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A9 ISO bracketing?


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Hi experts,

I ran into a high dynamic range situation which I was unable to adequately handle with my current skill set. Setting was the inside of a historical, roofed timber bridge with a view of the bright, sunny outside. I opted to not overexpose the bright parts, and was hoping I would be able to recover the dark areas during processing. This is the poor result:

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Obviously the dark areas are way too dark, which made me think that this would probably have been a good application of some sort of bracketing, which I had never done before.

Back home I started some trials, but was quite sobered to realize, that the body cannot communicate a variation of EV values to a purely mechanical lens like my Samyang 12mm f/2.8 fisheye.

Which makes me wonder:

Is there a way to set up "ISO bracketing" to simulate the effect of EV bracketing? I didn't find anything to that regard in the manual.

For completeness, this is the timber work I was trying to show. This is heavily edited at the jpeg level, so purely for documentation purposes:

 

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Experts and enthusiasts  ?,

I'm lazy and impatient - a difficult combination that I'm aware of.

So, for lack of expert opinions I was thrown back at some good experiments (see my tagline). And it wasn't that difficult to find out after all:

1. With camera in "Auto" mode and a bracket configured at 9 shots, each 1 full EV apart, going from underexposed => neutral => overexposed, I got 9 shots with identical exposure, because the body couldn't communicate the different aperture values to a fully mechanical lens. That was the beginning.

Next trial:

2. Setting the camera to "Manual" mode, with ISO fix at 100, all else being equal, I received 9 shots with variations of the exposure time:

1/2000

1/1000

1/500

1/250

1/125

1/60

1/30

1/15

1/8.

So that's pretty good already, although may not be suitable for targets in motion, because of varying motion blur.

 

3. Then I left camera in "Manual" mode, but set ISO to "Auto", and allowed ISO to float freely between 100 (minimum possible) and 204.800 (maximum possible). I had to run several tests with varying initial exposure times and initial aperture settings, to cover a full series of ISO increments. With the lighting condition at hand, and initial exposure time of 1/8000 and initial aperture of f/8, I ended up with a nice ISO-bracketing series of

ISO 125

ISO 250

ISO 500

ISO 1000

ISO 2000

ISO 4000

ISO 8000

ISO 16000

ISO 32000,

which I'm happy with. What's left for practical applications is to find out for each specific situation, which initial settings of timing and aperture would not clip the ISO bracketing series at either end. But on the other hand, there will rarely be the need for a bracket covering 9 EVs.

 

 

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Just for the record:

Since it will take while until I can try out the bracketing at the original location, I tried getting more out of the raw images as they currently are. And I was able to achieve much of what I originally intended by stitching the raw images in PTGUI Pro, and in the process adjust the histogram.

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I will report back when I have had a chance to try the ISO bracketing.

 

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