More on FAQ #1504

On TTG’s list of limits for combining exposures

  • 1504. Why is the list of limits so long? More

    Because there are numerous complexities that need to be spelled out for photos made with standalone cameras — things that are handled as a matter of course by smartphones.

  • 1. TTG has to allow the combining of exposures, because hundreds of millions of smartphones now routinely make photographs that way.
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    “Combining exposures” was not traditionally a part of making trustworthy photographs, but the technology has changed.

  • 2. However, even though TTG allows for combining exposures (in P5) “because of smartphones,” TTG cannot be device-dependent...
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    . . . so anything that users of smartphones can do — including combining exposures — must also be permissible for users of standalone cameras (and vice-versa).

    P5 | What does “device-dependent” mean?

  • 3. Of course, there is much greater potential for deception when combining exposures...
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    . . . and the TTG label was created to help the public identify non-deceptive photographs. That creates a problem.

  • 4. Smartphones — when all special effects are turned off — usually take care of meeting the Trust Test, even when combining exposures...
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    . . . because smartphone cameras combine exposures by default in many situations, and the public would not buy a device that “by default” doctored photos.

    See #9 below about that “usually”

  • 5. But there are no “guardrails” preventing deceptive photos when exposures are combined outside of a smartphone.
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    The fewer the limitations there are on how exposures can be combined, the more potential there is for the creation of untrustworthy images.

  • 6. Thus TTG’s list of limits had to be created for photographers who are combining photos outside of a smartphone.
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    None of the items on that list of limits are superfluous. If any of the requirements on that list were absent, it would be easy to make a photo that was less trustworthy — but would still qualify as TTG.

    Thanks to that list, all TTG-qualified photos that are made by combining exposures will always look like a single-exposure, undoctored photograph.

  • 7. TTG necessarily allows for combining exposures outside of a smartphone — but that doesn’t mean that performing such combinations is easy or practical.
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    While practices like focus stacking and HDR are allowed to be performed by standalone-camera users under TTG’s limits on combining exposures, in the real world the “one second” rule in P5 could prove frustrating or insurmountable for standalone-camera users who wish to do those things.

    “TTG was never intended to apply to all photographs.”

  • 8. But TTG’s allowance for combining exposures was not created for standalone camera users.
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    That allowance was created out of necessity (i.e., because of how the most popular cameras in the world — smartphones — make photographs) — and then the allowance was made as strict as possible.

    Couldn’t a standard be created that’s like TTG but less strict?

  • 9. Despite the Trust Test being partly based on smartphone defaults, smartphones do not always combine exposures in ways that meet the Trust Test.
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    More on those “smartphone defaults” that shaped TTG

    • By overriding a smartphone's default settings, numerous popular effects (such as the three effects listed in “A” of P2) are possible that disqualify the result from TTG — but most such effects can be easily Undone to make the photo eligible for TTG.

    • When a smartphone combines multiple exposures of a fast-moving subject in low light, the result can include visual artifacts that could not be removed in TTG-compatible ways; see FAQ #862.*

    (With a standalone camera, there are usually multiple ways of making TTG-compatible photographs of such scenes using a single exposure.)

    • When the photographer deliberately sets the smartphone to combine exposures that begin more than one second apart, as with special astrophotography modes, the result cannot meet P5 and the photo cannot qualify as TTG.*

    (A TTG-compatible photo of the same scene is possible by mounting the smartphone or a standalone camera on a star tracker.)

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    *When a photograph cannot fully meet the Trust Test even after all of TTG’s Allowable Changes are applied, the image is considered TTG-ineligible.