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Thanks Geoff. Email colinleggphotography @ gmail.blah
Unfortunately, PC timing is an issue for bulb ramping below 0.6 s. You need 0.001 accuracy between frames to smoothly follow the ramp and the best you can get from a PC is ~0.01. When I said earlier that bulb is only good for >= 0.1 sec, it's because +-0.01 is 10% inaccuracy. Just good enough for a single shot. 10% variation would still be noticeable as flicker though, if you strung a few of those together.
So, the way out is a microcontroller that does the timing. You can go 2 ways. 99% automatic with something like Little Bramper, or 100% auto with a custom controller like I have.
If you don't have Little Bramper or equiv, I have 2 spares from the first batch that I can lend out. It'll mean 2-3 seconds manually de-activating and re-activating the ramp within 10 sec of C2 and C3 and your ramp will be linear. I can send one over before I head off if you're interested.
The 3rd alternative is Promote Controller. It has bramping in the latest firmware. Unsure how sophisticated it is compared with LB?
And having said all that, it's likely you'll still see some flicker between 1/15 and 1/30 s. This is where even 0.001 is not fine enough. Better than the 1/3 stop alternative with AV or 1/8 in Full Auto though.
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