Why ETTR?

Started 11 months ago | Questions thread
CobaltFire
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Re: Why ETTR?
In reply to Ysbrand Galama, 11 months ago

ETTR is not a simple concept.

First the reason: the amount of information in each photo is tied to the brightness level. The higher the brightness, the more information (colors, detail) there is, until you exceed the DR of the sensor/camera and clip. You can test the relatively easily by manually shooting the same scene with offsets of two or three stops and looking at the file sizes (for a quick reference) and developing the photos (for a more thorough analysis). Note that the file may get SMALLER if you step up ISO, due to the loss of DR. This indicates that you've gone past the point of gaining anything.

Second is how to do it. This is not as simple as it sounds. I'm sure you are aware of the tradeoffs present in opening your lens up or slowing the shutter speed down. However, knowing if you can use ISO to slide your exposure is quite a bit more difficult. You must understand your camera and how much of an advantage you will gain by ETTR, then compare that to how much of a disadvantage stepping up the ISO will give you. As mentioned above raising ISO will cause a loss of DR. On many cameras the first stop of ISO (on my E-M5 400) is not actually that much of a loss. This is usually the "gimme" step that you know you can take. After that it's up to you to decide how much DR you can trade for more detail and color.

For example, I shoot an E-M5 and an A65. On the E-M5 I have it set to +1 Exposure Comp and stay with that down to ISO 800, with shutter speed based on subject (between 1/10 and 1/100) and f/stop based on subject. On the A65 I have the camera set to ISO 400 (no auto for P mode on that camera), f/2.8 to f/4, and let the shutter speed float. Both of these sets of numbers are from MY testing, MY expectations, and MY skillset.

Note that when I owned the GH2 I only biased 0.5 stops due to the camera offsetting RAWs more to the shadows (lots of information in the shadows, early clipping of highlights). This is another factor that must be understood and compensated for.

Once it's all said and done it's worth while for me, but it has ruined a few shots that were on the limits of my skills/equipment to capture. I don't think those pictures would have been worthwhile if they were that close, but it's possible they were.

Hope that all helps!

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