AGG 0.2.2 introduced the "Time offset" feature, which enables you to order chronologically images from different cameras, even if the clocks in the cameras were not in sync. This page explains how to use it.

Ideally, you wouldn't need such feature at all. If all images are taken with one camera, or there are multiple correctly-timed cameras, just enabling "Sort by exif data" from the File->Preferences menu would be sufficient.

But let's say we need to apply the correction. How to do this? Suppose we have two sets of images from the same event:

And:

Obviously, the second camera's clock was not set up correctly. It is nevertheless tracking time correctly (AGG cannot work when this is not true; that is, when all images' time are the same). Now we search for a pair of images (one from each camera), that seem to taken at approximately the same time (the less the time difference, the better). Let's say, we choose the ones, that are marked with an asterik above. To add them in AGG's time offset tracker, you should first browse to img_3032.jpg and then click on Gallery->Time Offset->Add. Then, browse to p0701237.jpg and, again, go to Gallery->Time Offset->Add. Then click on "Sort". The resulting order will be:

How does it work? AGG takes Camera #1 for the base in its calculations. Each other camera has some delta (time difference) against Camera #1, and this difference must be added to all camera's pictures, in order to get their times correctly. The delta is measured in seconds, and may be negative, as well as positive. In order to calculate the delta for Camera #2, having picture a.jpg from camera #1 taken at time X and picture b.jpg from camera #2 taken at time Y, the following equality is assumed:

X + 1 = Y + delta

This means, that AGG adjust matters so that b.jpg appears to be taken one second after a.jpg. For camera #3, it will be two seconds after a.jpg, etc. The idea of this assumption is that, after sorting, a.jpg, b.jpg, etc... will be consecutively ordered.

Of course, the "real delta" may be well above one second. If you need to be that exact, you may alter the calculated deltas for each camera. In order to do that, open up the Time Offset dialog and doubleclick on the corresponding camera's entry. It will show the current delta and prompt you to change it. Example: You have a.jpg from camera #1 and b.jpg from camera #2, and you know for sure, that they have been photographed 15 seconds apart. So, add them as you would in the Time Offset's list and then double click on the second entry. The (assumed) difference is currently 1, and we want to make it 15; thus add 14 to the delta value.

Notes/limitations:

• You may have as many cameras as you wish. You just have to select one image from each camera;
• The delta for cameras, not mentioned in the list, is assumed to be zero;
• A camera is recognized only by its signature - Manufacturer + Model name. If you have two different cameras from the same model, they won't be distinguished, and thus no time offset correction is possible;
• Images without EXIF data will not be treated correctly;
• Time offset only rearranges the image order. It does not correct the Exif Time/Date field in output images. Nor is camera data saved in the project. However, order is preserved when the project is saved to disk;
• The maximum accuracy is one second;
• Once rearranged, there is no way to Undo the sorting. If you are not happy with the results, recreate the project.