A guide to
Combining exposures
#9 of TTG’s Allowable Changes
This is a list of all applicable parts of the Trust Test
This list is primarily for users of standalone cameras, as smartphones usually take care of these requirements automatically.
Keep your expectations realistic! As explained in P4, P5, and the subpage to P4, it is very difficult to make a TTG-qualified photo from multiple exposures of a scene that has movement in it. (See also #862)
Ready?
In order for a combined-exposure photograph to meet the Trust Test, all of these must apply:
1. All of the combined exposures must begin within the same single second. No other pictorial information may be added that was not recorded during those exposures (P5; see also FAQ #1506–#1508).
2. The photo must depict one specific arrangement that occurred during exposure, or satode (P4).
3. There can be no repositioning or re-aiming of the camera or lens during or between successive exposures (P3).
Thus while panning is allowed for single-exposure photos, stitching together successive exposures recorded while panning disqualifies a photo from TTG.
(That's why photos made using the “Pano” setting on smartphones are always disqualified from TTG: there is no way to isolate individual exposures from those Pano images.)
4. After combining exposures, there can be no ghost objects or SMP effects (P4).
5. Combined-exposure photos face the same sasibe limitations that single-exposure photos face (P4).
6. All of the combined exposures must be recorded on one device, with one lens that is set at a single focal length.
Focal-length blending and zooming during the exposure both disqualify the result from TTG (P3).
7. After combining exposures, the photo held up to the Trust Test must be a “fixed” still image that appears the same to all who view it.
No viewer can see different lighting, focus points, depth of field, perspective, etc. than another viewer would see (P6; see also #1606).
8. The result of any combined exposures must be focus maximized (P3).
9. The result of any combined exposures must be optically plausible (P3).
10. The result of any combined exposures must meet P7.
Notes
• Even when exposures are combined, the various requirements in the Trust Test ensures that the result always looks like a single-exposure, undoctored photo (Why?).
• TTG makes no distinction between combining exposures or photographs “on the smartphone” vs. “in camera” vs. “in the darkroom” vs. “on a computer.” They are all treated equally.
• Why does TTG allow combining exposures when news organizations traditionally did not?