Why ETTR?

Started 7 months ago | Questions thread
gollywop
Veteran MemberPosts: 5,451
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You're definitely missing something
In reply to Ysbrand Galama, 7 months ago

Ysbrand Galama wrote:

ZodiacPhoto wrote:

Also, ETTR can be used with JPG shooting. For example, a scene with plenty of mid-tones, and some shadows, but without much of meaningful highlights. The "proper" histogram will show most information in the mid-tones, with shadows clipped on the left, and not much going on in highlights. If you use ETTR to move mid-tones to the right, you can rescue shadows and reduce noise. of course, you will have to reduce brightness in post-processing.

Exactly what I thought. It doesn make sense to me why ETTR only works for RAW. Why would it make any difference whether you develop to JPEG in camera, or let some PC-software do it later?

Actual ETTR works fine for jpeg.  By actual ETTR I mean that the exposure (aperture and SS), at base ISO, is maximized so that the sensor is just saturated without blowing desired highlights.

However, if the maximal exposure as determined by your shooting conditions (aperture and SS) are less than ETTR (base ISO), then it does make a difference when shooting jpeg as to whether the additional brightening is done in camera or later in an image editor on the computer.  These differences exist over and above those relating to the ISO-nature of the camera.

Jpegs differ from raw files in a number of significant ways that render out-of-camera processing far less effective and desirable than properly adjusted in-camera processing.  These differences include:

• jpegs are non-linear, already having a gamma applied.  Processing is best done with linear data, which, of course, the camera does in processing the raw data via the jpeg engine.

• jpegs are 8-bit files rather than 16-bit and are less robust to significant tonal and color adjustments.

• jpegs have a WB applied and are susceptible to color distortions when undergoing any needed WB alterations.

• jpegs have already suffered data losses during compression and are less tolerant to tonal and color adjustments. These losses can never be recovered.

• jpegs have already had a color space applied and have lost gamut (particularly if sRGB is used for the camera's color space) that can never again be recovered.

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gollywop

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