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ETTR OR EBTR
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May 28, 2014 16:19:58   #
Dandee Loc: Kentucky
 
I hate to sound like such a newbie but can someone explain what ETTR or EBTR is?. I saw these mentioned in the Photo Critique Section and I think they both have something to do with shooting RAW. Just curious, because I have no knowledge of RAW at all. Thanks.

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May 28, 2014 17:18:02   #
SharpShooter Loc: NorCal
 
Dandee, they are probably a reference to Exposing to the Right(ETTR), and to Exposing beyond the Right(EBTR).
Both a reference to shooting toward the realm of over-exposure, to record as much light as possible into a shot. ;-)
SS

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May 28, 2014 17:35:13   #
Dandee Loc: Kentucky
 
Thanks SharpShooter, I had no idea...

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May 29, 2014 07:26:41   #
ejrmaine Loc: South Carolina
 
This video does a good job of helping to understand the 'how and why' of ETTR.

https://www.youtube.com/watch?v=2vtxG6lcb0g

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Jun 2, 2014 12:03:25   #
Uuglypher Loc: South Dakota (East River)
 
SharpShooter wrote:
Dandee, they are probably a reference to Exposing to the Right(ETTR), and to Exposing beyond the Right(EBTR).
Both a reference to shooting toward the realm of over-exposure, to record as much light as possible into a shot. ;-)
SS


Just for the record, EBTR specifically refers to capturing the highest possible quality RAW image data (highest possible SIGNAL-Noise Ratio) by utilizing the Extra RAW-Accessible Dynamic Range (ERADR) provided by your camera to the RIGHT of the limits of the JPEG-adjusted histogram frame. Each camera must be tested for the anount of ERADR it has.

Also, EBTR is most definitely NOT "overexposure" of RAW data. I t certainly WOULD be overexposure if you were capturing a JPEG image file, based on the JPEG-adjusted histogram and thumbnail image provided by your camera.

HOW TO DETERMINE YOUR CAMERA'S ERADR :

Put your camera on a tripod, find a scene with highlights in which you hope to maintain detail as well as a few specular highlights that, by definition, should have no detail. Get a base "Expose to the right" (ETTR) exposure, i.e. ensure that the light pile is barely kissing the right side of the JPEG-adjusted histogram frame.
Set to Manual Exposure.
Set Daylight White Balance... or whatever you like OTHER THAN AUTOMATIC WB). If a one-pixel-width line climbs the right side and kicks on the "clipping blinker"...that's ok....just the specular highlights.
Set the ETTR exposure.
Set Manual Focus.

Now, take a series of exposures that increase steadily by 1/3 stop each using the next slower shutter duration (1/3 longer) each time.

After you've added about three full stops "Beyond the Right" download the series to your computer and open each, in sequence, in Adobe Camera Raw (ACR). Then, tonally normalize each image by sliding the Exposure slider to the left. Somewhere among those images you'll sooner or later encounter one ( the first of all the rest) in which your highlight detail is, indeed, blown / clipped/ burned out.

Did it happen with the second exposure "to the right? Then you have 1/3 stop of "ERADR".

If the sixth exposure "Beyond the Right" shows the first hint of clipped highlights, then your camera has 5/3 (1 and 2/3 stops) of ERADR".

If, as, happened when a friend and I were doing this recently with his new Nikon D800, it happened that the first appearance of clipped highlights was in the eighth exposure past ETTR! That meant HIS D800 has two and 1/3 stops of ERADR ! ( One full stop more, AND ONE AND 2/3 stops more than the only other D800 I'm aware of that has been tested. So you cant extrapolate from one camera to thers of the same model. Each camera needs to be individually tested.

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HOW TO USE YOUR CAMERA'S ERADR :

The practical use of all this means that when shooting RAW files of scenes offering the opportunity to determine the limit of ETTR* you then Expose Beyond the Right(EBTR) by adding your pre-determined ERADR. You'll be collecting image data of the highest possible quality with the least possible noise in the deep shadow regions ( because those deep shadow data points were collected far to the right of the left side of the ol' JPEG histogram, back where most noise lurks!)

*which means that fast-moving sports, children at play, and wildlife moving between regions of different light conditions are not good candidates for EBTR.

Best regards,
Dave in SD

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