Description
The Flats calibration wizard is failing to deterministically select a proper value. I believe the behavior indicated below is causing it. I am using a Nikon D5500 at the moment. Trying for a 10k mean ADU as a target flat. Feels low but Im not sure what the behavior below means to the quality of the flat being generated.
Link to Logs
Useful Info
Experimenting manually with exposure times I have noticed the following aberrations:
- Manually incrementing exposure times reveals a staircase response of exposure time to ADU values from about 0.7seconds and ~10k mean ADU. Steps start over around 0.15sec then go up to 0.3sec close to the saturation point.
- Manually asking for a 1/8000 or 1/4000 in decimal value in SGP Pro will not work. I get the next step up if I do that. I need to set the exposure time to 0 to get 1/8000 on my D500 and 1/4000 on my D5500. Is it possible the stair cases Im seeing is due to the exposure time not actually varying correctly?
OS: Windows 10 Pro
Ver: 3.1.0.558
Is there any way to get support for my question above please? I ran into another problem 2 nights ago while manually hunting for optimum flat exposure times (cant use the wizard as it fails depending on the value of the exposure) on an alternate panel. I increased the exposure time from 6 to 7 seconds. The exposure time increased… I can tell from the histogram in lightroom and pixinsight. But the exposure time recorded in the file remained 6.
what are you using as your light source?
The issues above were observed while using a gerd newmann Aurora flat panel. I also have a home made one using a tracer panel with ND filters and a 5mm acrylic front cover. The wizard fails with both depending on the ADU level I chose. The wrong recorded exposure time was when using the Aurora.
Have you tried getting the camera to take longer exposures? ie… diffuse the light and make it dimmer for the sensor. Right now the exposure lengths are quite short… just something to try. 
Yes I’m experimenting with this atm which is how I hit these bugs. Trying to verify the flatness of my panel against the Aurora and changing ND filters till I can get a good flat from my DIY panel in under 2 seconds with no filter in the image train. I’m using the Aurora as a reference panel and with 2 filters has flat exposures up to 7 seconds to get a half decent flat which is already too long IMO. The shorter exposures are from my DIY panel… not sure what the length of the exposures has to do with the flat calibration wizard successfully closing on a target ADU that I can reach manually readily enough though.