Exposure basics, lesson two point one (& ISO)

Started Mar 19, 2013 | Discussions
texinwien
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Exposure basics, lesson two point one (& ISO)
Mar 19, 2013

Rather than kick this off in a specific direction, at the outset, I'll just open this as a place for us to continue the discussion that started here:

Exposure basics, lesson one

and continued here:

Exposure basics, lesson two

Both of those discussions have reached 150 posts. Rather than kick this off with a specific theme, I'll leave it open and let those who are interested pick it up in the replies.

tex

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texinwien
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Re: Exposure basics, lesson two point one (& ISO)
In reply to texinwien, Mar 19, 2013

Continued from here .

bobn2 wrote:

texinwien wrote:

Interesting. Some posters think that the discrepancy between the E-M5 Camera ISO Settings and the DxO "Measured ISO" or saturation-based sensitivity measures would somehow allow Olympus to make it appear as though the E-M5 has better noise performance at any given camera ISO Setting than it actually has at that setting.

I think that's bunk. But it's a bit of an aside, anyway.

I think it's bunk also, at least if you take just that factor. However, one wonders why olympus has left so much headroom, instead of putting in a lower ISO setting that many would have appreciated. As I suggested, one good stratagem to make low light performance of a camera appear better than it really is is to make the multi-pattern metering recognise low light situations and dial in more exposure. If one were doing that, it would pay to have a bit of extra headroom.

I'm working to wrap my pea brain around the information here, so I hope you'll bear with me while I ask some questions and do a bit of reasoning out loud.

First, when you say 'dial in more exposure,' I take it to mean that the camera would lower the shutter speed. Assuming that's what you mean, is there any evidence that would suggest that the E-M5 does, indeed, do this?

Also, in your good example stratagem, the camera would be programmed to only lower the shutter speed when it recognized low light situations. With that in mind, I have a couple of questions:

What would you expect to happen in well-lit situations? I assume that you would expect to see 'correct' metering in these (correct based on the camera ISO setting).

Do you think most ISO test scenes used by DPReview, imaging-resource.com and other well-known testing outfits would count as low-light scenes in such a stratagem?

If we saw 'correct' metering in well-lit scenes (correct based on the camera ISO setting), we would see more noise in them than we would have seen had the E-M5's ISO settings been more closely aligned with its saturation sensitivity. Would you expect consumers not to notice this excess of noise in well-lit images?

tex

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texinwien
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Re: Exposure basics, lesson two point one (& ISO)
In reply to texinwien, Mar 19, 2013

Continued from here.

Could you clarify a couple of points for me?

Jack Hogan wrote:

texinwien wrote:

Interesting. Some posters think that the discrepancy between the E-M5 Camera ISO Settings and the DxO "Measured ISO" or saturation-based sensitivity measures would somehow allow Olympus to make it appear as though the E-M5 has better noise performance at any given camera ISO Setting than it actually has at that setting.

Yes, I have read the same thing many times.

I believe you have also agreed with that thing on at least one occasion. Would you say that you agree with that thing right now?

It appears that if one wanted to capture the very same tonal range from a scene with the EM5 and the G3, same exposure and all, one would have to set the EM5 at in-camera ISO 3200 while the G3 at in-camera ISO 1600, with roughly similar resulting SNR (EM5 slightly better as per DxO).

I'm following your example, so far.

On the other hand, if one set both at 3200 maintaining the same exposure they would no longer be directly comparable, but the G3 would appear noisier to a naive observer.

Would it appear noisier, and would the observer be naive to believe what he saw? If by 'maintaining the same exposure' you mean that the scene luminance, shutter speeds and f-stops were kept the same on both cameras as in the first example, the G3 would get exactly one additional EV of exposure, compared to the exposure it received in our first example, whereas the E-M5 would get the exact same amount of exposure as in our first example.

How will this fact affect the amount of noise in the final images?
What effect does bobn2's statement that "the bigger exposure will win" have in scenario #2, or does it have any effect at all?

tex

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bobn2
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Re: Exposure basics, lesson two point one (& ISO)
In reply to texinwien, Mar 19, 2013

Firstly, good idea starting a thread on a sub-theme from the last discussion. This question of the effect of REI and multipattern metering is really an interesting one, and deserves to be discussed in more detail. With luck, a thread that can result in new knowledge.

texinwien wrote:

Continued from here .

bobn2 wrote:

texinwien wrote:

Interesting. Some posters think that the discrepancy between the E-M5 Camera ISO Settings and the DxO "Measured ISO" or saturation-based sensitivity measures would somehow allow Olympus to make it appear as though the E-M5 has better noise performance at any given camera ISO Setting than it actually has at that setting.

I think that's bunk. But it's a bit of an aside, anyway.

I think it's bunk also, at least if you take just that factor. However, one wonders why olympus has left so much headroom, instead of putting in a lower ISO setting that many would have appreciated. As I suggested, one good stratagem to make low light performance of a camera appear better than it really is is to make the multi-pattern metering recognise low light situations and dial in more exposure. If one were doing that, it would pay to have a bit of extra headroom.

I'm working to wrap my pea brain around the information here, so I hope you'll bear with me while I ask some questions and do a bit of reasoning out loud.

As I say, worthwhile doing this thinking in the open, because maybe people will join in who have hard information on the topic, and we will all learn.

First, when you say 'dial in more exposure,' I take it to mean that the camera would lower the shutter speed. Assuming that's what you mean, is there any evidence that would suggest that the E-M5 does, indeed, do this?

That evidence would require a systematic investigation. If someone with an E-M5 wants to do it, then it would be most interesting to see the results. I would think you'd want to calibrate the E-M5's meter against a control meter of the integrating variety, and then go through a variety of scene types noting the exposures given by the control meter and the E-M5.

Also, in your good example stratagem, the camera would be programmed to only lower the shutter speed when it recognized low light situations. With that in mind, I have a couple of questions:

What would you expect to happen in well-lit situations? I assume that you would expect to see 'correct' metering in these (correct based on the camera ISO setting).

Well, remember that the point of multi-segment metering is to find a 'better' exposure than you get by simply using an integrating meter. On the one hand, one might say that the optimum exposure (from the output brightness point of view) is that which you'd get from an incident light meter, so you'd think perhaps that a multi-pattern meter should try to compute and replicate the incident light meter result. But another way of looking at it is that it should just give a more 'pleasing' result. So far as I know, no manufacturer reveals the algorithms behind their multi-segment metering, so we don't know in practice. But I would think they might do things such as lowering the exposure in high contrast scenes to try to avoid blown highlights, increasing the exposure where there seems to be a preponderance of dark to avoid noisy shadows and so on. When you start to think how multi-pattern metering would work, it seems pretty natural to think it's going to give more exposure in dark scenes (such as night shots) and less in bright high contrast (snowscapes and beaches, etc) because that is what most photographers would do.

Do you think most ISO test scenes used by DPReview, imaging-resource.com and other well-known testing outfits would count as low-light scenes in such a stratagem?

Mostly they look like mixed contrast scenes. Since DPReview, IR and the like don't use the camera metering for their tests (which invalidates the ISO rating, really) any meter effect would not affect them. However, I would not be at all surprised if the metering didn't get gamed for test scenes. There was a piece on the radio yesterday in which it was reported that motor manufactures are setting up their ECUs to recognise being driven to the statutory test procedures and lean out the engines to achieve apparently lower carbon emissions, wile in normal driving the emissions are unchanged.

If we saw 'correct' metering in well-lit scenes (correct based on the camera ISO setting), we would see more noise in them than we would have seen had the E-M5's ISO settings been more closely aligned with its saturation sensitivity. Would you expect consumers not to notice this excess of noise in well-lit images?

Most modern cameras have an excess of SNR (for most photographers) in well lit situations. Generally, an advanced photographer will trade a bit of that SNR for highlight protection, and I would expect that is what multi-pattern metering will do to.

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Bob

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texinwien
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Re: Exposure basics, lesson two point one (& ISO)
In reply to bobn2, Mar 19, 2013

bobn2 wrote:

Firstly, good idea starting a thread on a sub-theme from the last discussion. This question of the effect of REI and multipattern metering is really an interesting one, and deserves to be discussed in more detail. With luck, a thread that can result in new knowledge.

As I say, worthwhile doing this thinking in the open, because maybe people will join in who have hard information on the topic, and we will all learn.

I fully expect to learn some new things in this thread - thanks for sharing your thoughts.

First, when you say 'dial in more exposure,' I take it to mean that the camera would lower the shutter speed. Assuming that's what you mean, is there any evidence that would suggest that the E-M5 does, indeed, do this?

That evidence would require a systematic investigation. If someone with an E-M5 wants to do it, then it would be most interesting to see the results. I would think you'd want to calibrate the E-M5's meter against a control meter of the integrating variety, and then go through a varsiety of scene types noting the exposures given by the control meter and the E-M5.

It has just occurred to me that one forum member who owns an E-M5 and has, apparently, been photographing at least semi-professionally for four or more decades shoots only in full Manual mode and meters based solely on his trusty light meter (think it's a sekonic). I wonder if there would be a way for him to generate a report based on his RAW files that would be of any use. Not systematic, but perhaps of interest? I'd run systematic tests, but Spring is here, and I will be outdoors as much as possible for the next 8 or 9 months.

A note about my standard E-M5 usage practices - I always used spot-metering. I usually use aperture priority mode with ISO 200 in well-lit situations. I use either shutter priority mode or manual mode either with fixed ISO of my choice or Auto ISO limited to 1600. I also try to ETTR whenever I have the time to be deliberate. My subjective gut feeling is that I almost always have a good deal of room to add +EV - often well over a full EV.

Also, in your good example stratagem, the camera would be programmed to only lower the shutter speed when it recognized low light situations. With that in mind, I have a couple of questions:

What would you expect to happen in well-lit situations? I assume that you would expect to see 'correct' metering in these (correct based on the camera ISO setting).

Well, remember that the point of multi-segment metering is to find a 'better' exposure than you get by simply using an integrating meter. On the one hand, one might say that the optimum exposure (from the output brightness point of view) is that which you'd get from an incident light meter, so you'd think perhaps that a multi-pattern meter should try to compute and replicate the incident light meter result. But another way of looking at it is that it should just give a more 'pleasing' result. So far as I know, no manufacturer reveals the algorithms behind their multi-segment metering, so we don't know in practice. But I would think they might do things such as lowering the exposure in high contrast scenes to try to avoid blown highlights, increasing the exposure where there seems to be a preponderance of dark to avoid noisy shadows and so on. When you start to think how multi-pattern metering would work, it seems pretty natural to think it's going to give more exposure in dark scenes (such as night shots) and less in bright high contrast (snowscapes and beaches, etc) because that is what most photographers would do.

Just to be clear - is it your position that any 'cheating' on ISO tests that could possibly be done would have to be done through 'mis-metering', giving the camera more exposure than it should get, compared to other cameras, based on the scene?

I'm not trying to pin you down here - I'm just trying to make it clear for myself and others, since you seem to be saying that the only way to 'cheat' here would be by manipulating the exposure, and that if such manipulation were occurring, it's something we should be able to detect by running systematic tests.

Do you think most ISO test scenes used by DPReview, imaging-resource.com and other well-known testing outfits would count as low-light scenes in such a stratagem?

Mostly they look like mixed contrast scenes. Since DPReview, IR and the like don't use the camera metering for their tests (which invalidates the ISO rating, really) any meter effect would not affect them. However, I would not be at all surprised if the metering didn't get gamed for test scenes. There was a piece on the radio yesterday in which it was reported that motor manufactures are setting up their ECUs to recognise being driven to the statutory test procedures and lean out the engines to achieve apparently lower carbon emissions, wile in normal driving the emissions are unchanged.

It's good to be reminded that this kind of behavior occurs. As a software guy, it's interesting to try to imagine a way to program a camera to recognize when it's being used in this sort of test scene. The quickest, easiest way I could think of would be to have the camera recognize various test charts, which most of these shots contain.

With a little more work, you could get it to recognize the test scenes used by the most popular testing sites and agencies with high certainty - so, recognize with high certainty known test scenes and, as a fallback, recognize common test charts. If you see either, switch to 'multi-pattern metering for best ISO test results' mode.

If we saw 'correct' metering in well-lit scenes (correct based on the camera ISO setting), we would see more noise in them than we would have seen had the E-M5's ISO settings been more closely aligned with its saturation sensitivity. Would you expect consumers not to notice this excess of noise in well-lit images?

Most modern cameras have an excess of SNR (for most photographers) in well lit situations. Generally, an advanced photographer will trade a bit of that SNR for highlight protection, and I would expect that is what multi-pattern metering will do to.

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Bob

I asked this because I have seen multiple people complain about noise in daytime skies in photos taken with the E-M5. I ran some of my own quick and dirty tests here, and found that I could, in some cases, dial in a full +3EV of exposure compensation without blowing any highlights and cut way down on the appearance of noise in the skies.

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bobn2
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Re: Exposure basics, lesson two point one (& ISO)
In reply to texinwien, Mar 19, 2013

texinwien wrote:

bobn2 wrote:

Firstly, good idea starting a thread on a sub-theme from the last discussion. This question of the effect of REI and multipattern metering is really an interesting one, and deserves to be discussed in more detail. With luck, a thread that can result in new knowledge.

As I say, worthwhile doing this thinking in the open, because maybe people will join in who have hard information on the topic, and we will all learn.

I fully expect to learn some new things in this thread - thanks for sharing your thoughts.

First, when you say 'dial in more exposure,' I take it to mean that the camera would lower the shutter speed. Assuming that's what you mean, is there any evidence that would suggest that the E-M5 does, indeed, do this?

That evidence would require a systematic investigation. If someone with an E-M5 wants to do it, then it would be most interesting to see the results. I would think you'd want to calibrate the E-M5's meter against a control meter of the integrating variety, and then go through a varsiety of scene types noting the exposures given by the control meter and the E-M5.

It has just occurred to me that one forum member who owns an E-M5 and has, apparently, been photographing at least semi-professionally for four or more decades shoots only in full Manual mode and meters based solely on his trusty light meter (think it's a sekonic). I wonder if there would be a way for him to generate a report based on his RAW files that would be of any use.

What you'd need to know is how the camera metered the scene. That might be captured in the EXIF. If course, he'd need to have kept his metering set to multi-segment.

Not systematic, but perhaps of interest? I'd run systematic tests, but Spring is here, and I will be outdoors as much as possible for the next 8 or 9 months.

Meters are cheap on ebay. The little extra time to meter some shots and note the meter, and you can combine the experiment with your days to day photography, after all, what you want is a variety of shots.

A note about my standard E-M5 usage practices - I always used spot-metering. I usually use aperture priority mode with ISO 200 in well-lit situations. I use either shutter priority mode or manual mode either with fixed ISO of my choice or Auto ISO limited to 1600. I also try to ETTR whenever I have the time to be deliberate. My subjective gut feeling is that I almost always have a good deal of room to add +EV - often well over a full EV.

Ah, then if you're not using pattern metering, that won't do.

Also, in your good example stratagem, the camera would be programmed to only lower the shutter speed when it recognized low light situations. With that in mind, I have a couple of questions:

What would you expect to happen in well-lit situations? I assume that you would expect to see 'correct' metering in these (correct based on the camera ISO setting).

Well, remember that the point of multi-segment metering is to find a 'better' exposure than you get by simply using an integrating meter. On the one hand, one might say that the optimum exposure (from the output brightness point of view) is that which you'd get from an incident light meter, so you'd think perhaps that a multi-pattern meter should try to compute and replicate the incident light meter result. But another way of looking at it is that it should just give a more 'pleasing' result. So far as I know, no manufacturer reveals the algorithms behind their multi-segment metering, so we don't know in practice. But I would think they might do things such as lowering the exposure in high contrast scenes to try to avoid blown highlights, increasing the exposure where there seems to be a preponderance of dark to avoid noisy shadows and so on. When you start to think how multi-pattern metering would work, it seems pretty natural to think it's going to give more exposure in dark scenes (such as night shots) and less in bright high contrast (snowscapes and beaches, etc) because that is what most photographers would do.

Just to be clear - is it your position that any 'cheating' on ISO tests that could possibly be done would have to be done through 'mis-metering', giving the camera more exposure than it should get, compared to other cameras, based on the scene?

I'm not sure it is 'cheating', just allowing what the system and standards allow. So far as running a high headroom, that is if anything a relative disadvantage for nominal exposure for that ISO, since it results in a read noise contribution relatively higher than it could be with respect to the recorded raw levels.

I'm not trying to pin you down here - I'm just trying to make it clear for myself and others, since you seem to be saying that the only way to 'cheat' here would be by manipulating the exposure, and that if such manipulation were occurring, it's something we should be able to detect by running systematic tests.

In the end, what we are talking about is how different evaluative metering systems evaluate different kinds of scene, and it's only really a problem for the photographer who hasn't got their exposure management sorted out. After all, generally the exposure in low light is set by the shutter speed you can bear, the f-number you have available and the light. The ISO should follow along, not be dictating the exposure.

Do you think most ISO test scenes used by DPReview, imaging-resource.com and other well-known testing outfits would count as low-light scenes in such a stratagem?

Mostly they look like mixed contrast scenes. Since DPReview, IR and the like don't use the camera metering for their tests (which invalidates the ISO rating, really) any meter effect would not affect them. However, I would not be at all surprised if the metering didn't get gamed for test scenes. There was a piece on the radio yesterday in which it was reported that motor manufactures are setting up their ECUs to recognise being driven to the statutory test procedures and lean out the engines to achieve apparently lower carbon emissions, wile in normal driving the emissions are unchanged.

It's good to be reminded that this kind of behavior occurs. As a software guy, it's interesting to try to imagine a way to program a camera to recognize when it's being used in this sort of test scene. The quickest, easiest way I could think of would be to have the camera recognize various test charts, which most of these shots contain.

With a little more work, you could get it to recognize the test scenes used by the most popular testing sites and agencies with high certainty - so, recognize with high certainty known test scenes and, as a fallback, recognize common test charts. If you see either, switch to 'multi-pattern metering for best ISO test results' mode.

Yup, the real problem is you soon start thinking along the lines 'how could I manipulate this system', then you find lots of opportunities. The other thing is also that most cameras don't seem to run an absolute constant ISO, that is there is also adaptivity in the in-camera processing. After all, why not do that? It just helps the photographer think they are managing exposure better, which will make the camera seem better. I first noticed this when I started using the simple open source raw conversion tools, and suddenly my processed raws started showing quite big brightness variations with respect to the in-camera JPEGs.

If we saw 'correct' metering in well-lit scenes (correct based on the camera ISO setting), we would see more noise in them than we would have seen had the E-M5's ISO settings been more closely aligned with its saturation sensitivity. Would you expect consumers not to notice this excess of noise in well-lit images?

Most modern cameras have an excess of SNR (for most photographers) in well lit situations. Generally, an advanced photographer will trade a bit of that SNR for highlight protection, and I would expect that is what multi-pattern metering will do to.

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Bob

I asked this because I have seen multiple people complain about noise in daytime skies in photos taken with the E-M5. I ran some of my own quick and dirty tests here, and found that I could, in some cases, dial in a full +3EV of exposure compensation without blowing any highlights and cut way down on the appearance of noise in the skies.

I haven't thought about noisy skies, but I can imagine that there are some factors in play. Firstly, you have a very flat textureless area, which means what shot noise there is will be apparent. For that the higher the exposure the better. Then there is a relatively low red channel content, so red channel noise could cause perceptible noise. Same solution. The other thing is, just blur the blue sky. There is a technique I use to clean up skin which could work for sky. Make another layer, blur it. Give it an alpha channel based on the sky (skin) colour, invert the alpha channel and flatten.

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Bob

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Anders W
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Re: Exposure basics, lesson two point one (& ISO)
In reply to texinwien, Mar 19, 2013

texinwien wrote:

A note about my standard E-M5 usage practices - I always used spot-metering. I usually use aperture priority mode with ISO 200 in well-lit situations. I use either shutter priority mode or manual mode either with fixed ISO of my choice or Auto ISO limited to 1600. I also try to ETTR whenever I have the time to be deliberate. My subjective gut feeling is that I almost always have a good deal of room to add +EV - often well over a full EV.

It doesn't take much time to be deliberate pretty much all the time tex. I hardly ever meter in the conventional sense any more after getting the E-M5. The live view "blinkies" (highlight warnings) will tell me not only when but also where things will clip and most of the time I simply go by that. I use spot metering on the highlights for the few cases where the highlight warnings don't work quite the way they should. If the DR of the scene is such (decided by my guts feeling) that preserving all the highlights I'd like to preserve will make the shadows excessively noisy, I choose one of the following options depending on what is possible given the subject and the light conditions: a) let some of the highlights go, b) use exposure bracketing and select the best in PP or merge/align in PP, or c) shoot a burst at the same exposure and merge/align in PP.

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Jack Hogan
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Re: Exposure basics, lesson two point one (& ISO)
In reply to texinwien, Mar 19, 2013

texinwien wrote: Could you clarify a couple of points for me?

Jack Hogan wrote: It appears that if one wanted to capture the very same tonal range from a scene with the EM5 and the G3, same exposure and all, one would have to set the EM5 at in-camera ISO 3200 while the G3 at in-camera ISO 1600, with roughly similar resulting SNR (EM5 slightly better as per DxO).

I'm following your example, so far.

On the other hand, if one set both at 3200 maintaining the same exposure they would no longer be directly comparable, but the G3 would appear noisier to a naive observer.

Would it appear noisier, and would the observer be naive to believe what he saw?

He wouldn't be naive to believe that he saw more noise (he would). He would be naive in thinking that to capture the same tonal range (shadows and highlights) of the same scene with the same lens and Exposure (ss and f/n) as his friend's EM5 he would have to use the same ISO in the G3. His naivete would cost him a ton of IQ: one stop of highlight headroom and 1 stop of SNR, and he possibly would lose his National Geographic desk

On the other hand an intermediate photographer who understands this subject, would know that to capture the specified tonal range at the given ss and f/n with a G3 he would need to set his camera on ISO 1600 independently of what others need to do to capture the exact same scene and tonal range subject to the exact same artistic constraints. Given the same objectives, his friend with the EM5 and the same lens would need ISO 3200 at the same exposure.

What effect does bobn2's statement that "the bigger exposure will win" have in scenario #2, or does it have any effect at all?

It doesn't apply, because exposure stays the same in every scenario here, only ISO changes.

Jack

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richarddd
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Re: Exposure basics, lesson two point one (& ISO)
In reply to Anders W, Mar 19, 2013

Anders W wrote:

texinwien wrote:

A note about my standard E-M5 usage practices - I always used spot-metering. I usually use aperture priority mode with ISO 200 in well-lit situations. I use either shutter priority mode or manual mode either with fixed ISO of my choice or Auto ISO limited to 1600. I also try to ETTR whenever I have the time to be deliberate. My subjective gut feeling is that I almost always have a good deal of room to add +EV - often well over a full EV.

It doesn't take much time to be deliberate pretty much all the time tex. I hardly ever meter in the conventional sense any more after getting the E-M5. The live view "blinkies" (highlight warnings) will tell me not only when but also where things will clip and most of the time I simply go by that. I use spot metering on the highlights for the few cases where the highlight warnings don't work quite the way they should. If the DR of the scene is such (decided by my guts feeling) that preserving all the highlights I'd like to preserve will make the shadows excessively noisy, I choose one of the following options depending on what is possible given the subject and the light conditions: a) let some of the highlights go, b) use exposure bracketing and select the best in PP or merge/align in PP, or c) shoot a burst at the same exposure and merge/align in PP.

I'll suggest a stronger version of Anders' statement: metering in the conventional sense is essentially obsolete now that we have live blinkies.

There are some possible limits, as Anders points out, including issues of blowing single channels or how accurately the blinkies show clipping (or shadow blocking).

If we are in a typical situation, what would be the advantage of conventional metering, especially multi-pattern metering, over using live blinkies?

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texinwien
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Re: Exposure basics, lesson two point one (& ISO)
In reply to Anders W, Mar 19, 2013

Anders W wrote:

texinwien wrote:

A note about my standard E-M5 usage practices - I always used spot-metering. I usually use aperture priority mode with ISO 200 in well-lit situations. I use either shutter priority mode or manual mode either with fixed ISO of my choice or Auto ISO limited to 1600. I also try to ETTR whenever I have the time to be deliberate. My subjective gut feeling is that I almost always have a good deal of room to add +EV - often well over a full EV.

It doesn't take much time to be deliberate pretty much all the time tex. I hardly ever meter in the conventional sense any more after getting the E-M5.

I agree, and would also say that I rarely meter in the conventional sense any more, with a few exceptions. Those exceptions usually involve hurried timing, and often include candid people shots. Even in these situations, I've gotten reasonably quick at spot-metering on a dark enough part of the scene (with blinkies turned on) that I'm getting closer to the right (optimum level of exposure for minimizing noise) than conventional metering would have gotten me, even if I don't really have time to adjust EC up and down a bit to locate the exact spot before important highlights are going to blow.

The live view "blinkies" (highlight warnings) will tell me not only when but also where things will clip and most of the time I simply go by that. I use spot metering on the highlights for the few cases where the highlight warnings don't work quite the way they should. If the DR of the scene is such (decided by my guts feeling) that preserving all the highlights I'd like to preserve will make the shadows excessively noisy, I choose one of the following options depending on what is possible given the subject and the light conditions: a) let some of the highlights go, b) use exposure bracketing and select the best in PP or merge/align in PP, or c) shoot a burst at the same exposure and merge/align in PP.

I follow you, and agree. In short, I'd say you're right that it doesn't take much time to be deliberate, but sometimes, when a fraction of a second may count, I don't expend any effort or thought on it, focusing instead on composition, focus and an exposure that, if not optimal, will at least (hopefully) not be horrible

Over time, I fully expect that I'll grow more comfortable making split-second adjustments with the E-M5 - that is, if I manage to learn the new skill before my cognitive abilities have already slid too far in the direction of inevitable old-age dementia

tex

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texinwien
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Re: Exposure basics, lesson two point one (& ISO)
In reply to richarddd, Mar 19, 2013

richarddd wrote:

Anders W wrote:

texinwien wrote:

A note about my standard E-M5 usage practices - I always used spot-metering. I usually use aperture priority mode with ISO 200 in well-lit situations. I use either shutter priority mode or manual mode either with fixed ISO of my choice or Auto ISO limited to 1600. I also try to ETTR whenever I have the time to be deliberate. My subjective gut feeling is that I almost always have a good deal of room to add +EV - often well over a full EV.

It doesn't take much time to be deliberate pretty much all the time tex. I hardly ever meter in the conventional sense any more after getting the E-M5. The live view "blinkies" (highlight warnings) will tell me not only when but also where things will clip and most of the time I simply go by that. I use spot metering on the highlights for the few cases where the highlight warnings don't work quite the way they should. If the DR of the scene is such (decided by my guts feeling) that preserving all the highlights I'd like to preserve will make the shadows excessively noisy, I choose one of the following options depending on what is possible given the subject and the light conditions: a) let some of the highlights go, b) use exposure bracketing and select the best in PP or merge/align in PP, or c) shoot a burst at the same exposure and merge/align in PP.

I'll suggest a stronger version of Anders' statement: metering in the conventional sense is essentially obsolete now that we have live blinkies.

There are some possible limits, as Anders points out, including issues of blowing single channels or how accurately the blinkies show clipping (or shadow blocking).

If we are in a typical situation, what would be the advantage of conventional metering, especially multi-pattern metering, over using live blinkies?

The only advantage is one of spontaneity and quick reaction time (and, as I stated, I use spot-metering, so multi-pattern metering doesn't apply to me).

Also, I am STILL using blinkies even when I spot meter without taking time to fine tune EC, I'm just not using them as effectively as if I had 5 seconds rather than half a second to frame, focus, set exposure and shoot.

tex

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Jack Hogan
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Re: Exposure basics, lesson two point one (& ISO)
In reply to richarddd, Mar 19, 2013

richarddd wrote:

I'll suggest a stronger version of Anders' statement: metering in the conventional sense is essentially obsolete now that we have live blinkies.

There are some possible limits, as Anders points out, including issues of blowing single channels or how accurately the blinkies show clipping (or shadow blocking).

Yes.  Ideally it would be blinkies related to the Raw data as opposed to those related to an sRGB rendered image.

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Ulric
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Re: Exposure basics, lesson two point one (& ISO)
In reply to Jack Hogan, Mar 19, 2013

Jack Hogan wrote:

He wouldn't be naive to believe that he saw more noise (he would). He would be naive in thinking that to capture the same tonal range (shadows and highlights) of the same scene with the same lens and Exposure (ss and f/n) as his friend's EM5 he would have to use the same ISO in the G3. His naivete would cost him a ton of IQ: one stop of highlight headroom and 1 stop of SNR, and he possibly would lose his National Geographic desk

I give up; that is, I don't get it. Given the same exposure, why would the g3 on iso 3200 produce more noise than the em5 on iso 3200, but the g3 on iso 1600 would not?

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Jack Hogan
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Re: Exposure basics, lesson two point one (& ISO)
In reply to Ulric, Mar 19, 2013

Ulric wrote:

Jack Hogan wrote:

He wouldn't be naive to believe that he saw more noise (he would). He would be naive in thinking that to capture the same tonal range (shadows and highlights) of the same scene with the same lens and Exposure (ss and f/n) as his friend's EM5 he would have to use the same ISO in the G3. His naivete would cost him a ton of IQ: one stop of highlight headroom and 1 stop of SNR, and he possibly would lose his National Geographic desk

I give up; that is, I don't get it. Given the same exposure, why would the g3 on iso 3200 produce more noise than the em5 on iso 3200, but the g3 on iso 1600 would not?

The short answer: Because ISO labels are arbitrary, and in the case at hand Olympus called 6400 what Panasonic calls 3200, so if you set the G3 at 3200 you need to set the EM5 at 6400 to capture the same image information all else being equal. Pehaps an example would help?

You are an intermediate photographer and you have been given an assignement: shoot a game indoors with the same 50mm lens and two cameras, an EM5 and a G3. The desk tells you that anything other than a dof of f/6.3 and the blur stopping power of 1/800s will be accepted, and you need to get the highest IQ possible without blowing the highlights of the brightest object in the scene, the white helmets of the players. Easy, you say. You switch both cameras to full manual mode in order to set the mandated shutter speed and aperture on both - Exposure has therefore been fixed equally on both and will remain set there for the entire game. Then the issue of ISO comes up.

Quick like a fox you remember various DPR threads where this was discussed ad nauseam. You therfore take a sample shot at a guesstimate ISO of 800 on the G3 and see by looking at the hystogram* that the white helmets are more than 1 stop below clipping. You therefore dial in 1600 ISO take another sample shot, verify that the helmets are now all the way to the right of the hystogram just before clipping, and you are all set. You can now fire away, forgetting completely about Exposure and ISO and metering potentially getting fooled by lights or reflections and concentrate solely on getting the shot. You get some great shots.

At half time you move the lens to the EM5 and go through the same set up procedure. You verify that ss and f/n are the same mandated values of f/6.3 and 1/800s (therefore Exposure is the same as on the EM5) and you go through the exact same ISO setting procedure as for the G3. This time though, in order to ensure that the white helmets end up just before clipping you need to dial in a different ISO value. No sweat, the sample images from the two cameras look about the same in terms of noise and eDR as set up (the EM5 a tad better as DxO's graphs suggested) so you fire away forgetting that Exposure and ISO even existed. You get some even geater shots.

Same scene, same light, same lens, same Exposure (ss and f/n), same tonal range (image information) captured.  Why are the ISOs different?  You then remember DPR threads that mentioned that in-camera ISO labels are not consistent from camera to camera or from manufacturer to manufacturer. So what one calls 1600 the other can call 800 or 3200, the standard allows them to do it.  Does it matter? No, as long as you remember that in the same situation when the G3 calls for ISO 1600 that is instead called 3200 on the EM5.

HIH
Jack

*This is a simplification. To do it properly one would need a Raw hystogram or to learn how the sRGB hystogram of one's camera typically maps to the Raw one in a given light.

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texinwien
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Re: Exposure basics, lesson two point one (& ISO)
In reply to Jack Hogan, Mar 19, 2013

Thanks for your considered words. Before I offer my response, I need to request additional clarification on the question of exposure settings.

Jack Hogan wrote:

texinwien wrote: Could you clarify a couple of points for me?

Jack Hogan wrote: It appears that if one wanted to capture the very same tonal range from a scene with the EM5 and the G3, same exposure and all, one would have to set the EM5 at in-camera ISO 3200 while the G3 at in-camera ISO 1600, with roughly similar resulting SNR (EM5 slightly better as per DxO).

How is exposure set in the first scenario - that is, on what basis and by what method? Can we simply, for sake of argument, say that both the shutter speed and the f-number are manually set to be equal on both cameras based on what the G3's meter suggests, when the G3 is set to ISO 1600?

If you'd like to recommend another method for setting the exposure parameters, please feel free to do that. I would simply like to nail them down so there are no further open questions going forward.

I'm following your example, so far.

On the other hand, if one set both at 3200 maintaining the same exposure they would no longer be directly comparable, but the G3 would appear noisier to a naive observer.

Would it appear noisier, and would the observer be naive to believe what he saw?

He wouldn't be naive to believe that he saw more noise (he would). He would be naive in thinking that to capture the same tonal range (shadows and highlights) of the same scene with the same lens and Exposure (ss and f/n) as his friend's EM5 he would have to use the same ISO in the G3. His naivete would cost him a ton of IQ: one stop of highlight headroom and 1 stop of SNR, and he possibly would lose his National Geographic desk

On the other hand an intermediate photographer who understands this subject, would know that to capture the specified tonal range at the given ss and f/n with a G3 he would need to set his camera on ISO 1600 independently of what others need to do to capture the exact same scene and tonal range subject to the exact same artistic constraints. Given the same objectives, his friend with the EM5 and the same lens would need ISO 3200 at the same exposure.

What effect does bobn2's statement that "the bigger exposure will win" have in scenario #2, or does it have any effect at all?

It doesn't apply, because exposure stays the same in every scenario here, only ISO changes.

Jack

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Jack Hogan
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Re: Exposure basics, lesson two point one (& ISO)
In reply to texinwien, Mar 19, 2013

texinwien wrote: If you'd like to recommend another method for setting the exposure parameters, please feel free to do that. I would simply like to nail them down so there are no further open questions going forward.

The only method I use is one that maximizes captured light given artistic constraints.  Assume that they are set at f/6.3 and 1/800s for the reasons of the example in my post just above.

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Ulric
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Re: Exposure basics, lesson two point one (& ISO)
In reply to Jack Hogan, Mar 19, 2013

Right, I'm willing to accept that increasing the iso setting on the g3 from 800 to 1600 will reduce noise.What I wondered about was this exchange:

8<---

texinwien wrote: Could you clarify a couple of points for me?

Jack Hogan wrote: It appears that if one wanted to capture the very same tonal range from a scene with the EM5 and the G3, same exposure and all, one would have to set the EM5 at in-camera ISO 3200 while the G3 at in-camera ISO 1600, with roughly similar resulting SNR (EM5 slightly better as per DxO).

I'm following your example, so far.

On the other hand, if one set both at 3200 maintaining the same exposure they would no longer be directly comparable, but the G3 would appear noisier to a naive observer.

8<---

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Martin.au
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Re: Exposure basics, lesson two point one (& ISO)
In reply to Jack Hogan, Mar 19, 2013

Jack Hogan wrote:

texinwien wrote: If you'd like to recommend another method for setting the exposure parameters, please feel free to do that. I would simply like to nail them down so there are no further open questions going forward.

The only method I use is one that maximizes captured light given artistic constraints. Assume that they are set at f/6.3 and 1/800s for the reasons of the example in my post just above.

Process - Import as raw and export as jpeg from Aperture, downsize OM_D to E520.

Note: As expected by the ISO standard, equal exposure + equal ISO = equal final image brightness.

Seems to me that if one camera has, for example, 1 stop more highlight headroom, all you're doing is jacking up the rest of the image 1 stop.

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bobn2
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Re: Exposure basics, lesson two point one (& ISO)
In reply to Martin.au, Mar 19, 2013

Mjankor wrote:

Jack Hogan wrote:

texinwien wrote: If you'd like to recommend another method for setting the exposure parameters, please feel free to do that. I would simply like to nail them down so there are no further open questions going forward.

The only method I use is one that maximizes captured light given artistic constraints. Assume that they are set at f/6.3 and 1/800s for the reasons of the example in my post just above.

Process - Import as raw and export as jpeg from Aperture, downsize OM_D to E520.

Note: As expected by the ISO standard, equal exposure + equal ISO = equal final image brightness.

Well actually, they aren't.

-- hide signature --

Bob

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Martin.au
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Re: Exposure basics, lesson two point one (& ISO)
In reply to bobn2, Mar 19, 2013

Approximately.

They're equal brightness at 1/4 and 1/5, so 1/3 of a stop. I didn't really think 1/3 of a stop would matter to much to this discussion.

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