Hi Molly,

Sorry for being slow in responding, but I believe I've discovered the circumstances under which the particles disappear for me.

When the new DOF system was introduced I didn't quite know how to use it and always used the Perfect Focus Range to adjust the DOF distance. In that case the particles disappear when shown in front of a nearby surface.

Tonight I used the proper way and adjusted the Near Transition Region (linked to the Far Transition Region) to the same DOF distance. Now the particles are visible the whole time.

Of course, they are also visible when DOF is inactive.

I have created a project file with three animated cameras:

1. DOF_perf_focus_range, which has Perfect Focus Range at 10000 and Transition Range at 0. The particles show against the sky (Particles_against_sky_DOF.jpg), but will disappear when shown against a nearby background (particles_against_BG_DOF_perf_focus.jpg).

2. DOF_trans_region, which has Perfect Focus Range at 0 and Transition Range at 10000. The particles are shown throughout (Particles_against_sky_DOF.jpg; Particles_against_BG_DOF_trans_reg.jpg).

3. no_DOF, which has DOF inactive. As expected, the particles are shown throughout (Particles_against_sky_no_DOF. jpg; Particles_against_BG_no_DOF.jpg).

Link to project file: http://virtualrealist.com/uploads/dof_particle_test.zip .

In the attachment:
DOF is activated at the start of the animation causing the particles appear in the wrong order of display, as it shows as if behind the cube even tho the cube is illuminated to where the particles are supposed to be. Mid way the DOF is keyed to turn off to show the correct way the particles should be displayed.