One of the most useful innovations of mirrorless systems like m4/3 is the Live Histogram, which allows one to essentially prejudge exposure.

It seems to me that an obvious extension would be to have a metering mode that uses the histogram the same way we often do, setting the exposure to be as high as possible without clipping highlights too heavily (or at all) - in essence an expose-to-the-right (ETTR) metering mode. Unfortunately, while they've been able to all sort of other clever things (e.g. face detect AF), metering seems sadly to still be stuck in the stone ages - we've got spot, center, and matrix mode (ESP on Olympus), and even matrix mode is still biased to the illusive and fictional 'middle gray'.

Does anybody else think an ETTR metering mode would be useful? Or have any suggestions how to achieve such results today without having to babysit the exposure constantly?

Thanks,

DH

Using the exposure compensation wheel you can shift the meter's target to control ETTR.

What you can't do is change the shape of the histogram, unless you use Gradation (essentially a post-processing curves adjustment) or do something external to the light distribution in the scene itself.

I don't quite follow. Obviously using EC changes the exposure (per the name) but how does it affect the metering?

The shape is fine. All I want to do is have it shifted so the right tail is always at or very near the right edge of the histogram.

Thanks,

DH

I've read this before in a piece on Luminous Landscape and the author didn't have a particularly good grasp of the underlying concepts digital signal processing. Exposing to the right, only, and I do mean only, improves the S/N (Signal to Noise Ratio).

Since low noise has become such a huge metric for camera buyers, camera makes have been tweaking the metering for hotter exposures. When I bought my D200, the matrix metering tended to meter to preserve highlight details, which is critical for pictures of people. (Clip the red channel for a Caucasian skin tone and there is no post processing that will render a smooth transition from shadow to highlight.) All my more recent cameras tend to hot exposures for low noise rather than preserve highlights. This is why camera makes have included processing/exposure tweaks like Nikon's Active D-Lighting (which even effects RAW files just like Olympus' AUTO Gradation setting).

And less noise = more detail. I would say the major improvement of large sensors over small sensors and newer cameras over older ones is precisely in that regard - more and better detail.

Auto gradation is actually quite primitive - it drops exposure by 0.3EV and then boosts the shadows in JPEG processing. I believe ADL does somewhat more.

But my point goes beyond just ETTR. The meter today has access to a wealth of information from the sensor - and almost all of it seems to be ignored.

Though I don't think ETTR, implemented as I suggested, would cause you any particular problems. Simply set the highlights clipping area limit to 0% on the red channel.

DH

P.S. When postprocessing files from the E-PM1 shot with standard metering on a nice day, the first thing I have to do is increase the exposure on 75-80% of the files, so that clouds and foam are white (not gray). A 0.5 or 1EV push invariably means that the midtones are full of noise (and after NR, lacking fine detail).

All I meant about the exposure compensation is that you're telling the camera the neutral grey that the sensor is "seeing" is to be shifted from it's centered position, by over/under exposing. This effectively drags the histogram along with it.

The more you try to work the data off the sensor the more high speed processing you need to get through the calculations in small fractions of a second. The latest in camera multi-processors help, but it also needs high chip frequencies, and those are a real battery drain as well as producing too much heat for natural cooling to be sufficient.

I have noticed that some of my lenses seem to produce histograms that are a lot more evenly distributed for a given lighting situation, while others are quite narrow in their captures. In the old days we would have talked about the difference being that one lens was more contrasty than the other.

Really? My impression was that the metering occurred independently, and then the EC was simply applied linearly after the fact.

I don't think there's that much additional work involved. I mean, they're already rendering the image, with distortion correction, and computing the histogram on the fly. The exposure data can be computed directly from the histogram as it's being generated.

True. And I'll bet it's mainly the older lenses produce a much broader histogram on the cameras, thanks to that lower contrast (or occasionally, haze on the lens).

DH

DH, your Olympus has a very useful metering mode called Spot-Highlight. Just take a reading off your clouds and they will be exposed as highlights (i. e. they will be white, not gray).

I actually have one of CUSTOM modes on my GH2 permanently set to spot metering and +2 exposure compensation as an attempt to recreate this Spot-Highlight feature.

- Pavel

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As a truly great man, I hate people with delusions of grandeur.

It seems to me that you don't know what you're asking.

First, you can use the histogram display to show whether or not you've got any clipping, and the highlight/shadow display to show you where that clipping is, but there's no way for the camera to know whether or not any clipping is in an area that's important to you. The camera can't tell whether the clipping is because you've got a light source in the frame that's going to clip pretty much regardless of how you expose, or whether the clipping is a highlight on the face of a person in an area in shadow and that you want to maintain detail in that highlight. The meter can measure the light and give you info about what the dynamic range of the light in the scene is like, and the highlights/shadow display can show you where the clipping is occurring, but neither is capable of deciding whether or not clipping is a problem for you with that shot. That has to be your decision.

Second, you say all the modes are "biased to the illusive and fictional 'middle tray'". What do you want them to be based on? Middle grey isn't fictional or illusive. For a start it is rather precisely defined and it is the luminance value for scenes with an average range of lighting levels distributed evenly within the frame. It works for "normal" shots and gives a reasonable result. What would you have meters set to? You need to have them calibrated to some reference level. What level would you propose and why do you think that level would work better than middle grey?

Every light meter made, whether it be in a camera or separate, is calibrated to middle grey which became the accepted standard for good reason. No camera manufacturer is going to change from an accepted international standard without very compelling reasons so, if you think that there should be a change, what are your reasons and what do you think the standard should be changed to?

With an Olympus (at least with my E-P3), in menu D of the cogs menu there's an option called "Live View Boost". If you set that to "Off", the display will respond to changes in exposure compensation, showing how things in the frame will lighten or darken as you adjust exposure using the exposure compensation dial. Using the histogram display you also get to see the histogram move to the left or right depending on what compensation you're setting, and the highlights/shadow display is active also showing you how any areas of clipped highlights or shadows are increasing or decreasing as you adjust the compensation. You can shift the exposure to the right or left and see just what effect that will have in your photo as you're doing it. What more do you want? I've got a friend with a Nikon DSLR who would love to have that option.

My E-P3 actually gives me 3 spot metering modes, not one. A "standard" mode based on middle grey, a highlight mode and a shadow mode. I've tried working out what the differences in values between those 2 modes and the standard mode is and they seem to be set at + or - 2 to 3 stops from the standard, middle grey value. If I meter a shadow area using the shadow mode, the exposure produces a result that makes the area metered dark enough so that details aren't visible, basically zone 2 if you want to use the zone system. The highlight mode puts the metered area as light, also without visible detail, the equivalent of zone 8. I don't find the shadow mode useful but what you can do with the other modes is the following:

- using normal spot mode, set exposure compensation to +1 and meter caucasian faces and you will get the right skin tone. Set exposure compensation to -1 for dark skinned faces such as Australian aboriginals or african americans and you'll get that skin tone pretty right. Basically that's setting your camera to expose based on light or dark skin tones.

- using the highlight spot mode, set exposure compensation to -1 and meter the brightest area in the scene in which you want to retain detail. That will give you highlights with detail which is what you want if you're going to use ETTR. Just make sure you don't measure highlights like the sun or an exposed light or you'll end up with everything else underexposed which isn't what you want.

Even if you're using the ESP or centre weighted modes on an Olympus, if you set Live View Boost to "Off", you can watch the effects of changes in exposure compensation as you make them and simply "dial it in" until the viewfinder is showing things looking the way you want them to look in your finished shot.

The metering modes and exposure information available in the display of my E-P3 seems to me to offer pretty much everything anyone would want, provided they're prepared to spend a bit of time learning how to use the options available and taking a few test shots to see just how what they're seeing in the viewfinder matches up to the results they get when they process their photos.

You just have to learn to use what's there, and there's a hell of a lot more there in metering flexibility than you think.

Pavel, thank you for that tip. That function is available even in the lowly E- PM1; will have to test it. Converse setting (spot metering/shadow control) is also an option. Every day I learn of another gold nugget buried in those menus...!

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Chuck