Why Exposing to the Right (ETTR) is BAD!

Started Mar 30, 2013 | Discussions
schmegg
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Re: Why Exposing to the Right (ETTR) is BAD!
In reply to Barrie Davis, Apr 1, 2013

Barrie Davis wrote:

schmegg wrote:

gwlaw99 wrote:

Trying to catch up here without reading the entire thread.  Can someone explain to me how ISO crept into the discussion when ISO does not effect exposure?  Is the conversation now on whether it is better to use a higher ISO or increase brightness in post processing?

Hehe!

Indeed!

ISO should only enter the discussion at all if you intend to change it to achieve the exposure shift. And, even then, given all the other factors in play and the amount you are likely to be shifting the metered solution, it is a minor consideration and depends also on the particular camera you are using. (something I'm guessing some here don't wish to consider, or simply don't understand).

ETTR is all about maximising the saturation of the sensor for a given scene. ISO has nothing at all do to with this.

Q: So how do you do that without increasing the exposure?
A: You can't. There is no other way to increase the amount of light striking the sensor than to use a longer shutter duration and/or a wider aperture... (leaving aside the possibility of supplementing the lighting!)

Conclusion: If you increase the exposure, which you are obliged to do..

...then you are carrying out the same actions as using a lower ISO...

...with NO photographic difference whatsoever, and with the SAME photographic results.

With a similarphotographic result.

The sensor readout is not treated the same if the ISO setting is different. So exposing for ISO 200 with the camera set at ISO 400 is simply not the same as exposing at ISO 200.

As I've said, the difference is probably not particularly striking - depending on the camera - and it's also pretty irrelevant to ETTR.

So we should probably just let it go now eh?

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OntarioJohn
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Re: Why Exposing to the Right (ETTR) is BAD!
In reply to Sovern, Apr 1, 2013

Gary Friedman covers this in his 600 page manual for the Sony a99.

But the book needs to be read by a competent photographer.

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Take some shots and SHARE...more fun that peeping at pixels at some crazy ISO!!!

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NancyP
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digital facts of life for beginners
In reply to Sovern, Apr 1, 2013

1. If you shoot JPG, you need to shoot at the exposure that is as close to the final image as is possible. JPG files have limited post-processing capacity.

2. ETTR matters only if you shoot RAW and are willing to post-process. Do you know about curves, mid-tones contrast vs global contrast, etc? If not willing to post-process, shoot at the "ideal" exposure for out-of-the-camera use.

3. This is a beginner's forum. Don't do ETTR. Take a few post-processing classes (an introduction to Lightroom, PSE, PS, Aperture, whatever). Then revisit the subject.

4. There are situations where an experienced photographer shooting RAW will ETTR. ETTR is not inherently "BAD".

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Barrie Davis
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Re: Why Exposing to the Right (ETTR) is BAD!
In reply to schmegg, Apr 1, 2013

schmegg wrote:

Barrie Davis wrote:

With a similarphotographic result.

NO. You are wrong.

Under standardised lighting conditions the affect at the sensor is precisely the same every time you expose it for 1/100th second @ f/8. That is "the exposure"... and it made in accordance with an effective ISO, even if not the ISO the camera happens to be set at... (see below)

The exposure does NOT change because the processing changes. In this regard ISO is just processing.

The sensor readout is not treated the same if the ISO setting is different. So exposing for ISO 200 with the camera set at ISO 400 is simply not the same as exposing at ISO 200.

It doesn't matter what the ISO is at the point of exposure because ISO only determines output afterwards. Output from the exposure is variable depending on how it's processed, and doesn't itself determine the exposure unless you allow it to in reading the meter. As we have seen, you can overexpose or underexpose from the meter, anytime, if you choose to.

But a delivered 1/100th @ f/8 is always 1/100th at f/8, and that will always be the same exposure no matter how it is arrived at...

.... no matter how much underexposure is deliberately applied to nominally "higher" ISO settings, or how much overexposure has been added to nominally "lower" ISO settings. If the resultant exposure is 1/100th @ f/8, and that is what is delivered to the sensor by the shutter and diaphragm working together, then that is always the same, if the light strength is the same.

That is why 400-ISO shot with one stop's worth of overexposure for the sake of ETTR, is identical to 200-ISO shot straight. Please take note: Not just "similar in every way that matters"... but THE SAME, NO DIFFERENCE.

Now, you can fart about with the histogram as much as takes your fancy after the event, but at the point of shooting they are THE SAME, NO DIFFERENCE, photographically identical.

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schmegg
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Re: Why Exposing to the Right (ETTR) is BAD!
In reply to Barrie Davis, Apr 1, 2013

Barrie Davis wrote:

schmegg wrote:

Barrie Davis wrote:

With a similarphotographic result.

NO. You are wrong.

Under standardised lighting conditions the affect at the sensor is precisely the same every time you expose it for 1/100th second @ f/8. That is "the exposure"... and it made in accordance with an effective ISO, even if not the ISO the camera happens to be set at... (see below)

The exposure does NOT change because the processing changes. In this regard ISO is just processing.

The sensor readout is not treated the same if the ISO setting is different. So exposing for ISO 200 with the camera set at ISO 400 is simply not the same as exposing at ISO 200.

It doesn't matter what the ISO is at the point of exposure because ISO only determines output afterwards. Output from the exposure is variable depending on how it's processed, and doesn't itself determine the exposure unless you allow it to in reading the meter. As we have seen, you can overexpose or underexpose from the meter, anytime, if you choose to.

But a delivered 1/100th @ f/8 is always 1/100th at f/8, and that will always be the same exposure no matter how it is arrived at...

The amount of light that is gather by the sensor is the same - yes.

What happens to it then, though, is not.

The photons are collected and generate a voltage. This voltage is then read from the pixels and amplified. The amount of amplification is dependant upon the ISO setting you have selected. The amplification may also introduce noise - and the significance an magnitude of this varies depending upon the particular sensor you are discussing.

So - even though the exposure is the same, the raw values recorded from it will vary depending upon both the ISO setting and the sensors ADC capabilities.

Your assertion that a shot exposed for ISO 200 but taken with the camera set at ISO 400 is "exactly" the same as the same shot taken with the camera set at ISO 200 is just plain wrong.

.... no matter how much underexposure is deliberately applied to nominally "higher" ISO settings, or how much overexposure has been added to nominally "lower" ISO settings. If the resultant exposure is 1/100th @ f/8, and that is what is delivered to the sensor by the shutter and diaphragm working together, then that is always the same, if the light strength is the same.

Yes. The number of photons striking the sensor is the same.

That is why 400-ISO shot with one stop's worth of overexposure for the sake of ETTR, is identical to 200-ISO shot straight. Please take note: Not just "similar in every way that matters"... but THE SAME, NO DIFFERENCE.

No. The resultant raw file is different.

Now, you can fart about with the histogram as much as takes your fancy after the event, but at the point of shooting they are THE SAME, NO DIFFERENCE, photographically identical.

No. Similar - and I'd go as far as to agree that in many circumstance the difference would be trivial and irrelevant - but, still, not the "same".

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Barrie Davis
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Re: Why Exposing to the Right (ETTR) is BAD!
In reply to schmegg, Apr 1, 2013

schmegg wrote:

Barrie Davis wrote:

In both cases the amount of light striking the sensor is identical... that is, an amount that is correctly exposed for 200-ISO. The fact that for one of the shots the camera happens to be set, not at 200, but to 400-ISO with 1 stop of overexposure for ETTR, alters NOTHING.

They are both 200-ISO exposures.

In other words, they are photographically the same, both exposed at 200-ISO, by means of shutter speed and aperture settings commensurate with that 200-ISO rating.

It is, after all,  shutter speed and aperture settings USED which determine which ISO was USED.

As you have stated yourself, the ISO on the dial means nothing, because what happens AFTER the 200-ISO's worth of light has been recorded by the sensor is neither here nor there. The ISO setting of the camera is indeed irrelevant to the strength of the exposure which has already been made...

... all it does is "position" the features of the histogram after the event with more or less amplification in firmware...

...or in SOFTWARE, if you are messing about with the tonal structure afterwards in a computer the way proponents of ETTR would have us do.

Now, does THAT make it any clearer for you?

Yeah - that's a much better reply - thanks for taking the time. I do appreciate it, as I'm sure others do too.

The only caveat I'd add - and you may disagree with, of course - is that, when the sensor is read at ISO 400, the readout signal will be treated differently to how it will be treated at ISO 200.

And this could, depending upon the particular camera, affect the final result - either in a good way or in a bad way. Though, as I said earlier, I doubt it would be particularly significant in most cases. Particularly in the case of adjustments made for ETTR.

I did tests with two different camera marques to find out what their responses were to processing via ETTR and subsequent tonal correction in Photoshop (ACR)..

...as compared with the USUAL WAY of invoking a lower ISO (!)... ;-)...

... and the results were so close to identical I was amazed at how different they were NOT. Indeed, I had expected to see some kind of difference -(well you would, wouldn't you?)- but despite looking as close as I could, if there was a difference, it was invisible to me. I do have some experience in evaluating photographs, it has to be said.

For this reason I feel completely vindicated in taking the stance that I do regarding the usefulness of ETTR.

However, that comment should be qualified. My conclusions extend only so far as the two cameras I checked... and that was six years ago.. (no, seven). If ETTR has gained validity in the meantime I don't know that it has, and suspect that it hasn't...

....but I have to admit that it is not impossible.

I ask, because for most people it doesn't, at least not usually. Most people just argue, and I'm not in the mood for that, I'm afraid.

Yeah - fair enough. I can understand that.

I would add though, that if you wish to make claims in these forums - particularly in beginners forums - you should really be prepared to explain them if people have questions. At least IMHO (for what it's worth).

No offence meant by that Baz - it's difficult to word the sentiment in a way that is not perhaps in danger of being perceived as insulting - but that is certainly not my intention at all!

The forums are really a place for people to share experiences and learn from each other. So your explanation is very much a good thing - and I'm sure it didn't really hurt all that much.

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Baz
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schmegg
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Re: Why Exposing to the Right (ETTR) is BAD!
In reply to Barrie Davis, Apr 1, 2013

Barrie Davis wrote:

schmegg wrote:

Barrie Davis wrote:

In both cases the amount of light striking the sensor is identical... that is, an amount that is correctly exposed for 200-ISO. The fact that for one of the shots the camera happens to be set, not at 200, but to 400-ISO with 1 stop of overexposure for ETTR, alters NOTHING.

They are both 200-ISO exposures.

In other words, they are photographically the same, both exposed at 200-ISO, by means of shutter speed and aperture settings commensurate with that 200-ISO rating.

It is, after all,  shutter speed and aperture settings USED which determine which ISO was USED.

As you have stated yourself, the ISO on the dial means nothing, because what happens AFTER the 200-ISO's worth of light has been recorded by the sensor is neither here nor there. The ISO setting of the camera is indeed irrelevant to the strength of the exposure which has already been made...

... all it does is "position" the features of the histogram after the event with more or less amplification in firmware...

...or in SOFTWARE, if you are messing about with the tonal structure afterwards in a computer the way proponents of ETTR would have us do.

Now, does THAT make it any clearer for you?

Yeah - that's a much better reply - thanks for taking the time. I do appreciate it, as I'm sure others do too.

The only caveat I'd add - and you may disagree with, of course - is that, when the sensor is read at ISO 400, the readout signal will be treated differently to how it will be treated at ISO 200.

And this could, depending upon the particular camera, affect the final result - either in a good way or in a bad way. Though, as I said earlier, I doubt it would be particularly significant in most cases. Particularly in the case of adjustments made for ETTR.

I did tests with two different camera marques to find out what their responses were to processing via ETTR and subsequent tonal correction in Photoshop (ACR)..

...as compared with the USUAL WAY of invoking a lower ISO (!)... ;-)...

... and the results were so close to identical I was amazed at how different they were NOT. Indeed, I had expected to see some kind of difference -(well you would, wouldn't you?)- but despite looking as close as I could, if there was a difference, it was invisible to me. I do have some experience in evaluating photographs, it has to be said.

For this reason I feel completely vindicated in taking the stance that I do regarding the usefulness of ETTR.

However, that comment should be qualified. My conclusions extend only so far as the two cameras I checked... and that was six years ago.. (no, seven). If ETTR has gained validity in the meantime I don't know that it has, and suspect that it hasn't...

....but I have to admit that it is not impossible.

we will likely kill the thread discussing this - but it is interesting and the basic premise of the thread is rubbish anyway!

Out of interest, which different camera marques did you use?

TBH - I agree that it's no big deal. I simply expose to get the image I'm after. I don't fuss with theoretical best practice. I look at the scene, I make the exposure, I review, and if it's not what I'm seeing then I go again. And quite frankly, the meter does a damn fine job unless the light is low and it's trying to turn night-time into daytime!

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Robgo2
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Re: Why Exposing to the Right (ETTR) is BAD!
In reply to Sovern, Apr 1, 2013

There is no way that I am going to read all 146 posts in this thread, so I don't know if anyone has referenced this article yet, but Ctein at The Online Photographer (TOP) agrees with the OP's premise regarding ETTR.  I realize that one could consider this an ad hominem argument, but I believe that Ctein knows more about the subject than most people who have offered their opinions so far.  Take it for what it is worth.

Ctein: "Expose to the Right" is a Bunch of Bull.

Rob

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Barrie Davis
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Re: Why Exposing to the Right (ETTR) is BAD!
In reply to schmegg, Apr 1, 2013

schmegg wrote:

Barrie Davis wrote:

schmegg wrote:

Barrie Davis wrote:

With a similarphotographic result.

NO. You are wrong.

Under standardised lighting conditions the affect at the sensor is precisely the same every time you expose it for 1/100th second @ f/8. That is "the exposure"... and it made in accordance with an effective ISO, even if not the ISO the camera happens to be set at... (see below)

The exposure does NOT change because the processing changes. In this regard ISO is just processing.

The sensor readout is not treated the same if the ISO setting is different. So exposing for ISO 200 with the camera set at ISO 400 is simply not the same as exposing at ISO 200.

It doesn't matter what the ISO is at the point of exposure because ISO only determines output afterwards. Output from the exposure is variable depending on how it's processed, and doesn't itself determine the exposure unless you allow it to in reading the meter. As we have seen, you can overexpose or underexpose from the meter, anytime, if you choose to.

But a delivered 1/100th @ f/8 is always 1/100th at f/8, and that will always be the same exposure no matter how it is arrived at...

The amount of light that is gather by the sensor is the same - yes.

And that is all that matters, photographically.. that is, to the business of taking the picture.

What happens to it then, though, is not.

What? Do you think you can process more Depth of Field into the shot by pushing the histogram around after shooting..?  Or maybe get better camera shake suppression or subject movement freezing?

These are things which are dependant on the effective ISO; the shutter speed and aperture settings available for use at the point of exposure. As stated repeatedly, Exposing To The Right reduces effective ISO and that alters the photographers ability to take photographs.

In this respect, ETTR is the same as the "normal" way of shooting at low ISO... which low ISO constrains the shooting of images (the "photography") the same either way.

That is my point....

ETTR is just a somewhat inconvenient way of invoking low ISO because of the post processing needed to put the tones on the histogram back where they came from.

If the shot is capable of being recorded with a low ISO invoked in the "normal" "NOT inconvenient" way, then that would be the sensible thing to do. My tests, done with specially sought subjects of short tonal range, suggest that the results are so similar as to be the same.

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Baz
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Tan68
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Re: Why Exposing to the Right (ETTR) is BAD!
In reply to schmegg, Apr 1, 2013

schmegg wrote:

... You still have not commented on this though - instead you seem to simply imply that I don't know what I'm talking about - which I find to be a cop out and, most likely, an avoiding tactic.

"Avoiding tactic" is generous.  I thought to make a comment a few hours ago.  At that time, I thought the fellow had a little trouble with his explanation.  If you have explained things countless times yet no one understands, maybe it is worthwhile to re-evaluate the explanation.  etc.

Of course taking a picture at two different gains/ISO aren't the same.  What he means, though, is that the end product will look pretty much the same.  The ISO 400 shot with one stop of ETTR will be brighter than the ISO 200 shot 'properly' exposed.  When the brightness of the ISO 400 shot is reduced one stop in post processing, the two images will have very similar characteristics with respect to noise and etc.  So, effectively, the image taken at ISO 400 + 1 stop ETTR is the same as the ISO 200 picture.

Taking two pictures with different gain settings are not the same.  Most people will not see it as the same because there is a different camera setting involved.  That is simple and obvious.  In trying to explain a concept to people it is worthwhile to not create a point of confusion and instead admit that the settings on the camera are different but the end product, the final result will be the same and here is why.  That is a way to explain things to people.  The fellow you are dickering with has chosen another way to explain things.

For some cameras, it actually isn't the same to use two different gain settings.  This gets more technical and it is not something I can explain very well... One camera may have basically the same read noise at both ISO 200 and 400.  Another camera may have less read noise at ISO 400 than at ISO 200.  For this first camera, to say "ISO 400 + 1 stop ETTR = ISO 200" is pretty much right.  For the second camera, to say  camera, to say "ISO 400 + 1 stop ETTR = ISO 200" is not entirely correct.  Why cameras some have different read noise at some ISO and not at others and other cameras have the same read noise at different ISO, I don't know.  Hmm, I think it is read noise at issue.  In any case, the scenarios I have described exist.  Still don't know why.

So, in trying to help people understand a concept, it is sometimes better to see things from their point of view, explain you understand their point of view, and then explain how things can be looked at differently.

Telling someone two different gain settings are the same when what is meant is that the end result may be the same is another way of explaining things.

Telling someone that two different gain settings with the higher gain receiving +1 stop, will produce the same result isn't always true.  The results vary by camera and by the particular gains/ISO being used for each camera.

Anyway, I hope this helps you understand that I think the fellow is trying to explain that the end result is the same and this is once the brightness of the ISO 400 +1 has been reduced to match that of the ISO 200 +0.

I believe this will be true for most cameras.  It is not true for all cameras and it is not true for all cameras for all available ISO's...  The differences may be more or less..  But this is a thread about very particular exposure so the small differences should be considered.  If you want to be particular...

I think, out of hand and finer points set aside, that what the fellow is telling you is a fine rule of thumb.

PS - I have read even a few more posts!  Shortly after your post that I replied to, you mentioned different read out noise and etc.  So, I needn't have mentioned all that to you.  I am glad things are approaching fusion between you and the other fellow.  It seemed a singularity was approaching...

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