The Fallacy of the "JPEG+Raw" option
Dec 20, 2016 12:06:48 #
The subject of the "JPEG+Raw" option arose in another thread. Rather than hijack that thread to continue this secondarily introduced topic, it seemed altogether meet and proper to start a new thread for discussion thereupon.
THE FALLACY OF THE "JPEG+ RAW" OPTION
In recommending use of the "JPEG + raw" option offered by many cameras, you are urging emasculation of the major part of the advantages provided by properly exposed raw image data over a normally exposed JPEG file.
For a raw image data capture to deliver the vastly improved image data quality of which it is capable, it must be exposed by using at least some additional dynamic range beyond that available to expose the JPEG file. Sure, a raw file captured with the same exposure as a JPEG file will have enough "headroom" with which to recover some blown highlight data. The problem is that one camera may have an extra 1/3 stop of raw-accessible DR, while another camera of the same brand and model may have as much as two and 2/3 stops to perhaps even three full stops or more of that extra raw-accessible DR. It is in testing one's camera for, and then using that extra allotment of raw-accessible DR that the great advantages of capturing raw image data are fully realized.
It is not convenient (nor, evidently, sufficiently profitable) for the camera manufacturers to disclose their failure to determine and then report on each camera's allotment of that extra DR beyond the amount necessary to meet the needs of an 8-bit JPEG file. They thus incur no need for an in-camera raw histogram adjusted to the DR available for raw exposure.
It is no problem to assure that a given sensor will offer a specific dynamic range of exposure. The manufacturer evidently cannot, however, predictably assure how much extra dynamic range exists in each sensor! This problem of "process variance"/"performance variance" has been a bug-a-boo of the silicon-based semiconductor device production industry since Shockley invented the transistor back in the late 1940s. It includes our cameras' light sensors...and it continues today....it's simply a fact of life with silicon-based semiconductor devices.
So, in restricting exposure of a raw capture to that necessary for a JPEG image file, the "JPEG + raw" option relegates the captured raw data to the same data quality (sound:noise ratio) as that of its paired JPEG partner. The raw image data so exposed thus becomes functionally an 8 bit-depth image file delivered in a 16 bit depth environment.
Depending on the amount of unused raw-accessible DR the Raw data file will, in most cameras, suffer a 50% to 75% (or more) loss of its potential tonal and color spectra. that's an incredible waste considering that the sensor accounts for 1/2 to 2/3 of the price you paid for the camera body!
The question may be asked: "Will one only gain an advantage in raw by using an exposure that will blow the highlights in the JPEG file?
The short answer is an unqualified "YES !"
Why?
Because: If one shoots JPEG + raw and exposes enough to the right to gain benefit from the more properly exposed raw image data, the JPEG file will, indeed, be irretrievably overexposed. The raw image data, however, will show its advantage in being able to be completely tonally normalized in the raw converter ( like Adobe Camera Raw) with no blown highlight detail as long as the exposure did not exceed use of that particular camera's extra raw-accessible dynamic range (which must be determined for each individual camera by the new owner). The camera manufacturers don't do this for the purchaser. It may be a reasonable assumption that the per-unit cost of doing this would result in an unacceptable increase in the price of each camera. The camera manufacturers are silent on this matter.
Thus, the "JPEG+raw" option is a sop offered to the uninformed photographer who wants to feel as if he were in the vaunted vanguard using the highly touted "raw capture".
In summary, no favor is done by advising use of the of the "JPEG+raw" option without simultaneously informing the advisees of the cost they incur in severely reduced raw image data quality resulting from limiting its exposure to that suitable only for a JPEG image file.
Until such time as the camera manufacturers provide an accurate in-camera raw histogram, the fallacy of the "JPEG+raw" option will persist.
Regards,
Dave
THE FALLACY OF THE "JPEG+ RAW" OPTION
In recommending use of the "JPEG + raw" option offered by many cameras, you are urging emasculation of the major part of the advantages provided by properly exposed raw image data over a normally exposed JPEG file.
For a raw image data capture to deliver the vastly improved image data quality of which it is capable, it must be exposed by using at least some additional dynamic range beyond that available to expose the JPEG file. Sure, a raw file captured with the same exposure as a JPEG file will have enough "headroom" with which to recover some blown highlight data. The problem is that one camera may have an extra 1/3 stop of raw-accessible DR, while another camera of the same brand and model may have as much as two and 2/3 stops to perhaps even three full stops or more of that extra raw-accessible DR. It is in testing one's camera for, and then using that extra allotment of raw-accessible DR that the great advantages of capturing raw image data are fully realized.
It is not convenient (nor, evidently, sufficiently profitable) for the camera manufacturers to disclose their failure to determine and then report on each camera's allotment of that extra DR beyond the amount necessary to meet the needs of an 8-bit JPEG file. They thus incur no need for an in-camera raw histogram adjusted to the DR available for raw exposure.
It is no problem to assure that a given sensor will offer a specific dynamic range of exposure. The manufacturer evidently cannot, however, predictably assure how much extra dynamic range exists in each sensor! This problem of "process variance"/"performance variance" has been a bug-a-boo of the silicon-based semiconductor device production industry since Shockley invented the transistor back in the late 1940s. It includes our cameras' light sensors...and it continues today....it's simply a fact of life with silicon-based semiconductor devices.
So, in restricting exposure of a raw capture to that necessary for a JPEG image file, the "JPEG + raw" option relegates the captured raw data to the same data quality (sound:noise ratio) as that of its paired JPEG partner. The raw image data so exposed thus becomes functionally an 8 bit-depth image file delivered in a 16 bit depth environment.
Depending on the amount of unused raw-accessible DR the Raw data file will, in most cameras, suffer a 50% to 75% (or more) loss of its potential tonal and color spectra. that's an incredible waste considering that the sensor accounts for 1/2 to 2/3 of the price you paid for the camera body!
The question may be asked: "Will one only gain an advantage in raw by using an exposure that will blow the highlights in the JPEG file?
The short answer is an unqualified "YES !"
Why?
Because: If one shoots JPEG + raw and exposes enough to the right to gain benefit from the more properly exposed raw image data, the JPEG file will, indeed, be irretrievably overexposed. The raw image data, however, will show its advantage in being able to be completely tonally normalized in the raw converter ( like Adobe Camera Raw) with no blown highlight detail as long as the exposure did not exceed use of that particular camera's extra raw-accessible dynamic range (which must be determined for each individual camera by the new owner). The camera manufacturers don't do this for the purchaser. It may be a reasonable assumption that the per-unit cost of doing this would result in an unacceptable increase in the price of each camera. The camera manufacturers are silent on this matter.
Thus, the "JPEG+raw" option is a sop offered to the uninformed photographer who wants to feel as if he were in the vaunted vanguard using the highly touted "raw capture".
In summary, no favor is done by advising use of the of the "JPEG+raw" option without simultaneously informing the advisees of the cost they incur in severely reduced raw image data quality resulting from limiting its exposure to that suitable only for a JPEG image file.
Until such time as the camera manufacturers provide an accurate in-camera raw histogram, the fallacy of the "JPEG+raw" option will persist.
Regards,
Dave
Dec 20, 2016 12:18:34 #
Dec 20, 2016 12:20:37 #
Well Dave that was a pretty comphensive lesson on JPEG + Raw. As a former user of both, i had no idea i was restricting my Raw files. Thanks for the tutorial eventhough i now exclusively shoot Raw.
Dec 20, 2016 12:23:00 #
BassmanBruce wrote:
Thank you Dave.
Zhou are welcome, Bassman Bruce,
Best regards,
Dave
Dec 20, 2016 12:31:12 #
Excellent presentation, Dave.
--Bob
--Bob
Uuglypher wrote:
The subject of the "JPEG+Raw" option aro... (show quote)
Dec 20, 2016 12:42:24 #
NJFrank wrote:
Well Dave that was a pretty comphensive lesson on JPEG + Raw. As a former user of both, i had no idea i was restricting my Raw files. Thanks for the tutorial eventhough i now exclusively shoot Raw.
You are welcome, Frank.
Back when i first acquired a camera that delivered raw image data ( a Sony DSC-F828...for which I which I still find productive use) I did, for a while, fall under the spell of the "JPEG+Raw" fallacy until having the opportunity to read Bruce Fraser's Adobe white paper:
Fraser, Bruce,
"RAW Capture, Linear Gamma, and Exposure"Adobe White Paper, 2004,
http://www.adobe.com/digitalimag/pdfs/linear_gamma.pdf
and Michael Reichmann's essay in Luminous Landscape:
Reichmann, Michael, essay in Luminous Landscape, 2003
"Expose Right"
http://www.luminous-landscape.com/tutorials/expose-right.shtml
Insights from these articles set me on a path of learning more about the details of raw image data capture and proper exposure of raw image data resulting in awareness of raw image data as an imaging medium totally distinct from JPEGfiles, and requiring a very different approach to exposure in order to take full advantage of raw capture.
Best regards,
Dave
Dec 20, 2016 12:44:40 #
I am not sure this is absolutely accurate. When I shoot RAW I get 41 mb image and when I shoot RAW+JPEG I get a 41 mb RAW image. Dave, is your discussion about a paticular brand or camera? As an Sony user, I can not see where I am losing data.
Dec 20, 2016 12:47:41 #
Though I have been following some of the ETTR discussions, this is the first I have read on why not to choose jpg and raw for the same shot. Really interesting to know, Dave, and will definitely affect future photo ops. Thank you!
(my reason for shooting jpg+raw to date was purely a convenience thing - viewing the jpgs in Picasa prior to choosing which raw file to edit in PS Elements via ACR and the other software I have.)
(my reason for shooting jpg+raw to date was purely a convenience thing - viewing the jpgs in Picasa prior to choosing which raw file to edit in PS Elements via ACR and the other software I have.)
Dec 20, 2016 13:04:55 #
This is very useful Info.. Thanks for explaining so well.
Dec 20, 2016 13:20:16 #
chapjohn wrote:
I am not sure this is absolutely accurate. When I shoot RAW I get 41 mb image and when I shoot RAW+JPEG I get a 41 mb RAW image. Dave, is your discussion about a paticular brand or camera? As an Sony user, I can not see where I am losing data.
Hi, Chapjohn,
My comments are applicable, from my experience and first hand observations to camera models providing both JPEG
and raw captures from a variety of manufacturers including several Sony camera models of my own (Sonys being my camera brand of choice) The size of the captured raw files are not indicative of the image data quality captured. Image data quality is dependent upon the dynamic range used and exposure. File size depends upon the format ( JPEG, TIFF, and the proprietary raw data file format of your camera's manufacturer).
Dave
Dec 20, 2016 13:32:10 #
I shoot straight raw but had no idea the combo would affect the raw capture. A lot is over my head but I really enjoyed the links you provided. They are good reading!
Dec 20, 2016 13:32:43 #
rmalarz wrote:
Excellent presentation, Dave.
--Bob
--Bob
Thanks, Bob. I have felt it was long overdue and am a bit ashamed for having taken so long to prepare it and present it.
Dave
Dec 20, 2016 13:34:13 #
Uuglypher wrote:
Thanks, Bob.
For some, like you, I know it's "...preaching to the choir" I have felt it was long overdue and am a bit ashamed for having taken so long to prepare it and present it.
Dave
For some, like you, I know it's "...preaching to the choir" I have felt it was long overdue and am a bit ashamed for having taken so long to prepare it and present it.
Dave
Dec 20, 2016 13:36:44 #
Hi, Linda, Martin, and Carol,
I'm glad you found it useful.
Dave
I'm glad you found it useful.
Dave
Dec 20, 2016 13:49:44 #
chapjohn wrote:
I am not sure this is absolutely accurate. When I shoot RAW I get 41 mb image and when I shoot RAW+JPEG I get a 41 mb RAW image. Dave, is your discussion about a paticular brand or camera? As an Sony user, I can not see where I am losing data.
Chapjohn...
...to be more clear...You asked:
"I am not sure this is absolutely accurate. When I shoot RAW I get 41 mb image and when I shoot RAW+JPEG I get a 41 mb RAW image"
To more fully respond to your question:
We must realize that every exposure results in capture of a mass of "raw" data. When the photographer elects to receive a JPEG file, that 8 bit-depth file is extracted from the massive captured data, processed according to the manufacturer's algorithms to result in a presumably acceptable image straight out of the camera (SOOC). The rest of the data is discarded.
When the delivery option "JPEG + raw" is chosen, the extracted JPEG file, as well as a file of raw image data are presented to the photographer...unfortunately with the raw image data having been exposed only as if it were a jpeg file.
Did that clear things up a bit? Sorry I wasn't more clear on that point.
The following graphics may (I hope) help clarify what my words may not have....
Dave
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