Expose to the left?

[bjanes]

IF that's what he means, there are at least two of us misunderstanding his writing.

Film: Expose for the shadows, develop for the highlights (we've heard this for eons).

Digital: Expose for the highlights (ETTR, don't blow them out), develop for the highlights (render so you have the detail that's there).

I don't see how he can say the are similar....

Exactly. Examination of the characteristic curves of negative film and digital shows why film should be exposed for the shadows and digital exposed for the highlights.

With a typical B&W negative film, a minimum exposure is needed to record density above fog on the negative. This minumum exposure is not significantly affected by development. One should expose so that the deepest shadows where some detail is required will be above the fog level of the film. Development can help place the highlights and the shoulder on the curve (not well shown on the curve shown) will help losing the highlights. With high dynamic range subjects, the highlights might become blocked up and one might give less exposure to preserve them. Film tolerates overexposure better than underexposure.

[attachment=14988:TriX.gif]

With digital, there is no shoulder and the highlights clip abruptly. Clipping of shadows does not occur, but eventually shadow detail is limited by the signal to noise ratio. Normally, best results are obtained by exposing so the highlights are just short of clipping. With high dynamic range subjects, one might have to compromise, but clipped highlights are usually more objectionable than noisy shadows. Highlight recovery depends on intact channels (usually red and blue with daylight exposure), and one should expect to recover more than one stop. Digital degrades rapidly with overexposure.

[attachment=14989:ResultsGraph.png]

[PeterAit]

Unclear semantics on my part. Last stop being shadows. When you expose to the right, you place as much data there as possible, the results being the most data one can record in the last stop (shadows) or if you prefer, first stop (shadows):
http://www.digitalphotopro.com/technique/c...ng-for-raw.html

What you say is true but it's only part of why we ETTR. We want to get as much data not only in the shadows but throughout the entire photograph.

Peter

[PeterAit]

I think what Eric and I are saying is that ETTR is about placing your highlights as far right as possible without clipping highlights (highlights that you care about, anyway). While this does give you cleaner shadows, it is not exposing for the shadows. Placing the highlights is what determines your exposure, and the shadows fall whereever they fall. WIth digital cameras there's more latitude to bring up the shadows than there is to bring back clipped highlights, so digital exposure shares more in common with slide film than negative film.

Taken literally, the authors recommendation is to use a meter reading from the shadows to determine your exposure, without any regard to highlights at all. That is not exposing to the right;  it is exposing for the shadows. The two are not the same.

While you determine your exposure based on the highlights, the reason you do so is to get as much details (and as little noise) as possible in the shadows. In this sense you are exposing for the shadows.

Peter

[dwdallam]

While you determine your exposure based on the highlights, the reason you do so is to get as much details (and as little noise) as possible in the shadows. In this sense you are exposing for the shadows.

Peter

Yes, this is how I "interpreted" what the guy was saying, although I will give the rest of you that his explanation was convoluted, to say the least. He could have taken a bit more time and written an elegant explanation taking the two methods at the same time. The reason I interpreted it this way is that any other way doesn't make sense, and the guy obviously knows photography. So I gave him the "principle of charity" in reading his explanation.

[Eric Myrvaagnes]

Yes, this is how I "interpreted" what the guy was saying, although I will give the rest of you that his explanation was convoluted, to say the least. He could have taken a bit more time and written an elegant explanation taking the two methods at the same time. The reason I interpreted it this way is that any other way doesn't make sense, and the guy obviously knows photography. So I gave him the "principle of charity" in reading his explanation.

So what he said was both stupid and wrong, so he must have meant the opposite. Sounds a little like the defense some folks like to make of the "Your camera doesn't matter" guy. 

[JeffKohn]

While you determine your exposure based on the highlights, the reason you do so is to get as much details (and as little noise) as possible in the shadows. In this sense you are exposing for the shadows.

Peter

You can choose to look at it that way if you want, but it's a misuse of term 'exposing for the shadows', and will cause confusion for photographers who are familiar with the term. There's a reason the term 'expose to the right' was coined; it's a different technique for determining exposure.

[digitaldog]

You can choose to look at it that way if you want, but it's a misuse of term 'exposing for the shadows', and will cause confusion for photographers who are familiar with the term. There's a reason the term 'expose to the right' was coined; it's a different technique for determining exposure.

Perfectly stated. We're in total agreement!

[dwdallam]

So what he said was both stupid and wrong, so he must have meant the opposite. Sounds a little like the defense some folks like to make of the "Your camera doesn't matter" guy. 

I don't think what I said was that his writ was stupid or wrong.

 What I said is that if the person knows photography, then he would not make a mistake like that. He may have written a sloppy explanation, but it doesn't mean he doesn't know what he is talking about.  It's a simple matter of emailing him and asking if what he meant is how I and others interpreted it, or not.

I admitted it was confusing, but if you are exposing for the shadows and at the same time exposing in order to NOT blow the highlights, then the two methods seem to be interchangeable, with small discrepancies for film and sensor, respectably.

In other words, if you expose for shadows and NOT blow highlights, then you are exposing to the right in both cases. This is true because in each case the brightest you can make the shadows is limited of how far you can take the highlights before they blow.

Another way to put it is expose for the shadows w/o blowing the highlights: Wait! That's what he said. The confusion is that even if you expose for the shadows, you may not be able to properly expose the shadows without blowing highlights.

[Rob C]

The confusion is that even if you expose for the shadows, you may not be able to properly expose the shadows without blowing highlights.

No, no, no! That´s not confusion at all. It is perfectly accurate and it is not to be confused with confusion: it is Catch 22, the greatest catch of them all.

Rob C

[dwdallam]

No, no, no! That´s not confusion at all. It is perfectly accurate and it is not to be confused with confusion: it is Catch 22, the greatest catch of them all.

Rob C

True, but that's what has everyone worked up. It is perfectly accurate because if you expose to the right as far as you can, then you've exposed for the shadows as much as you can. It's two sides of the same coin.

[Guillermo Luijk]

He didn't mean 'Expose to the left', since exposing to the left, according to the histogram naming convention in digital photography would mean to take your histogram to the left as much as you can, and this is not what the guy is saying (he says expose as much as you need to have your shadows right). ETTL would actually be a stupid move without any other advantage than allowing fast shutter speeds, but regarding the quality of capture would be a ruin.

But he is not meaning 'Expose to the right' either, since he is not taking any care of not clipping the highlights in his advice.

So he is proposing a method to expose, that would be the opposite in conception to ETTR, but that cannot be called ETTL.

I wouldn't be too much interested in attending a seminar by Mr. Eugene Foster though.

Regards.

[Schewe]

I wouldn't be too much interested in attending a seminar by Mr. Eugene Foster though.

That's the best response so far!!!!

Look, you guys all seem to meander all around the basic facts and fail to get the basic fundamentals...more photons equals less noise...

Michael kinda got it wrong in his article...the ETTR really has nothing to do with "bits" and has EVERYTHING to do with PHOTONS!!!!

I can't say for a fact what the heck the original author of the opening meandering discussion about exposure was meaning to try to get across but the bottom line is if possible, give your sensors MORE PHOTONS. That's what ETTR is really all about. If you underexpose AT ALL and have to up-process your captures, you're making noise blossom. If you want reduced noise, expose more...give your sensor MORE PHOTONS!!!!

Can I get any more explicit? Do you get the fact that MORE PHOTONS is better for your signal to noise ration? That having more signal gives you less noise? Underexposing sucks...

Sure, you want to maintain the degree of highlight detail you need in the final capture...but don't look at your camera's histogram if you want any true guidance...look at your friggin' light meter!!!

Sorry, GLuijk is right...if this guy is actually teaching classes at ICP, I gotta think somebody should put a hit out on him...seriously, this crap only get everybody completely confused (and apparently willing to pay good money to take a class to get it all figured out).

Oih!!!

[John Camp]

I tend to agree with dwdallam -- that the guy probably knows what he's talking about, but wrote it badly.

I think Schewe overstates the argument. (He also states it badly, as did the guy who started the controversy.) You don't always want MORE photons, because then you'd have nothing but a white exposure, with everything blown; what you want is the OPTIMUM number of photons for whatever you're trying to do. You MAY want the MOST photons you can get without blowing the highlights. But maybe not -- in some photographs, you may choose to completely blow the highlights, because there's something in the shadows that's more important to get right.

This goes back to my dark church example. You may want to expose for the shadows and let the highlights go, something that happens when you are in dark places where flash is not allowed, but you'd like to get a sense of the colors. It happens in churches, museums, etc. If you are shooting, say, a great colorful painting in a dim gallery lit with clerestory windows -- not an uncommon situation -- you may want to let the window highlights blow so you can get the best possible, accurate, noise-free color in the painting. In this case, you don't care about the highlights: they're irrelevant. You may even crop them out later. In effect, you're exposing for the shadows. So, I don't think that idea is in any way stupid or wrong, it's just not the conventional use of a camera in catching a landscape. (Though sometimes the same thing comes up in landscapes, when you choose to deliberately blow the highlights, particularly if you're shooting close to the setting sun, but don't want the sun, only the raking shadows.)

In fact, I'd say that perhaps in a majority of indoor photos where flash is not allowed, but where there are cracks or small windows or reflections or other hot lights, but where the main action is in shadow -- a wedding -- you may be much more interested in the shadows than in not blowing certain highlights, which, in effect, act like specular highlights in a normally exposed photograph. That is, they are completely blown, but nobody cares, because they are small and irrelevant. In a very dark church I can easily imagine choosing to blow background candles in order to get a little noise-free color in the bridesmaids' dresses...

On another matter, I appreciate Andrew Rodney's attempt to explain to me about shoulders, but there were several words in the explanation that I didn't understand.

JC

[bjanes]

Michael kinda got it wrong in his article...the ETTR really has nothing to do with "bits" and has EVERYTHING to do with PHOTONS!!!!

I can't say for a fact what the heck the original author of the opening meandering discussion about exposure was meaning to try to get across but the bottom line is if possible, give your sensors MORE PHOTONS. That's what ETTR is really all about. If you underexpose AT ALL and have to up-process your captures, you're making noise blossom. If you want reduced noise, expose more...give your sensor MORE PHOTONS!!!!

Can I get any more explicit? Do you get the fact that MORE PHOTONS is better for your signal to noise ration? That having more signal gives you less noise? Underexposing sucks...

While it is true that the signal to noise ratio is largely determined by photon counting statistics, one must remember that a sensor can effectively record the maximum number of photons only when it is used at the the base ISO. For each doubling of the ISO setting over base, the maximal number of collected photons that can be collected without clipping in the analog to digital converter is halved. Proponents of ETTR are concerned if their histograms fall a half stop to left at base ISO, but think nothing of shooting at double or even quadruple the base ISO as long as the histogram is snugged up to the right or the exposure meter indicates "proper" exposure for the ISO for which the camera is set.

When depth of field or motion freezing considerations require the use of a higher ISO, dynamic range does not suffer as much from the reduced number of collected photons as would be expected from photon counting statistics alone, since the read noise is reduced at higher ISO with current dSRLs. Read noise is the predominant source of noise in the deep shadows, and what one loses at the high end is recovered in part at the low end. However, as ISO is increased further, improvements in read noise reach a maximum. For example, with the Canon 1D Mark III, it makes no sense to increase the ISO beyond 1600 as explained here. After that point, one should increase the effective ISO with the raw converter, thereby obtaining increased headroom in the highlights, even though the histogram will be to the left. However, the JPEG preview shown on the camera LCD will appear dark.

[Tim Lookingbill]

Still don't know any more than I did before reading through this thread.

No one yet has shown through real world images the advantages of ETTR.

More photons? Of course you want more photons. It's called letting more light in. The problem with that is digital sensors are unpredictable in letting you gauge what light is available and how it will be captured because sensors don't behave the same way our eyes respond to light. Sensors respond and record how much light is REFLECTED BACK from how many DARK and LIGHT objects are contained in a scene regardless of how much overall light is in the scene.

This becomes quite clear when shooting a high contrast scene for example a frame equally composed of a sunlit concrete sidewalk and a tall cedar fence with shrubbery in shadow at its base. I guarantee you'll be using two drastically different exposures when equally including both the dark fence and the sidewalk compared to having about 80% of the frame taken up by the dark cedar fence. Even if you ETTR that fence and let the small portion of sunlit sidewalk clip to white, the fence is going to have noise no matter the ISO setting. I get this with my Pentax K100D DSLR all the time.

On the other hand I was shooting this same scene with diffused light from a cloud that happened by covering the sun that required drastic exposure changes by comparison to how my eyes perceived the amount of light that had been reduced. I shot other outdoor scenes in similar situations shooting two frames of the same scene with the same exposure where with the second frame the edge of a cloud just slightly obscured the sun in a way my eyes didn't notice a change in light level but caused the histogram in ACR between the two shots to move from the 1/4 zone to just slightly left of the mid zone. That's a big jump to have to compensate for when capturing quick shots.

So from all this IMO ETTR is too much of a hassle having to out think the camera's sensor in how it sees and captures light combined with gauging the moving target of changing light levels and predicting when and if clipping occurs.

And another question that comes to mind is are you suppose to ETTR a low lit scene whose ACR histogram would normally fall just slightly left of the 3/4 zone if choosing an exposure to make the preview look correct in ACR. Are we to overexpose that kind of scene to make ACR's histogram move to the middle? 1/4 zone? Where? How much ETTR for that scene?

I've ETTR'ed such a scene and I didn't get any more noise in the shadows than I did if I hadn't ETTR'ed when normalizing the look of the scene in ACR.

[JeffKohn]

It's a common misconception that ETTR is the answer to every exposure situation. ETTR really only makes sense when the contrast range of the scene you're shooting easily fits within the dynamic range of the camera.

[Tim Lookingbill]

It's a common misconception that ETTR is the answer to every exposure situation. ETTR really only makes sense when the contrast range of the scene you're shooting easily fits within the dynamic range of the camera.

How does one gauge contrast range to match the dynamic range capabilities of a camera's sensor shooting out in the field? Is there a DR to contrast table calculator for each sensor from the guys at ISO? What does that look like?

I need to shoot pictures at an exposure level that requires the least amount of post processing possible. If I nailed it in camera what difference does it make if I ETTR'ed since ETTR's benefit is to reduce noise that would be increased and corrected through edits if I hadn't ETTR'ed? And I don't see that much of change in noise levels either way.

Dynamic range gauging and matching sounds like another moving target to me and way too much work and thought required than it's worth.

[Tim Lookingbill]

Jeff,

Saw you are a Texan and checked out your Garner State Park shots. I think you and I may have passed each other since I was there about the same time as your Fall of 2008 pix indicate. The colors in your well composed images  show a clearly different and nicer looking point of view than my somewhat dull looking Pentax PEF's shot of the same area.

Nice work.

[Panopeeper]

How does one gauge contrast range to match the dynamic range capabilities of a camera's sensor shooting out in the field? Is there a DR to contrast table calculator for each sensor from the guys at ISO? What does that look like?

How do you match the dynamic range capabilities of a camera's sensor shooting out in the field? Do you wait until a cloud covers the sun? Short of "coming back another time", one has to live with the dynamic range of the scenery and make the best of it. The latter includes the decision sometimes about what to sacrify: the very highlights or the very shadows.

Except if the dynamic range of the scenery is clearly less than the camera's capability, accurately or close to accurately seeing the raw exposure is critical, and that is not possible without a special neutral setup coaxing the camera into displaying histograms, which are closely resembling the raw histograms. There is at least one MFDB, which does display raw histogram (I forgot which one, but someone posted this on LL), but otherwise you have to fool the camera.

I need to shoot pictures at an exposure level that requires the least amount of post processing possible

Well, then ETTR is certainly not for you.

If I nailed it in camera what difference does it make if I ETTR'ed since ETTR's benefit is to reduce noise that would be increased and corrected through edits if I hadn't ETTR'ed? And I don't see that much of change in noise levels either way

If there are underexposed areas in the image, then the noise is there, it can only be suppressed. If the result is good enough for you, then you are right, you have no reason to care for this aspect.

[Rob C]

Sure, you want to maintain the degree of highlight detail you need in the final capture...but don't look at your camera's histogram if you want any true guidance...look at your friggin' light meter!!!

And there lies a problem. I have done that using guidance from the Minolta Flashmeter that I have, and I get a reading that works well when copying a painting (my own, relax) with bright highlights such as white or silver. Also, the camera´s matrix metering works closely in harmony with what the Minolta says. But, remove those highlights (different original painting) and then the same incident light reading no longer fits the matrix reading nor the ETTR histogram. So, in effect, digital capture is far less reliable/simple to nail than is transparency material.

Perhaps, in the end, one should forget ETTR and just go with the matrix metering and look at the flashing highlights mode instead of the histogram.

On the understanding that transparency films were never going to do both ends of the range justice at the same time (normal subjects), then perhaps the problem is not digital capture but rather what we imagine it should deliver. If we can accept that nothing in life is going to be perfect, perhaps using digi capture will become more pleasant and just as fast/simple to get "right" within what can be achieved. Perhaps yes; perhaps not.

This, of course, would only apply in cases where you want to make a single exposure of your subject and not a selection for afterwork.

Rob C