Alley in Pisa, Italy

by Lars Kotthoff

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RAW files capture a higher dynamic range than JPEGs, like 13EV (in the best case) for my Sony NEX-5R.

This lets me make more adjustments in post, but I have trouble visualizing what those adjustments would be. Is there a way for me to get Lightroom 5 to show me more of the data in the RAW file, so that I can realize that a particular adjustment would make sense for this photo?

For example, if Lightroom could do exposure fusion when I press and hold a button, I could see the full potential of the image, and realize that this photo would benefit from exposure fusion.

As another example, I can drag the exposure / shadows / highlights slider up and down, but I don't know at what point it stops showing me data in the RAW file and starts doing lossy math on the data, essentially synthesizing new information. I wish Lightroom had an exposure / shadows / highlights slider that stops short of synthesizing new information, and merely controls how the 13-bit EV RAW data is converted down to 8 bits.

I phrased this question in terms of dynamic range, but it really applies to getting Lightroom to show me any information captured in the RAW over the JPEG.

As I said, the problem I face is that I can take advantage of the extra information only if I foresee an adjustment I'd like to make, but I can't think of that adjustment without first seeing all the information in the photo.

What's the way out, other than experience?

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Dynamic range is defined as the distance between the highlight clipping point and the noise floor. You can easily see where the highlight clipping point is in Lightroom by turning on the highlight clipping warning (the triangle in the top right corner of the histogram).

You can visualize the noise floor (the point where shadow details is lost to noise) by boosting the shadows until noise starts to dominate.

That's all you need to do to visualize the dynamic range you have to work with.

I don't know what you mean by "what point it stops showing me data in the RAW file and starts doing lossy math on the data". The only thing in lightroom that does anything like "synthesizing new data" is the highlight recovery slider. Everything else is showing you real data from the RAW file, albeit with some mathematical manipulation (which is technically lossy although the data will be held internally at a higher bit depth minimising losses).

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Yes, thanks, I'm aware of the highlight clipping warning, and the shadow clipping warning, too. I tried to clarify in the comments on Michael's answer. Do they help? Thanks, again. –  Kartick Vaddadi Feb 20 at 11:04
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When you manipulate the tone curve of an image so that both the darkest shadow detail and the brightest highlight detail from a 14-bit RAW file that uses the full dynamic range available is visible at the same time on an 8-bit monitor it tends to "flatten" the image a little. Techniques such as HDR, Exposure fusion, using layers to set different exposure levels for various areas of an image are an attempt to increase local contrast in the image so that it still has some "pop" while preserving the detail in both the shadows and the highlights.

Depending on how you have LR set to display a RAW file when an image is first opened the 8-bits of information your monitor can display are usually taken from the middle of the full dynamic range. Moving the exposure slider to the left doesn't synthesize new information that wasn't already present in the RAW file, it just shifts which range of values in the RAW data are depicted between black and white. The value at which full saturation is displayed is increased, but so is the value that is rendered as full shadow (black). Moving the exposure slider in the other direction lowers the black point and white point so that details of shadows are made lighter at the same time dimmer highlights are displayed as full saturation (white). Sliding the highlights, shadows, or black sliders increase or decrease the exposure for only the pixels that fit that part of the luminance range in the image.

You can do the same thing with contrast, color temperature, saturation, etc. There is no way for an 8-bit monitor to simultaneously display all of the information contained in a 12- bit or 14-bit file. When you move the sliders you aren't telling the program to synthesize something that isn't already in the RAW file, you are telling the program what parts of the information in the RAW file you wish it to display.

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So if I move the exposure slider all the way to the end, I'm seeing the top 8-bit slice of the 13-bit exposure range? Won't Lightroom at some point move past the 13-bit range of the RAW and end up having to multiply the pixels with a scale factor in order to make them brighter (closer to white)? Clearly this must be the case, because I can edit a JPEG in Lightroom, and increasing the exposure transforms an 8-bit image to another 8-bit image, rather than deciding what part of a 13-bit image to display. If I'm right, then I would like to know at what point LR starts "synthesizing" data. –  Kartick Vaddadi Feb 20 at 10:49
    
To put it differently, let's say I shoot a scene in RAW and in JPEG. When I open the photos in Lightroom, I can move the sliders much more for the RAW file than I can for the JPEG, for the same loss of quality. Correct? Now, I wish Lightroom had a way to show me this delta. How far can I adjust exposure, shadows or highlights without resulting in noise or other artefacts created when LR multiplies the pixels by a scaling factor as opposed to merely showing me a different subset of the data in the RAW. –  Kartick Vaddadi Feb 20 at 11:02
    
Thanks, again, Michael and Matt for putting up with my apparently hard to understand question and trying to help me out. One-click exposure compensation would be another example of helping me visualize the entire data in the RAW file. –  Kartick Vaddadi Feb 20 at 11:02
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@KartickVaddadi it's not as simple as lightroom just showing you different portions of the 14-bit RAW data as you adjust exposure comp, RAW data is linear, what lightroom shows you is "curved" to make it look more natural, so lightroom is "synthesising" data by multiplying pixel values all the time. –  Matt Grum Feb 20 at 11:23
    
@KartickVaddadi ultimately at the end of the day the only way to reliably tell whether you have pushed exposure comp past the "end" of the RAW data is to use your eyes and look for the noise that is always present in the very bottom end of the RAW data. –  Matt Grum Feb 20 at 11:25
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