# High ISO vs Underexposing



## mitchbooth (Mar 6, 2017)

Hello everyone,

Just returned from the Indoor State Track meet where I took about 1500 photos.  As with most indoor venues the lighting was sub par.  I met several photographers from MileSplit Ohio who ranged from shooting in sports mode to underexposing every photo by 3 or 4 stops in Raw only to bring up in post production.  I was typically at 640 shutter speed and around 3.2-4 on aperature and my iso was set on auto ranging from 2000-10,000.  I also used all large Raw files with no JPEG at all.

I'm new in photography and have the Canon 70d, Tamron 24-70 F2.8 and Tamron 70-200 F2.8 as my first ever camera.  I've finally gotten out of auto modes and relatively comfortable with the camera and operating in manual mode.  I use Adobe Lightroom for organizing and editing my photos.

I've been trying some night photography and typically leave Long Exposure Noise Reduction off.  I have been leaving High ISO Noise Reduction on but have heard by doing so you sacrifice some definition in the photos...? 

My question to you more experienced photographers is this.  Should I shoot indoor events underexposed by 3 or 4 stops and then bring them up in Lightroom or should I use higher ISO for the Canon 70D and let it properly expose them in camera.  Which way gets the better result?  Is it poor practice to leave the High ISO Noise Reduction off in camera?



Mitch


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## Overread (Mar 6, 2017)

Higher ISOs result in higher levels of noise for the same level of exposure in the overall scene. 

However underexposing and then raising the brightness in editing will result in more noise than if you'd exposed correctly and used a higher ISO.

Thus its always preferable to expose correctly in camera, even if that means using a much higher ISO. You basically want the most light-data that you can get to ensure the best possible result. The "expose to the right" theory is one you should look up and make use of, where practical. Indoors it won't always be possible where you've got a limit on your shutter speed (to avoid blur) and a limit on your aperture (it can only go so wide) - so sometimes you will be underexposing even at your cameras top ISO value. 



Also note that Sony and Nikon have more recently pushed what can be recovered from underexposure. Thus you're more likely to run into shooters of both with new end cameras who can be a bit more lenient on underexposing and still getting back good quality results after brightening. This is a more recent change and reflects advancing in sensor technology. Canon are still very good, just not quite the same; plus the expose to the right theory still stands - its just that the limits are a bit wider now than in the past.


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## runnah (Mar 6, 2017)

3 to 4 stops seems a bit extreme.

Also noise is not a big deal. Unless it looks like static on an old TV most people won't notice unless they are pixel peeping internet photo warriors. 90% of people consume photos on their phones, tablet or small laptop so you can get away with a number of small technical issues.

Worry about composition and light before things like noise.


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## mitchbooth (Mar 6, 2017)

runnah said:


> 3 to 4 stops seems a bit extreme.
> 
> Also noise is not a big deal. Unless it looks like static on an old TV most people won't notice unless they are pixel peeping internet photo warriors. 90% of people consume photos on their phones, tablet or small laptop so you can get away with a number of small technical issues.
> 
> Worry about composition and light before things like noise.




Yes, I agree.  99.9 percent of the photos are being viewed on smartphones or tablets.  I was just trying to figure out what process produces less noise.  I hear one person say it produces more and the other says post production produces less and I have no idea who is more correct.  I'm just trying to learn at this stage of the game.


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## runnah (Mar 6, 2017)

mitchbooth said:


> runnah said:
> 
> 
> > 3 to 4 stops seems a bit extreme.
> ...



A lot depends on the sensor. My canon I can pull the shadow a few spots before the noise starts to show up. With my Sony FS5 I actually overexpose by a stop and then darken to reduce noisy shadows. Best thing would be to practice in non critical situations and learn what your particular camera can do.


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## Pedro_lopez (Mar 6, 2017)

Just to kind of reinstate the op's original question since I too am wondering. When using high ISO is it better to leave noise reduction off?


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## KmH (Mar 6, 2017)

That depends on if you can wait for the noise reduction to be applied in the camera.

See page 226 of your D300 Reference Manual.


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## Derrel (Mar 6, 2017)

If you would like more scientific info on underexposing and then compensating in post software, look on the web for articles on the topic of "ISO invariance".


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## Overread (Mar 6, 2017)

Pedro_lopez said:


> Just to kind of reinstate the op's original question since I too am wondering. When using high ISO is it better to leave noise reduction off?



That depends:
1) Most DSLRs have a menu function called "long exposure noise reduction". This form of ISO noise reduction is based on noise generated by sensor HEAT rather than simply a high ISO setting in the camera (or underexposure followed by brightening). It's typically used in astrophotography where exposures can last many minutes a time and the sensor heats up a lot.
It works by taking two exposures, one after the other. The first is normal, the second the shutter blades don't open so the only data that should be recorded is noise spots from the heat of the sensor. The camera then uses code to deduct the second from the first and outputs the final adjusted photo. As a result each shot takes twice as long (at least) because it has to take two for the same duration. 
Also note that normal photography doesn't induce enough heat to make this mode worthwhile to use.

2) In camera noise reduction settings apply to the JPEG only. So if you're using in-camera generated JPEGs the noise settings will affect how harshly (or not) the camera applies noise reduction. Note that this is always global; it will apply to the whole photo equally. In editing in the computer you can specify where noise reduction takes place; applying more to low detail areas (eg backgrounds) that show noise more readily; whilst applying less to high detail areas (main in focus segments) where noise doesn't show as readily; and where you want to retail crispness of detail. 

3) RAWs won't have any in-camera editing noise reduction applied, however some RAW processing software might use in camera settings to set a default starting position when you start editing. 


NOTE - In this I've said that the camera applies no noise reduction to RAWs - this is a lie. 
The camera does have built in noise removing features, however they are universally applied to every RAW and subsequent JPEG regardless of user settings. As a result its simpler to ignore as you can't get any other result from the camera.


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## Ysarex (Mar 6, 2017)

mitchbooth said:


> My question to you more experienced photographers is this.  Should I shoot indoor events underexposed by 3 or 4 stops and then bring them up in Lightroom or should I use higher ISO for the Canon 70D and let it properly expose them in camera.  Which way gets the better result?  Is it poor practice to leave the High ISO Noise Reduction off in camera?
> 
> Mitch



You got some pretty good info already from Overread. And as Derrel noted you may want to look into the topic ISO invariance. Your camera does not have an ISO invariant sensor and so there's *no question about what you should do; use the camera ISO settings to get the best result.* Raising ISO reduces noise.

A few more comments about your question as you mentioned you save raw files. When you raise the ISO on your camera two things occur: 1) The meter system in your camera is adjusted to calculate a reduced exposure. If you rely on the meter in the camera, raising ISO causes the camera meter to calculate an underexposure for the sensor. When you raise the ISO the camera does not properly expose your shots in camera as you suggested. The sensor is underexposed exactly as if you simply forced an underexposure at base ISO. You force a 3 stop underexposure the sensor is underexposed by 3 stops. You raise the ISO 3 stops and the meter calculates a 3 stop exposure reduction and the sensor is underexposed by 3 stops -- no difference at that point.

The second thing ISO does 2) is a post processing job. It occurs after the underexposure. The signal coming off your sensor is analog and is processed in the camera through circuitry we call the ADC (analog to digital converter). The ADC turns analog electrical signal into the numbers that are stored as you raw file. Ultimately this is an engineering issue and is addressed by different camera manufacturers in different ways. What they have to do is compensate for the underexposure and what most cameras do now is apply a signal boost to the sensor output as part of the ADC processing. That analog signal boost has as an advantage an improved noise profile: ISO reduces noise. What's been happening behind the scenes in recent years is that the sensors are becoming so good with output so clean that the manufacturers have started to skip the analog signal boost  -- no benefit -- and replace it with digital scaling (just upscale the digital content) which is less expensive (always cheaper to do it in software). These are ISO invariant cameras. There are also hybrid implementations now where both a partial analog signal boost is combined with digital scaling.

Because what ISO does other than bias your camera meter is a post exposure process, that of course means it could be saved for later if it's digital scaling. And so the underexposed raw file can be digitally scaled in the raw converter. To do that you want a camera with an ISO invariant sensor, *you don't have one so this is just informational.*

From our standpoint as users this starts getting pretty esoteric -- raise the ISO on your camera as needed and get on with your life. My previous camera (Fuji X-E2) was ISO invariant. It took me awhile after some testing to really believe it, but eventually I just started to ignore the camera ISO setting entirely. The last year and a half that I owned the camera I never touched the ISO dial. It was nice to be able to ignore it, but no big deal. When I got my new Fuji X-T2 I tested it and it certainly is not ISO invariant. It's a new sensor and there's no way I can treat it like my old X-E2 so I'm back to changing ISO -- no problem.

There was one advantage that the ISO invariant sensor gave me. When the sensor capture is analog boosted or scaled up all the data is equally raised in value and so it's possible to clip highlights in the process. Something of a paradox but you can set a camera to ISO 1600 and underexpose the sensor by 4 stops and still get clipped highlights because of the signal processing through the ADC. Well, if you skip the signal boost/scaling and leave the raw file as-is underexposed you'll typically retain all highlight detail. Here's an example:






I got roped into bringing my camera along to a recent event and grabbed some snaps. This was the X-E2 and I just left the ISO at base and underexposed as needed. Given the indoor lighting I was underexposing 2 and 3 stops. It was an overcast day but nonetheless the light outside (through window) was much brighter than indoors. Had I raised the ISO much of the data out the window would have been blown out. It was easy enough processing to mask the windows.

Putting that in very technical terms when you raise the ISO on your camera the post processing that takes place reduces the dynamic range of your sensor. With an ISO invariant sensor you avoid that DR reduction.

Joe


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## Soup du Jour (Mar 6, 2017)

mitchbooth said:


> I was just trying to figure out what process produces less noise.



I think neither. The gain (amp gain) penalty comes in the end with the image in both cases. With one method you have to remove noise relative to an already sufficient gain level, while with the other you need to first make the image brighter with software (increased gain on an insufficient signal) and then remove noise. If a question is "which method gives more signal information" I think the high ISO method, but with the higher noise. 

If you try to lift an extreme underexposure too far, there is no data there to do it. More data is there in the high ISO capture but with higher noise.


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## KmH (Mar 6, 2017)

Overread said:


> NOTE - In this I've said that the camera applies no noise reduction to RAWs - this is a lie.
> The camera does have built in noise removing features, however they are universally applied to every RAW and subsequent JPEG regardless of user settings. As a result its simpler to ignore as you can't get any other result from the camera.


The camera does not apply any noise reduction to a Raw file _in the camera_ - unless the Raw file is to be further processed as a JPEG in the camera.

Raw converters external to the camera, like ACR/Lightroom Develop module, perform some combination of tone mapping, edge detection, anti-aliasing, *noise reduction*, and sharpening to a Raw file as part of the demosaicing process that makes the Raw file a photo that looks like the real world.


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## Ysarex (Mar 6, 2017)

Soup du Jour said:


> mitchbooth said:
> 
> 
> > I was just trying to figure out what process produces less noise.
> ...



With an ISO invariant sensor, noise is the same with or without the ISO analog signal gain. With a non ISO invariant sensor noise is much worse without the analog signal boost compared with the result obtained from the gain applied. Raising ISO with a non ISO invariant sensor reduces noise.



Soup du Jour said:


> If you try to lift an extreme underexposure too far, there is no data there to do it. More data is there in the high ISO capture but with higher noise.



The amount of data recorded is a function of exposure and only exposure. Raising the ISO does nothing to increase the amount of data captured. With a non ISO invariant sensor, the increased noise resulting from failure to apply the analog signal boost will result in the weakest data masked by the increased noise. Raising the ISO in this case reduces noise and prevents slight loss of the weakest data.

Joe


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## petrochemist (Mar 7, 2017)

KmH said:


> Overread said:
> 
> 
> > NOTE - In this I've said that the camera applies no noise reduction to RAWs - this is a lie.
> ...


Sorry Keith but Overread is quite correct. At least some cameras do apply noise reduction to the signal before storing the RAW file.  It caused quite a shock when it was discovered Nikon did this, as RAW was always considered to be unprocessed data. I suspect Nikon are not the only ones who do it. The amount of processing of RAW data is minimal so more will be needed but some is done.


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## DarkShadow (Mar 7, 2017)

Yep Some camera's do apply noise reduction of the raw file for example the Nikon D3300  but supposedly its less then it would be if turned on.


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## mitchbooth (Mar 7, 2017)

Yes the Canon D70 also has an option to turn on High ISO Noise Reduction which is applied to all files JPEG and RAW.  I tested this, this morning. 


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## Ysarex (Mar 7, 2017)

mitchbooth said:


> Yes the Canon D70 also has an option to turn on High ISO Noise Reduction which is applied to all files JPEG and RAW.  I tested this, this morning.
> 
> 
> Sent from my iPhone using ThePhotoForum.com mobile app



The High ISO noise reduction is not applied to raw files. A flag is set in the metadata of the raw file and may be processed or not by the raw conversion software. The CR2 files remain unaffected by the High ISO noise function in the camera. Here's a reference article from Canon: Canon DLC: Article: High ISO Noise Reduction

"And for RAW image shooters, if you use Canon’s DPP software, the High ISO Noise Reduction settings you apply on your camera’s menu can still represent a time-saving and efficient starting point. *You can, of course, completely change how noise reduction is performed during RAW image processing* (and DPP offers extremely fine control of this, as mentioned previously), but knowing the camera settings and their impact can save some workflow time at the computer." [emphasis mine].

Joe


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## mitchbooth (Mar 7, 2017)

Joe,

Thank you so much for that link.  I get more confused by the day in this hobby.  I appreciate everyone's responses and help.  I just got off the phone with the Canon rep and he was able to confirm that the Canon 70D did apply noise reduction to even the RAW files.  I wasn't sure so I took two photos at ISO 12,600 with High ISO NR applied to one and High ISO NR not applied to the other and there was a noticeable difference on the live view screen on the back of the camera when comparing the two.  Joe does this make any sense at all?  Did I somehow misunderstand the Canon rep?

Thank you for any help you are able to provide.

Mitch


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## Ysarex (Mar 7, 2017)

mitchbooth said:


> Joe,
> 
> Thank you so much for that link.  I get more confused by the day in this hobby.  I appreciate everyone's responses and help.  I just got off the phone with the Canon rep and he was able to confirm that the Canon 70D did apply noise reduction to even the RAW files.  I wasn't sure so I took two photos at ISO 12,600 with High ISO NR applied to one and High ISO NR not applied to the other and there was a noticeable difference on the live view screen on the back of the camera when comparing the two. Joe does this make any sense at all?



It makes complete sense, you're seeing the effect of the High ISO NR on the camera. The camera is showing you the JPEG processing. The camera can only show you the JPEG processing. You're not seeing what is or is not applied to the raw file -- that's not a viewable option on the camera.



mitchbooth said:


> Did I somehow misunderstand the Canon rep?



Possible, but it's also very likely the Canon rep has no clue (very common). What the article I linked describes is probably the case. With High ISO NR engaged you of course see the effect in the JPEG the camera generates. The camera then places an entry in the metadata stored with the CR2 file indicating High ISO NR was used. The raw converter (DPP for example) can read the metadata entry and apply the same NR while processing the raw file. But that's an option. And if it's an option to do or not do in the raw converter that means the NR is not actually applied in the raw CR2 file. Otherwise you wouldn't have an option to back it off.



mitchbooth said:


> Thank you for any help you are able to provide.
> 
> Mitch



Joe


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## greybeard (Mar 7, 2017)

I just read this

ISO Invariance: What it is, and which cameras are ISO-less

I think I will start shooting my D750 with *highlight priority* metering


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## Ysarex (Mar 7, 2017)

greybeard said:


> I just read this
> 
> ISO Invariance: What it is, and which cameras are ISO-less
> 
> I think I will start shooting my D750 with *highlight priority* metering



As long as you're happy processing the raw files and don't mind trashing under-exposed JPEGs. You're right in thinking that with highlight priority metering the camera will tend to hold highlights at all cost and reduce exposure to do that. If you don't raise the ISO you get the benefit of the full DR range of the sensor.

One other caveat: Processing software matters. You'll see marked variation between raw converters in how well they handle noise when lifting the shadows. I won't swear to this but I have it from a source I'm inclined to trust; the difference is in math precision. Some converters (notably LR) sacrifice precision for speed. Frankly I endorse that taking the position that we're photographers after all, but the result is more noise in the lifted shadows as a trade for software performance. For best results on the other end of that stick look at Capture One and RT for raw conversion.

Joe


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## Derrel (Mar 7, 2017)

petrochemist said:
			
		

> Sorry Keith but Overread is quite correct. At least some cameras do apply noise reduction to the signal before storing the RAW file.  It caused quite a shock when it was discovered Nikon did this, as RAW was always considered to be unprocessed data. I suspect Nikon are not the only ones who do it. The amount of processing of RAW data is minimal so more will be needed but some is done.



As I recall, Tom Hogan mentioned that one of the earlier Sony A7 models he reviewed was producing "cooked RAW" data, which as I recall, was being saved as 11-bit data. This has been going on three years now, so my memory might be a bit off on this.


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## Ysarex (Mar 7, 2017)

Derrel said:


> petrochemist said:
> 
> 
> 
> ...



I'll second that.

Joe


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## mitchbooth (Mar 7, 2017)

Ysarex said:


> mitchbooth said:
> 
> 
> > Joe,
> ...



Got it that makes complete sense to me know!!  
Thank you



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## greybeard (Mar 7, 2017)

Ysarex said:


> greybeard said:
> 
> 
> > I just read this
> ...


I use Nikon ViewNX 2 as my initial step.  I set exposure, pull up shadows, set light balance, set color saturation, and crop and then convert from RAW to tif.  I then import the tif into LR and finish it up.  I doubt that any software can convert Nikon .NEF files any better than ViewNX 2.   Not the fastest workflow but it  work for me.


ISO 100 Highlight priority :  


light uncorrected by TOM STRAIGHT, on Flickr

Same shot with the shadows maxxed: 


light corrected by TOM STRAIGHT, on Flickr


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## smoke665 (Mar 9, 2017)

Ysarex said:


> The High ISO noise reduction is not applied to raw files.



I've been trying to get a reference source on this for some time. I agree with you, that I think it is an entry in the metadata, but I can't find written confirmation of that fact, specifically as applies to the later Pentax models. Obviously there has to be some noise reduction on the raw file based on the higher ISOs, especially on those that achieve it internally as apposed to a CPU software increase.


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## dasmith232 (Mar 9, 2017)

mitchbooth said:


> ...I get more confused by the day in this hobby...


That's the way it's supposed to be! This just means that you're doing it right! 



mitchbooth said:


> ...I just got off the phone with the Canon rep and he was able to confirm that the Canon 70D did apply noise reduction to even the RAW files...


One thing to remember is that the RAW file is more than just the "original" pixels. A RAW file does contain the "original" pixels (but even then, there has been processing from the physical Bayer (or whatever layout of the pixels). However, the RAW file *also* includes a small JPEG file. And information about settings like white balance. And information about sensor dust mapping. And information about noise.

It's up to the software to use that data (or not) from the RAW file. Canon's DPP software knows about all of the additional details in the RAW file and provides tools to further manipulate the image. Programs like Adobe's LR or PS are pretty good about that as well. But not all software is created equal. It's entirely possible to have a post-processing workflow that isn't aware of (or doesn't use) the extra information about noise.


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## Ysarex (Mar 9, 2017)

smoke665 said:


> Ysarex said:
> 
> 
> > The High ISO noise reduction is not applied to raw files.
> ...



This gets into engineering details way beyond my pay scale but I'm sure it's technically possible to apply noise reduction to the signal prior to ADC which would then be a case of a noise filtered raw file. I suspect it's been done but good luck to any of us getting the manufacturers to actually tell us. Here's a interesting read: Sony a7S noise reduction in-camera processing of raw files

I'll wager the guess that in 90 + % of the cases where noise reduced raw files are suspect what in fact is happening is as we've surmised nothing more than a metadata tag passing instructions to the raw converter which means the actual raw data is unfiltered.

Joe


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## smoke665 (Mar 9, 2017)

Ysarex said:


> I'll wager the guess that in 90 + % of the cases where noise reduced raw files are suspect what in fact is happening is as we've surmised nothing more than a metadata tag passing instructions to the raw converter which means the actual raw data is unfiltered.



Part of the issue is the semantics of what actually constitutes an altered raw file. When I go to Highlight Correction, it works by selectively underexposing areas of the sensor. Granted that didn't actually "alter" the raw file, but it effectively did. When I use Shadow Correction, it writes to the metadata, so no. As Overread pointed out previously Slow Shutter Noise reduction uses two images combined to create one. Again it didn't actually "alter" the raw file but effectively did. Several other current features by their actions, effectively alter the raw file.

In the case of the High ISO Noise Reduction, would Raw Digger give you the ability to compare different raw files to determine if there really was a change (not metadata) when using it versus not?


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## Ysarex (Mar 9, 2017)

smoke665 said:


> Ysarex said:
> 
> 
> > I'll wager the guess that in 90 + % of the cases where noise reduced raw files are suspect what in fact is happening is as we've surmised nothing more than a metadata tag passing instructions to the raw converter which means the actual raw data is unfiltered.
> ...



Pentax Highlight Correction effects raw files by first forcing an underexposure of the entire sensor (raise ISO) and then withholding the signal boost prior to ADC that would have normally been applied due to the ISO increase. This results in an underexposed raw file. That's a real effect evident in the raw file. The alteration occurs during the creation of the raw file.



smoke665 said:


> When I use Shadow Correction, it writes to the metadata, so no. As Overread pointed out previously Slow Shutter Noise reduction uses two images combined to create one. Again it didn't actually "alter" the raw file but effectively did. Several other current features by their actions, effectively alter the raw file.
> 
> In the case of the High ISO Noise Reduction, would Raw Digger give you the ability to compare different raw files to determine if there really was a change (not metadata) when using it versus not?



So they're not going to do anything that would actually alter the raw file after it's been generated. If they're going to make alterations it'll be in the signal processing before or during the ADC generation, good example your camera's Highlight Correction which simply withholds part or all of the ISO signal boost. I very very much doubt that any camera manufacturer would return to the raw file after it is generated to alter it.

So semantics yes -- I think when you encounter folks complaining about this or that camera manufacturer (Sony) cooking their raw files what they're talking about is in fact data cooking that occurs prior to or during analog to digital conversion.

Raw Digger would show you exposure variations and so could be used to verify the function of Highlight Correction but I doubt that noise processing would be evident in the Raw Digger histograms or data.

Joe


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## Derrel (Mar 9, 2017)

I thought this was interesting, from the Hogan review of the earlier Sony A7 models:

"But let me lay out the basics: the D800E will shoot 14-bit raw files with no underlying artifacts and fully recoverable data. The A7r will shoot 11-bit raw files with potential posterization issues in the data. The same is true of the A7 versus a D610, too.

Let’s start with the 11-bit thing. Sony always uses compression in storing raw files. The way they do that is quite clever. They slice each pixel row into 32 pixel blocks. In a Bayer sensor, that means two colors, each with 16 data points). For each 16 pixels of a color, Sony looks at the minimum and maximum pixel values for each and stores that. For the _other 14 pixels_ they store a _7-bit value_ that is offset from the minimum value. In essence, they get 32 pixel values stored in 32 bytes, when normally 11-bit storage for that data should take 44 bytes.

This is _not_ lossless compression. It is highly lossy. Nor is it visually lossless. That’s because when you have an extreme set of values in the 32-pixel block (e.g. sun peaking out from behind tree edge), you get posterization of data. Don’t believe me? See this article, which describes it better than I can in the limited space of a review. Indeed, every A7/A7r owner should probably have a copy of RawDigger so that they can understand exactly where the issues in their raw files lay. Even Nikon’s optional visually lossless compression scheme does a better job at this, as it hides its posterization only in very bright values that our eyes just don’t resolve."

*So....when is "RAW data" not really unaltered data, right off of the sensor*? Has Sony adopted this same 14-to-11 bit squish-down in later cameras in the A7 line, or in other cameras?


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## smoke665 (Mar 9, 2017)

Derrel said:


> "But let me lay out the basics: the D800E will shoot 14-bit raw files with no underlying artifacts and fully recoverable data. The A7r will shoot 11-bit raw files with potential posterization issues in the data. The same is true of the A7 versus a D610, too



I read through this until I started to get brain pain (out of practices on concentrating that hard anymore) LOL  Noise, Dynamic Range and Bit Depth in Digital SLRs -- page 3   By Emil Martinec, Professor of Physics at the University of Chicago. I'll leave it to others to debate the validity of his statements.

Basically the paper claims that none of the 14 bit cameras (circa 2010) could utilize all the data because "in the absence of noise, the quantization of an analog signal introduces an error, as analog values are rounded off to a nearby digitized value in the ADC. In images, this quantization error can result in so-called _posterization_ as nearby pixel values are all rounded to the same digitized value". The author continues to say that there is sufficient loss in data that the reality is, there wouldn't be that much difference in an 11 bit file, versus a 14 bit, and unless you have something beside a standard monitor, 8 bit would be sufficient. Applying this to the OP's original comment about underexposing, doing so would be effectively reducing the bit depth of the raw file

As to the differences in compression he says "The "lossy" form of NEF compression is a clever use of information theory to save space by eliminating redundant raw levels. The noise which is unavoidably present in light effectively dithers tonal transitions so that the compression is _lossless_ in that the image is still encoded without loss of visual information. In this sense, "lossy" compression is perhaps an inappropriate appelation. Amusingly, Nikon engineers seem to have forgotten the logic behind the thinning of raw levels when upgrading to 14-bit tonal depth -- the NEF compression table has roughly four times as many entries (2753) for the 14-bit table as it does (689) for the 12-bit table in the D3 and D300, even though there is no purpose to the extra values given the relation between noise and quantization step in efficient data encoding".


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## Derrel (Mar 9, 2017)

If you read the Thom Hogan article, iot seems that theory from 2010 and reality diverge, and there is an actual and an observable loss of quality in the resulting photos made from these heavily-compressed files, at least to the observer who is trained in noticing fine details and subtle differences. Not that posterization is all that tough to spot...

Hogan draws the point that the D800 and the A7s were using vastly different RAW file writing strategies. Look at the horrible posterization from an 11-bit Sony "RAW" file that's been compressed, heavily. Not using Nikon's much better lossy compression, but using Sony's routines. and not on Nikon .NEF files, but on Sony files. Different beasts.

RawDigger: detecting posterization in SONY cRAW/ARW2 files | RawDigger

Now this shot? image02.png

That is flat-out some *pretty AWFUL posterization*...which makes the 2010 theoretical article pretty much not much more than theorizing, about a perfect system, and flat-out wrong about an actual product sold by a real manufacturer, some years later.

Nikon's lossy NEF compression is excellent, but it's clear that Sony taking a full sensor capture, and then crushing it into an 11-bit and horribly compressed raw file is not the same thing as a Nikon .NEF file.


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## smoke665 (Mar 9, 2017)

Derrel said:


> If you read the Thom Hogan article, iot seems that theory from 2010 and reality diverge, and there is an actual and an observable loss of quality in the resulting photos made from these heavily-compressed files, at least to the observer who is trained in noticing fine details and subtle differences. Not that posterization is all that tough to spot...



Wouldn't be the first time theory and reality ran on separate tracks. The truth likely lies somewhere between the two.


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