High ISO vs Underexposing

[mitchbooth]

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]

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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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

 

[mitchbooth]

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

 

[Ysarex]

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.

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.

Thank you for any help you are able to provide.

Mitch

Joe

 

[greybeard]

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

 

[Ysarex]

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

 

[Derrel]

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.

 

[Ysarex]

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.

I'll second that.

Joe

 

[mitchbooth]

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.

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.

Thank you for any help you are able to provide.

Mitch

Joe

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



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[greybeard]

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

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

 

[smoke665]

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.

 

[dasmith232]

...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!

...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.

 

[Ysarex]

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.

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

 

[smoke665]

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?

 

[Ysarex]

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.

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.

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