Bulb Ramping

The Bulb Ramping mode is intended for Time-Lapse users who would like to take Time-Lapse videos in changing light conditions, such as a sunset or a sunrise. It works by varying camera Bulb exposure in very small increments, achieving a nearly flicker-free exposure transition from bright to dark, or dark to bright. This material assumes familiarity with basic Time-Lapse concepts.

A bulb ramping sequence consists of taking a set of pictures with constant exposure, then changing exposure in very small increments or decrements for a certain period of time, and then taking another set of pictures with constant exposure. The resulting exposure set can be visualized by the following curve:

The exposure can be increased (as in above example) if your light levels will drop (as with a sunset), or decreased if your light levels will rise (as with a sunrise).

Settings

The following settings are available:

Start 1/20   ea 10s

Begin Ramp  in 01h00m

End  2”     in 01h30m

Finish Seq  in 02h00m

The above screen would result in a bulb ramping sequence that starts with a 1/20 second exposures taken every 10 seconds. This continues for 1 hour. After that time Promote Control starts slowly ramping the exposure to 2", and will arrive there in 1 hour 30 minutes from now, so the exposure ramping changes will take 30 minutes. It will then continue taking 2" exposures until 2 hours from current moment elapse.

Usage

Bulb ramping may greatly benefit from additional preparation work before you start. If you can, get exposure metering of a scene at a time of day when you bulb ramping is planned to be finished. For example, if you plan a sunset session, get an exposure of the same scene the night before. Do NOT use ND filters when metering, and set your camera ISO setting to a fixed value. Remember the final exposure time and the ISO value used.

Use the following workflow to prepare for bulb ramping:

1.Switch your Promote Control to the "Bulb Ramping" mode.

2.Setup your camera on a tripod and connect the Promote Control as described in the Connections section. Make sure Bulb Ramping Assistant Cable is also connected.

3.Disable automatic focusing on your camera, choose a fixed aperture and set ISO to the same fixed value you used when measuring your end exposure as described above. If you did not pre-meter your end exposure, use any ISO setting such as 200. Do NOT use automatic ISO feature, if available in your camera.

4.Set your camera flash synchronization mode to default setting. Any other setting, such as "rear curtain" sync, will interfere with the Bulb Ramping mode.

5.Disable Mirror Lock-Up mode on your camera. Promote Control cannot ensure correct exposure timing in Bulb Ramping mode with Mirror Lock-Up enabled.

6.Perform "Shutter close delay" calibration as described in Promote Control Setup section. You may skip this step if you have previously calibrated it for this particular camera.

7.Take ND filters off if you plan on using them in Advanced Bulb Ramping.

8.Set your camera to Manual exposure mode, take a few test pictures and and pick a shutter speed that yields an acceptable picture. IMPORTANT: if you plan on using ND filter handling in Advanced Bulb Ramping, make sure to meter without ND filters. Otherwise ND filters will be taken into account twice and this will result in an incorrect exposure.

9.Specify the current shutter speed as "Start".

10.Use interval of 10 seconds for general bulb ramping. Lower interval values will result in slower time-lapse videos. Note that too short of an interval may limit your exposure range. Higher interval values will result in faster time-lapse videos.

11.Specify a delay to start the exposure ramping using "Begin Ramp in" setting. If you work on a sunset, this delay would be the time from now to when the sunset starts, plus 5 minutes to allow yourself to complete this setup. You can obtain sunset start times using various tables and/or weather reports.
 
NOTE: You may optionally enable a Setup setting called "Keep bulb ramp length on start time change". With this setting enabled, changing bulb ramping start delay will simultaneously and change bulb end delay and sequence delay, keeping the total bramp and sequence duration the same. This may be useful if you want to memorize a currently set ramping duration and simply change the moment when the ramping starts.

12.Enter the "End" exposure using "End" setting. If you pre-metered the end exposure as described above, enter that exposure time here.

13.Use the next setting to set a delay to end the exposure ramping period. Most sunsets/sunrises take about 30 minutes, so this delay should be "Begin Ramp" delay + 30 minutes.

14.Finally, specify when to end the complete sequence. For best results you may want to use "Begin Ramp" delay + 2-3 hours here.

As you change the values, Promote Control calculates and displays how many total images will be taken. Make sure your memory card can fit that many images before you proceed.

In many circumstances your start exposure will be shorter than what Promote Control allows you to choose. For example, you set your aperture to F/8 with ISO 100, and your camera says you need to use exposure of 1/100 second. However, Promote Control will only allow going as short as 1/20 second (this may vary depending on camera model). This case would require installing and keeping ND filters in front of your camera lens to make exposures longer than 1/20 second, or enabling Advanced Bulb Ramping. The Advanced Bulb Ramping mode, available exclusively with the Promote Control, allows for automatic ISO changes, as well as dynamic ND filter calculations and usage. See Advanced Bulb Ramping section for more details.

Pre-Flight Checklist

Once everything is setup, go through the following steps before you begin:

1.Make sure your camera ISO is not set to "Auto". Doing so may interfere with bulb ramping.

2.Set camera exposure mode to Bulb.

3.Disable automatic focusing on your camera.

4.If your camera is set at an angle, and your lens is prone to unexpected zoom/focus changes due to gravity, for example of Canon EOS 28-135 USM lens, you may want to use scotch tape to fix the zoom/focus rings. On ultrasonic lenses focus setting will not move, but zoom setting may change.

5.If your memory card allows, set your camera to RAW image format. This will make post-processing much easier. If you find yourself changing image quality setting at this time, re-check that your camera can still fit the planned number of images as pre-calculated by the Promote Control.

6.If you plan on using ND filters in Advanced Bulb Ramping, and your ND filters require a holder (such as Cokin series), mount your ND filter holder now.

7.If your pre-flight checklist took more than a few minutes, make sure that "Begin Ramp" and "End" delays are still valid.

8.Press "Start" on Promote Control. Depending on your settings, one or more prompts may be shown, clarifying the next step. Otherwise, the image sequence will begin immediately.

Depending on your camera model, you may be able to preview the images as they are taken on your camera rear LCD. Note that current Nikon cameras currently will not be able to provide image previews if Advanced Bulb Ramping is used.

If a particular set of settings eventually fills your camera buffer, it means the images are being taken too fast, and your camera cannot write them to the memory card quickly enough. In that circumstance, use Promote Control Setup setting called "Bulb ramp / bulb HDR image buffer time". Promote Control uses this setting to safeguard bulb HDR and bulb ramping exposure sequences from overfilling the buffer. Its default value of 1800ms is adequate for most cameras. You may try increasing that setting if you experience symptoms described above.

Using Live Modifications

The Live Modifications (or Live Mod) feature is useful when you realize that the ramping settings were not correct. You do not want to stop the ramping sequence to readjust your settings - this will result in an abrupt exposure change that we are trying to avoid.

Instead, use the Live Modification, or Live Mod feature. It is only available when the bulb ramping sequence is active, and offers a way to gradually shift the complete ramping curve up or down as necessary. When you apply a Live Modification, the whole set of exposures is shifted, including constant zones. If you were to apply a Live Mod in the very beginning of your sequence, it would slowly go from "Original" curve below to the "Modified" curve:

The change will not applied at once - this would result in an unpleasant flicker in your final time-lapse video. Instead, Promote Control will automatically and gradually apply the change across a number of frames, so that in the final video this change looks like a smooth transition. You can vary the number of frames used to spread the Live Mod by changing the corresponding Setup setting called "Bulb ramping live mods are applied" (see Setup Menu section for more details). With a default setting of 30 frames the change will be take about 1 second of a final video in NTSC format (~30 frames per second), or 1.2 seconds in PAL format (25 frames per second). Use the following table to set the live mode spread frame count:

Live Mod spread across...	Transition Duration in Video
	NTSC	PAL
25 frames	~0.83 seconds	1 second
30 frames	1 second	1.2 second
50 frames	~1.67 seconds	2 seconds
60 frames	2 seconds	2.4 seconds
600 frames (max)	20 seconds	24 seconds

You may optionally set this Setup setting to "Immediate" - this will apply the complete amount of Live Mod to the next frame after you finish changing the Live Mod value.

To apply a Live Mod, simply press Up or Down buttons on Promote Control when a bulb ramping sequence is active. The "Modify" value will change accordingly - a positive "Modify" value will gradually make your sequence brighter, while negative "Modify" value will gradually make it darker. The Promote Control will wait until you finish changing this setting, and then start applying it. When it is being applied, "ACT" will be indicated next to Live Mod amount. As the Live Mod is applied, the amount will get closer to 0 unless you start changing it again.

Note that Live Modifications may not always be possible - such as when you are trying to modify an exposure sequence curve past the limits defined by shortest obtainable exposure and your interval. Promote Control will not let you enter a Live Mod that violates the above constraints.

Using Live Ramp Shifting

Live Ramp Shifting is similar to the Live Modifications, but instead of shifting your curve up or down, it shifts the actual ramping left or right - moving the moment when the ramping begins closer or farther in time.  It is only available when the bulb ramping sequence is active, and only until the ramping has started. This may be useful if e.g. the sunset started kicking in, and you realize that you delayed your ramp start too far into the future. In this case, press or hold Left button on Promote Control to reduce the time before the ramp starts. On the contrary, if you feel like your ramping is about to start too early, press or hold Right button on Promote Control to increase the time before the ramp starts.

When using Live Ramp Shifting, you will see "Ramp .. in" timer countdown change as you press Left/Right buttons. You cannot make the ramp start immediately - the quickest the ramp can be brought back is 1 (one) minute from now. This is intentional, and is made that way to ensure that you have that 1 minute to rethink your decision - and, if required, delay the ramp by pressing Right button again. So if you need the ramp to start as soon as possible - press/hold Left until you have it start in 1 minute from now, and then let that time pass. Note that once the ramping part starts, Live Ramp Shifting cannot be used any more.

Using Live Ramp Shifting will impact both ramp start and end times simultaneously. In other words, it will only make the ramp start earlier or later - it will not affect the duration of the ramping part of the exposure curve, or the remaining duration of your previously programmed sequence.

Pausing Ramp

If you feel like the light stopped changing, you may want to pause your ramping. This will NOT pause shooting - images will still be taken, but the exposures will not be changed while ramping is paused. When the ramping is resumed, exposures will continue ramping towards the same end exposure that you set earlier. Pausing your ramping will extend the total time your bulb ramping sequence takes for the duration of the pause.

To pause or resume your exposure ramping, press Left+Right buttons at the same time while Bulb Ramping sequence is under way. Please note that ramping pause/resume is only available before the ramping portion of the exposure curve above is completed.

Packing Up

A bulb ramping session can take as long as a few hours and may require extra items to bring with you. The following checklist may be followed when you pack for a bulb ramping trip:

1.Promote Control, Bulb Ramping Assist Kit, shutter cable, USB cables.

2.An optional Promote Control Tripod Case may be useful (available from Promote Systems).

3.ND filters with holders & adapter rings if required (Advanced Bulb Ramping only).

4.Backup memory cards. We recommend cleaning them in advance.

5.Backup batteries for camera and Promote Control (2x AA).

6.Tripod, camera tripod mount plate. You may want to check the plate you pick fits both the tripod and your camera well.

7.A portable GPS navigator may be useful to mark locations.

8.Mini flash light.

9.Scotch tape.

10.Drinks, snacks, coat / blanket (if required by upcoming weather conditions).

11.Permission paperwork if required for restricted locations.

We highly recommend trying the Bulb Ramping mode for a few times prior to planning an actual field trip. Getting yourself familiar with all the exciting possibilities of Time-Lapse videography in changing light. When you are ready to step up, make sure to read Advanced Bulb Ramping section to even further extend your creative horizons with Promote Control.