# Developing From the Right



## Andrew1 (Jun 28, 2016)

Much has been written (and argued) about "Exposing To the Right", but this is more about "Developing From the Right".

Given an exposure-bracketed sequence, in which NONE of the frames show any highlight clipping, 
am I correct in thinking that I should always target my Development efforts at the one whose histogram stretches furthest to the right as it will contain more "information" than the others (especially in the darker tones)?

Or am I missing the point?


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## RikkFlohr (Jun 28, 2016)

Yes. It will contain more tonal information.  As a consequence, the signal to noise ratio in the darker regions of the image will be greatly improved.  See this video. https://www.youtube.com/watch?v=ADCmUs6b8Do


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## Andrew1 (Jun 28, 2016)

Thank you, that video neatly addresses exactly the situation I'm looking at and clearly shows me the sort of things I should be aware of.
[How could you have known, seven years ago, what I was going ask?]


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## tspear (Jun 28, 2016)

Rick,

Does the ETR change based on more modern sensors? I read somewhere that some brands are better to expose right, others are expose left; and this was based on some technical evaluation of the sensor data that was WAY above my head.


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## Johan Elzenga (Jun 28, 2016)

ETR is something you do, not the sensor.


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## RikkFlohr (Jun 28, 2016)

ETTR is a concept based upon the mathematics of Tonal Value and how it is distributed from Dark(Left) to Light(Right). The math doesn't change from sensor to sensor. 1/2 of your light, hence 1/2 of your tonal value, is in the brightest F-stop of exposure-namely the right-hand side of the histogram.

Theoretically, if you have an 8-Stop Dynamic range and a 12-Bit Raw file (10-year old benchmark), your brightest Fstop contains 2048 tonal values. Your darkest Fstop has 16 tonal values. Noise lives throughout the image. If the noise is (hypothetically) 3, 3/16 is pretty significant - especially if you are tweaking exposure/shadows/blacks upwards. 3/2048 is pretty insignificant by comparison.  All images survive a one-stop reduction in exposure far better than they will a one-step increase in exposure. 

Extending. If your camera has a 10-Stop Dynamic range and a 14 Bit Raw file  (more modern benchmark), your brightest stop contains 8096 tonal values and your darkest still has only 16 tonal values. If noise is still 3 - or let's say its better(improved noise tech), only 2, that still leaves 2/16 vs 2/8096.  Signal to noise ratio, though improved across the board, and bit-depth, though improved across the board, is not that much better at the darkest discernible stop. It is much better at the brightest stop. 

These are gross generalizations for demonstration purposes and mileage varies from manufacturer to manufacturer, year to year, model to model and even Camera to Camera.


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## tspear (Jun 28, 2016)

Rick,

Cool. Thanks for the math; it took a few reads to follow...


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## tspear (Jun 28, 2016)

JohanElzenga said:


> ETR is something you do, not the sensor.



But ask why you do it. 
Rick got my question, I was wondering why ETR matters. I had read a blog post about how some sensors are better at low light versus brighter lights and therefore it is better to expose left. All I recall from the blog is that I could not follow the math, and it did not apply to my camera at the time.


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## Johan Elzenga (Jun 28, 2016)

Anyone can post something on the internet, even the biggest BS. Rick already explaned very well why you should *always* expose to the right to get the most information, no matter what sensor. Even a sensor that is particularly good (noise free) in the shadows will still benefit from ETR just as much as any other sensor, because *all* sensors are linear: half the tonal values are in the highest stop, half of the remainder in the second stop, etcetera. If you'd expose to the left, and as a consequence would leave the first stop empty, you would lose half the tonal values the sensor can capture. That means your 14 bits sensor would effectively have become a 13 bits sensor.


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## Johan Elzenga (Jun 28, 2016)

Maybe I should add something that may clarify some confusion. Some people think that ETR is the same as simply always overexposing one stop. Like setting your camera to +1 EV exposure compensation all the time. It is not. ETR means that you maximize the effectiveness of the sensor, by never leaving a 'gap' in the right part of the histogram. For some scenes (relatively dark scenes) it means you will indeed have to expose more than the scene would require (and the camera suggests), and then reduce the exposure in Lightroom. For other scenes it may mean that you do not change the exposure at all, compared to what the camera suggests, because a 'normal' exposure already leaves no gap.


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## Tony Jay (Jun 29, 2016)

To support what John and Rick have been saying:
I shoot with the Sony A7R mark II.
The sensor in this model has, arguably, the biggest dynamic range of any sensor available.
I still shoot according to ETTR principles when possible
Certainly landscapes when I shoot from base ISO I always employ ETTR.

The improvements in file quality are undeniable - as is the ease of post-processing as a consequence.

Tony Jay


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## rob211 (Jun 29, 2016)

And although the fellow in the video didn't go into detail about it, note that he shot brackets. Even though he does ETTR. The sun went away, and so he saved the best because he was bracketing. Even when using some fine tuning with where you measure exposure, and using the histogram, you can still mess up and maybe clip some highlights. Hence bracketing, even if you're not gonna do HDR. Sometimes it's tough to figure how bright you can go in the field.

BTW, this is a good reason to use FastRawViewer to cull. The histograms it shows can be more helpful than the ones you might see in Lr since they are based on the RAW data. They have some good tutorials on their website if you're interested in using histograms in culling and editing.


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## Johan Elzenga (Jun 29, 2016)

Correct. The biggest problem with ETTR is that you can't trust the histogram of your camera, or the 'blinkies' that signal clipping, because these are based on in-camera jpegs, not raw. If you expose in such a way that the camera does not show any clipping at all, then you will definitely not expose to the right. Your exposure will be much too conservative. You have to allow for some clipping (according to the camera), but how much clipping is the real challenge. Bracketing can help in this case.


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## Tony Jay (Jun 30, 2016)

JohanElzenga said:


> Correct. The biggest problem with ETTR is that you can't trust the histogram of your camera, or the 'blinkies' that signal clipping, because these are based on in-camera jpegs, not raw. If you expose in such a way that the camera does not show any clipping at all, then you will definitely not expose to the right. Your exposure will be much too conservative. You have to allow for some clipping (according to the camera), but how much clipping is the real challenge. Bracketing can help in this case.


To expand on this.
Learn how many stops of headroom one really has with a particular camera.
Check the headroom in Lightroom or another raw converter.
After that one knows that one can go x stops above what the camera histogram tells you is the threshold.

Tony Jay


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## tspear (Jun 30, 2016)

Tony, 

I find the number of stops changes based on the picture. If I have an image with a broad range of shadows and harsh sunlight, I am rather limited. But if I have a more narrow lighting level I can get away with two or three stops easily in dark conditions, but only one in bright/sunny conditions. This is with a Canon 6D.


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## Johan Elzenga (Jun 30, 2016)

tspear said:


> Tony,
> 
> I find the number of stops changes based on the picture. If I have an image with a broad range of shadows and harsh sunlight, I am rather limited. But if I have a more narrow lighting level I can get away with two or three stops easily in dark conditions, but only one in bright/sunny conditions. This is with a Canon 6D.



The point is not how much extra you can expose compared to what the camera says is 'correct exposure'. As I explained earlier, that is exactly what ETTR is all about. The point is how much extra you can expose *when the camera starts to show clipping in the histogram*. That should not differ that much from photo to photo, because this is due to the difference between raw and jpeg.


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## tspear (Jun 30, 2016)

Actually, I have used the in camera histogram to determine the number of additional stops and where I start to get clippings. 
However, the in camera light sensor is fairly good matching what I can do compared to using the histogram manually; as a result, I tend to use the in camera sensor the majority of the time.


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## Johan Elzenga (Jun 30, 2016)

tspear said:


> Actually, I have used the in camera histogram to determine the number of additional stops and where I start to get clippings.
> However, the in camera light sensor is fairly good matching what I can do compared to using the histogram manually; as a result, I tend to use the in camera sensor the majority of the time.



Perhaps you should re-read some of the messages here, and also Google a bit on ETTR... For proper ETTR you *must have* clipping in the histogram, because the histogram is jpeg-based.


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## PhilBurton (Jun 30, 2016)

tspear said:


> Tony,
> 
> I find the number of stops changes based on the picture. If I have an image with a broad range of shadows and harsh sunlight, I am rather limited. But if I have a more narrow lighting level I can get away with two or three stops easily in dark conditions, but only one in bright/sunny conditions. This is with a Canon 6D.


At the risk of sounding positively Last Century, read up on the Zone System developed by the landscape photographer Ansel Adams.  Here are two places to get started:  Zone System - Wikipedia, the free encyclopedia and Zone System  - Luminous Landscape.  He has a whole series of books aimed a people who do their own darkroom work to produce fine prints.  Obviously the specifics don't carry over 100%, but the exposure situations you describe haven't changed, and you might get some good ideas from Adams.

Phil Burton


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