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Full Version: How to use qDslrDashboard and Auto Holy Grail
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How to setup a shot with Auto Holy Grail:
  • Set Camera to RAW+JPG (smallest size), no Liveview!
  • Switch to the "LRT" screen in qDsrlDashboard
  • Click on Capture Sample - a preview shot should appear. If not, something with the connection or your devices is wrong, please ask for technical support at !
  • If an image appears, set the camera settings in order to get a correctly exposed image. You can use "Capture Sample" to check the histogram after changing the settings.
  • Now setup an external intervalometer to trigger the camera. Don't use one of the internal ones that some cameras provide. Use one that does not block the camera! See this post about how get the best performance with your intervalometer.
  • While running Display next JPG brings the next image shot to the screen. (But only one, this will save battery. You can always click on "Display next JPG" once you want to see a current preview.
  • Now set the parameters for the Auto Holy Grail: Sunset/Sunrise and the boundaries for the ramping (Min/Max ISO, Longest Shuttertime). As long as you don't know the performance of your system, Longest Shutter should be max. 3 seconds below the interval. If this works you can experiment wit 2 seconds "Dark time" (Interval - Longest Shutter) or even 1 second. This might or might not work depending on your setup.
  • Now you can activate the Ramping with "Auto Holy Grail". This will set a reference value automatically that the Auto Holy Grail will hold.
  • If during auto holy grail, you feel the images get too dark, click on the "+" Button next to "Set Reference" once or twice to increase the reference value. If you eventually feel the images get too bright, click on the "-" Button. This allows a manual intervention.
Some more hints:
  • You can activate Aperture ramping in the settings menu on the bottom of the LRT-Screen in qDDB. Then you will have to set boundaries for Max and Min Aperture too.
  • The crucial point is, that the dark-time (interval minus longest shutter) is long enough for the camera to be able to transmit the preview and receive any commands from qDDB to change it's settings. How short the dark time can be, will be determined by the whole setup and especially the intervalometer used.
  • I don't recommend using the intervalometer built in in qDslrDashboard because it mostly does not deliver constant intervals. Apart from that, should the app or tablet crash, your whole sequence will be gone. If you use an external intervalometer, you can just restart qDslrDashboard at any time and continue the Auto Holy Grail.
  • I don't recommend using "Auto Direction" since that feature is not well tested.
Default qDSLRDesboard wil check every 3 image for the correct exposure. Have you experimented with longer intervals. For example, with 5 images?
You can change it in the settings, but I always leave it on the default value, I see no reason to change it. If you change it however, you shouldn't set a lower value to prevent that the adjustments happen too close to each other.
I'm shooting a Nikon D750 with the Dynamic Perception Stage One Slider and NMX controller for a multi-axis Milky Way time-lapse. Will the NMX controller work ok as my intervalometer?

Yes sure.

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Spot on, Gunther. I wish I had read this several months ago but this is almost exactly what I came up with based on trial and error. I shoot with a D7000 and a D7100 and use the MX2 for the intervalometer even if I don't move the camera on my sliders. To save my camera battery I also turn off image review and power down the LCD. I also direct the jpgs to the second SD card to make it easier to discard them after shooting.
You know that the LRTimelapse importer has an option to ignore the jpg when bringing the sequences to your harddrive?

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Last evening I tried the "Auto Holy Grail" with "Sunset" but when the scene become dark the APP changed the ISO / Shutter Time values so that the recorded images were very very bright.

Was this happening because the APP get as reference the histogram of the first image then try to change ISO/Shutter Time so that every following image match the histogram of the reference?

If not, what is the algorithm behind modification of ISO/Shutter Time?

It's as good as impossible for an algorithm to predict the luminance progression (and rather unnecessary to), that's why we do that in post when editing the keyframes. While shooting you just have to take care to stay inside the dynamic range of your sensor.
This is why you can and should from time to time change the reference during shooting (see last bullet point in the faq above). If you feel that the images get too bright, just decrease the reference value.
Thank you for the explanation.

Please help me to understand the logic of "Set Reference" button:

- If I press "-" it set the camera to make the next image "darker", meaning reducing Shutter Time or lower ISO
- If I press "+" it set the camera to make the next image "brighter", meaning increasing Shutter Time or increase ISO

Is my understanding correct?


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