Can development or scanning really increase film dynamic range to 17 stops?
Asked 1/8/2019
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I often see film described as having around 9–11 stops of dynamic range, but some sources claim as much as 17 stops is possible with special development or scanning techniques. For someone new to film, what development tricks are they referring to? Can methods like push/pull processing, compensating developers, two-bath developers, or scanning actually increase the usable dynamic range, or do they mainly compress the scene’s tones into the film’s existing range? I mostly shoot architecture and long exposures, so I’m interested in getting the best highlight and shadow retention possible.
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
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17 stops sounds...wishful. A film's characteristic curve is, for the most part, set. One can change the slope (contrast) by adjusting development or purposefully expose to the left or right of the curve and then bring it back in development (push/pull)...but there really isn't a way to extend the curve to where base+fog moves further left or blocked highlights moves further right.
If one has a super contrasty scene, you can use a compensating developer to keep the highlights from blocking up...but again, this isn't really moving the curve, simply finding a way to compress your scene into the given curve. Hence the adage, expose for the shadows & develop for the highlights.
The next compression comes at print time...where you have to decide which values in the tonal range to keep, because no print can match film's range.
Originally by user67377. Source · Licensed CC BY-SA 4.0
user67377
7y ago
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Not in the sense of truly changing the film’s native range. A film’s characteristic curve is mostly fixed, so development can change contrast and tone placement more than it can extend the actual limits of shadow detail and highlight detail.
What these “tricks” usually do is compress a high-contrast scene so more of it fits within the film’s usable range:
- Push/pull processing shifts how tones fall on the curve.
- Compensating developers help restrain highlight buildup so bright areas don’t block as quickly.
- Two-bath developers such as Diafine can increase apparent dynamic range by letting highlights self-limit while shadows continue developing more gently.
- Scanning/printing choices can further recover or preserve tonal detail already present on the negative.
So claims like 17 stops are best treated skeptically as workflow-dependent, “apparent” or extractable range, not a true extension of the film itself.
A good practical summary is: expose for the shadows, develop for the highlights. For architecture and long-exposure work, developers and careful scanning may help retain more usable detail, but they are mainly tone-management tools rather than a way to fundamentally expand film’s dynamic range.
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