that it just reveals manufacturers shortcomings then we know who to blame

Wouldn't that be ironic...

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Ken Strain
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Re: On Sharpness, ISO and Shutter Speed
In reply to Jack Hogan, 9 months ago

Jack Hogan wrote:

Ken Strain wrote:

These data are puzzling, two features disturb me most:

The spread between H and V gets to about 20% in several of the plots, including the points for the EM5 at 1/4000s.

Yes. That is the EM5 at ISO 6400, where it is very, very noisy - the noisiest of the sample by a fair margin. I mentioned in the other thread that I believe the spread there is due to the data being too noisy for a reliable MTF50 reading. I included it for completeness in case someone saw something else in it, but otherwise I would be tempeted to ignore it as being outside of usable range. I should experiment a bit with noisy images to see if that is indeed the case.

The EM1 plot is the only one that looks somewhat like I would expect if shutter shock were the main cause of the spread, but even here it appears that something else breaks the H-V symmetry with the opposite sign (such that there is roughly 6% discrepancy between the averaged H and V scopes of the 3 fastest speeds)

Fair point, I'd missed that.  Error bars or at least some statement, local to the results, of the random error in the MTF50 result would help.

Yes, I also wonder about that switch. The other camera that shows it is the A7r (but not the A7). Same problem?

I would be very interested to see a series of properly taken images form the EM1 and A7r at these same apertures with shutter speeds from a couple of seconds to 1/4000th every 1/2 stop or so to see whether I could pinpoint the issue.

A better-controlled set of inputs would help: such as two shutter speeds per exposure, two camera orientations per case, to look for AA filter asymmetry,  two camera mounts for each case - at least some variation to change the motion induced by shutter shock without changing other variables, and at least two samples of each camera.  But that becomes a huge task (16 pictures per case - and it would be good to take a few each time).

Ken

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Anders W
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Re: On Sharpness, ISO and Shutter Speed
In reply to Austinian, 9 months ago

Austinian wrote:

Anders W wrote:

External damping does help. Put the camera on a heavy and perfectly rigid surface (like for example a stone floor) and you won't see any sign of shutter shock even with lenses far more sensitive to the problem than a short tele. I have tried it with my Oly E-M5 and Pany 100-300 at 300 mm (600 mm EFL) and see no problem at all under those conditions. When shooting the same combo from a reasonably sturdy tripod, however, I can't get blur-free images in the critical range of shutter speeds (about 1/25 to 1/250 with the peak about 1/100 or slightly higher).

Interesting. I'm guessing the camera isn't actually attached to the stone floor (as it would be for a tripod), so I wouldn't think it would provide much internal damping.

Correct. That's the point of the test. It rules out displacement of the body as a whole but it does not rule out what we might refer to as bell-type vibration.

Perhaps the vibrations really are causing whole-camera movement, rather than my original notion of sensor-only movement.

The tests I am aware of suggest that bell-type vibration isn't involved at all, at least not as a rule (exceptions may exist with certain specific pieces of equipment). Rather, the blur occurs because of displacements of the body in direct response to the way the shutter blades move and stop inside the camera. When these displacements are completely prevented, as they are with the camera on a very heavy and rigid surface, there is no blur.

Your info opens up a good deal of speculation on my part; would the problem be minimized by hand-gripping the tripod and camera (with consequent damping),

No, since the mechanism is not that of bell-type vibration.

and/or by leaving the IBIS on even when using a tripod?

Based on my testing, there is no evidence that IBIS (of the type used in the E-M5 and some later Oly bodies) misbehaves as a result of vibration when used on a tripod. While the manual recommends that you turn it off when shooting from a tripod, I have seen no ill effects from forgetting to do so, as I sometimes have, even in cases where I was shooting specifically for the purpose of sharpness testing.

On the other hand, I have seen no evidence that IBIS helps against shutter shock either. Regardless of whether you shoot hand-held or on a tripod, the evidence I have suggest that IBIS doesn't exacerbate the blur due to the shock but doesn't help against it either. The reason why it does not help is in all likelihood that the displacements involved are faster than the range the IBIS system can handle.

I have found one instance where the stabilization system is indeed able to counteract the shock: the OIS on my Panasonic 14-45/3.5-5.6. Since the OIS on this lens is also about as effective as the E-M5 IBIS, shutter-shock aside, I use OIS rather than IBIS when I have this particular lens mounted.

This appears to be a rather special case, however. I have found no evidence that the OIS on the other two OIS lenses I have (Pany 45-200/4-5.6 and 100-300/4-5.6) help against shutter shock. Rather, just like IBIS, it neither hurts nor helps.

Shutter-shock issues aside, there may be instances where it is a good idea to leave the stabilization system on in tripod-based shooting. If you have trouble with the wind, for example, the displacements involved may well be slow enough for the stabilization to cope with them. This is not something I have tried to test however.

 Anders W's gear list:Anders W's gear list
Panasonic Lumix DMC-G1 Olympus OM-D E-M5 Olympus E-M1 Panasonic Lumix G Vario 14-45mm F3.5-5.6 ASPH OIS Panasonic Lumix G Vario 7-14mm F4 ASPH +21 more
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