What I learned from Gollywop -- and what I wonder

Started Mar 26, 2013 | Discussions thread
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bowportes Veteran Member • Posts: 3,488
What I learned from Gollywop -- and what I wonder

As an old fart of a photographer, I thought I knew all about exposure -- you know, aperture, shutter-speed, and ISO.  The point was to nail the proper exposure as given by the camera. Behaving like I had ektachrome loaded in a digital camera, I rarely over- or under-exposed unless I had a situation of backlighting or snow.  The Panny G-series cameras, by shifting the color of the histogram to yellow (caution) if I used the thumb-wheel to increase/lesson exposure, encouraged me to keep it white -- right where the camera automatically exposes.

This may be fine general practice for JPEG shooters, but it turns out it was wrong for capturing raw.

Gollywop's recent post encouraged me to think instead of maximizing the sensor's exposure to light. Rather than accepting the camera's exposure, I should overexpose images just (but not quite) to the point of clipping highlights at base ISO (ETTR). The histogram may go yellow and the image may appear too light in the viewfinder, but as long as the right side of the histogram has not reached the right edge of its axis, go ahead and overexpose.  My raw-processed image will be better for it, in spite of the fact that it doesn't look as good in the EVF at +2/3 exposure as when it's not set to overexpose.  Watching the histogram (or blinkies on an Olympus) is your key for how far to amplify exposure.

Something that's not as clear to me though.  If ISO is at base (160 for most Pannys and 200 for Olympus), the lens is at maximum aperture, and shutter-speed can't be set slower, but the histogram still sits right in the middle -- not overexposed at all -- if I understand correctly, I might get some improvement in image quality by raising the ISO to 400 or 800 in order to overexpose the image, as long as I'm careful not to overexpose to the point where I'm clipping highlights. I'd like confirmation that this is correct.

Another situation that I've commonly encountered in the past is desiring to have the lens wide open in bright daylight. This typically means ISO is at 160 (base), my F1.8 or 2.8 lens is wide open, and shutter speed is as fast as my G5 can take it.  In the past, the EVF still sometimes indicated this gave too much light, so I was compelled to reduce my aperture since ISO couldn't be lowered and SS couldn't be increased, and my goal was to achieve proper exposure for my raw file. But now, if I understand the Gollywop thread correctly, I should be pleased with the overexposure and leave the aperture wide open, as long as it doesn't clip highlights.

So my understanding is that the point is to fully charge the sensor.  Rather than thinking, as I used to, in terms of proper exposure (as my G5's visual indicators still recommend), I should instead think of full exposure, giving the sensor as much light as it can take (without clipping).

I need to stop thinking in film terms; they would never have led me to these conclusions.

Thanks to Gollywop and others who contributed to the discussion. I hope I am getting some of the practical implications right.  If not, please correct me.

 bowportes's gear list:bowportes's gear list
Panasonic Lumix DMC-G5 Fujifilm X-M1 Fujifilm X-T1 Fujifilm X-Pro2 Panasonic Lumix G 20mm F1.7 ASPH +13 more
Panasonic Lumix DMC-G5
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