Metering values: Have they been changed?

privatebydesign

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Jan 29, 2011
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So I mentioned this on another thread but felt it might be interesting, though I freely admit it doesn't have any of the trigger phrases in it, no dynamic range, OVF vs EVF, etc etc.

So many of you probably know and understand the way cameras meter and give a value for exposures, for many years if you took a picture of a defocused evenly illuminated monotone, irrespective of it's reflectance (within some limitations), you got a histogram spike around half a stop below center, the infamous 12% vs 18% variation. Well I have been playing with my cameras and I noticed that when I do that now I get a spike in the histogram that is centered.

ANSI standards, as I understood them, mean reflectance meters should be set to 12% grey, 1/2 stop below midtone, yet mine are now giving an equivalent exposure of the meter being set to 18%. I actually had both in camera meters set to -2/8 as I set them up when I got them and did cursory testing to set them there. What I didn't allow for was the fact that they don't seem to be behaving the same way as all my previous in camera meters.

Has anybody else noticed or have an explanation of this?
 

privatebydesign

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Hi Don, two 1DX MkII's, it is distinctly different from my old 1Ds MkIII's and the 1Ds MkII and 1D before that.
 

3kramd5

EOS 5D MK IV
Mar 2, 2012
3,043
375
Interesting. I always considered 18% to be middle gray. Which ANSI standard talks to it? Do Japanese vendors work to ANSI standards?
 
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Maybe they've changed the way they calculate the histogram? Different Gamma or something along those lines since it's not a linear scale. When I set exposure for video with my 1DX2 I usually dial in an 18% gray card to spike at about 40% on the histogram to leave highlight headroom. That works reasonably well but I should probably get out my old light meters and do some tests. Thanks for the heads up. My 1DX2 does have a tendency to overexpose IMO. My standard exposure compensation is -2/3 of a stop but I should look at that again as well. Maybe it's just the histogram pushing values to the right.
 

Mt Spokane Photography

I post too Much on Here!!
Mar 25, 2011
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Check the Wikipedia for a good write up. Its Illuminating!

he ISO 12232:2006 standard
The ISO standard ISO 12232:2006[63] gives digital still camera manufacturers a choice of five different techniques for determining the exposure index rating at each sensitivity setting provided by a particular camera model. Three of the techniques in ISO 12232:2006 are carried over from the 1998 version of the standard, while two new techniques allowing for measurement of JPEG output files are introduced from CIPA DC-004.[64] Depending on the technique selected, the exposure index rating can depend on the sensor sensitivity, the sensor noise, and the appearance of the resulting image. The standard specifies the measurement of light sensitivity of the entire digital camera system and not of individual components such as digital sensors, although Kodak has reported[65] using a variation to characterize the sensitivity of two of their sensors in 2001.
The Recommended Exposure Index (REI) technique, new in the 2006 version of the standard, allows the manufacturer to specify a camera model’s EI choices arbitrarily. The choices are based solely on the manufacturer’s opinion of what EI values produce well-exposed sRGB images at the various sensor sensitivity settings. This is the only technique available under the standard for output formats that are not in the sRGB color space. This is also the only technique available under the standard when multi-zone metering (also called pattern metering) is used.
The Standard Output Sensitivity (SOS) technique, also new in the 2006 version of the standard, effectively specifies that the average level in the sRGB image must be 18% gray plus or minus 1/3 stop when the exposure is controlled by an automatic exposure control system calibrated per ISO 2721 and set to the EI with no exposure compensation. Because the output level is measured in the sRGB output from the camera, it is only applicable to sRGB images—typically JPEG—and not to output files in raw image format. It is not applicable when multi-zone metering is used.
The CIPA DC-004 standard requires that Japanese manufacturers of digital still cameras use either the REI or SOS techniques, and DC-008[66] updates the Exif specification to differentiate between these values. Consequently, the three EI techniques carried over from ISO 12232:1998 are not widely used in recent camera models (approximately 2007 and later). As those earlier techniques did not allow for measurement from images produced with lossy compression, they cannot be used at all on cameras that produce images only in JPEG format.
The saturation-based (SAT or Ssat) technique is closely related to the SOS technique, with the sRGB output level being measured at 100% white rather than 18% gray. The SOS value is effectively 0.704 times the saturation-based value.[67] Because the output level is measured in the sRGB output from the camera, it is only applicable to sRGB images—typically TIFF—and not to output files in raw image format. It is not applicable when multi-zone metering is used.
The two noise-based techniques have rarely been used for consumer digital still cameras. These techniques specify the highest EI that can be used while still providing either an "excellent" picture or a "usable" picture depending on the technique chosen.
 

Viggo

EOS 5D SR
Dec 13, 2010
4,033
568
I’ve always dialed in a offset with the 0 ev value on all my 1-series about 7/8 of a full stop. Even then I often dialed in a slight overexposure in camera .

I find the eos r to need at least one stop, sometimes two. So in practical use I feel all cameras I’ve owned needs 1,5 stops up in general.
 

Mt Spokane Photography

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Mar 25, 2011
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The way I read the article about the 2007 standard is that after 2007, cameras which output raw images and have multi-zone metering must use the REI technique which has no fixed methodology or gray card values to deterrmine exposure. It basically allows them to come up with a method that they feel produces the best exposures. It may also be that the ISO standard was just catching up with the CIPA standards that camera manufacturers were using.

To me, that means that trying to use 12% or 18% gray cards is not going to give the results expected due to the multi zone metering. The metering method is likely more complex and is proprietary to the individual camera model and manufacturer. Hopefully, this does not mean that we will see different exposures for cameras designed after 2007, but, since the intent is to let manufacturers define the method that works best for the camera design, there will be differences from camera to camera based on the composition of he scene as manufacturers work to provide better exposure mechanisms.

"The Recommended Exposure Index (REI) technique, new in the 2006 version of the standard, allows the manufacturer to specify a camera model’s EI choices arbitrarily. The choices are based solely on the manufacturer’s opinion of what EI values produce well-exposed sRGB images at the various sensor sensitivity settings. This is the only technique available under the standard for output formats that are not in the sRGB color space. This is also the only technique available under the standard when multi-zone metering (also called pattern metering) is used."
 

privatebydesign

Would you take advice from a cartoons stuffed toy?
Jan 29, 2011
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Interesting. I always considered 18% to be middle gray. Which ANSI standard talks to it? Do Japanese vendors work to ANSI standards?
18% reflectance is/has been considered to be 'middle gray' for print purposes.

ANSI standard:- American National Standard for General-Purpose Photographic Exposure Meters (Photoelectric Type) ANSI PH3.49-1971. I appreciate that is now out of date but up until my 1DS MkIII's it held true.

My belief was that they did, or used to. I always found Thom Hogan to be extremely accurate and reliable and he said "talk to the Nikon Japan camera engineers, and you get a different story, as they'll respond "yes" when you ask if the Nikon meters are calibrated to ANSI standards; and yes, I had the chance to ask them a few years ago when I was in Japan" . But if they did or didn't is slightly moot as their in camera meters used to give equivalent results.
 
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privatebydesign

Would you take advice from a cartoons stuffed toy?
Jan 29, 2011
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Maybe they've changed the way they calculate the histogram? Different Gamma or something along those lines since it's not a linear scale. When I set exposure for video with my 1DX2 I usually dial in an 18% gray card to spike at about 40% on the histogram to leave highlight headroom. That works reasonably well but I should probably get out my old light meters and do some tests. Thanks for the heads up. My 1DX2 does have a tendency to overexpose IMO. My standard exposure compensation is -2/3 of a stop but I should look at that again as well. Maybe it's just the histogram pushing values to the right.
It seems Mt Spokane's first reply gives us the answer and yes the standards have been changed. I originally dialed in 0-2/8 on the AE meter reading to get my exposures closer to where I was used to, but I was investigating it more fully recently and realized the reading were consistent, just not what they used to be.

To be sire I don't care what the meter actually says, just so long as I understand what it is saying so I can make relevant adjustments.
 

privatebydesign

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The ITR sensor in the newer cameras can effect metering as well.
It seems the widespread adoption of zoned metering and color sensitive metering is the key behind the changes and realistically the only way to allow for such metering types and the fact that RAW image exposures are crazy dark without a subjective gamma curve applied.

Having said that as a straight exposure off a monotone, zone metering shouldn't impact EV results.
 

privatebydesign

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Jan 29, 2011
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I’ve always dialed in a offset with the 0 ev value on all my 1-series about 7/8 of a full stop. Even then I often dialed in a slight overexposure in camera .

I find the eos r to need at least one stop, sometimes two. So in practical use I feel all cameras I’ve owned needs 1,5 stops up in general.
What 1 series? As I understand, from Mt Spokane's excellent link, the newer standard wasn't implemented into cameras until at least the 1D MkIV or more probably the 1DX.

But your findings run contrary to mine. I found the older cameras needed more exposure than suggested and the newer cameras pretty much spot on.
 

privatebydesign

Would you take advice from a cartoons stuffed toy?
Jan 29, 2011
7,614
694
119
The way I read the article about the 2007 standard is that after 2007, cameras which output raw images and have multi-zone metering must use the REI technique which has no fixed methodology or gray card values to deterrmine exposure. It basically allows them to come up with a method that they feel produces the best exposures. It may also be that the ISO standard was just catching up with the CIPA standards that camera manufacturers were using.

To me, that means that trying to use 12% or 18% gray cards is not going to give the results expected due to the multi zone metering. The metering method is likely more complex and is proprietary to the individual camera model and manufacturer. Hopefully, this does not mean that we will see different exposures for cameras designed after 2007, but, since the intent is to let manufacturers define the method that works best for the camera design, there will be differences from camera to camera based on the composition of he scene as manufacturers work to provide better exposure mechanisms.

"The Recommended Exposure Index (REI) technique, new in the 2006 version of the standard, allows the manufacturer to specify a camera model’s EI choices arbitrarily. The choices are based solely on the manufacturer’s opinion of what EI values produce well-exposed sRGB images at the various sensor sensitivity settings. This is the only technique available under the standard for output formats that are not in the sRGB color space. This is also the only technique available under the standard when multi-zone metering (also called pattern metering) is used."
I believe you are absolutely spot on! Interesting that there hasn't been more said about the issue considering how everybody loves a controversy!

Like you say the 'standards' ended up coming up with a very pragmatic approach to an issue that couldn't be standardized! With RAW files with no gamma applied and zoned and color sensitive metering all done in a proprietary manner it would make a 'standard' unworkable. Amazing that the powers that be were so pragmatic.

As I said with a monotone the fact that a metering system is multilane shouldn't impact the suggested EV, however in any other situation it should. I tested with both spot and multi zone and got the same results but only when metering a monotone and only when the illumination was within certain limits. It's as though the metering has an idea of how reflective the scene is in relation to the ambient light. Metering has certainly come a long way in my lifetime....
 

Kit.

EOS 6D MK II
Apr 25, 2011
1,108
526
Metering off the 18% gray card (in spot or averaging mode) is metering of the incident light. Ideally, it should give you color channel saturation on the objects that are 0.5+ stops more reflective (in the corresponding color channel) than a 100% diffuse white card, and then, using exposure compensation, you can shift the saturation point.

I remember metering grass as if it were 18% gray card. While grass in green channel is brighter than 18% gray card in green channel, averaging over the spectral sensitivity of the older light meters gave you about the same reading. Not sure if this trick still works with modern metering; hopefully yes.
 

privatebydesign

Would you take advice from a cartoons stuffed toy?
Jan 29, 2011
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Metering off the 18% gray card (in spot or averaging mode) is metering of the incident light. Ideally, it should give you color channel saturation on the objects that are 0.5+ stops more reflective (in the corresponding color channel) than a 100% diffuse white card, and then, using exposure compensation, you can shift the saturation point.

I remember metering grass as if it were 18% gray card. While grass in green channel is brighter than 18% gray card in green channel, averaging over the spectral sensitivity of the older light meters gave you about the same reading. Not sure if this trick still works with modern metering; hopefully yes.
Metering off a grey card is not incident metering, it is reflective metering, you are not measuring the light source directly, you are measuring the amount of that light reflected by the card.
 
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Kit.

EOS 6D MK II
Apr 25, 2011
1,108
526
Metering off a grey card is not incident metering, it is reflective metering, you are not measuring the light source directly, you are measuring the amount of that light reflected by the card.
Metering off a grey card is using a reflective meter to obtain results equivalent to incident metering.
 

Viggo

EOS 5D SR
Dec 13, 2010
4,033
568
What 1 series? As I understand, from Mt Spokane's excellent link, the newer standard wasn't implemented into cameras until at least the 1D MkIV or more probably the 1DX.

But your findings run contrary to mine. I found the older cameras needed more exposure than suggested and the newer cameras pretty much spot on.
Yeah, I can’t remember when, but I think at least the mk4 had it... and so should every camera on the planet..