Feature request: Do not dither after the end of a sequence

[Sebastian G]

Hi,

If the dither interval is set to a multiple of the total number of files, a dither will still be initiated even if the current target has already been completed and a slew to the next target is about to happen.

1. Set up 2 targets in the simple sequencer.
2. Set the total number of files to 12 and the dither interval to 3.

After the sequence finishes, a dither is performed, before the mount slews to the next target.

I would like to suggest that a dither should only be performed if at least one frame needs to be taken in the current target sequence. Otherwise, the sequencer only takes up time for the obsolete dither.

Thanks,

Sebastian

‌

[Linwood Ferguson]

I’d like to suggest extending this a bit further, and not dither after the last image prior to anything that will stop guiding, e.g. a flip, filter change (if set to stop guiding), recenter, etc.

While it is not a lot of wasted time, all these do waste some time that can add up if you dither frequently and also have a lot of activity in your sequence.

I am GUESSING that dither is associated now only with the completion of an exposure. I wonder if there is a way to move it before an exposure, e.g. the end sets a “dither needed”, anything that stops guiding clears that flag, and the start of a new photo checks the flag.

[Stefan B]

For that fine granular control of dither you shouldn’t use the trigger but rather the specific dither instruction instead in a loop that is customized to your need. Instructions don’t look ahead and this would introduce a lot of guesswork of what the user is trying to do

[Linwood Ferguson]

I don’t quite see how that solves the issue of “last”. If I want to dither every 2, and shoot 10 images, how could I structure that so it only dithers 4 times?

Maybe I’m missing the obvious. Any chance of an example that’s somewhat generalizable?

OTOH a pending dither that can be cleared seems pretty clear – ANY scope movement negates the need for a dither (I think also without doubt?) It’s not a look ahead it’s a state, much like whether I’m guiding (and in particular whether I was guiding before entering a step requiring guiding to start afterwards). It’s more of a look back than a look forward.

‌

[Dale Ghent]

Regardless of how you want to frame it, the decision to dither or not and would still require the instruction to look ahead to whatever is next and attempt to infer the intentions/desires of the user. My feeling is that this issue is much ado about nothing. I don’t feel that an extra dither here or there is something that will make or break whether an extra exposure will be lost or gained. These ops take a few seconds, after all. And if you’re dithering so frequently (once per exposure, for some) then I have to further question how important it really is that one excess dither is avoided since you’re already sinking a lot of time into them.

As Stefan said, if you really want exacting control over when a dither occurs, don’t use the trigger; use the dither instruction inside the loop itself and place it in front of the exposure. Having instructions or triggers act implicitly rather than explicitly is its own minefield.

‌

[Linwood Ferguson]

I certainly agree it’s not a big deal, but putting a dither in front of an exposure doesn’t change the waste. The only way I can see to do it is if I wanted (say) 10 exposures dithered 2, is loop 4x dithering after each 2, then fall into an instruction outside the loop for 2 more exposures without a dither. It’s just – ugly. Again, unless I am simply missing how to structure this. But… I’ll stop lobbying, as it’s clearly counter-culture and not that important.

[Sebastian G]

Thanks for discussing this feature request.

[Brian Weber]

Somewhat related, but a little different: the dither counter seems to persist through target changes even if dithering parameters are set in each target. This causes strange things like I’m dithering every 5 frames on my second target, but it dithers after the first frame.

[Stefan B]

Fix Issue #866 - DitherAfterExposures will only trigger when the next item is an exposure item of type LIGHT

→ <<cset a2b5badddedb>>

[Stefan B]

With regards to the dither counter - the progress is taken from the image history and this is currently not aware of target switching